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Transmission cooler thermostat '05

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I've been overheating the transmission, mostly on slow and go hill climbs.

05 48RE, 136K on it with ATS valve body, TC and overhaul.

I've recently learned that the cooler has a thermostat, just like the engine radiator, and mine seems to be stuck closed.

I've surmised this based on a digital probe on either side of the top drivers side corner, where I'd heard it would be located.

Apparently this thermostat is not replaceable, and I need to replace the entire cooler.

Anyone have a work around for that?

Should I be annoyed with the transmission shop that didn't think about this contributing to my high temps, and was trying to sell me an auxiliary cooler to alleviate the issue?

Thanks,
Dave
 
The cooler is large enough for stock situations. There is a check valve at the connection that some guys have drilled out . Someone with more experience will chime in.
 
I assume you mean the low connection to the hoses.

I was told, and my laser probe supports the idea that the blockage is at the top corner. There appears to be a threaded cap where the tubing has a 90 degree connection. I had 190 deg in the vertical tube below this and 125 deg at the horizontal run at the top.

I am assuming the thermostat is behind the cap, but it allegedly not replaceable.

Just trying to see if there is some lower hanging fruit than replacing the entire unit.

Thanks.
 
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In the heat exchanger the is a rectangle device on the upper portion of the heat exchanger ( dont remember which) that allows the oil to bypass the heat exchanger and return to trans to allow warmup. It’s adjustable, I don’t know if it’s removable, but it could be stuck in bypass. It’s theory is path of least restriction, so if open its passes through, if closed it forces it through the heat exchanger.
 
Thanks TCD. That piece up top is the one I am suspicious of, but the dealer and ATS say it is not a separate part and that I need to replace the entire cooler.

Do you know if I can replace it or even adjust/ free up the stuck valve?
 
Its tricky to remove, but can be done.A lot of owners remove it entirely If you live warm climate during NOV-FEB, the Exchanger mounted on the driver side of the engine warms the fluid to a certain level, but if the bypass is open 100% it will take considerably longer to warm the fluid in cold -0F temps
 
I do plenty of winter driving, but it's pushing a heavy camper and towing a sled trailer. Seems like it would warm up pretty quickly, but I don't want to strain it running cold fluid.

Looking at it, I see the screw cap, but I hadn't noticed the retainer ring.

Might go try to remove that.

Sure looks like a part that should be replaceable, doesn't it?. I have not seen this as a separate part. What is the source of the breakdown schematic above ?

Thanks again.
 
Not serviceable and no parts available. Replace with a new cooler, should have done that with the trans rebuild as there is no way to adequately flush those coolers.

The o-ring is the problem it is special. Disturb it on an older vehicle and they like to leak.
 
Thanks guys. I was trying to find a work around, but will replace it.

Does this feel like something ATS should have investigated when they rebuilt my transmission, or maybe even before doing so, as heat was my main complaint!
 
Cerb I have a few 1000s O-Rings I'm sure I have one fits......

DFrank, its hard to say..... and its a bypass Valve, What % to max ? So it may not be the problem.
 
So I got a full rebuild and all the crap from the cooler is now in my new unit. Nice.

Cerb, you chimed in a bunch over the years as I was trouble shooting this; thanks.

I had them do work on transmission for two reasons: getting stuck in 1st and 2nd, which still happens occasionally, and overheating on hill climbs.

They did the Valve body the TC, and a full overhaul and I am still overheating on slow and go climbs' and still struggling to shift out of low gears from time to time, like after using it to descend a long hill.
 
Easy to find one that fits, not so easy to find one that will stand up to the hot ATF. That seems the biggest issues if they are ever replaced.

Dfrank, when you are seeing hot temps what gear are you in and what speed? Is the TC locking on these climbs.

The way I fixed the crappy shifting, TCS front servo and a 4.2 lever. That has done more for cleaning up the 1-2 and 2-3 shift than anything. The rest is just programming what can be adjusted for better feel.
 
Temps get above 200 easily, but get scary hot if Im doing a slow and go or mountain pass climb that doesn't let the TC stay locked.

I do sometimes manually go to 2nd to try to keep it locked more.

I'll pass on that technical 4.2 lingo to my tech. I don't know what it refers to, but thanks.
 
With a tight TC temps at the cooler outlet line will spike to 200-220 easily when loaded but as soon as the TC locks and you have air flow they drop again. On long slow grades manual 2nd or they will get out hand and you really need a lockup switch as 2nd lockup is not exactly what it should be. Withe switch you will get 1st gear lockup and that is needed sometimes.

If you are seeing over 200 in the pan then it is much hotter at the cooler output line. I have seen close to 300 degrees at cooler output in a really hard unlocked pull.
 
What is your boost pressure when this happens? Due to location of the heat exchanger, right behind the intercooler, it will pick up heat from it. I run the same heat exchanger, but I have a manual trans and set up a a pump to circulate my trans oil. It works great, however when climbing steep grades at 23K in the summer, the heat from the high boost coming off the intercooler actually raises the oil temps, not lowering the temp. So I shut it off during this, and hope to get the BD cooler under the flat bed.
 
Many Transmissions just don't have adequate circular pump..We added the Same cooler garbage Trucks use for cooling the Hydraulic Fluids, Some of these truck have 60 Gallons of Fluid, ..Yep it took much longer for the fluid to reach MAX temp but it still did, We even installed Temp sensors in the return line , Fluid was getting warmer as it reach the transmission.

You can add all the coolers you want ...it won't change the flow to cool ratio..

Now to keep the Mod happy at the TDR, TCD does not sell Transmission parts at this time....or accessories.
 
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