Monday, October 31, 2005


ALLISON MD 3060 AUTOMATIC TRANSMISSIONS

Allison MD 3060 Automatic transmissions are electronically controlled and the only transmission we use in our school bus fleet.

The one element these transmissions do not get along with is moisture which causes problems like crossed signals and fault codes. In our Thomas ER pusher buses the engine and trans. are located in the back end where all the moisture, salt, dirt etc. is sucked up like a huge vacuum. Wiring is another problem, mainly from rubbing along the frame and constant vibration from being encased in plastic loom.

Of course these problems are not caused by the manufacturer, the Allison MD 3060 is an excellent design that monitors every input and output and adjusts transmission operation instantly when required.

Below are some pics of the PRO - LINK, the diagnostic tool needed to troubleshoot these transmissions.

Checking For Fault Codes is the most important procedure in the troubleshooting process.


Hooking up Pro-Link to data link found under dash, the very first step... gathering information.


On-Board Diagnostics

Allison MD 3060 Electronic transmissions require a'Pro-Link' reader for troubleshooting purposes. This tool connects to a data link that will tell you what's going on with the trans. including trouble codes, temperatures, clutch engagement, rpm's, throttle position and much more.

The Pro-Link also performs on-board troubleshooting with action requests. With pressure guages hooked up to each clutch pack pressure port, we can use the Pro-Link to engage whatever clutch we desire while the bus is stationary. Comparing each clutch pressure reading to main pressure indicates if there is a worn clutch pack, which will cause excessive heat and slippage.

This tool is invaluable and without it you're pretty well sunk unless you can physically find open or shorted wiring. We have been finding a lot of faulty wiring from the Electronic Control Module to the transmission externally mounted speed sensors and Throttle Position Sensor. The wiring is a twisted pair so we replace it all, with new shielded wiring. This is much faster compared to finding where the exact fault is and doing a spot repair.



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  • 50 comments :

    Marty Schreiber said...

    John...How can I clear the throttle calibration on the MD3060 after I replaced a "bound up" TPS..cable would not retract. (I replaced the tPS sensor) I dunno if I really need the tool, cuz I do not do a lot of World Trans work? Like how much are they...can I use my Snap On scan tool? Please advise, Sincerely, Marty Schreiber ASE CERT. Master SChool Bus TEch.
    susymart@pacbell.net

    John Whelan said...

    Marty,
    The throttle calibration must be reset with the PRO-LINK reader. The on-board computer most likely would have logged the throttle position when the TPS cable failed.
    If your trans. shifts hard after replacing cable you will have to see a dealer who has a PRO-Link, it only takes a few minutes to recalibrate Throttle.
    Hope this helps! JOHN

    Anonymous said...

    John,
    Really enjoy your blog. I am currently working as a mechanic for a city municipality in Colorado, USA. I have already learned alot from your blog and appreciate you sharing your expertise with us younger techs. We have several dump trucks with the 3116 and 3126 engines in them and your blog has given me a good crash course about those engines. Thank you.
    William Cole
    WCole72@msn.com

    Oregonbythesea said...

    John, I have an MD3060 in a 97 Safari motorhome. The problem is when I shift into N, it will not go back into gear. If I start the engine and hold down the D or R just as it starts, it will go into gear and funtion just fine as long as I don't use N. One shop told me it was the controller which I sent to DMR Electronics. They said they couldn't fix it and sold me a used one that funtions the very same way. I know think it is in the wiring or one of the solenoids. I also have a leak from where the wiring goes into the top of the tranny. My original problem with the shifting, I think, was because of the leak when the tranny got 6 quarts low. What do you think. I need to fix it myself this time. I say this because our local Allison dealer is talking about tearing down the tranny. I have a lot of years experience as a mechanic but mostly marine. What do you think? Thanks.

    Anonymous said...

    d help on a pin out form a wtec ii transmission

    i got a engine and tran s from a wrecked fire truck and have no knowledge where the trans ecu go

    do you have a wiring diagram to sell me>>>

    i also need a ecu as mine is set at 4 spds and i want 6 spds

    thansk for any help in this!

    rwoody@fullnet.net

    Gary said...

    John

    I have a 1998 FL60 with an 8.3 cummins 12v and MD3060 with about 85,000 miles. The tranny works fine except when downshifting from second to first, it slams into first gear. 1 out of 25 times this is smooth/normal downshift, but the rest of time it shifts so harsh the truck shutters and "clunks" into gear. the transmission has been maintained. I am the 3rd owner and it has done this for the past 4 years I have owned it. Very annoying to say the least. Does this sound like a problem or just how it works? I've never had one of these big boys before.

