: Anyone using a transmission cooler in their 77-92 fullsize caddies?



Fleetwood472
07-06-13, 08:10 PM
I'm working on finding the best setup with brackets and cooler for my 78 fleetwood. I'm throwing around ideas on which cooler to use. I've looked at a few different setups at the salvage yard and was thinking about using one out of a GM pickup truck that has 3/8 lines with crimped rubber hose. My plan is to pull it with the lines and cut them at the metal ends towards the chassis. Then re-flare them and use a reducer to run them down to my 5/16 lines. If anyone has any recommendations on coolers they've used or if they even have pictures of how they rigged up the brackets that would be great. I've already pulled some brackets from various GM vehicles that i'm going to modify to fit and also picked up an aftermarket cooler but it doesn't have threaded ends. It just has the barbed ends so I may end up using another one to make it as close to factory looking as possible. Thanks - Justin

deVille33
07-07-13, 09:20 AM
The use of a trans cooler helps your transmissions longevity, without question, especially when pulling one of these heavy cars, even when it is a lighter version of the heavier land yachts Cadillac manufactured earlier. I would use the cooler you found from the pick-up. A lot of Cadillac parts have an association with Chevrolet/GMC trucks. Study how the cooler was mounted to the truck. As long as the cooler is in the airstream, it will function as it was intended to.

carnut
07-07-13, 06:24 PM
And I would run it in series with the existing cooler in the radiator. You are adding more oil capacity and it works best at around engine temperature for good lubricitity and longevity of the trans internals.

Submariner409
07-07-13, 07:01 PM
If you're not doing extended heavy towing, mountain climbing, or daily autocross - don't sweat it.

The oil cooler in the radiator end tank keeps the transmission fluid right about 200 degrees +/- , which is design operating temp.

IF you have monitored fluid temperatures and find it to be above 225 on a regular basis, then consider the additional piping ........

carnut
07-07-13, 08:11 PM
I agree! If you are doing this simply because you think it best for the transmission, its a waste of time and money. You have a TH 400, probably the most reliable transmission ever made. You need the money to fill the gas tank!

cadillac_al
07-07-13, 10:22 PM
I have a trans temp gauge on my Chevy 4x4 with standard trans cooler in radiator and it never ever overheats. The only time it ever started getting hot was when it was low on fluid. I don't think a cooler is needed unless you really towed heavy trailers on a regular basis; even then the th 400 would be up to the job.

Fleetwood472
07-07-13, 10:40 PM
I'm using it on my setup because I put a switch pitch trans in it so when in high stall it has higher than normal stall speeds. This makes the trans run hotter so I wanted to add an auxilary trans cooler to my existing radiator cooler. Everything has run great but I want to make sure this trans doesn't get too hot when driving in high stall. I'll look into a trans cooler from a pickup truck. If anyone is running one and has pics it would be awesome if they could post up some pictures so I can get some ideas for my setup. Thanks.

csbuckn
07-07-13, 11:49 PM
We used one off a 9C1 box caprice once and just used zip ties though the radiator. Didnt look good but we had no problems with it.

cadillac_al
07-08-13, 06:27 PM
The trans cooler in the truck is just like the Cadillac, inside the radiator. You should buy a trans temp gauge if you are concerned about the heat. The switch pitch isn't in high stall long enough to heat up the trans in my opinion. Those switch pitches were every bit as reliable as any other th400. I sure miss those, that was a nice set up.

Fleetwood472
07-09-13, 01:51 AM
I just figured i'd add it to be safe. I have Bruce Roe's Switch Pitch controller also and it runs great.

carnut
07-11-13, 12:58 PM
The switch pitch was invented to lessen creep at a stop sign and allow a lower curb idle setting. It would change the pitch of the vanes within the torque converter at idle and not creep forward as much in gear. A small micro switch was on the throttle linkage to switch back to a conventional torque converter vane angle at a designed throttle opening. So, there is no more heat generated while driving simply because it has a switch pitch converter! Because the vanes allowed more slippage ( heat) at idle the fluid temp would be warmer at idle than as driven.

Aztec ETC ECS
07-12-13, 04:30 PM
I have an external cooler only without going through the rad in my BIG Olds w/600HP 455, TH400 & 4000 stall 10" converter.
Fluid stays cherry red. I've never seen a 400 run too cool.
Use the largest that can fit by itself. I've done it in many cars. It will also keep the trans heat out of the engine coolant & prevent coolant/trans fluid mixing in case of rupture (not common in these cars but possible).

Fleetwood472
07-12-13, 11:15 PM
Like I said i'm using Bruce Roe's Digital controller. It goes into high stall more than just at idle. It monitors throttle position, if the brakes are on, and engine vacuum. I'm not using the stock microswitch on mine. Things can heat up a lot at idle. Even in a stock 65-57 cadillac it was used in more than just idle being stopped at a red light. It's a torque multipler when in high stall which in improves fuel economy at lower speeds. Plus I can pick up a nice used cooler from the junkyard for 10 bucks so it's not a big deal to me. I know plenty about the TH400 and how strong it is. No matter how strong it is you can kill it once the seals blow which can happen prematurely due to excessive heat. I've rebuilt mine completely. It's a TH400 from a 1970 deville with a short shaft tail I put on it. I modified the forward drum for 6 clutchess the intermediate for 4 clutch packs using a 4L80E piston and i'm using 6 clutches on my direct drum with a 32 element sprag. I'm also using the cast iron rings instead of teflon for a higher tolerance to heat. Still i'm not taking a chance overheating the trans and trashing the seals in the drums. My question wasn't should I run the cooler it was if anyone had any examples of them in their fullsize Cadillacs. I'm just looking for mockup ideas. Another thing is the earlier TH400's had 3/8" cooler lines vs the later ones that use 5/16" lines. Pushing a 2.28 rear in high stall will build heat too.


The switch pitch was invented to lessen creep at a stop sign and allow a lower curb idle setting. It would change the pitch of the vanes within the torque converter at idle and not creep forward as much in gear. A small micro switch was on the throttle linkage to switch back to a conventional torque converter vane angle at a designed throttle opening. So, there is no more heat generated while driving simply because it has a switch pitch converter! Because the vanes allowed more slippage ( heat) at idle the fluid temp would be warmer at idle than as driven.