Allison Transmission Questions

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

  1. Triple E

    Triple E Senior Member

    Keep checking in gentlemen, our guro is traveling but will check in soon. Please provide as much details as you can. Multimedia, WELCOME!!
  2. LEN

    LEN Senior Member

    Multimedia check that the keypad has power when the key is turned on, the hot lead from the on/off start switch.

    Cowboy Check the plugins on the shifter pad are not coming loose and on the trans itself. there appears to be a communication problem.

  3. dbarton291

    dbarton291 Senior Member

    Just to have the info, I'd first run a stall test. Make sure the engine is up to power and the trans isn't slipping or having torque converter problems.

    Also, check the connector at the base of the selector. Look for loose terminals, etc.

    If the light comes on, there should be a trouble code. What's that code(s)?
  4. dbarton291

    dbarton291 Senior Member

    Greetings all from China.

    Sounds like the trans TCM or the shifter aren't getting power. Make sure the power is connected, and the TCM sees the ignition signal. It'll take a vehicle wiring diagram and some patience. Good luck.
  5. JackG

    JackG Junior Member


    Hi AllisonMan, have a 05 FL M2 with 3000 TRV with Transynd. Intermittant engine flare occurs at 35mph shift (2nd to 3rd gear?). Seems to occur more so when at operating temp. It was suggested by a tech at Freightliner could be solenoid connection. What does your experience tell you with this type of problem.
  6. dbarton291

    dbarton291 Senior Member

    How many engine RPM is the flare? Does it occur at wide open throttle or part?
    Loaded or unloaded? Since it's a TRV, I assume you pull a trailer. Does the flare occur right after the trailer is taken on or off the truck?
    Any trouble codes?
  7. Cammac

    Cammac Junior Member

    Allison code 6834

    Good Morning I have a 1993 Gulfstream and it will not go into gear. The Allison display has of its led segments lit (kind like a crossed out 0). "Do Not Shift" lit on the dash and trouble code 6934 on the shifter. Any help? It is in a 40 foot diesel pusher.
    Thank you.
  8. LEN

    LEN Senior Member

    Here is what the book says,

    SerialCommunicationsInterface Fault
    69 27, 28, 29,33, 34, 35,36, 39, 41,42, 43
    a.Clear diagnostic code and retry vehicle start.
    b. If code recurs, reprogram or replace ECU.
    ECU Malfunction

    This all said if your handy I would unplug and replug all the way from the trams to the ECU, before option b.

  9. Cammac

    Cammac Junior Member

    Thank you.
  10. dbywaters

    dbywaters Junior Member

    View attachment 210

    This is what I have, 1993 Gulfstream SunVoyager Diesel Pusher, MT643 Automatic, 230 hp B5/9 Cummins, push type cable modulator valve, 3:30 rear end ratio.
    My problem is an erratic 3-4 shift at full throttle, sometimes even at part throttle worse when transmission has warmed up. Down shift from 4 to 3 is great, no problem at all but the 3-4 shift will go back and forth something awful. I compensate the shift by holding selector in 3rd until RPM's exceed the normal 3-4 shift point and manually shift to 4th, which occurs perfectly. I have been living with this since installing the MT643 (previously from a school bus) for a couple thousand miles.

    I installed electronic pressure sensors to monitor the main pressure and governor pressure while driving. Governor pressure is not erratic, it modulates with wheel speed just fine. Main pressure does drop some (10-20psi) during shifting but not greatly. My next step is to move one of the sensors to the Lockup signal circuit to see if what I am feeling is lockup cycling rather than 3-4 shift (I don't think so since Lockup is very noticeable after 2-3 shift) I have read and re-read the MT-600 service manual and studied signal circuits until about memorized and I can not come up with a reason this thing is litterally such a jerk. I previously replaced the lockup piston (cracked) when I first installed the transmission, so I am sure lockup occurs.

    I have adjusted travel on modulator cable all over the place, even purposely left slack (causing early shifting) this prevented the problem but the coach is not driveable like that.

    I am open to about anything, I also verified fluid level (calibrated dip-stick) so I am pretty sure i has enough ATF.....which is new. Also have a minor leak at tailshaft that new seals just don't seem to stop, so I am thinking of doubling up on seals . This leak would not be a big deal if it did not affect parking brake.

    Any suggestions or ideas would be appreciated. I've been inside of a couple automatics so I am not afraid of it, but I don't like to shotgun problems by replacing parts.

    Thanks in advance!

    BTW, I have read and searched this thread and the internet and can not find a similar problem with exception of the electric modulator valve problems related to gas engine applications.

    Attached Files:

  11. dbarton291

    dbarton291 Senior Member

    Shift cycle 4-3 and 3-4. First do a stall check to make sure the engine is making the right power.

    There should be a governor screen under a large plug in the rear cover. Pull that out and make sure it's clean.

    If the transmission was formerly in a bus, it may have a non-modulated 3-4 shift. What is your transmission assembly number?


  12. dbarton291

    dbarton291 Senior Member

    Another possibility. Are you sure with those 3.3 gears, this vehicle has enough horsepower to get up to highway cruising speed and stay there? The vehicle may be struggling to maintain speed.
  13. dbywaters

    dbywaters Junior Member

    Thanks DB for your time!