    Thanks

    Gary

    John Whelan said...

    Anonymous,

    The ECU has to be calibrated by the dealer to change the speeds.
    To replace the ECU you need the numbers off the trans. so the parts guy can match the correct replacement.
    I can get you a wrg. diagram for a WTEC 2 just send me an email.


    Gary,

    Press both arrows together (ignition on) on the shift pad for codes. They are 4 digits i.e 35 - 00

    You'll see 'd1' then the 4 digit code press 'mode' for more than one code you will see 'd2' a second code or nothing at all.
    Press 'mode' a third time you'll get 'd3' and so on.

    The hard shift could be electrical since it's intermittent. The trans will shift automatically down to first when the engine and road speed is right. If one of these signals is incorrect a hard shift will develop.

    Anesha said...

    Hi Nice Blog. Data data conversion services indiacan range from a simple one for one import to a complex procedure where non-relational data needs to be imported, validated, cleansed and split up into multiple tables in a new relational database structure.

    Trey Lewis said...

    I have a question about a MD3060 Trans you can email me at trailerrepair@doneritemfg.com if you don't mind.

    Sam Murray said...

    John, great site. I have a motorhome with a MD3060 I purchased the two filters and would like to know what to torque the bolts to?

    Thanks,

    Sam

    Pet Cages Guy said...

    Hi Sam,

    Thanks for the comment!

    The bolts can be torqued to 32 ft. lbs.

    One important tip I must add is never use air tools on these filter housing bolts.
    This causes the aluminum threads in the trans. hsg. to wear out and eventually strip out.
    Always do the whole operation by hand. I use a speed wrench which really helps out a lot.

    viktorskyler said...

    Hi John,

    My problem child is a 1997 Ford CF6000 medium duty cab-over, Cummins 8.3 with MD3060 -- 100,000 miles since new.

    Problem -- No power to the 'remote pushbutton shift selector' next to the driver seat. No lights, no action.

    Key ON results in full dash sweep, but no starting activity.

    Engine starts/runs when starter is hot-wired.

    Ground issue?

    thank you!,
    viktor -- Cottage Grove, Oregon
    viktorskyler@yahoo.com

    John Whelan said...

    Start at the battery, the Trans ECU receives battery voltage directly from the battery. The pos and neg cables run directly to the VIM (vehicle interface module) and downsizes to #18 wires. The VIM is under the dash and can be accessed inside where there is a neutral start relay with fuses. Try these steps first. Comment back if you need any more help Good Luck

    viktorskyler said...

    Hi John,

    [I worked on aircraft for three decades, just enough experience to frustrate myself royally on this!]

    My 1997 Medium duty with 3060 has power to the VIM and ECU. Both are safe inside the cab.

    1) In the VIM, I swapped the good-appearing relays. I swapped the good-appearing twin 10Amp fuses with new.

    2) My VIM has 12VDC with the IGN ON, no juice while the IGN OFF.

    Do you suggest I run a dedicated fused line directly from the battery (and back)? If so, at the VIM, which color wires do I tap?

    3) My no-power push-button shifter has five (5) wires:
    purple and white,
    yellow and teal,
    red and blue,
    yellow and red,
    black.

    Which is power, which is ground?

    Do you suggest I run a dedicated line from the battery (and back) to power the shifter? If so, which color wires do I tap?

    4) After reading
    http://www.transmissioninstruments.com/
    about wear in push-button shifters, I checked inside mine. Looks clean and dry and good.

    None of the VIM or ECU or remote shifter has a burned odor.

    5) I fiddled with this for a week, so tomorrow afternoon, I will probably hire a wrecker to tow it to Freightliner of Sacramento -- US$124 an hour shop charge, one hour minimum!

    viktor -- stranded in Roseville, California

    John Whelan said...

    Here is a link to most of my Allison Trans posts.
    http://schoolbusmechanic.blogspot.com/search?q=allison+transmission
    If the link does not work do a search for "allison transmission" on my blog.This will give you a better idea on the electronic side of the 3060 Model.

    Looking a wiring diagram the 12 volt battery is constant to the VIM and goes through a 10 amp fuse.

    On the VIM output there are 2 terminals E1/R1 and E2/R2. This the connector plug in contacts.

