Allison Transmission Questions


dbarton291

Senior Member
450 kPa is only 65 psi at idle. Should be at least 150. You may have a pump that is worn and not producing enough pressure, or a worn forward clutch. The clunk you feel is probably forward clutch dropping out and then re-engaging. Most likely not first clutch. Something is giving you low main pressure.

the modulator, if it's a mechanical cable should be moving smoothly from idle to wide open throttle. The transmission may be a reduced modulation calibration so you don't feel any difference in the shift points until you are near wide open throttle.

Hope this helps. The pressure thing is bad news, but 65 psi is too low.

DB

purpledecker;82794 said:
Hi, Hoping you may know any common problems that may help with our MTB647. The transmission is dropping into neutral every time it downshifts from 2nd to 1st. Originally it was only when the transmission warmed up, now it every time. When coming to a stop or near stop (anytime it wants to drop into first) there is no response from 1st gear. At idle it takes 5-10 seconds to re-engage, if you raise the revs, it engages quicker. It appears to be the 1st Clutch, because if you try engaging Reverse, it has the exact same delay. Please note, there is no slippage as such, you can hear the whir as the box stops spinning and the mild clunk at is locks in. Immediately after the clunk you can put your foot to the floor and it will pull like a train. Please note, that this only happens on the downshift. When you shift from neutral to either Forward or Reverse it immediately firmly engages (except when it has just downshifted, in which case it doesn't matter what you do). We are a repairer, but we do not want to start dismantling the transmission until we have exhausted all the easy problems. Here is some of items we have checked and noted:
1. Changed Pan Filter & Fluid
2. Main Pressure at idle 450kpa
3. Modulator appears correct when compared to similar bus. It has a Cummins L10 250hp, and the Modulator uses a slide connection which does not actually come in play until heavy throttle is applied.
4. Checked shift selector position for correct alignment.

Other items we have noticed that may not necessarily be associated:
1. Slight flaring/clunk when upshifting from 1st to 2nd under heavy acceleration.
2. Reverse judders but doesn't appear to be actually slipping, more like rapidly engaging and disengaging. (Does not happen in any other gear at all)

If I had to guess, I would have said it seems like the 1st Clutch Valve is sticking, but then it doesn't do it when engaging from neutral.

Your thoughts appreciated.

Kind Regards, Jason
 

dbarton291

Senior Member
Check the modulator cable adjustment. That will have an effect if the cable is pulled out toward wide open throttle when the throttle is really at idle.

George Meehan;82282 said:
Hi--I have a MT654 Allison trans in my 1986 military truck --has a cummins ntc250 diesel--this trans has 10w motor oil in it--military standard------I have a very pounding downshift 2nd to 1st--the drivetrain jumps like I hit a hole in the road----is there any adjustment for this--thanks---I use this as my RV
 

Roy SDA

Junior Member
Hello am newbie,
Please help us.
My Kenworth truck with Cummins ISX 475, Allison transmission RDS 4500 , some of days (the period of one month) we obtain problem of "double CAT EYE", is that We do is the following:
1.Inspection thoroughly "Wiring Harrness" for ECM Engine, Cabin CECU, Shifter, Allison TCM, all Solenoid, Pressure Switch, Switch Solenoid Allison, all Connector.
2. Inspection of all Control valve jammed or damaged.
3. CAN Inspection line at all locations (Engine, Shifter, CECU, Allison TCM: all resistance of 60 Ohm.
3. Replace with a new Allison TCM with the same program.
4. Try TCM, Shifter, CECU, Throtlle Pedal from the damaged unit to unit operating (running) the result is all the components are working properly.
5. Allison oil pressure test on the standard result: approximately 240 psi.

Of all these measures did not seem damaged components and all measurement results are good.
So far Diagnostic Tool (Noregon / Nexiq) still can not connect, but for Cabin CECU (ESA) and Cummins INSITE can be connected.
I do not know exactly what to do, seems to have been a maximum.

Help ideas, suggestions from comrades RV Talk Forum so we look forward, thank you for your time and attention.
 

michaelsmd

Junior Member
Hi Allisonman, I appreciate your offer to answer questions about these transmissions!

I just purchased a 1993 motorhome that has an Allison md3060 and the shifting seems to be taking longer and is harder than I am used to. Maybe you can tell me if this is normal or not? My only point of comparison is a 2007 motorhome with an allison, which shifted much faster and smoother.

