Thread: Transmission Cooler lines

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So the short story is that I fried a perfectly good transmission, 4L80E, in my quest to get my 37 LaSalle ready for the Goodguys show two weeks ago. Now I will replace the transmission and have some questions on keeping in cool.

I have limited options for installing the transmission cooler, but I do have a transmission cooler in the Universal radiator I am using from Speedway. I have had mixed reaction to using the tranny cooler included in the radiator. However, I have hot exhaust on one side of the car and brakes and wiring taking up much of the other side. I would have to bring lines upa nd over the transmission to put a cooler on the "cool side" of the car.

Here are my questions:
1. Should I use the integrated tranny cooler in the existing radiator?
2. Any good ideas about how to mount an external tranny cooler? Pics would be great.
3. What size line should I use? I have some long lengths of 3/8 hard line but the transmission is plumbed for 5/16. I can get adapters/fittings. Would the bigger diameter line help with cooling or create other unintended consequences?

Thank you

Originally Posted by 37 Caddy

So the short story is that I fried a perfectly good transmission, 4L80E, in my quest to get my 37 LaSalle ready for the Goodguys show two weeks ago. Now I will replace the transmission and have some questions on keeping in cool.

Here are my questions:
1. Should I use the integrated tranny cooler in the existing radiator?
2. Any good ideas about how to mount an external tranny cooler? Pics would be great.
3. What size line should I use? I have some long lengths of 3/8 hard line but the transmission is plumbed for 5/16. I can get adapters/fittings. Would the bigger diameter line help with cooling or create other unintended consequences?

Thank you

Can I ask, how did you hurt the tranny? Pulling hole shots? The reason I ask is a friend has an overdrive tranny (GM, but I think it's a 700R4) and he's been running it for 2 years now with no cooler and I'm not sure how he gets away with it!

question 1. I would and usually do. I first go through the radiator cooler then loop into a auxillary cooler set in front of the radiator.

#2, sorry - no pics, but, a simple mount from angle stock always seems to work for me.

# 3, I usually work with 3/8". The size causes no issues that I know of.

On my 34 right now I have the lines tucked along the block mounted on a bracket I made that comes off a couple base pan bolts. Hope this helps.

The tranny's demise may have come from several factors. Rather than putting a bypass loop in where the tranny cooler lines go...I just capped them. I should have freshened the tranny fluid before driving it. It may also have been damaged before I got it running.

Capping the cooler lines may have caused your problem...zero flow is bad.

Use synthetic fluid on your next build, it is worth at least 10-15 degrees.

Radiator cooler should be fine except for long cruises in low gear...the major heat source is the converter...at low speed and unlocked, it is really putting the heat into the fluid.

mike in tucson

Originally Posted by 37 Caddy

The tranny's demise may have come from several factors. Rather than putting a bypass loop in where the tranny cooler lines go...I just capped them. I should have freshened the tranny fluid before driving it. It may also have been damaged before I got it running.

Thanks for the info. My bud has a coil of tubing and I guess it acts like a cooler. Simply comes out of the trans, makes 3 or 4 loops then right back in. I'm not condoning this, just a fyi...

Get yourself a heat sink or convection style two pass cooler and mount it on the frame rail. It doesn't need to be out in the air and will work fine for your application.

Originally Posted by robot

Capping the cooler lines may have caused your problem...zero flow is bad.

Yeah, I talked to a guy at Hughes transmissions today and when I mentioned that he said, "OOHHHH, that's not good".

"Heat of stirring" (converter) is incredible.

I know of water heaters based on this principle
that furnish on demand hot water for large shower rooms.

Originally Posted by brian41chevy

Get yourself a heat sink or convection style two pass cooler and mount it on the frame rail. It doesn't need to be out in the air and will work fine for your application.

By the way--this guy is a tranny guy and knows his stuff!

I got a B&M Hi-tek cooler that has a 7" electric fan and thermo switch on board, beauty of this thing is you can mount it anywhere! I put mine between the frame rails underneath my radiator in my '59 1/2 ton and plumbed 3/8 hard line along the block - next time I will spend the time to tuck the lines into the frame rails, much cleaner...

There are some really neat 1 or 2 pass heat-sync style trans coolers, check them out at summit, here is a Derale, other vendors make them too, Moroso even has a filtered version

Obviously some cooling is better than no cooling, hot is bad. I bypassed the thermo switch on my cooler and run it full time with the engine, no problems so far

Good luck

just my opinion but i would never use a cooler in the rad, It was a cost cutting exersize by the manufactorers in my opinion, Imagine it did leak water in the trans means instant rebuild, much better to use a stand alone cooler with 3/8" pipework mounted in a good air flow or assisted with a small fan. they are not expensive are they ?
Also cooling trans fluid with hot water can't be a great idea
Cool trans fluid usually means long life

There isn't much point in a thermo switch as you can't really overcool an auto trans.

Originally Posted by gearGrinder

I got a B&M Hi-tek cooler that has a 7" electric fan and thermo switch on board, beauty of this thing is you can mount it anywhere! I put mine between the frame rails underneath my radiator in my '59 1/2 ton and plumbed 3/8 hard line along the block - next time I will spend the time to tuck the lines into the frame rails, much cleaner...

There are some really neat 1 or 2 pass heat-sync style trans coolers, check them out at summit, here is a Derale, other vendors make them too, Moroso even has a filtered version

Obviously some cooling is better than no cooling, hot is bad. I bypassed the thermo switch on my cooler and run it full time with the engine, no problems so far

Good luck

Originally Posted by roadster32

just my opinion but i would never use a cooler in the rad, It was a cost cutting exersize by the manufactorers in my opinion, Imagine it did leak water in the trans means instant rebuild, much better to use a stand alone cooler with 3/8" pipework mounted in a good air flow or assisted with a small fan. they are not expensive are they ?
Also cooling trans fluid with hot water can't be a great idea
Cool trans fluid usually means long life

Well, I've been playin' with cars for better than 30 years. I've never seen a cooler leak either into a trans or trans into a radiator. Not saying it can't just I ain't seen it yet. As far as overcooling. In some parts of New England it can get very, very cold and the heat put into the trans from the cooler can be a good thing. I have seen it when the trans won't shift right because the temp has the fluid too thick! I'm not saying my street rod will be driven when it's that cold! And that's my opinion!