Allison Transmission Questions

Discussion in 'General RVing' started by AllisonMan, Apr 5, 2003.

  1. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    Okay. Don't do it for more than about 30 seconds to prevent overheat. The Allison place should be able to tell you what the proper stall speed is. Low and High are normally 200 RPM or more. If it's high, you've got either C1 or C5 slipping in the trans.

    If stall is normal, my opinion is to start looking at sensor readings.
     
  2. Triple E

    Triple E Senior Member

    Re: Allison Transmission Questions



    Stall Test. Start - Water temp = 160, Transmission = 122, Rpm's =750.

    1st. test 25 Sec. - Water temp = 161, Transimission = 127, Rpm's = 800.

    2nd. test 25 Sec. - Water temp = 163, Transmission = 134, Rpm's = 800.

    3rd. test 25 Sec. - Water Temp = 163, Transmission = 144, Rpm's = 900.

    4th test 25 Sec. - Water temp = 163, Transmission = 156, Rpm's = 900.

    5th test 25 Sec. - Water temp = 164, Transmssion = 165, Rpm's = 900.

    The rpm's returned to 750 after each test.

    Ok, I hope this tells you something. Once again dB thank you, -Steve
     
  3. Triple E

    Triple E Senior Member

    Re: Allison Transmission Questions

    Just so you know dB, the oil level in the transmission is about 2/3's up from the add mark. That is where I normally keep it.
     
  4. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    Wow. That's wide open throttle? That engine is barely getting off of idle. You did set the brakes, select drive and mash the throttle, right? The vehicle didn't move, right?

    Two possibilities:

    1. Engine power is way low.

    2. The stator is freewheeling backward in the torque converter. That is an extremely rare failure.

    My vote is to share the results with the Cat place and have them check out the engine starting with looking at the sensor readings. Sounds like something is keeping the engine from getting fuel or air.

    Your trans oil level setting is perfect. Above add, and allowing some room for thermal expansion. That's the way I keep my transmissions, too.
     
  5. Triple E

    Triple E Senior Member

    Re: Allison Transmission Questions



    Yep, throttle pedal to the metal. Yes, the brakes set. Yes, in 1st. gear. Nope, the vehicle did not move. However when I put it in neutral she will ramp right to 2500 rpm's. This is the only reason I have not change the fuel or air filter. If it is starved for fuel or air, would it pick back up so quickly??? Do you think I should do these filter's, air and fuel,change before I call CAT?

    Oil Level, I read one of your posting where you recommended not to fill to the full mark. So that has been my practice every since. :cool:
     
  6. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    2500 RPM in neutral, there's no load on the engine. It doesn't take that much fuel or air to do that.

    On this engine, once a load is introduced (the torque converter turbine at stall), this engine cannot get out of its own way. Air and fuel restriction can do that. A sensor malfunction telling the engine controller to limit fuel can do that too.

    I guess the filters would be cheaper than taking it to a shop, so it's up to you. It may fix it, it may not. Depending on the cost, I'd probably do it before taking it in.

    My money's on an engine problem. But like I said, the stator could be malfunctioning. It is rare, but it does happen. I don't know of any way to check the stator besides dropping the tranny and pulling the torque converter apart.
     
  7. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    OH, there's nothing else in the transmission that can cause such a low stall speed I am aware of.
     
  8. Triple E

    Triple E Senior Member

    Re: Allison Transmission Questions

    Ok dB. I will keep you posted on what we find. A cigar and cold beer will be waiting for you at the Meet & Greet. -Steve
     
  9. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    Ahhhhh. Thank you. I love cigars. I'm smoking a Gran Habano right now. If I'm in the country, I'm planning on being there at least to visit for a while.

    I had to quit drinking, though. Me and my old pal Jim Beam had a falling out if you know what I mean. Haven't had a drink for ten years.

    Keep us posted on what you find. This one's a keeper.
     