The motorhome is a 1993 coachmen royal rd, with a cummins 8.3 250hp and I would guess that it weighs about 23,000 lbs. I have experienced all this driving on flat roads in 100+ degree weather. There are no warning messages and the fluids/temps are all good.

The transmissions seems to shift 1-2 before or around 1500 rpm and the rest of the gears seem to change around 1700 when under light throttle. This all works fine, but the shifts can seem hard at times and they almost all take several seconds to change gears. Almost like I can feel it coming out of gear and then (2 or 3 seconds later) I feel it shift into the higher gear with a noticeable "kick". This happens every time under light/medium throttle, but under full throttle, the shifting is much faster and almost seems smoother.

Thanks for info or help anyone can provide!
 

dbarton291

Senior Member
Does the engine RPM increase more than 200RPM or so between shifts?

michaelsmd;83867 said:
Hi Allisonman, I appreciate your offer to answer questions about these transmissions!

I just purchased a 1993 motorhome that has an Allison md3060 and the shifting seems to be taking longer and is harder than I am used to. Maybe you can tell me if this is normal or not? My only point of comparison is a 2007 motorhome with an allison, which shifted much faster and smoother.

The motorhome is a 1993 coachmen royal rd, with a cummins 8.3 250hp and I would guess that it weighs about 23,000 lbs. I have experienced all this driving on flat roads in 100+ degree weather. There are no warning messages and the fluids/temps are all good.

The transmissions seems to shift 1-2 before or around 1500 rpm and the rest of the gears seem to change around 1700 when under light throttle. This all works fine, but the shifts can seem hard at times and they almost all take several seconds to change gears. Almost like I can feel it coming out of gear and then (2 or 3 seconds later) I feel it shift into the higher gear with a noticeable "kick". This happens every time under light/medium throttle, but under full throttle, the shifting is much faster and almost seems smoother.

Thanks for info or help anyone can provide!
 

dbarton291

Senior Member
There can be many causes for shift selector cat eyes condition. I recommend you communicate with the following company so you can discuss all the details with someone knowledgeable on Allison 4000 series transmissions:
Malaysia

Selangor

Maju Engineering Services
Allison Direct Dealer
79 Jalan Pendamar 27/90, Section 27
Shah Alam , Selangor 40400
Malaysia
603-51910945(Phone)
603-51918206(Fax)

I have been to Maju and they were very knowledgeable.
DB


Roy SDA;83716 said:
Hello am newbie,
Please help us.
My Kenworth truck with Cummins ISX 475, Allison transmission RDS 4500 , some of days (the period of one month) we obtain problem of "double CAT EYE", is that We do is the following:
1.Inspection thoroughly "Wiring Harrness" for ECM Engine, Cabin CECU, Shifter, Allison TCM, all Solenoid, Pressure Switch, Switch Solenoid Allison, all Connector.
2. Inspection of all Control valve jammed or damaged.
3. CAN Inspection line at all locations (Engine, Shifter, CECU, Allison TCM: all resistance of 60 Ohm.
3. Replace with a new Allison TCM with the same program.
4. Try TCM, Shifter, CECU, Throtlle Pedal from the damaged unit to unit operating (running) the result is all the components are working properly.
5. Allison oil pressure test on the standard result: approximately 240 psi.

Of all these measures did not seem damaged components and all measurement results are good.
So far Diagnostic Tool (Noregon / Nexiq) still can not connect, but for Cabin CECU (ESA) and Cummins INSITE can be connected.
I do not know exactly what to do, seems to have been a maximum.

Help ideas, suggestions from comrades RV Talk Forum so we look forward, thank you for your time and attention.
 

dluv

Junior Member
Hey man, I hope you can help me? I have a 2001 Chevy HD Crew Cab 3500 with an 8.1 liter engine. I'm not sure what Alison I have in it? Here is the problem I was driving home from my job to my house, witch is about 25 miles when I got off my exit the tranny if my truck was stuck in 1st gear for some reason. I was going about 40 mph at about 3500 rpm. After my son's 2 hour baseball game I got into the truck to see if I could make it home and the truck drove totally normal like nothing happen. The truck was shifting fine......I don't know what to do I took the truck to 2 different transmission shops and they said oh you need to rebuild you tranny.

