Allison Transmission Questions

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

  1. sdjuandar

    sdjuandar New Member

    Allison Transmission Questions

    Allisonman,
    I have a Monaco Executive 1992. I lost my speedometer and odometer. I make the assumption that they are electronically driven, whereas that would be an extremely long speedo cable.
    Any possible suggestions as to troubleshooting and or repair?

    I believe that I have found the sensor on the output of the transmission. It is approximately 2-3" square and has two wires coming off of it.

    Waiting patiently in Central Oregon.
    sdjuandar
    &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
    quote:Originally posted by AllisonMan

    Hi there. I have worked on Allison Transmissions for 27 years. If you have any questions, please post and I will check back once a week and try to answer them all. Thanks and have a great day! :)
     
  2. sdjuandar

    sdjuandar New Member

    Allison Transmission Questions

    Allisonman,
    I have a Monaco Executive 1992. I lost my speedometer and odometer. I make the assumption that they are electronically driven, whereas that would be an extremely long speedo cable.
    Any possible suggestions as to troubleshooting and or repair?

    I believe that I have found the sensor on the output of the transmission. It is approximately 2-3" square and has two wires coming off of it.

    Waiting patiently in Central Oregon.
    sdjuandar
    &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
    quote:Originally posted by AllisonMan

    Hi there. I have worked on Allison Transmissions for 27 years. If you have any questions, please post and I will check back once a week and try to answer them all. Thanks and have a great day! :)
     
  3. sdjuandar

    sdjuandar New Member

    Allison Transmission Questions

    Allisonman,
    I have a Monaco Executive 1992. I lost my speedometer and odometer. I make the assumption that they are electronically driven, whereas that would be an extremely long speedo cable.
    Any possible suggestions as to troubleshooting and or repair?

    I believe that I have found the sensor on the output of the transmission. It is approximately 2-3" square and has two wires coming off of it.

    Waiting patiently in Central Oregon.
    sdjuandar
    &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
    quote:Originally posted by AllisonMan

    Hi there. I have worked on Allison Transmissions for 27 years. If you have any questions, please post and I will check back once a week and try to answer them all. Thanks and have a great day! :)
     
  4. sdjuandar

    sdjuandar New Member

    Allison Transmission Questions

    Hey Allisonman,

    I own a Monaco Executive 1992 model. My speedometer has stopped working, which makes the odometer inactive as well. My mechanic is AZ has indicated the possibility of a bad electronic speed sensor on the tranny.
    Any possible suggestions to troubleshoot and/or repair?

    Waiting patiently in Central Oregon.

    sdjuandar
     
  5. gringo

    gringo New Member

    Allison Transmission Questions

    allison man see neww topic allison series 4000
     
  6. jljeeper@msn.com

    jljeeper@msn.com New Member

    Allison Transmission Questions

    I have an Allison MD 3060 in my 1994 Southwind. I finally figured out with out any doubt why my Cruise control doesn't work. It is a bad VSS (Vehicle speed sensor)signal comming from the Allison relay box (pin H2) I'm getting .3 to .8 volts AC when I vary the vehicle speed. The cruise box needs 1.4 volts AC minimum to operate. What do I need to replace?

    I bought a ford transducer pickup from NAPA to substitute the VSS signal by hooking it to a power drill and verified that the Cruise control is fully fubctional with the substitute signal. What can be causing the poor signal from pin H2 of the Allison relay box? Please help. I can find nothing in the search.

    Thanks for any help

    Jon
     
  7. dbarton291

    dbarton291 Senior Member

    RE: Allison Transmission Questions

    The speedo head and odometer question. won't be sensor at transmission. If that was bad, trans wouldn't shift. May be bad speedo head. Could also be speedo signal wire from Allison ECU to speedo head. Speedo signal from ECU to speedo head is simply a rectified version of signal from sensor at back of trans. If there's been any recent repairs, speedo head has to have switches in back set properly for speedo signal from ECU. If that hasn't been messed with, most likely signal wiring or ECU.
     
  8. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    Martin: Put the transmission temperature gauge sender in the to cooler line. The one that goes from the transmission to the cooler. This is the hottest place in the cooler circuit.
     
  9. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    jeeper: did that cruise control ever operate properly? The signal you refer to should be the same as the one going to the speedo. To troubleshoot this one properly will require a vehicle schematic I believe.
     
  10. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    Hi AllisonMan, I am looking for a part #. We have a 1967 GMC 3/4 ton pickup w/industrial V6 351. After some fooding in our area we hit a fire extinghisher and killed the flexplate. Without a part # our search for a replacement part has been difficult. Any help would be most appreciated.

    I think you're looking in the wrong place. A 1967 GMC pickup with a V-6 engine did not have an Allison transmission as an option.....unless it's been installed as a regear. If it's a regear, there's no telling what's in there.
     
  11. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    "have a 1988 Rockwood RV with a allison 4 speed auto transmission. I have been trying to find the model number. I stopped at a truck service place and was told it was a 545.
    A concern is going down mountains etc. It was recommended that I not get any kind of exhaust brake that it's hard on the engine???
    Any thoughts?"

    Exhaust brake won't work on a vehicle with an AT545 because there's no lockup clutch, or torque converter clutch, in the transmission. You've got a fluid coupling between the wheels and the engine. Industrial Automatic Transmission Service in Irving, TX has done lots of MT643 installations in AT545 equipped motorhomes and made a much better vehicle out of these things. It's not cheap, but if you plan on keeping the vehicle it sure makes em nice. Go to www.allisontransmission.com and use the service locator to find their number if you like.
     
