Allison Transmission Questions

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

  1. dbarton291

    dbarton291 Senior Member

    RE: Allison Transmission Questions

    Most air to oil coolers are used as auxiliaries in addition to the water to oil cooler the OEM typically engineers into their vehicle. My opinion is, the choice of which one to use is not normally based on a sound definition of additional cooling requirements, rather it's what will fit and not cost a bundle.

    The performance of a water to oil cooler is predictable and can be tested. A water to oil cooler will also dissipate much more heat in a manageable size than an air to oil cooler. That's why Allison works with OEMs on either cooling calculations or testing requirements for water to oil anytime a new application is designed by an OEM. You can take the engine water flow and the transmission oil flow, using the cooler curve for the cooler the OEM is using, and compare the heat the cooler is capable of dissipating, to the transmission heat rejection at the selected test point, which is usually 80 or 85% torque converter efficiency depending on vehicle type. Torque converter efficiency is the speed ratio times the torque ratio.

    If the cooler can dissipate more BTU/min than the transmission is producing, it will keep the transmission cool at that design point. If the cooler dissipates less BTU/min than the transmission is producing at that point, the transmission temp can't stabilize and the transmission will keep getting hotter.

    An air to oil cooler depends completely on airflow vs oil flow. What you need to know is:
    1. The cooler curve for the air to oil cooler you want to use which shows at a given air flow and oil flow how much heat the cooler will dissipate. Good luck finding this for most air to oil coolers.

    2. The exact air flow you will be producing in whatever unit of measure the cooler manufacturer uses in his published data on the cooler....that is if they even have and publish cooling capacity data on the cooler.

    3. Run an iscaan on your vehicle to find out the transmission heat rejection at 80% converter efficiency. An Allison distributor should be able to run you an iscaan for a fee.

    4. Take the heat rejection being produced by the transmission at 80% converter efficiency and find that point on a cooler curve for an air to oil cooler. That will tell you what air flow the cooler needs to see to dissipate that much heat.

    I would be willing to bet money, it will take an air to oil cooler of enormous size to dissipate the heat produced by an Allison at 80% torque converter efficiency and full throttle.

    In my experience, vehicles that use an air to oil cooler as a primary method of cooling the transmission oil, and there are only a few, have cooling capacity that is highly suspect. As you are finding out, the information needed to predict the performance of these types of coolers is not easy to find, and because they are normally used as an auxiliary cooler rather than a primary, few people will commit to what they are capable of.

    I don't know what reference to remote coolers on the Allison site you are referring to. I know for a fact, Allison does not endorse or sell specific air to oil coolers. Any reference to a remote cooler by Allison normally refers to a remote MOUNTED oil to water tube and shell type cooler, as opposed to a cooler mounted in or on the radiator.

    The only cooler Allison currently will sell with their transmissions is an integral cooler for retarder equipped transmissions. It is water to oil, and it's not cheap. All other coolers are sourced by the vehicle OEM.

    That's probably more than you wanted to know. But, if you want to proceed with trying to re-engineer your vehicle to use an air to oil cooler, whatever cooler you choose to use, I would suggest mounting oil temperature gauges on both the to and from cooler lines (at the transmission) to monitor what's going on in that cooler circuit.

    If you can stand another one of my opinions, I wouldn't do it. I'd stick with oil to water. If you don't trust your radiator to stay together in your 1998 vehicle, put one of the remote mounted tube and shell oil to water coolers on the vehicle and bypass the radiator. I think Rocore in Indianapolis is a good source for those.
     
  2. dbarton291

    dbarton291 Senior Member

    RE: Allison Transmission Questions

    It helps to know exactly what temperature your vehicle is reading. I believe the pickup trucks use the sump thermistor as their indication of transmission temperature. Max temp on an Allison in the sump is 250 deg F. Don't get her over 250.

    The HEMTTs probably used a gauge put in the vehicle by Oshkosh that was labeled red at 220. Keeping those below 220 is a good thing. That keeps the GIs from approaching 250 under non-combat conditions.

    If you really want to do a complete job of watching the transmission temp, watch both the to cooler temp and the sump. The to cooler line is the line that takes the hot oil out of the torque converter and sends it to the cooler.

    Max temp at the to cooler line is 300 deg F. At 300 deg F, transmission fluid starts to break down.

    Hope that helps!

    DB
    PS: Been to Taipei, Shanghai and I'm now in Xian China. Got a couple of more places to go before I get my feet back where they belong.... I got a new John Deere delivered the day I left on this trip. Can't wait to get my diesel can filled up and do some puttin around.
     
  3. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    Forgot one. I've also been to Kaohsiung, Taiwan. Man, was it hot.
     
  4. washtub51

    washtub51 New Member

    RE: Allison Transmission Questions

    thankyou dbarton291, i havent been this turned on since i delivered my first baby calf. i completely understand your position and have been down that engineering road. your opinions are prized by me as they make sense. your idea of cost is what $1000,$2000. i would pay that in a heartbeat to save $15000. if a 3060 has a rated input of say 225kw converting that to btu and knowing it as max thermal load and then understanding what hp/kw/btu load is required to pull this circus down the road at 60 at an ambiant of say 80f and forget the mountain climb for now, would that not get me close to sizing and air to oil cooler?. i will call rocor today and pic their brains. dont throw up you hands on this. just think about it. i know your busy. jim
     
  5. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    Pulling down the road at 60 isn't a huge heat load. The trans is in lockup under those conditions. It's the torque converter mode you have to be concerned about. The transmission heat rejection goes way up anytime you're not in lockup, such as under a full throttle load and low output speed, as well as starting off. I'm not exactly sure on the cost, but I think you're about right. Keep in mind a rebuild on an MD3060 should be $5K or less.
     