The funny thing is the guy at AMCO showed me the codes that came up. The first code was an electrical code in the tranny that failed and the second code was a tranny default code because the tranny failed and was stuck in 1st gear? Any suggestions
 

dbarton291

Senior Member
I'm afraid from the description you have given, I can't help very much. You first need to find out which transmission you have. The Allison transmission was an option in that truck. You may not even have an Allison.
The description of the codes you gave doesn't make any sense either.
If the electrical codes referred to specific circuits, I would make sure those circuits have no opens, short or shorts to ground. Sounds like an electrical intermittent may be the cause, but I can't be sure from what you've written.


dluv;83974 said:
Hey man, I hope you can help me? I have a 2001 Chevy HD Crew Cab 3500 with an 8.1 liter engine. I'm not sure what Alison I have in it? Here is the problem I was driving home from my job to my house, witch is about 25 miles when I got off my exit the tranny if my truck was stuck in 1st gear for some reason. I was going about 40 mph at about 3500 rpm. After my son's 2 hour baseball game I got into the truck to see if I could make it home and the truck drove totally normal like nothing happen. The truck was shifting fine......I don't know what to do I took the truck to 2 different transmission shops and they said oh you need to rebuild you tranny.

The funny thing is the guy at AMCO showed me the codes that came up. The first code was an electrical code in the tranny that failed and the second code was a tranny default code because the tranny failed and was stuck in 1st gear? Any suggestions
 

donz63

Junior Member
I have a 2001 3500 4x4 duramax with an allision tranny .pulled 5th wheel all last summer no problems .This year pulled it for first time and tow haul button did not work .I found the problem broken wires at shifter base like i find out most do. However there was a clean cut . and it has two wires inside the orandge cover .I have soldered the back together . and tow haul now comes on.I then had tranny flushed for maintanace themechanic stated the tran fluid looked good but we did it anyways for maintanance .He put in bg synthetic fluid. Now I have pulled it twice and the tranny has went into the limp mode were it locks it in third gear I think it is third anyway .It codes 730 and once it coded 700 as well but only once on the 700. Is it possible to have crossed the wires on the tow haul that would be causing thois or is the bg synthetic fluid a bad match for the allision. I went from no problems to this for no apparent reason .The are the only things that have changed . Any suggestions
 

LEN

Senior Member
If were me, I took a quick look at the chart on the BG and saw nothing about your trans, I would be going to transynd fluid the Allison recommended fluid. Or do some research on the BG and see if it is a cross over.

LEN
 

Leroy

Junior Member
Hello Allison man. I have a 2004 Chevy silverado 2500 4x4 with the duramax and Allison transmission. When I am driving at slower speeds or slowing down it seems that the transmission switches to neutral and then it sounds like it is whining like it is trying to go into hear. If I shut the truck off and let it sit for a few minutes and restart it it goes into gear and goes. It does this in reverse sometimes to and the digital on the speedo says shift inhibitor or something along that line. I change the NSBU switch but it still does it randomly and it's a pain when it happens at a red light with traffic. Any other ideas what the problem could be? Thank you Leroy.
 

dbarton291

Senior Member
Hmmmm. I wonder if you're hearing the lockup clutch disengage but that doesn't happen in reverse. If that's not it, my gut reaction is to check for trouble codes and check the oil and make sure oil level is good. Then put the pressure gauges on it and recreate the problem to see if there's a pressure problem.

Leroy;84046 said:
Hello Allison man. I have a 2004 Chevy silverado 2500 4x4 with the duramax and Allison transmission. When I am driving at slower speeds or slowing down it seems that the transmission switches to neutral and then it sounds like it is whining like it is trying to go into hear. If I shut the truck off and let it sit for a few minutes and restart it it goes into gear and goes. It does this in reverse sometimes to and the digital on the speedo says shift inhibitor or something along that line. I change the NSBU switch but it still does it randomly and it's a pain when it happens at a red light with traffic. Any other ideas what the problem could be? Thank you Leroy.
 

dbarton291

Senior Member
The lockup clutch is supposed to disengage at low speed. That puts the transmission back in its mode where the torque converter is acting as a fluid coupling. That's how an automatic works. It's in fluid coupling mode (or vortex flow) at stop so you don't have to have a clutch pedal.
 

driller2948

Junior Member
Hello Allison man! I have a new 2013 GMC Duramax with the Allison 1000 auto transmission! With 1,000 miles on the truck I pulled my 12k 5th wheel into Colorado from Texas! Pulling some decent 6% grades with a GCWR 20K. With ambient temps running around 90 deg. I saw engine temps of 200 -210 and tranny temps of 154 – 175. However my brother-in-laws 2007 GMC Duramax with the Allison 1000 auto transmission with a GCWR of only 18K! Engine temps of 210-230 and tranny temps of no less than 210 and peaked around 230! Why such a big difference? O’ the 07 only has 45k! The dealer he contacted said those temps were well in spec and he has nothing to worry about! I’m not so sure about that, what do you think?
 

