Allison Transmission Questions

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

  1. joegrab

    joegrab Junior Member

    Hello all,
    I am new to RV and have a bus conversion P8M4905A that was converted to use an Allison V730. It has a shifter that is pneumatic controlled by wires from the driver' seat (up and down shift wires, indicator light wires). The pneumatic shifter has one piston working for downshifting which will take it from reverse to neutral to drive to 2 to 1, but the other air piston will not upshift it. I cannot get it apart as there are frozen bolts on both ends (my removal tool broke in them so I cannot drill into the removal tool - I have 7 out of 8 off on both ends). The sides come off and I cleaned it out. Does anyone know where to get this part? View attachment 381
    Any help would be appreciated.

    Attached Files:

  2. dbarton291

    dbarton291 Senior Member

    The air shifter mechanisms that OEMs put on V730s I think came from the Williams Air Controls company, but I don't know if after all these years any of those parts are still available. I know there are also Stone Bennett shifters that can be mounted on the V730. My suggestion would be to head over to and join their forum. I'll bet there's somebody over there that knows what that part is and whether or not it's still available.
  3. ANT

    ANT Junior Member

    Thanks for the help. It ended up being the valve body. Not sure what, as F solenoid, valve,spring and sleeve were new. Fitted all the parts into another body casting and solved the fault. Result!! Thanks again Mr Barton :) This forum is invaluable
  4. ANT

    ANT Junior Member

    Here's another to peruse at your leisure if you would be so kind :confused:Intermittent DTC, PO842. ( C solenoid pressure switch stuck on) Kicks in after half hour of driving. Once everything is switched off and restarted, transmission operates perfectly ( well, for another half hour!). Changed internal loom, PSM and ran a new wire from TCM to pressure switch C. Even swapped TCM with one from 'sister' vehicle. All to no avail. C shift valve isn't sticking ( used clutch test on allison doc and it shifts up and down no problem). Any advice would be welcomed. Thanks, Ant
  5. dbarton291

    dbarton291 Senior Member

    Are you a bus operator, or a repair shop, or something like that?

  6. vmcc

    vmcc Junior Member

    AllisonMan I have an Allison 545 transmission and when it is put into reverse it delays approx. 15 seconds before engaging. Any ideas on what the problem might be?
  7. vmcc

    vmcc Junior Member

    Can anyone tell me why my Allison 545 transmission has a 15 second delay before engaging into reverse?
  8. dbarton291

    dbarton291 Senior Member

    It could be several things.
    First check the oil level, the modulator linkage adjustment (if it's not a vacuum modulator) and the shift linkage adjustment.
    Next, you need a 0-300 psi pressure gauge. Plug into the main pressure port.
    Check main pressure in reverse. It should be 250 psi or so.
    Then select reverse and let's see what the gauge does.

    If the pressure in reverse isn't up to 250, you probably have a worn pump in the transmission.
    If pressure is ok, you select reverse and the pressure gauge stays real low for the 15 second delay and then slowly comes back up as reverse engages, you've probably got a leak somewhere internal in the trans or a fourth clutch that's worn or a sticky fourth trimmer valve.
    If the pressure dips for only a second or two then pops right back up but reverse isn't engaged, fourth clutch is slipping for some reason. May be worn, or the fourth trimmer is sticking open just a bit.
  9. 1992monaco

    1992monaco Junior Member

    Hello Allison Man

    First thank you for all the time you put in to this I tied a search and could not find the right answers. I have a 1992 Monaco Signature with a Cummins L10 300 mechanical. It has an Allison MT 647. I am have to replace an engine the way it is mount we are pulling eng/tranny as a unit. Before the engine failure my speedometer acted up would not work for about 3 mile then would sweep sometimes backward and then work good until the next time I stopped. I have upload some pictures in the album labeled "Allison MT 647 " would mind looking at them and tell me what the different switches/sensors are. We are doing a fluid and filter(s) change. Can't remember how many miles. I want to change the VSS and see if that fixes the speedo. Do you have a part # for one. Also would that help with downshifts. You know when you downshift.

    Thankk You
  10. hdtruck

    hdtruck Junior Member

    I have a allusion 654 that shifts into forward gears fine. It has a delay into reverse when you first start it up, but when you shift from first into reverse it doesn't have a delay. It is strong in both fwd and rev gears once it shifts. Again when it is warmed up to seems to shift fine when going from fwd to rev and rev to fwd. It is just out of neutral into rev when you first start it up cold.
    We changed the filter and the fluid is to correct level. I am not sure but it may have stated to have this issue just after changing the filter. What are your thoughts?
  11. dbarton291

    dbarton291 Senior Member

    From what I can tell from the pictures, I see a reverse warning light switch, a neutral start switch (next to the selector lever), and a signal generator for the speedometer. Allison never sold the signal generator for the speedo. There were several drive gears available in the MT647, one of which was a tone wheel. The OEM purchased the driven gear assembly or signal generator for the speedo. A lot of them were made by Airpax in Connecticut.
    Changing the VSS shouldn't affect the downshifts at all.
    I didn't see a modulator in the pictures. That is what affects the downshifts. It's usually connected to the engine throttle with a cable, or some of them were electric step modulators and some were actuated by air. The cable modulator is best for shift quality and can be adjusted. The modulator would be on the left side of the transmission just forward of the name plate. This is the opposite side of the transmission from the selector.
  12. dbarton291

    dbarton291 Senior Member

    A lot of MTs had what we used to call morning sickness. First thing in the morning there was a delay going from neutral to drive. What type of oil did you put in it?
  13. 1992monaco

