Hi All,

I’m considering putting a tranny cooler in my truck. So I started by doing a little bit of homework and research.

Looking at the FSM, it looks all trucks (at least for 2001) have a auxiliary tranny cooler installed between the radiator and AC heat exchanger. The FSM talks about a thermostat, and when the oil is “cold” the cooler is bypassed.

Well… in a few threads I have read on DF, it looks like most folks are inserting these coolers after the auxiliary cooler.

The problem I see with this is that the auxiliary cooler has a bypass thermostat in it. When the fluid is below operating temperature, the fluid id diverted and not sent through the auxiliary cooler.

That’s all well and good until you add an additional cooler in that return path. Theoretically, you could have fluid below operating temperature that is being diverted from the stock auxiliary cooler, but is then fed through an aftermarket cooler.

I guess I’m just curious to see what other folks have done/seen. I would imagine this isn’t going to be too big of a problem. I just don’t want to do something that I think will help and end up shooting myself in the foot.

I live in Oregon… and temperatures usually don’t go too much lower than 20F (at least where I live) in the dead of winter.


Thanks,
Cartman

 

my 01 didn't have a real transmission cooler, it only has the little cooler that's integrated to the radiator and no thermostat bypass that i know of. i think they only have a real (separate) cooler if they have the tow package option.

if you do already have a tow package/separate cooler, then there's little need for another one, and you could overcool the fluid.

 

Trans coolers have always been optional. There is no thermostat to control cooler flow.
There is a small bypass tube in the OEM cooler though, that's it.
Get a good aftermarket cooler and install it either in front of the condenser or between condenser and radiator.
I like the plate style cooler like "tru cool" as they are self regulating and recommend installing it so the hot fluid runs to the aux cooler first and then through the radiator cooler before returning to the trans.
This way you are protected against over cooling the trans in cold weather and you lessen the load on the engine cooling system during very hot weather.

 

While living in Montana , purchased a new '94 JGC(5.2L,auto, with tow package). It seems when it was cold (around 0 deg. F), the vehicle would not shift into overdrive. The dealer had a TSB, a kit that bypassed external tranny cooler in cold temps. A neighbor bought a brand new '96 Ram, 5.9 L, auto, with tow pkg.. Informed the neighbor about the TSB and he was told by the dealer that his vehicle was delivered with TSB installed.

 

We used to install that bypass for some customers who lived on the highway.
The trucks and Jeeps with these trannies won't shift into overdrive until the fluid reaches a certain temp. The PCM locks it out. PITA for some people. You can turn off the cold overdrive lock out with the DRB scan tool if you install the bypass kit. The problem with the bypass is you have to cut the factory lines and re route them to install the valve. The bypass also reduces the cooling capacity of the system so it can cause trans overheating in hot weather or heavy use. I wasn't a fan of them for that reason.