dbarton291

Senior Member
I wonder if your 13 is reading sump temp and the 07 is reading temp to the cooler.
In any case, even for to cooler temps (which is the hottest in the system), those are well within spec. Dexron is good to 300 F.
After 300, Dexron begins to break down. And fluid life is inversely proportional to temp. The hotter it runs, the shorter the life of the fluid.

driller2948;84077 said:
Hello Allison man! I have a new 2013 GMC Duramax with the Allison 1000 auto transmission! With 1,000 miles on the truck I pulled my 12k 5th wheel into Colorado from Texas! Pulling some decent 6% grades with a GCWR 20K. With ambient temps running around 90 deg. I saw engine temps of 200 -210 and tranny temps of 154 – 175. However my brother-in-laws 2007 GMC Duramax with the Allison 1000 auto transmission with a GCWR of only 18K! Engine temps of 210-230 and tranny temps of no less than 210 and peaked around 230! Why such a big difference? O’ the 07 only has 45k! The dealer he contacted said those temps were well in spec and he has nothing to worry about! I’m not so sure about that, what do you think?
 

Leroy

Junior Member
sometimes it disengauges when I am driving at slow speeds then its like it in netrual and wont engauge to take off and I hear a whining sound so when I go to put it in park it kind of make a loud grinding sound. I then shut it of and when I restart it it goes for awhile but does it again. if I give it throttle it just makes a faster whining sound but still wont move. sometimes when I am taking off from a dead stop to get to highway speed it also stalls between shifts and acts like it is in netraul then I have to pull over and go through the shut off and restarting engine to take off again. some times it seems to drive normal and other days are a pain in the butt. could it have anything to do with the powertrain modual not sending it the right info for changing gears?
 

dbarton291

Senior Member
Assuming the fluid level is good, it sounds to me like it's time to put the pressure gauges on it and find out what's going on in the transmission itself. How many miles are on it?

Leroy;84103 said:
sometimes it disengauges when I am driving at slow speeds then its like it in netrual and wont engauge to take off and I hear a whining sound so when I go to put it in park it kind of make a loud grinding sound. I then shut it of and when I restart it it goes for awhile but does it again. if I give it throttle it just makes a faster whining sound but still wont move. sometimes when I am taking off from a dead stop to get to highway speed it also stalls between shifts and acts like it is in netraul then I have to pull over and go through the shut off and restarting engine to take off again. some times it seems to drive normal and other days are a pain in the butt. could it have anything to do with the powertrain modual not sending it the right info for changing gears?
 

Leroy

Junior Member
dbarton291;84134 said:
Assuming the fluid level is good, it sounds to me like it's time to put the pressure gauges on it and find out what's going on in the transmission itself. How many miles are on it?
It has over 200k on it. just bought it a couple months back. I checked the fluid level and that is full. I havent checked the transfercase fluid level yet though. Ive used the code reader on it and and have cleared all the codes and I get a code that says my tcm needs replaced or reprogramed another says read speed sincer and sometimes I get a bad ratio code. and when I clear each time it gives me a different bad gear ratio. one time it may be 1st gear another time it may be 4th or 5th. when I take off and drive down the highway and set the cruise it seems to be fine but when I let of the peedle sometimes it just goes into netraul and I have to pull over and shut off truck for a couple minute and when I restart it it works again for a while. I've read a lot of other forums and tried to pin point the problem but with all the different sulutions its kinda hard to know where to start. one person said if the transfer case is bad that would cause it to slip into netral also. and if the rear speed sincer on the transfer case is bad that would cause it. or a clutch sliping. kind of confusing. seems that the cluches work fine going through all the gears, its just when I let off is when it goes into netrual. for example if I am traveling 65mph and come to a town where the speed reduces to say 35. its almost like it hangs up between a gear rather than making a complete shift. I understand that 1st and 2nd run off the turbine, but it does this even in say 3 and it seems like 4th to. from what I understand it is suspose to be locked in in 3rd gear and up and runs off the turbine in 1st and 2nd gears. somedays I wont have a problem with the shifting and others are a nightmare. lol.
 
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