    You should have 12 Volts output at both these terminals. One is pink # 136-V16 the other is Pink #136-V1.

    They plug into the ECU / Shifter module at the grey connector - terminals 1 and 16.

    There are also 2 grounds as well at the grey connector via the VIM straight from the battery to the ECU. Both Grey #143-V17 / 143-V32.

    Just make sure you are getting your ground and positive feeds to the ECU first.

    Good Luck

    viktorskyler said...

    A sad case of Operator Error!

    Although I confirmed 12VDC power (several times!) through the circuit breaker outside the battery box, I failed to check the amount of power the circuit breaker was capable of carrying.

    This circuit breaker feeds the VIM, and over the years got to the point it couldn't carry the load required.

    Thanks everybody for the help.

    John, keep up the good work.

    viktor -- HQed in Cottage Grove, Oregon, 100% mobile

    John Whelan said...

    That's great news. The battery source is the first and most important check for these transmissions (it's happened several times...speaking from experience). I'm glad you were able to avoid the tow job.

    ashflat said...

    I bought a 5.9 cummins from a rear engine motor home that burned & it has a MD3060 hooked to it. How much trouble as in money would it take to hook up this trans & make it work? I assume I will need the ecm & wiring harness & the shifter box. The wiring at the trans is fine, just where it is attached up high is melted. Where might the ecm be located? its a 1993 model. Thanks

    John said...

    If you can salvage all these components,ECM,VIM & harnessit is possible. You need to hook up to a radiator for cooling and the engine battery to operate the ECM. Do a search on my blog for allison trans and you will find all my posts.

    HWAYNER71 said...

    John
    just purchased 24v cummins with allison md3060 out of 98 allegro motorhome . Wiring harnes is gone cut 6in out of trans no twist connector ,no selector box .I have a tcm out of 05 motorhome with 3060 with a cat in front of it . Can this be reprogramed for mine and will i have to replace the wires inside of the trans ? thanks

    John said...

    You have to get the trans.serial number and contact the dealer. They can tell you what part numbers you need that are compatible with your trans. There is a large age gap between the 2 transmissions with different systems wtec 2 and wtec 3.

    Todd said...

    John, Im working on a School bus that has a MD 3060, it all of a sudden wouldn't shift into FWD on a run, then after several attempts the driver got it to go & drove it 20 mi back to the school, & I pulled codes 2511, 2522, & 2312. the bus still will not go FWD, but has REV. do you think & have Electrical or Clutch issues.

    John Whelan said...

    Todd,

    If it isn't going into forward you may have a clutch solenoid not activating. There has to be 2 clutches engaged to get forward gears. I will check the codes and get back to you.

    J. E. Whelan said...

    Code 2511 is the output speed sensor has a zero speed reading. Check the speed sensor and connection, the ohm reading should around 300 ohms. Also check the ECU connectors. Make sure they are tight,clean and undamaged. Check the fluid level and check wiring to the sensor has no opens, shorts between wires or shorts to ground.

    Code 2522 is related 22 being a subcode.

    Code 2312 is the shift selector. Check ECU for connectors, shift selector connector, check selector for proper operation and check the wiring harness for opens, shorts between wires and shorts to ground.

    We have had lots of wiring issues and repaired a lot of these problems by running a new coaxial wire from the sensor to the ECU. There seems to be some resistance in the wire that causes improper signals to be relayed to the ECU.

    Another area there has been faults is the shift selector pad. You can get a kit for the selector which isn't hard to replace.

    If it's hard to push the selector to get into gear that's the first sign of trouble and a new selector pad would fix the problem.

    wes said...

    Hi John

    I have a problem with an MD3060P in a 2001 KW T300 with a Cat 3126. The truck will not start due to a blank selector pad. I'm assuming it is because the truck doesn't recognize that the transmission is in neutral. I started by checking the 10 amp supply fuse in the battery box, which is good. I also have power on pins 1 and 16 and good ground on pins 17 and 32 on the gray connector at the ecm. I also have power on on wire atd 136d and ground on wire atd143c in the harness going to the selector pad. I spoke to the service department at the locdal KW dealer after I could not locate the vim and they told me that one does not exist on this old of a truck. They also told me from the info that I gave them that I had a bad selector pad,which I purchased for $600 and did not cure the problem. I still have a blank selector. Any advice you could give would be greatly appreciated.