    Regarding power:
    The coach weighs around 18k, and I pull a 4k Saturn Vue at 4k. The rear end is stock Dana 80. I repowered with a 230hp Cummins vs the 190 hp originally in the coach with a AT542. I have more power now than before, actually quite spry without the toad.
    I did move the governor springs up a couple clicks to increase the Max RPM, moved the throttle plate and tightened the smoke adjustment to allow throttle to come on faster. Hills are not a problems (here in VA) as I rarely drop out of 4th. I am at 1900 rpm around 58mph. Normal road speed is about 5-8psi boost and 800 degrees EGT. Hard throttle can see 1100 -1200 degrees and 25 pounds of boost until 2500 rpm when it starts to de-fuel.

    I checked the governor screen and attached a photo. I also removed the governor and attached a photo of it, everything is clean.

    The combo must have been in am International bus. The transmission is a ReNewed AR29516802 with a S/N 318056 rebuilt around 11/15/04. It is very clean inside with no hint of burnt clutches. The 643 had a pull type modulator on it in the bus configuration, it was also broken. The transmission did the same jerk thing before I replaced the lockup piston in the convertor….. it was not as noticeable as it is now.

    I did not mention that the transmission usually shifts perfectly when cold, and may shift fine for 60 miles but once it becomes a jerk it seems to seems to stay that way, it even can jerk with light throttle. I tend to believe it is starving for oil, but I would think it would have symptoms other than during 3-4 shift. I also suspect something is going on with the relay valve or shift valve but I don’t have enough experience to know what to look for. Transmission temps stay below 160 degrees, I am using a coolant to fluid heat exchanger to cool the unit. I plumbed it inline with the return line from the radiator.
    View attachment 216 View attachment 217 View attachment 218 View attachment 219 View attachment 220

    Attached Files:

  14. dbywaters

    dbywaters Junior Member

    as an addendum, I started it up, put it in gear and held it to the floor. RPMS topped out at 1500rpm, boost had not kicked it yet so I believe the injector pump was holding the engine back, no smoke either. I have a 150psi electric gauge on transmission mainline pressure, it is usually maxed out after starting the coach. I notice it momentarly drops to 120psi when I engage into reverse, no change in forward gear.. this test was at idle around 700 rpm. There was no drop at all at 1000 rpm so I believe pressure is good.
    I re-checked fluid level and it indicated it was in the lower part of cold level, so I added another 2 quarts of fluid and it bought the level to the hot indicator. I plan on camping next weekend about 25 miles from home, there is a pretty good grade inbetween so that should be a good test. Diesel is too expensive for joy rides :)
    I am a little concerned about having too much fluid, but I am sure it will let me know if it pukes out the fill tube...
  15. dbywaters

    dbywaters Junior Member

    adendum to the addendum...

    I just had a revelation... I have a pac-brake, it actvates with the brake light circuit...I need to disconnect it to allow proper stall testing.


  16. dbarton291

    dbarton291 Senior Member

    Disconnect that PAC brake and run a stall in drive. Let's see what RPM you have. If it holds stall that means first and forward clutches are OK.
    Good stall speed indicates good power.

    Pressure should be higher than 150 in reverse. What is main pressure in reverse? Reverse is first and fourth clutches. If pressure is low in reverse, you may have an issue with fourth clutch. You should be seeing about 250 in reverse.

    I suppose you might also have some issue with the 3-4 shift valves, or the 3-4 relay valve or their springs. fourth clutch trimmer is also a possibility. But, first let's see what main pressure is in reverse.

    It's an International Renewed transmission. I wonder if that's why the Allison outlets weren't too wild about working on it. That's not an Allison authorized rebuilt. Those are something that's built, sold and warranted by International dealers last I knew.

  17. dbarton291

    dbarton291 Senior Member

    Governor screen looks OK.
  18. dbarton291

    dbarton291 Senior Member

    Cold level means cold. You may now be overfull on fluid. The best fluid check is at operating temperature.

    I just noticed you are using a 150 psi gauge. You need a 300 psi gauge to check pressure in reverse.

  19. dbywaters

    dbywaters Junior Member

    MT643 rough 3-4 shift

    Thanks for the reply, I have been out of state since Sunday. I have a mechanical guage to test the pressures. I have to crawl around under or rig a hose and helper. I will be driving the coach this weekend, I hope to test it before we leave. The drive is pretty short, less than 20 miles one way. I will post as soon as I have some data.

    93 GS Sunvoyager
    Saturn Vue Toad
    Flint Hill, VA

  20. dbywaters

    dbywaters Junior Member

    3-4 shift problem

    I drive 22 miles from home to a nearby campground Friday. Transmission shifted perfectly, and for the first time up-shifted under full throttle to 4th on a grade steep enough to require a 4-3 downshift. I believe my problem is related to the amount of ATF in the transmisison. I checked the hot fluid level after returning home yesterday and it appears I was at the lower portion of the hot range. I still plan on completing the stall test and pressure checks as soon as I can. I sure hate the extreemly long fill tube and dip-stick...

    Power is a non issue with my engine, I've towed and camped since 88 and this coach is down right quick compared to others I have driven.


Share This Page