Transmission overheating

[Tim Bentley Co-Admin]

Need help with a transmission problem.  My Allison 4000 is running hot.  It usually runs at under 200 Degrees, but is now running at 220 to 235.  If I keep my speed at 60 in 5 gear, I can keep it at temp below 227.  My transmission fluid and filters were changed less than 1000 miles ago.  Three Questions.  What can cause a transmission to run hot?  Can I continue my trip, about 500 more miles, without damaging the transmission?  Is it possible that they could have put the wrong type of fluid in at the change, is there more than one type of TranSynd?

I have no warning lights or Fault codes.

[Gerald Farris]

Tim,
A few questions. First, are you sure that the transmission is full of fluid (check fluid level with transmission shift pad)? Next, does the transmission read the same temperature on your Aladdin as it does on your dash gauge?

There is the possibility that you have a gauge failure, and the transmission really is not that hot. Therefore the need to check more than one gauge. There is only one TranSynd as far as I know.

If your transmission really is running that hot on the highway, I would have it checked if possible before driving another 500 miles.

Gerald  

[Tim Bentley Co-Admin]

I have checked the fluid level and it is OK, Both gauges read the same.

I really would like to drive home taking it easy.  Will I get a check transmission warning light before any serious damage is done?

[Gerald Farris]

Tim,
I do not know. The thing that is the most concerning to me is, what is causing the overheating?

Gerald

[Edward Buker]

Tim,

Some discussion here with some feedback regarding 250F being a limit requiring cooling down. The fluids degrade at a higher rate as the temperature goes up but having Transynd is much more forgiving.

http://www.irv2.com/forums/f22/allison-trans-temp-73891.html

It is a matter of flow, both fluid and air, and if there is any slippage in the transmission. If the heat exchanger for the transmission is clean, then I would guess the next thing to try is to pull the transmission filters and see what they look like for particles, proper installation, and fluids. That could be done by a road service in the campground. Just a thought along with calling Allison for advice.

Later Ed

[Steve Jewell]

Did you check for transmission codes? Are the radiators clean?

Steve Jewell

[Tim Bentley Co-Admin]

Haven't cleaned in radiator in awhile, will do that but not sure if a dirty radiator would cause a 30 degree rise over night. The fact that it started after the service should be a clue.  I did check the fluid cold at the dip stick and it was low, have not checked it hot yet.  The fluid level read ok up front at the shifter, is it possible that reading is incorrect?

[Bill Sprague]

The shifter/keypad is supposed to be more accurate than the dipstick.

When you are in 5th at 60, does the Aladin show 5C (clutch) or 5L (locked)?

[Keith Duner]

Several thoughts.  A sudden temperature increase of 30 degrees, while not major, is also not normal and should be investigated.  If fluid level has been confirmed by the shifter method (less chance of a miss-calibrated dipstick giving false readings) then the next step would be to review the cooling system.  Several logical suggestions have already been given regarding the inspection and cleaning of the radiator.  I'm assuming there is no associated increase in engine temperature?  Question, were genuine Allison filters used at the recent change?  Some aftermarket filters have been known to collapse under normal operating conditions.  Internal transmission failures that would result in sudden increase in temperature would usually also be associated with some performance problems.  Converter stator failure can cause overheat but would also result in a significant reduction in acceleration, a greater than 30 temperature spike, and will usually produce aluminum "sheen" in the fluid.  Slipping clutch packs can cause temperature increases but would again result in noticeable performance problems and specific diagnostic codes.  Please note that Allison provides specific thresholds to define Overheat and where to measure those temperatures.  Per their Operators Manual (available for free download from Allison's website http://www.allisontransmission.com/index.jsp [search for Operators Tips]),  SUMP TEMP shall be considered Overheat above 250 F. TO COOLER shall be considered Overheat above 300 F.  If the unit is equipped with a transmission retarder, then RETARDER OUT temp of above 330 F is considered Overheat.   As has already noted, TRANSYND is a very forgiving synthetic fluid so you should not experience any reduction in life based on a short term (relatively minor) fluid temp increase.  However for something like this, my two cents is to contact an authorized Allison service outlet for guidance.  Allison's website has a service locator that can point you in the right direction for service support based on your location.  Good luck.

[Edward Buker]

Tim,

Even if the fluid was a bit low I do not think that would be a reason for such a temperature rise. Lower volume of fluid might account for a small shift in traditional temp due to fluid volume differences, but with proper flow it still sees the cooler and the pan should still have volume in it as a reservoir to pull from and the temperatures should be stable within a few degrees.

Given these transmissions are very reliable by design I agree that it is likely that some error in the service is the most logical source to have induced this issue. This problem timing just does not seem likely due to chance. When you look at the service performed there are two components, fluid and filters. Even if they inadvertenty used Dexron it would still not account for a significant temeprature shift, That leaves filters or a possible fluid or particle contamination of your transmission. (like antifreeze fill from a bulk system selection error} Like Keith I'm still thinking that improper filter PN or install may be involved. Not sure what your status is right now but I would be looking to have the filters inspected and changed and a fluid sample analysed to see where the current fluid maintenance stands and if it can shed some light on your problem. These transmissions are just too expensive to not sort this issue out when in doubt.

Regards Ed

[LarryNCarolynShirk]

Tim,

Just a thought.  When we changed from Dextron to TranSyn in our '98 Patriot, the transmission and engine temperature dropped about 30 degrees.  It is possible they put in Dextron.  I think the color is different, but you know me and colors.

Larry

[Tim Bentley Co-Admin]

Still working on a fix for this problem.  Allison in St George, Utah says fluid level and type are OK.  They suspect its  the transmission cooler, did not want to interupt trip to fix at this time.  Will drive 58 in 5th to keep temp below 230, max temp is 250 so should not harm unit.  

[Bill Sprague]

.....  Will drive 58 in 5th........  

My fuel mileage improves significantly when I do that.  

[Tim Bentley Co-Admin]

Not so good news on our transmission.  Looks like a transmission cooler leak allowed coolant to enter the transmission.  The transmission cooler and transmission need to be replaced.  As we have found out before, any coolant in the transmission will ruin  it.  

[Joel Weiss]

Tim--

Sorry to hear your diagnosis.  That's one of the frightening issues I hope never to have to face.  I did some surfing and it does appear that there are a fair number of remanufactured 4060 tranny's for sale.  Good luck.

Joel