Th400 Oil Cooler Line Maximum Pressure

Hi, after reading all the recommendations and info on this site I decided to put in an aux transmission cooler. I decided to install the cooler in series after the stock radiator cooler to help with warming up the trans on the colder days. I followed the recommendations here and used AN 8 and replaced all my stock hard lines. Too be safe I also decided to tee in a pressure gauge on the oil cooler feed line (bottom line) as close to the trany as I could get. What is considered the normal operating pressure range for a TH400 oil cooler lines? I am concern as I have read about TH400’s blowing thrust bearings when the pressures in the T/C are too high. I understand that the oil cooler pressure can be an indicator of the T/C pressure as directly measuring the T/C pressure is difficult.

I am seeing 75psi in park/neutral/drive when cold.

40-50psi in park/neutral/drive when hot, (approximately 180F oil temp)

80psi in LO 1 & LO 2 when hot, (approximately 180F oil temp)

Can get to 100psi in reverse if I hold the brake and rev the engine to stall speed.

I also measured the trany main line pressure and they seem good to me. What I get is 185psi in LO 1 & LO 2. Typically sits at 80psi in drive cruising in 3rd.

After this I was concerned the aux cooler was the problem so I unhooked it and just used the stock rad cooler. Pressures did not change.

Does anyone know what is considered normal and what the maximum cooler line pressure is before thrust bearing issue could occur? I have a small block 350 in front of trans. Approx. 2700-2800 stall.
 
You don't want more than 110 psi Line pressure in a Turbo 400 continuous driving.
Drag Racing sometimes raised to 130-160 psi for 2000hp to 5000 Hp.
Yes they can be pushed that far Custom Turbo 400 Builds. No other Automatic is stronger .

The clutches and Steels are huge compared to all other transmissions.
Much more surface holding area.

If this 1974 Corvette TH400 Trans is stock its best to look in the Original GM 1974 Corvette Service manual to get exact pressure range they used .
It varies by application.
Some were meant for Heavy Duty Drag Race from factory.
Others Towing duty.
Others Land Yahts with 450+ ci V8 engines.

I don't have the service manual for your 1974 Corvette.
It's about right correct from memory.

With Trans Apart the Front pump regulates cooler line pressures with a factory drilled orfice.
It's this office that gets resized for Drag Race Use.
 
the answer was in several previously posted sub links,
but here I posted in more obviously

https://www.monstertransmission.com/Transmission-Line-Pressures_ep_201-1.html

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The Monster Heavy Duty TH400 Is ok to look at.
Means thier budget TH400 for up to 600Hp street and towing duty to me.
They bumped up to 120psi.

They all do thier own stuff each Turbo 400 builder.
No 2 are the same from any builders.
 
I can look in my 1970 Pontiac Service Manual later.
1970 RAIV CODE PQ.
It's the Ultimate Pontiac TH400 ever built stock. And super rare now to find.
 
Thanks guys I have come across the main line pressures chart before, what I can't find is what are normal and maximum pressures for the trans oil cooler lines as this pressure can be an indicator of the T/C pressure. I am concern that the T/C pressure might be to high and I don't want to have any engine thrust bearing issues.
 
Thanks Maniacmechanic1, I just re-read your first post, the 110psi you mentioned was that the cooler line pressure? If so I would assume in forward gears? Yes it is a 74 vet trans. I don't have a service manual but I should probably get one. I am interested in seeing what your Pontiac manual might say.
 
Thanks Maniacmechanic1, I just re-read your first post, the 110psi you mentioned was that the cooler line pressure? If so I would assume in forward gears? Yes it is a 74 vet trans. I don't have a service manual but I should probably get one. I am interested in seeing what your Pontiac manual might say.
I will take a picture with my cellphone today and post.
Can not go by it exact.
GM custom tailored every TH 400 for each application.
 
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