  12. gymgeek964

    gymgeek964 New Member

    RE: Allison Transmission Questions

    I have been rebuilding transmissions on cars for years. I have recently rebuilt a couple of allison transmissions (545) they have all turned out fine except for this last one. This one I am having a problem with, I have rebuilt it twice and am still having problems. Transmission has aproximatly 150 psi when cold. After transmission warms up, pressure drops to 30 psi. Was wondering if it was a common problem or if there is anything that I sould look at like the center support or the pump for a crack because it seems like the transmission is loosing perssure somewhere. Any advice or info as to where I can locate the maunal would be greatly appreacieated. Thanks
    Jon
     
  13. dbarton291

    dbarton291 Senior Member

    RE: Allison Transmission Questions

    Not an easy problem to find. Might be main pressure regulator spring in front support is weak or wrong spring. Could be charging pump clearances too wide. Charging pump crescent worn. Or the dreaded "leak somewhere".
     
  14. foutsdw

    foutsdw New Member

    RE: Allison Transmission Questions

    Have you gotten an awnser yet?

    I have a 1988 Rockwood with a 4 spd allison. My speedometer just went out also.

    I called Spartan and they sent me 3 pages of Speedo Drive Data. It's all greek to me.

    Dave
    Oceanside, CA
     
  15. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    foutsdw: The 4-spd Allison has a mechanical speedo drive on its output shaft. There is a drive gear in the trans that turns either a speedo cable for a mechanical speedometer, or a signal generator for an electric speedo. You could have either. You need to start by finding out what you have.
     
  16. foutsdw

    foutsdw New Member

    Re: Allison Transmission Questions

    Thanks for the reply.

    The rig is in the shop 75 miles north of me. Waiting to hear from the shop.

    I think they are going to say "they don't work on these problems".
     
  17. jljeeper@msn.com

    jljeeper@msn.com New Member

    Re: Allison Transmission Questions

    Sorry for the late response I guess I didn't have the email notification turned on. I think it's on now.


    The cruise is the factory cruise control. I assume it did work at one time, but not since I have had it. I did get the factory cruise control schematics from Freightliner and everything tests perfectly except the speed signal from the Allison Control box (6 relay box). I have no other wiring diagrams from that point, I do get a speed signal but it's not what the cruise control expects to see. I even bought a new ford cruise control module, still the same issue. I can fake the speed signal with a ford speedo sender connected to a power drill and the cruise will function fine. I did this with the coach on jack stands. The cruise modulates the throttle while I control the speed of the drill motor. Is there a setting in the ECU that sets the output speed signal voltage? It just seems that the signal is in the wrong voltage range for the ford cruise. I even tried to intercept the VSS signal right at the transmission and that wasn't correct either.

    1994 Southwind 5.9 Cummins with Allison MD3060

    Thanks for any pointers

    Jon
     
  18. dbarton291

    dbarton291 Senior Member

    RE: Allison Transmission Questions

    There is no setting in the ECU that sets the voltage of the speed signal. The signal right out of the output speed sensor on the transmission will be a sine wave. I don't remember the exact values of the peaks, but it's greater than the voltages you quoted. The ECU doesn't read voltage however, in calculating speed. It uses the FREQUENCY of the signal. You really have to use an oscilloscope to diagnose the signal itself properly. I know a VOM has trouble telling us much more than whether or not a signal is present on this kind of a circuit and it's not really good for trying to measure peak voltages or frequency.

    The signal for a speedo, or a cruise control, is typically a rectified square wave. Again it's the frequency of the signal that is used to calculate speed....normally this also requires an oscilloscope to diagnose the signal properly.

    If the transmission is shifting properly, the output speed sensor and its signal is okay.

    One important two part question:
    a. Is the vehicle's speedometer working correctly?
    b. Is the vehicle speed signal that drives the speedo also coming from the Allison Vehicle Interface Module?
     
  19. jljeeper@msn.com

    jljeeper@msn.com New Member

    RE: Allison Transmission Questions

    I don't know where the signal for the speedo comes from. I do know where the cruise control signal comes from. (Pin H2 on the Allison 6 relay control box, according to Freightliner) The speedo and transmission work fine. The factory cruise control is the same as a 1990 vintage ford P/U truck. That is also what Freightliner sent me for troubleshooting documentation. I'm now wondering if the Ford cruise needs some sort of modification to work with the Allison signal. I'm pretty puzzled. The cruise does work fine with the correct speed signal. I tested the signal right off the Allison relay box and it is the same voltage and freq as I get at the cruise control unit. I also tried tapping right off of the transmission speed sender unit, still doesn't work. Of course it shouldn't work with the measured voltages I get according to the Ford cruise troubleshooting manual. My only thought is the Allison ECU is not passing a correct signal. But no one really knows much about the subject.

    Thank for your suggestions

    I know how to use an O-scope. I just need to find out who has one I can use. Maybe that will shed some light on the issue. Maybe I just need some sort of amplifier circuit
     
  20. dbarton291

    dbarton291 Senior Member

    RE: Allison Transmission Questions

    jeeper: This is really a stumper. If the transmission works okay, then the speed sensor itself is fine. I believe the output signal speed signal from the ECU that is used for cruise is a zero to five volt square wave. You might try the Allison technical assistance center at 1-800-252-5283 to verify this. I also went back and read one of your previous posts. You said the cruise box needs an AC signal. If the Allison output speed signal at the VIM is a rectified square wave, that's obviously not an AC signal. Maybe the cruise never worked in this vehicle and the signal needs to pass through an interface before being fed to this cruise module. Tallk to the guys in TAC and see if they can help. I may be missing something here.
     

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