TH400 converter feed restriction, 3/32 or 5/64?

[Pablo]

I put a 7/64" restrictor in my trans and my cooler line feed is too high. If I loop a hose right at the trans inlet and outlet I get mid 40s but if I connect the cooler I am up to 85-90 psi on cold start up.

This after I changed to 3/8ths cooler line, and a tube and fin cooler. The stacked plate setup and stock lines would peg my 100 psi gauge.

Now I'm pretty pissed that I'm going to have to take the trans out of the car. I only want to have to do this once.

What would you suggest, going to a 3/32 restriction or down to a 5/64?

The other thing I am worried about is whether or not I have already damaged my thrust bearing from just starting it up a few times and idling for a few seconds at over 100psi cooler line pressure. Any thoughts on this?

 

[Alky V6]

7/64" should have done it for you. You can try smaller if you want, but I'd make sure you cover all the other crossleak areas that can contribute to excessive converter feed pressure first.

 

[Dusty Bradford]

I put a 7/64" restrictor in my trans and my cooler line feed is too high. If I loop a hose right at the trans inlet and outlet I get mid 40s but if I connect the cooler I am up to 85-90 psi on cold start up.

This after I changed to 3/8ths cooler line, and a tube and fin cooler. The stacked plate setup and stock lines would peg my 100 psi gauge.

Now I'm pretty pissed that I'm going to have to take the trans out of the car. I only want to have to do this once.

What would you suggest, going to a 3/32 restriction or down to a 5/64?

The other thing I am worried about is whether or not I have already damaged my thrust bearing from just starting it up a few times and idling for a few seconds at over 100psi cooler line pressure. Any thoughts on this?

I just sounds like the cooler is to restrictive if it sees that much difference between the loop and the cooler.

The thrust should be fine. It's WOT passes for long periods of time that cause the damage.

 

[Alky V6]

I just sounds like the cooler is to restrictive if it sees that much difference between the loop and the cooler.

The thrust should be fine. It's WOT passes for long periods of time that cause the damage.

It's hard for a tube and fin to be restrictive, but I guess it's possible, especially if it's used and was involved with a damaged transmission.
I've heard of the crank thrust going quickly in some cases (trip around the block). Check the crank thrust travel, and your filter. That will be your best indicators, besides pulling a cap.

 

[Alky V6]

If you don't find any other obvious sources for a crossleak, I wouldn't trust the pump and I'd change it out for another. Not worth the gamble.

 

[Dusty Bradford]

It's hard for a tube and fin to be restrictive, but I guess it's possible

I agree. It shouldn't be restrictive. But the pressure test proves that it or the fittings on the cooler are a problem.

I have personally seen the quick couplings some want to use at the trans cause a major restriction.

 

[Alky V6]

I agree. It shouldn't be restrictive. But the pressure test proves that it or the fittings on the cooler are a problem.

I have personally seen the quick couplings some want to use at the trans cause a major restriction.

If the crossleaking is on the edge, just the little bit of restriction that the cooler can present would be enough to push the gauge over acceptable limits. 45 psi with the line looped, if this is at an idle, does not sound real good to me.


I've heard the same with the fancy quick disconnect fittings, too.

 

[Pablo]

Yeah I think I might have trashed the thrust bearing already. I just measured the thrust clearance at .020

What is the downside to restricting the converter feed to acceptable pressure levels in lieu of fixing a crossleak issue?

 

[Alky V6]

Yeah I think I might have trashed the thrust bearing already. I just measured the thrust clearance at .020

What is the downside to restricting the converter feed to acceptable pressure levels in lieu of fixing a crossleak issue?

None that I can think of. But, please check the basics like no burrs or high spots on the mating surfaces holding the pump halves apart, pump gearset face clearance (.001 target), stator support bushing clearances.
Even though a stator bushing may look good, the clearance can be excessive.

If you have drilled and tapped the converter feed hole in the pump cover, make sure that you've knocked down any raised metal on the mating surface in the general area of the hole with a fine mill file. Drilling and tapping will cause the metal to rise around the hole.

 

[Pablo]

None that I can think of. But, please check the basics like no burrs or high spots on the mating surfaces holding the pump halves apart, pump gearset face clearance (.001 target), stator support bushing clearances.
Even though a stator bushing may look good, the clearance can be excessive.

If you have drilled and tapped the converter feed hole in the pump cover, make sure that you've knocked down any raised metal on the mating surface in the general area of the hole with a fine mill file. Drilling and tapping will cause the metal to rise around the hole.

I did file down the raised metal but didn't check the other stuff. I just I restricted the converter feed down to 5/64. In previous threads you've stated that as long as I get 1 qt in 20 secs im good right? And to shoot for perhaps 40 psi at stall?
I'm pretty sure I'll have close to those numbers. If I am down under 40 psi at stall should I be concerned?

I'm going to install it and see what I get.
Then I have to pull the engine and replace the thrust. Stupid girdle. The fun never ends on these cars.

btw how does one check the clearance on the stator support bushing?

 

[Alky V6]

I did file down the raised metal but didn't check the other stuff. I just I restricted the converter feed down to 5/64. In previous threads you've stated that as long as I get 1 qt in 20 secs im good right? And to shoot for perhaps 40 psi at stall?
I'm pretty sure I'll have close to those numbers. If I am down under 40 psi at stall should I be concerned?

I'm going to install it and see what I get.
Then I have to pull the engine and replace the thrust. Stupid girdle. The fun never ends on these cars.

One quart in 20 seconds is more important than the pressure.
I've restricted down to zero psi in one particular case, and still had one quart in 20 secs.

If the trans suffers from signs of lubrication problems in the rear section, then you might start thinking you need more cooler line pressure, but I sincerely believe you won't run into a problem.

Besides, I'd much rather replace a trans geartrain than have to deal with an engine thrust problem.

 

[lazaris]

Take a main line pressure read. That also effects what your feed pressure will be. If its too high it will jack up the converter feed pressure.