Use AC for cooling trany?

[MojaveJoe]

Seems when Im running with my AC on the transmission temps are always a little lower. (5-10 degrees) Am I imaging this or is it possible?



Getting ready to depart on a cross country RV trip towing 13K. Could use any advice as to how to get trany fluid temps down when they are up there around 260F. Particularly when stopped or in slow construction zone traffic.



Thanks Joe

 

[cerberusiam]

When the AC is on the fan is engaged more often so its moving more air. That will impact your trans temps some. Where are you reading the trans temp? That will make a difference about how serious your temps are.



As for keeping them down, use 2nd gear manually and get the TC locked up a much as possible, especially with that weight you are hauling. Wrap the engine up to 2500 rpms or more if you have to, it will be better than lugging along unlocked.



If 260 is the max you are seeing don't sweat it, just change the fluid every 20k and you should be fine. ATF+4 was tested at 320 degrees for 1500 hours to pass the tests so 260 once in a while is no big deal. As long as you are not getting a check engine light and codes the ECU thinks things are fine.

 

[MojaveJoe]

My trans temp (X-Monitor) comes right off the transmission ECM wiring. So Im guessing it is measured at the discharge end of the transmission. Only at 260+ for about 10 minutes, then took it for a ride to cool it off. But those ATF+4 testing numbers (320F) are very encouraging. Was wondering if I should change my fluid again (4 days old). Guess I'll let it ride for now. Ive hit 260+ before but never had the transmission downshift by computer override due to overheating. So perhaps 260 isn't such a critical number.

Also, will try the locked in 2nd trick. Would locked in 1st be as good at even lower speeds?

Great advice, thanks.

 

[WStephens]

Get a double deep pan for your transmission that will increase you fluid capacity and help cool the fluid. You can get them from Geno's Garage.

 

[nunya]

double deep pan does help and so does the manual lock up in 2nd, 1st doesn`t lock up, bummer! Great info on the temps ... ... . I got excited at 220 on the temp. Thanks! I tow 15K 5er and always lookin for good info.

 

[cerberusiam]

My trans temp (X-Monitor) comes right off the transmission ECM wiring. So Im guessing it is measured at the discharge end of the transmission. Only at 260+ for about 10 minutes, then took it for a ride to cool it off. But those ATF+4 testing numbers (320F) are very encouraging. Was wondering if I should change my fluid again (4 days old). Guess I'll let it ride for now. Ive hit 260+ before but never had the transmission downshift by computer override due to overheating. So perhaps 260 isn't such a critical number.



Also, will try the locked in 2nd trick. Would locked in 1st be as good at even lower speeds?



Great advice, thanks.

If you reading temp that way its pan temp and reliant on the transducer being calibrated correctly and the reader being calibrated correctly. Experience says they are not always the most accurate. The 260 might very well be 220 on an analog gauge. The 260 number is supposed to be the threshold when you get a transmission light and it does weird things when shifting. If your not seeing it then it is probably not quite there.



A deeper pan will help some with the added capacity but your best bet is manual 2nd in slow speeds or even a lockup switch to hold lockup in 2nd. Unless you modify the VB it will not lock in first with the stock pieces.



I would just keep an eye on the fluid for color change and any hint of a burnt smell. Unfornately by the time you see that the damage is done but at least you know to change driving habits to help keep the trans happy.

 

[MojaveJoe]

Terrific info guys.

I kinda think X-Monitor calibrated their unit high to avoid people running up to the limit on transmission temps, then trying to sue them. Never had the computer kick in and down shift like they say it will at excessive temps. Never smelled burnt fluid or seen it in this truck, so I could well be within operating limits even at 260. On open road towing Im usually about 230 in 100F ambient.

My DoubleDeep transmission pan seemed to drop my temps about 10 degrees last summer when I installed it. Good investment. I guess I should invest in an analog gauge and stick it in the pan fitting MagHytec provides, just to see whats up at about mid depth fluid level.

Thanks for your help and happy towing
Joe

 

[cerberusiam]

On open road towing Im usually about 230 in 100F ambient.

Based on what I am seeing with with an analog gauge in the cooler hot line your temp looks to be 30-40 higher. Every truck and every situation is different but it looks like your 260 max correlates to 220-230 in slow-n-go which is right where mine will be if I let it.



The electronic gauges are nice but I gotta question the accuracy of all of them. It seems they are all off anywhere form 10-20 percent. As long as its high its not a problem but... ... .



I think as long as you see a consistency in the readings its probably good. If the temps ever go a lot higher or lower thats a good indication of problems.

 

[GaryOwen]

I went with a larger transmission cooler on my 95 to help with cooling. Not sure if the 3rd gens have room for one though.