  6. washtub51

    washtub51 New Member

    Re: Allison Transmission Questions

    i talked to rocor and they are interested and say they are able to construct an air to oil cooler for my needs and yes they talked about what converter i had and the cooler is based around that. most of my mild hilly driving is done in 5th and the big hills are usually done in 3 or 4th so i can see where the heat would come from. rocor acted like they understood the issues. side note, a customer of mine recently lost his tranny to water intrusion and the overhaul out the door was about 7 grand and the tow was 1200 and the food and lodging for 2 weeks was 1500 and a radiator where this all started was 4500 and the damage to his rig from the tow about 1000... soooo i should know friday and will let you know whats up. they also talked about a thermal bypass and a thermostaically controlled 12 volt fan running at 2500 cfm. i know what there gonna do i just dont and cant yet get the thermal requirements of the tranny if i knew the data i could be a jethro bodine 00 roket sientist. will let u know. jim
     
  7. Triple E

    Triple E Senior Member

    Re: Allison Transmission Questions

    Jim, what exactly happen to your friends radiator? Could their problem have been prevented some how? I have only heard of this kind of damage to a transmission twice.
     
  8. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    I'd be interested in the dimensions of the cooler and where you mount it. It would also be interesting to know which fan you use and at what temps they kick the fan on and off.

    I would suggest using temp gauges at both the to and from cooler ports on the trans.
     
  9. HR READY

    HR READY New Member

    RE: Allison Transmission Questions

    HI ALLISON MAN. I AM PURCHASING AN 01 HOLIDAY RAMBLER 40FT WITH A ALLISON 3000 6 SPD. ANY PROBLEMS WITH THIS TRANS THAT I SHOULD BE AWARE OF. I DON'T NEED ANY MORE PROBLEMS. THANKS FOR ANSWERING OUR QUESTIONS.
     
  10. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    Back from Asia now. Should be around for a couple of months.
     
  11. dbarton291

    dbarton291 Senior Member

    RE: Allison Transmission Questions

    Nothing inherent. Pretty good trans.

    See if you can get some service records with the unit just to make sure the previous owner did the maintenance.

    How many miles on it?
     
  12. billshed

    billshed New Member

    RE: Allison Transmission Questions

    Hi Allison Man,
    I have a Safari on a 1992 Oshkosh Chassis with an MD 3060. Recently as I was driving, the transmission shifted into Neutral several times. I could get it into drive for a few seconds. I did this several times until I could pull off in a safe place. The 'DO NOT SHIFT' light on the dash lit up also. I checked the fluid and it seemed low so I added four quarts and it worked fine. It is very difficult to get an accurate reading on the 7' long dipstick. There appears to be a leak around the valve body gasket. Is a valve body gasket leak common on an older Allison? If you overfill this transmission, will it overflow or puke out anywhere? Could a plugged vent (mud diver) cause a leak and where is the vent located?
    Thanks,
    Bill
     
  13. dbarton291

    dbarton291 Senior Member

    RE: Allison Transmission Questions

    A control module gasket leak is not common, but does happen. If you overfill the transmission a lot, fluid will come out the breather in operation, not sitting still.

    A plugged breather may cause input and output seals to leak, before it will cause the control module gasket to leak. The breather is on top of the transmission.
     
  14. billshed

    billshed New Member

    RE: Allison Transmission Questions

    Allison Man,
    I pushed my up/down arrows to get the codes. I don't have a fluid level indicator. I got a 3-5, 0-0 code which I think means power interuption. Could this have been my problem with the transmission kicking into neutral several times? I read the code about a week after the issue with it kicking into nuetral and the ignition was turned on / off several times and it was driven about 1,000 miles. Would that have cleared a week old code?
    Thanks,
    Bill
     
  15. dbarton291

    dbarton291 Senior Member

    RE: Allison Transmission Questions

    No. Once the trans is in gear, if the power is shut off to the TCM, the transmission stays in a gear. The only thing that can kick that transmission into neutral going down the road is a clutch losing capacity due to the trans being way low on oil, or a failed clutch.

    Staying in gear during power interruption is an FMVSS requirement.

    A few ignition cycles does not clear codes.
     
  16. MoparMuscle

    MoparMuscle New Member

    Re: Allison Transmission Questions

    I have an MD3060 that is leaking in the center of the output yoke. Is there an oring or seal under the bolt? What is the torque spec on this bolt?

    Thanks,
    Richard
     
  17. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    MDs beginning with serial number 06510184819 there is an O-ring on the retainer plug and the bolt. Torque on the bolt is 70 - 80 Nm.
     
  18. MoparMuscle

    MoparMuscle New Member

    Re: Allison Transmission Questions


    My serial number is 6510004249 in a 1993 Foretravel 3116 Cat.
     
  19. dbarton291

    dbarton291 Senior Member

    Re: Allison Transmission Questions

    Do you have one or two bolts holding the output flange onto the output shaft? If you have a single bolt, the torque spec I quoted is correct.
     
  20. MoparMuscle

    MoparMuscle New Member

    Re: Allison Transmission Questions


    I haven't pulled the driveshaft yet. As soon as I get it out I'll post.

    Thanks,
    Richard
     

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