    Thanks

    Wes
    wes@bentwoodnursery.com

    J. E. Whelan said...

    You have to have a VIM to operate high idle, exhaust brake and other extras. It is the interface between the engine and the trans ECU. It won't be very far away, there will be a connector out of the ECU that will lead to it. There is also a neutral start relay & fuses in the VIM that you can check. Reply back here to let me know what you find and we can get more in-depth with troubleshooting. P.S. I have never seen a failed ECU in these systems.

    J. E. Whelan said...

    Also do a search for allison transmission in the search box at the top left of my blog homepage. You will see all my posts on the subject.

    Anonymous said...

    John,

    I am putting a wet kit on a fl80 with the MD3060. Directions say to hook into wire #106 or J1-6(TCM). I have torn the dash apart and looked at countless numbers stamped into wires but have not found 106. Also, I cannot find wiring daigram for TCM to find J1-6. Any experience with this?

    Thanks,
    Mike, MCGG

    Larry said...

    Joe... I own a Monaco motor home with a 1994 vintage Cummins 5.9 and MD3060 WTEC II. My problem is the Pacbrake was installed aftermarket and seems to be wired without benefit of the throttle position switch which is supposed to prevent retarder operation when the throttle is >0.

    My question. Does my engine have a mechanical TPS and where is it located?

    reference: http://www.pacbrake.com/PDF/L5114.PDF

    J. E. Whelan said...

    Mike,
    I took a look at a schematic for a WTEC 2 system (mid to late 90s) 106 is an oil level circuit? Going from the ECU to a trans connector for pre 1995 units. I found a J1 terminal at the Vehicle Interface Module which supplies battery power to the Trans ECU module.

    J. E. Whelan said...

    Larry,
    That year you will have a cable TPS hooked to your throttle linkage. trace back from that point and you will find the TPS control box with plug in harness.

    Nick Frost said...

    just bought a 93 gulfstream motorhome we drove about 100 miles did just fine has allison MD3060 trans next moring we went to move it get a do not shift light and no lights at shifter any ideas

    Nick Frost said...

    We just bought a 1993 Gulfstream 2000 on a Spartan chassis. It has an Allison MD 3060 and six button shifter. When we first drove it the "Dont Not Shift" light took a long time to turn off. The second time, later that day, the DNS light began to go on and off while driving, while the all lights on the ECU were blinking. It did drive 100 miles and shift all the way up to 6th and back without any problems. The next morning the display did not come on at all, though later on it came on briefly before going out completly. It did this several times as we tried to figure out the problem. When we opened the panel the ECU was very hot. Since then, the ECU has not lit up at all.

    Nick Frost said...

    Hi John,
    We checked the connector for voltage and ground. The chassis ground and both battery grounds are grounded, and both battery voltage pins are hot at almost 13 volts when the engine is not running. I've only tested black connector. It appears the blue connector has a red "hot" wire running into it, but there seems to be no ground wire on this connector so I have not tested it.

    So, from driving 100 miles, I'd say the mechanical parts seem sound, and the connector is supplying voltage and ground. I'm new to this, so operator error also seems likely. Looks like it's either that or a bad ECU, so right now I'm hoping for simple.
    Thanks,
    Nick Frost

    Happy 4th!

    J. E. Whelan said...

    Nick,
    If you have good battery voltage to the ECU I'm thinking it's a bad ECU. First I would go to the VIM (vehicle interface module) and see that the battery voltage is getting through to the ECU. The VIM houses the relays and connects with chassis circuits like exhaust brake, high idle etc that requires an ECU signal to engage each circuit. If you go back to my blog do a search for allison transmission or md3060 wiring. I have a schematic on one of my posts. I'll have a look as well.

    J. E. Whelan said...

    Nick, Check out this link http://schoolbusmechanic.blogspot.com/2007/10/allison-automatic-transmission-wiring.html or search for allison automatic transmission wiring. You'll find the VIM in that post and see the 2 fuses for ignition and main power.

    Nick Frost said...

    John,
    Thank you for the response! I checked the VIM at the fuses and plugs going into it. Power and ground in all the right places.

    Today I'm going to find an Allison certified mechanic and see if it lights up on a test bench. If it is a bad ECU, I'll search the Dallas-Fort Worth area junk yards and see if I can locate a working one. (Ebay has ten Allison ECUs today, and ronthebusnut.com has many more, but none are of the type I need.)