    1992monaco Junior Member

    Allison Man

    Thank you again. I have an air modulator. I tested both signal generators and they appear to be working right. The concern about the signal generators was my speedometer is dead at first after about 3 miles does funny things on sweep the works fine. Test both signal generators(with drill) and they both produces a stable AC signal changing as I change input speed. Once I got it out found the temp switch just above the cooler out line. While it is out I am going to do a fluid and filters change.
  14. jmyweed

    jmyweed Junior Member

    Hello Allison man, I'm running a 1999 Adventurer with a Allison MT643 trans connected to a 275 Cummins.
    I am getting a intermittent banging while driving. this occurs at low speeds 10-15 mph as well as high speeds 50-60 mph. hot or cold
    The trans has recently been serviced and the shift modulator was replaced by shop to correct complaint but it didn't stop. Any ideas as where to look now shop hours are expensive with an intermittent problem. Thanks
  15. dbarton291

    dbarton291 Senior Member

    I assume by intermittent banging you mean sometimes you are getting a harsh shift.
    What kind of modulator is in this vehicle? Is it air, cable or electric?
    How long have you had the vehicle? Has it always done this?
  16. ScottSpence

    ScottSpence Junior Member

    Allison Man,

    Great service you provide, I have an '04 4000MH. Problem started when my alternator had a dead short, my unit started shuttering when shifting around 1500RPM, usually from 3rd up. I assumed it was due to the battery voltage dropping. I replaced the alternator and tried it...still doing it. I changed the fuel filter to eliminate starvation, I checked and added fluid to the tranny. I disconnected the chassis battery for an ECU reset. The Unit is throwing the code 6340 "service brakes status input,failed on". I cleared the code and tried again, re throws the code. Only thing I haven't tried is clear the code, then disconnect the chassis batts. Any ideas what to try?
  17. dbarton291

    dbarton291 Senior Member

    Disconnecting the battery does not reset the Allison ECU. The adaptive values are written to an EEPROM on power down. It doesn't require constant power.
    When the alternator failed, it may have failed the ECU.

    Anyway, this code means one of the two inputs for an input function auxiliary range inhibit is in a different state (on or off) from the other input for longer than two minutes. The way to troubleshoot this is to plug in Allison DOC and see what two input wires are calibrated to control the service brake status switch. Trace those wires to find out why one of them is either on when the other is off or vice versa. You may not be able to do this on your own because you probably don't have access to DOC. This code is self clearing if the switch status input returns to a proper state.

    If there's no problem in the wiring for the service brake status switch, the electrical event created when the alternator failed may have failed the Allison ECU.
  18. 20GOLD

    20GOLD Junior Member

    Hello Allison man

    I have a 1997 Country Coach with a 3060P will get stuck 3 to 4 4 to 5 5 to 6 may shift if you let out of throttle
    Thanks Don
  19. dbarton291

    dbarton291 Senior Member

    The first thing I would do, and the most likely cause, is make sure the engine is making its rated power and RPM to make those shifts.
    When you back off the throttle, the transmission uses a lower shift point. So a vehicle with an engine not making rated HP and torque, or not making rated RPM can be forced to upshift by backing off the throttle.
  20. 1992monaco

    1992monaco Junior Member

    Poster : Hugh Turner

    Manufacturer: Monaco

    Model: Signature 40ft

    Year: 1992

    Production serial number: 28121

    Engine model: CumminsL10

    Transmission: Allison MT 647 with Stone Bennett shifter

    System(s):Transmission shifter

    Problem and as much information as possible (what have you tried, when did it start, etc)

    I am working on getting the coach back on the road after 2 ½ years down for the bad engine. Here is where I am at the used replacement engine is back in and have order the replacement driveshaft that the wrecker driver lost(long story).

    On the shift indicator in neutral it shows on bar in upper right hand corner. Coach will not start hear click up front. Jacks do not work. If I move the shifter manually on transmission the shift indicator show the right gear the backup camera comes on in reverse. Shift will not shift transmission. Have gone back and disconnected the neutral safety switch on transmission and jumpered with no change. I also disconnected the shifter plug Battery voltage is good (12.9)

    Any help will be appreciated.

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