Installing a Tranny Cooler

I thought installing a tranny cooler would be a good idea. Keeping the tranny cool would let it live longer and adding a tranny cooler would help cool the coolant also. Seemed like a good idea!

The top long cooler is actually an oil cooler off of a 90s GM Suburban. It's about 14 inches long. The bottom one is a small old style cooler.

The above tranny coolers were ones that I went back to the wreckers because I thought that the tranny cooler that I had installed (see below) was blocking the radiator and stopping it from cooling. The engine was running on the warm side. I found out that the fan belt was slipping and not driving the water pump efficiently. Sometimes the solutions are really simple!

Orginally, I had a couple of coolers that I picked up over the years. The first one that I looked at was the old traditional style: big tubes and lots of fins. The idea is that bigger is better

Old style tranny cooler

Unfortunately, it was too big to fit in front of the radiator and the hood latch brace. On to plan B (I seem to be doing a lot of plan B stuff...), I went to the local parts supplier and checked out their tranny coolers. They only carried one line of the new style coolers. Rather than have one big tube snaked back and forth with lots of cooling fins. The new style has about 30 hollow fins where the tranny fluid flows through. It is a better design and significantly smaller. The best part was I had one already at home!

Here's the new small style tranny cooler installed - I even have room to put another one if needed!

I used small spare 1/2 dia tubing that I had to make the upper and lower cross braces. I just had to hammer down the ends and drill some mounting holes. I used tube clamps to mount the tranny cooler to the upper and lower braces. The hardest part was drilling holes in the radiator mount without removing the front grill.

Here you can see the upper cross brace mounted from one side of the rad frame to the other

The best place to route the tranny fluid is between the return line of the transmission and the radiator's built-in tranny cooler. This way the new tranny cooler will further cool the fluid after it leaves the radiator. So the question is which line from my T350 tranny is the return line? On a T350 the tranny fluid lines are located vertically (one above the other), the top line is the return line. A quick check of the routing and everything got connected up the way I wanted.

Transmission Coolant Line Identification

Powerglide - OEM
Fitting Location     Thread Size   Flow Direction
Upper                 1/8" Pipe      Return/in
Lower                 1/8" Pipe      Cooler feed/out

Powerglide - Dedenbear
Fitting Location     Thread Size   Flow Direction
Upper                 1/4" Pipe      Return/in
Lower                 1/4" Pipe      Cooler feed/out

TH200C Metric, 2004R
Fitting Location     Thread Size   Flow Direction
Upper                 1/4" Pipe      Cooler feed/out
Lower                 1/4" Pipe      Return/in

TH350, TH250
Fitting Location     Thread Size   Flow Direction
Upper                 1/8" Pipe      Return/in
Lower                 1/8" Pipe      Cooler feed/out

TH400
Fitting Location     Thread Size   Flow Direction
Upper                 1/4" Pipe      Return/in
Lower                 1/4" Pipe      Cooler feed/out

700R4/4L60/4L60E/4L65E
Fitting Location     Thread Size   Flow Direction
Upper                 1/4" Pipe      Return/in
Lower                 1/4" Pipe      Cooler feed/out

4L80E (1991-1996)
Fitting Location     Thread Size   Flow Direction
Upper                 1/4" Pipe      Return/in
Lower                 1/4" Pipe      Cooler feed/out

4L80E/4L85E (1997 & later)
Fitting Location     Thread Size   Flow Direction
Rear                  1/4" Pipe      Return/in
Front                 1/4" Pipe      Cooler feed/out

Ford Transmission Cooler Fittings

C3, C4, C5, C6
Fitting Location     Thread Size   Flow Direction
Front                 1/4" Pipe      Cooler feed/out
Rear                  1/4" Pipe      Return/in

AOD
Fitting Location     Thread Size   Flow Direction
Upper                 1/4" Pipe      Cooler feed/out
Lower                 1/4" Pipe      Return/in

AODE/4R70W
Fitting Location     Thread Size   Flow Direction
Upper                 1/4" Pipe      Return/in
Lower                 1/4" Pipe      Cooler feed/out

E4OD/4R100
Fitting Location     Thread Size   Flow Direction
Front                 1/4" Pipe      Cooler feed/out
Rear                  1/4" Pipe      Return/in

Chrysler Transmission Cooler Fittings

All Torqueflite

Fitting Location     Thread Size   Flow Direction
Front                 1/8" Pipe      Cooler feed/out
Rear                  1/8" Pipe      Return/in

Note: It's not critical that the return line be used, the tranny cooler will work either way. It will just be a little more efficient on the return line.

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Copyright July 2011 Eugene Blanchard