    If I pull one from anything other than a motorhome It'll have the wrong programming. Can these be reprogammed using modern tools (say, something using the J1939 standard) or do I need to use the old Pro-link 9000? If I can't reprogram it myself, I suspect an Allison certified shop can probably do the job, but not inexpensively.

    If barking up that tree yields no results, one of those mail-it-away ECU repair specialists is my next choice. I've seen transmissioninstruments.com, ecmking.com, ecutogo.com, and dmrelectronics.com. I'm hopeful I can find one that will charge me just an arm and not bill for the leg too.

    Also, I have heard of "ECU rebuild" kits, which I'm guessing has replacements for most of the parts inside the ECU, except circuit boards. The way it died slow, in a "I'm losing power" way makes me think it's not a circuit board problem. I'm not afraid of a soldering job, I have more experience with electronics than mechanics, but messing around with such an expensive unit seems like borrowing trouble. Still, have you heard of or do you have any experience with these kits?
    Nick Frost

    Brian B said...

    John,
    I have a 94 gmc Topkick bucket truck, 82k miles with an Altec boom. It has a Cat 3116 and an Allison MD 3060 Trans. The problem I'm having is that the electronic shifter is now stuck on for lack of better diescription, Lightening Bolts. The truck will not start. Just prior to this the shifter dropped out of drive into nuetral a couple of times. I checked the codes and got a 35-00 which I read as power interuption. I checked for wiring problems but don't really know what I'm looking at, or where to look actually. An Allison service adviser said to check the nuetral safefty switch, but I haven't found out what it looks like or where it's located. I have read on your blog that moister is a problem and I have 2 electronic boxes mounted on the frame by the tranny with thier connectors exposed to the weather. The truck was just inspected and the engine and tranny were proforming well. Any sugestions would be deeply appreciated.

    scottsman said...

    I have a Allison push button wtec 3. P/N 29538360. I lost the lights to R, N, F. Have lights to shift indicator and light for economy. I need a schematic for this if possible.

    scottsman said...

    I have a Allison wtec 3. P/N 29538360. I need a schematic. I lost the lights to R,N,F. I had them, then last week I went out and they didn't light up.

    Charles Creach said...

    My 1994 Monaco rv is showing code 2511 it is at the mechanic they replaced the output sensor and the two wire twisted pair, but still will not shift out of first and e "do not shift light" is on. THey said they need a wiring diagram, any idea where I can get one? Thanks for any help!

    John Whelan said...

    Charles
    You might have more than one code going on there. Have you pushed the 2 arrows on the shift pad with ignition on? After you get the first code of 4 digits push the "mode" button on the shift pad to see if there is another code and just keep going. Maybe there is a stuck shift solenoid or something similar.

    Duane said...

    Mr. Whelan,

    We have a 1994 RV with a 5.9 Cummins and MD3060 transmission with wtec-ii control. The transmission is showing 35-00 "power inturruption." I took the rv to the local Allison service center, and they swapped our TCM out several times with their test TCM. Every time their unit was in place, the 35-00 code did not appear... and our original TCM throws the code every time. Long story short... Bad TCM. I have gone through the Allison troubleshooting procedures myself and have confirmed that voltages and grounds appear to be good at the control.

    Question: How detrimental to the tranny and drivetrain is this? As far as I understand, the issue is that the computer loses all of it's stored shift points when you see the 35-00 code. Since the code sets every time the ignition is cycled, every time you go for a drive the computer goes to a default setting and starts to relearn the shift points again. While it's doing this, some of the shifts can be rather harsh for the first several runs up and down through the gears, especially on the downshifts. Will this cause accelerated wear to the transmission or other drivetrain components? Do you think the TCM is on it's way out completely and should be replaced before it strands us far from home? I only ask because it is a somewhat costly repair, especially on a 22 year old RV. Thanks in advance.

    -duane

    Duane said...

    Update:

    I went ahead and had the TCM repaired. As far as I can tell, the TCM is no longer losing it's stored shift points, but I still see the 35-00 code. The tranny shifts very smooth every time I start the engine and go for a drive now, whereas before it used to take several cycles up and down through the gears before it would start to smooth out.

    The folks that repaired the TCM said that the 35-00 code does not necessarily mean the loss of stored shiftpoints, and that they fixed the power supply in the TCM that was causing that particular problem... 35-00 just means that there was a power interruption.

