Transmission overheating

[CrewCabDiesel]

I have a rebuilt 48re automatic that overheats during in town driving only. In town it can hit 220+ degrees internal temp and 190 degrees pan temp. Highway or over 45mph runs about 160 degrees internal and 150 degrees pan temp. Outside temps have no effect, same happens from 100 degrees down to 40 degree outside temp. Trans shifts fine except from 1st gear, if I pull the shifter into 1st it feels like the transmissions shifts but rpms stay the same. Transmission has upgraded clutch packs, shift kit and billet internals, triple lock converter and a bd deep cooling trans pan. Also per trans rebuilder I have removed the transmission/coolant cooler and use only front transmission cooler. Infrared probe shows front cooler working. transmission was rebuilt before I did the motor so the 1st gear shift didn't really show. Any one have some any ideas what I should look for?
Thanks
Kyle

 

[cerberusiam]

Sounds perfectly normal. It is not unusual to see 220 or thereabouts in stop and go driving without any air flow. With the heat exchanger removed it will be even warmer. All you can do is hook the heat exchnager back into the system or add a thermo activated aux cooler for those conditions.

 

[CrewCabDiesel]

I am taking it in today for the rebuilder to check it out, the 1st gear issue worries me and its under warranty. as for the aux cooler I like the idea, where would a good place to fine one? these trucks use 1/2 lines so off the shelf is not option. As for reinstalling the oem coolant system, not a chance, seen too many failures. Seems like a bad start since I have yet to tow with the new trans with a heavy load.
keep the ideas coming,
thanks
Kyle

 

[Bob4x4]

Summit racing sells a cooler with 1/2 lines and a fan

 

[CrewCabDiesel]

OK I will look into it, any idea best place to locate aux cooler?

 

[DavidC]

OK I will look into it, any idea best place to locate aux cooler?

Of the few I have seen it is under the front of the bed.

Dave

 

[sag2]

You will not get any better performance than from the OEM coolant to fluid cooler. If your worried buy a new one instead of using the old one.

 

[Prairie Dog]

I used one of those expensive fan-cooled units ( I think it was from Jegs) under the bed of my older Dodge.
It made absolutely no difference.

 

[CrewCabDiesel]

Just got done talking with the rebuilder, they are boring the valve body to deal with some wear issues. guess there was some fluid getting by causing the trans to shift wrong with a light foot. 30% or more throttle it worked fine. The owner of the shop has been dealing with my truck himself, he is impressed with how it runs and has asked me for a build list for his truck. I tend to drive it like I have an egg under my foot until I see a ford or rice burner. The rebuilder also wants me to add a aux cooler and restrict fluid a little, sounds weird but they are saying fluid is moving too fast to cool correctly without having the oem cooler.
Next, regear to 3:73 or a gear venders overdrive?
Thanks
Kyle

 

[Ozymandias]

The OEM Cooler is fine, only wrong handling with wrenches kills them. It is a proven industrial design.

Oil to Water is far more efficient then Oil to Air.

 

[rscurtis]

The rebuilder also wants me to add a aux cooler and restrict fluid a little,

Don't believe it. The more fluid flow you have, the more BTU's are removed by the cooler. The delta T may be smaller, but more heat is being removed. When your engine needs more cooling, does it slow down the flow through the radiator by closing the thermostat down? On the same token, is air flow across the radiator slowed down so it has more time to pick up heat?

 

[Freebore]

I have a rebuilt 48re automatic that overheats during in town driving only. In town it can hit 220+ degrees internal temp and 190 degrees pan temp. Highway or over 45mph runs about 160 degrees internal and 150 degrees pan temp. Outside temps have no effect, same happens from 100 degrees down to 40 degree outside temp. Trans shifts fine except from 1st gear, if I pull the shifter into 1st it feels like the transmissions shifts but rpms stay the same. Transmission has upgraded clutch packs, shift kit and billet internals, triple lock converter and a bd deep cooling trans pan. Also per trans rebuilder I have removed the transmission/coolant cooler and use only front transmission cooler. Infrared probe shows front cooler working. transmission was rebuilt before I did the motor so the 1st gear shift didn't really show. Any one have some any ideas what I should look for?
Thanks
KyleView attachment 89930

I agree it is not uncommon to see trans fluid temperatures of 200-220F, but it is not without consequences. I work every day with hydraulic system design and second to contamination is the heat problem. There are a lot of places where you can find information about how for every 10 degree C temperature increase over 80 C, the fluid loses about half of its life, regardless if it is synthetic or not. The additive packages are destroyed as the temperatures increase and the higher they get the more the consequences. Here's one link showing a temperature / life chart that gives you a general idea:

http://myautomatictransmission.com/temperature-chart.htm

I modified an older GM I had which had a chronic transmission heating problem and it stayed at 225F in the sump in most summer driving. I added the biggest plate type cooler I could fit in series with the factory heat exchanger and managed to drive the temperature down to 175-180F. It was a Tru-Cool - here is where I found it:

http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=2&Category_Code=tru-cool-hd

You can add a bypass if you want to. No large pan required (condition the fluid you have - don't add more unless it is because of a bigger cooler). I did not have any problems with overcooling as the plate type cooler would self regulate and would not flow across all plates when the fluid was real thick. I sold the truck at 260k miles with the original transmission still working fine. I continued to change fluid every 30k miles to make sure all was well. I haven't monitored my pan temps yet on my current truck, but will likely be doing so soon as well as updating the cooling system for the trans.

 

[rscurtis]

Were it my truck, I would be looking into why the transmission is producing so much heat to begin with.

 

[cerberusiam]

That chart is so bogus it is laughable. Same old tired cliche trying to promote products and services not needed. Total BS becasue the fluid change interval completely negates its intent.

Those temps ar enot even cause for concern and totally normal for a heavy vehicle high TQ application in slow-n-go situations. Change the fluid a little more often and go.

Note that ATF+4 is rated for 1500 hours at 315 degrees and still pass all the ISO tests that contribute to what the fluid is supposed to do. Periodically replace the contaminated fluid with new and they work well.

 

[CrewCabDiesel]

Thanks for all the information, I got the truck back last night and got stuck in Greenville SC rush hour for a little over an hour with the highest trans was 196 degrees. Transmission shifts great and no other problems. The rebuilder had to bore out the valve body due to wear, some of the valving was leaking. I still plan adding an aux cooler later when I have more time and money. Next project regear to 3:73, and ideas?
Thanks
Kyle