Allison Transmission Questions

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

  1. dbarton291

    dbarton291 Senior Member

    That is definitely possible. Any foam or bubbles on the dipstick?

  2. dbarton291

    dbarton291 Senior Member

    The dipstick may not be calibrated properly for that transmission. You can check the dipstick calibration with a procedure in the MT Mechanics Tips booklet. I've posted a link to that book on here before.

  3. dbywaters

    dbywaters Junior Member

    No foam on the dipstick. It take about 5 tries to finally see the level since the fluid is so clear. It might be that my coolant lines and cooler capacity keeps an air bubble until run up to temperature. I'm going to add another quart before next trip.

  4. JackG

    JackG Junior Member

    Sorry it has taken me this long to get on here. The flare occurs at part or full throttle, loaded and unloaded. The flare is intermittant, not connected with towing.
    Should I be checking harness plugs (unplug, replug), etc. Filters are recent, fluid is clean no burnt smell. Thanks for your help.
  5. dbarton291

    dbarton291 Senior Member

    about how many engine RPM is the flare?

  6. dbywaters

    dbywaters Junior Member

    I have the MT service liturature, and the overhaul manual for 600 series transmissions. I calibrated the dipstick using a clear mason jar, I disconnected the dipstick tube from the pan and held it away from the pan far enough to slip a the glass jar filled with transmission fluid up over the tube to the height specified in the service manual as "cold full". At the same time I had my son pull the dipstick and check it multiple times to verify the level coorisponded on the stick. We adjusted the stick until it did. I then re-attached the tube to the pan and filled it with fresh ATF.

    Since my last note, I have taken a couple trips with additional fluid, my hot level is now correct. I noticed the 3-4 shift was much improved but still not as clean as the other shifts. I have always noticed I had smoth 3-4 shifts after removing and replacing the governor, this led me to think I might have a governor problem so I ordered a new governor from sonnex and replaced it this week. I compaired my old governor against the new one, found the first section of the govenor shaft adjacent to the gear was worn 1- 1/1000's of an inch more than the rest of the shaft. I also noticed the leading edge of the spool valve was worn.. actually rough in appearance. The remainder of the governor looked ok. I drove the coach with the new governor and noticed all shifts occured at higher RPM's, as if I had adjusted the modulator cable (but I hadn't) My 3-4 shift has definitely improved, and I could not reproduce a shift problem. I did not drive a long distance, probably less than 10 miles so I cannot say that I definitely have a better shifting transmisison yet. I will be driving 300 miles next weekend so I will report my findings then.

    thanks so much for the replys and suggestions. I hate to shot-gun troubleshoot, but the governor was only 60 bucks and takes about 10 minutes to replace.... so I took a chance replacing this unlikely part.

  7. dbarton291

    dbarton291 Senior Member

    A worn governor usually causes unusually high upshifts. I don't know about the aftermarket Sonnax governors, but I know the Allison governors are marked on the top 460, 461, 462, etc. to match them with the valve body calibration, and they're different part numbers. If the RPM of all your upshifts increased, the new governor is different from your old one. That's not necessarily a bad thing, especially if the 3-4 shift improved. Raising the shift point almost always improves shift quality, because if you get up close enough to max governed speed, or in the droop, the engine is starting to pull itself out of fuel. Less power, less bang as the oncoming clutch engages.

    I've never heard of using a glass jar to calibrate a dipstick. If it works, that's great. I've attached a wire to the dipstick tube and marked it, then compared it to the dipstick. I've also made a tool by drilling out a drain plug and attaching clear tubing to a fitting in the drain plug and held that up next to the transmission and measured. On the WTs, the dimensions are published so you can measure the tube and dipstick, do a little arithmetic and calibrate.
  8. dbywaters

    dbywaters Junior Member

    The sonnex gear is also a 461, same as the one removed and identical in appearance. Glass jar was simple and required no math :) before I removed the tube from the pan I marked the correct fluid level on the tube with electrical tape, then removed the tube from the pan, filled a mason jar with atf and held the jar over the tube with fluid level to the electrical tape. Then had my son check the dipstick over and over again, adjusting the length of the stick to calibrate. I just could not think of anything simpler than that and I did not have to waste any AFT in the process...I had thought about drilling an tapping a drain plug..
    BTW, my shifts are within a 100 rpm of prior shift points, the big test is the weekend.

    Thanks for all your advice.

  9. Emile

    Emile Junior Member

    was woundering If you used Amsoil synthetics or not in the allison tranny
  10. LEN

    LEN Senior Member

    Amsoil no Transynd is the synthetic for allison.

  11. dbarton291

    dbarton291 Senior Member

    Sounds like the 2500 has the downshift preselect wired to the brake and is on all the time. The 3500 doesn't. Doesn't sound like a problem to me, unless there's times you want to coast down a hill in the 2500.

  12. DBLB

    DBLB Junior Member

    I have a 1999 Fleetwood discovery. The odometer is reading about 1.3 miles for every mile I travel. I had the sensor at the tranny cleaned. Unfortunately that did not solve the problem. Speedometer is working correctly. Any ideas?
  13. LL1956

    LL1956 Junior Member

    What size of tire do you have? 235/80 was the OEM size. If you have a smaller diameter size on. It will cause the reading to be higher.
    Any Cummings shop can reprogram the EMC for how many RPM your tires turn.

    With that said the Speedometer should be off the same as well. When traveling at 60 MPH it should read maybe 63 MPH
  14. dbarton291

    dbarton291 Senior Member

    Do you know when this started? Has it always done it since new, did it start recently, did it start after any transmission or other service work?

    Is the speedo also 30% fast? The tire size is also a good question.
  15. DBLB

    DBLB Junior Member

    Tires are orignal OEM size, Speedometer is working correctly. I have checked several times with GPS.
  16. dbarton291

    dbarton291 Senior Member

    If the speedo is correct, there's no problem with the signal from the transmission. Sounds to me like the speedo head itself has a problem.
  17. George Meehan

    George Meehan Junior Member

    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

    Attached Files:

  18. mcnairt

    mcnairt Junior Member

    I am the new owner of a 06 Chevy Duramax with Allison 1000 trans. Owners manual states if high trans temp noted when towing to pull over and place in N (nuetral), set brake, and high idle until temps come down. Also noted when outside temp F below 32 high idle enable warms up trans fluid. Does fluid pump to cooler/heater work more effectively in N? and If so why not place in N for more effective warm up on cold temp mornings? Does the trans fluid pump move more or less fluid through the cooler(heater) in N than park or are there check valves that prevent some fluid transfer in P?
  19. purpledecker

    purpledecker Junior Member

    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
  20. dbarton291

    dbarton291 Senior Member

    In neutral or park, the fluid moving from the trans to the cooler is the same. The only difference between neutral and park, is in park, the parking pawl is locking the output. If you want to warm it up a little quicker, put the trans in gear and go to high idle for a little while. Once the trans is in gear and the vehicle is stopped, the turbine side of the torque converter is stopped because it's now connected to the output. Give it a little RPM and you've got friction between the fluid and the turbine which creates heat. Just be careful. Don't do it too long. Watch the temp.



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