  10. Triple E

    Triple E Senior Member

    Re: Allison Transmission Questions

    I hear that. Me and George Dickle had to have a heart to heart back in "97". But who's counting. :(
     
  11. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    I thought about this some more last night. I'm now almost sure it's an engine issue. You took the vehicle out and got to fourth gear but it would go no further. If the stator was the problem, once you get into lockup, you should be able to make speed.

    A lack of engine horsepower will limit road speed.
     
  12. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    How ya doin on this one Triple E? Any news to share?
     
  13. Triple E

    Triple E Senior Member

    Re: Allison Transmission Questions

    Well as I was changing the filters I came across a dry oil filter. Although I have over 30 pounds of oil pressure, at idle, and a dip stick that indicate full I have no oil in the filter. I called CAT and they believe I have a busted oil by-pass line under my valve cover which would limit the pressure to the HUEI pump under a load. So today I had her towed in to CAT. I should know more by Saturday. I hope.
     
  14. Triple E

    Triple E Senior Member

    Re: Allison Transmission Questions



    Ok for all who wants to know what is going on, I can now give you what I know. The "Injection Actuation Pressure Control Valve" is putting out to much pressure to the "HEIU" pump. The computer sees this high pressure and puts the engine into lock-out mode. The fuel and air flows are fine. Now for what they do not know.... Why is the oil filter not getting oil?? This one has them stumped. So when I know the answer to that I will be back.

    dB, you are right, it is not an Allison problem. Well at least not yet. :laugh:
     
  15. LEN

    LEN Senior Member

    Re: Allison Transmission Questions

    My Son said it was the Injection Actuation Pressure Control Valve , but thought it might be getting to little pressure to let the injectors go to high output. Well he got the area right anyway, but the oil filter had him stumped too.
    he is a diesel mech.


    LEN
     
  16. cummin8.3

    cummin8.3 New Member

    RE: Allison Transmission Questions

    AllisonMan, I am having an issue that I cannot find anyone else having. Its a long post but covers just about everything I am seeing.

    I am having an issue with my Coach. I am at 2500 RPMs at 60 MPH...2800 RPMs at 65 MPH. I am at red-line just to drive at highway speed.
    I verified my Tach is correct using a Handheld Digital on a pulley on the engine. I had my wife hold RPMs at 1000, 1200, & 1500. Each time they matched the Handheld Laser Tach I used. ( The Handheld Tach is a great tool )

    1992 Safari Ivory, Cummins 6CTA8.3 ( Red Line is around 2600 RPM ), Allison MT643. All Mechanical ( No Computer ). Rear End is a 391. Tires 9R22.5, PAC Brake not connected to Tranny. I didn’t drive it for about 2 years. It fires right up but below is the issue:

    It is shifting all 4 gears but this is what I'm feeling:

    I can feel it shift from 1-2, then from 2-3, and while in 3rd the rpms drop a second time, about 200-300rpm drop before shifting into 4th. I believe the drop in RPMs is the converter locking.

    THEN;

    After it shifts to 4th gear I get the initial drop in RPMs but don't get the second drop like I do in 3rd gear. Tranny not locking in 4th? I think it suppose to lock in 3rd and 4th. Though RPMs are still high in low gears. ( see below )

    I can remember having to downshift to get up a couple of hills by my house last time I drove it 2 years ago, but now I don't have to down shift, the RPMs are high like it's in a low gear but I know its shifting to 4th gear, MAYBE the tranny isn't locking correctly? I have no idea but RPMs seem high even in 1st gear.

    PAC brake is turned off, I even removed air line to make sure it wasn't on.
    Tranny Service is 3 years old, only about 1000 miles since having it serviced. Fluid looks good and no smell of burning. I don't feel any kind of slippage either.

    FYI, Transmission Never Shifts into a Passing Gear when I step on Peddle, almost as if it’s always in Passing gear. ( just realized this today! )

    Below are the RPMs each time it shifts. I think the RPMs are too high even in 1st gear. I thought at first Tach was off, but engine seems to be screaming and peddle is at the floor to get to 66 MPH.