    I think the power interruption is happening when the engine is cranking, because the code only sets after the ignition has been turned to "on" and the engine turns over. Is it possible that voltage in the "always on" wire to the TCM is dropping below the threshold during engine cranking? I would have to splice into this wire somewhere to check it since the engine won't crank if the TCM is removed. What is the best way to do this? Which wires should I be testing? I thought perhaps the chassis battery is kind of small for a cummins @ 600cca, but I have two agm house batteries each with 1100cca.

    What should my next step be? I don't think the code is causing me any issues with performance... but if it's possible to solve the issue it seems like I should.

    Thanks!

    John Whelan said...

    Duane
    The TCU power is direct from the battery. A positive and negative feed is coming from the battery on a #10 or #12 gauge wire. You might have a bad spot in the wire causing a voltage drop. You could test with an alternate 12v source to the TCU or do a voltage drop test. Eventually you may have to replace wrg.

    Duane said...

    Hi John,

    I did as you said and started inspecting the wiring. I downloaded the Allison Trouble shooting manual for the MD3060, which has a very good wiring diagram. What I found was kind of a surprise. When I checked the voltage at the VIM that was supposed to be coming direct from the battery there was nothing. Not a single volt. I traced the wires from the VIM to the battery (nice big 6 gage wires) and found that the hot wire had been cut. I couldn't understand how the TCM was getting any voltage, but figured I'd go ahead and repair the wire. When I did that, the TCM lit up and wouldn't turn off regardless of the ignition being on or off. Weird.

    I then crawled under the dash and unplugged the VIM... when I did that, the TCM went off, and at the same time there were relays in the dash that were clicking on and off. It seemed like voltage was backfeeding into the chassis ignition system from the VIM... so I pulled the cover off the VIM and VOILA... someone had soldered a jumper across terminals R1 and S1... basically, instead of repairing the main power wire from the battery, they jumped the switched ignition power to the VIM over to where the main 12v power was supposed to come in. When I removed the jumper that was installed, the TCM started to work as it should, and the 35-00 code disappeared...

    It's been shifting better since this fix... but It's still holding on to 5th gear way too long on the downshifts. It won't go into 4th gear until about 30mph. When your in 5th gear and going 30 mph, the engine is way below the torque band, and it just belches black smoke and lugs really bad if you try to accelerate... and even if you floor the accelerator, it doesn't seem to want to kick down into 4th. I'm guessing there's a TPS adjustment necessary? I've checked the swing on the TPS and it's right in the middle of it's travel... and checking the resistance across the tps over the stroke reveals no dead spots and in spec.

    What do you think? Probably time for a trip to the Allison dealer?

    -duane

    John Whelan said...

    The dealer can do a road test and re adapt shifting sequence. Trans Relearns proper shift points

    scottsman said...

    I have the same transmission with a cat 3126B engine out of a motor home. A couple of years ago I put this and all the other stuff that goes with it in a 1980 Chevy K30 pickup I had. I didn't have any problems but the shift was horrible. I got off the Internet "Motor Home Series" for allison shifting. On page 32 through 36 talks about how to get the shift properly done for its application. I did it off and on a few days and after a while it smoothed out good. If it's cold at first it holds a little longer, due to its original application. Then shifts good after warm up. This set up with a 300 hp at 2400 RPM witk 860 pounds of torque at 1450 RPM is high, but it will last forever. Hop this helps.

    Duane said...

    OK, so after some miles with the wiring corrected, and after having the TPS set for idle and WOT, the tranny has been shifting great. For the first time ever, the transmission now kicks down a gear when I mash the throttle instead of just lugging the engine.

    Now I have a new problem. 5 or 6 times now, when trying to put the transmission into gear, the TCM just flashes and beeps and won't engage. The manual says this is due to RPM being too high... but it's not. It idles at 750. I've even

    I have discovered that when it's doing this, all i have to do is rev the engine up to maybe 1200 or 1500 rpms and when it goes back down to an idle it will then go into gear, although when it does it goes in kind of hard. What could be causing this new issue? There are no codes.

    -duane

    Duane said...

    John,

    I'm wondering where the tachometer on our 94 HR motorhome with 12v 5.9 cummins and MD3060 gets it's signal. Do you know if the Allison TCM has the ability to send a signal to the tachometer? I originally thought the alternator ran the tach, but we have a one wire self exciting alternator that I've disconnected totally, and the tach still works. I assume the signal is coming from the VIM, but I don't see an output labeled on the Allison wiring diagram... thoughts?

    -duane