    0-12ish MPH 2500ish RPM 1st Gear
    12-20ish MPH 2300ish RPM @12mph it shifts to 2nd gear
    20-25ish MPH 2300ish RPM @20mph it shifts to 3rd gear
    25-35ish MPH 2500ish RPM @35mph it shifts to 4th gear

    Any ideas would be appreciated. I'm afraid if I drive it I will damage something. Engine is already leaking diesel it never leaked before, I think the High RPMs may have caused an injector and high pressure fuel line to leak.
    [FONT= 'Verdana']Someone mentioned it could be the Kick Down linkage?[/FONT]

    Several Others with the same Tranny, Engine, Rear End as me said they are all around 1900 RPMs @ 60 MPH.

    Here are the links to pictures of Dashboard showing speed and RPMs.

    http://i238.photobucket.com/albums/ff24/patcherman/IdleRPMs-1.jpg
    http://i238.photobucket.com/albums/ff24/patcherman/43mph1800rpm.jpg
    http://i238.photobucket.com/albums/ff24/patcherman/55mph2300rpm.jpg
    http://i238.photobucket.com/albums/ff24/patcherman/60mph2500rpm.jpg
    http://i238.photobucket.com/albums/ff24/patcherman/66mph2800rpmpeddlefloored.jpgSorry for the long post..AL
     
  17. Allison Expert

    Allison Expert New Member

    Re: Allison Transmission Questions

    cummin8.3...
    Sounds to me to be either a sticky governor and/or a modulator issue. On the side of the transmission just behind the shifter arm you will have some kind of modulator...air, mechanicle, or electronic...if its air, could just be leaking and would need to be replaced. A mechanicle type has a cable that goes up and attaches to the throttle linkage, and that could be out of adjustment or a broken/sticky cable. If its electronic, then you want to make sure you are getting 12volts at about 60-70% throttle at the connector. You could also try pulling the governor out and making sure its not hanging up. It is behind a cover with 4 bolts in the rear cover of the trans. Once the trans gets lock up in 3rd, you wont see a drop again in rpm in 4th because lock up stays in. Are the up shifts rough or any kind of flare, and how are the down shifts???
     
  18. cummin8.3

    cummin8.3 New Member

    RE: Allison Transmission Questions



    ALLISON EXPERT: I think the Rpm mystery has been solved ( I think ). I used a handheld laser tach on the Crankshaft to verify tach was accurate. I tested at Idle, 1200, & 1500 Rpms. All Rpms matched both the Handheld Tachand Dash Tach. But, with a suggestion of another poster I checked the Tach at Full Throttle ( governed RPM ), with the peddle pressed to the floor the Dash Tach was at 3000 Rpms and the Handheld was at 2550 RPMs. Apparently the Dash Tach is not accurate at the higher RPMs. I hope this is the real issue and my experience (wasted time) helps someone else. Next is to figure out what is wrong with the VDO tach, or possibly the alternator is sending bad information. Strange that it'saccurateto 1500 rpms but not at full throttle.

    The Transmission shifts smooth and I don't feelany slipping. The only time I noticed a real JERK downshifting was on a fairly steep hill. I was going very slow and all of a sudden it downshifted hard, almost as if it had stalled. Other than that no other issues.

    Thanks......
     
  19. Allison Expert

    Allison Expert New Member

    Re: Allison Transmission Questions

    It could just be that the engine speed sensor is picking up some static noise or vibrations that is more noticable at a higher rpm. Its hard to say though without actually expierencing it for my self. As for the downshifts being rough/jerky at times, I still go back to the modulator. It would be worth having that checked just for the heck of it and to eliminate another possibility.
     
  20. cummin8.3

    cummin8.3 New Member

    Re: Allison Transmission Questions

    Allison Expert, Its a 1991 Safari Ivory, all mechanical. I have a kickdown cable attached to the throttle. I made sure it's not binding, etc.
     

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