Max 200 PSI + 50 PSI drop when hot

[DorianL]

Hi All,

It has been a while. I was installing a new adjustable TV bracket and decided to do a pressure test.

at 1500 rpm, my pressures look normal. At full TV, All my pressures seem to max out at 200 PSI. I remember reading 240 the first time I installed the trans.

Also, but this is probably normal when cruising my PS drops 50 PSI once the trans is hot.

Dropped the pan - the oil looks fine and smell grrrrreat as the tiger said.

One last thing, my last race I did find a loose bolt in the VB. Shifter side the last one in the rear. It was losing pressure there. I am guessing the leak might have affected the gasket which I am going to replace.

Thanks fer any thoughts,

D

 

[Alky V6]

There shouldn't be any pressure drop between cold and hot.

 

[DorianL]

Thanks...

Hmmmmmm

 

[DorianL]

Grmbl

well, I am quite sure I found the problem. I dropped my trans yet again... if we are counting, that is 8.

The inside faces of both halves of the body are slightly grooved. I compared it to an older pump I had and the faces are clearly smoother than this one.

That would presumably explain the in ability of this pump trans to reach more than 200 PSI and for the idle PSI to drop when hot.

According to my searches on the forum, the kind of damage can come from over tightening the pump bolts. That seems about right, I was surprised how much more torque it took me to loosen the bolts on the damaged pump. Hmpf - that pump has less than 2000 miles on it.

Anyway, I am sending it to be rebuilt here.

More later...

D

 

[Alky V6]

Eight! My gosh. You have the patience of an elephant.

 

[DorianL]

Thanks- what can I say... once you have an overdrive it is hard to go back. That and (re)building something like this in Belgium yer on yer own!

 

[DorianL]

And here is my 18-inch garage

 

[Alky V6]

I pray you use jackstands in the rear too.

The car looks very nice.

 

[chris718]

My testing has proven that even with a brand new pump the pressure will drop at least 25 psi between hot and cold.Some new pump only 15.I use new pumps on every job and have verified this.Anyone doing in car testing should be able to verify this.This is due to oil viscosity.Slight scoring of the pump pocket doesnt cause a 50 psi drop either .The transgo or sealed power pump rings always cause minimal pump scoring especially with large boost valves and heavy pr springs.

 

[Alky V6]

My testing has proven that even with a brand new pump the pressure will drop at least 25 psi between hot and cold.Some new pump only 15.I use new pumps on every job and have verified this.Anyone doing in car testing should be able to verify this.This is due to oil viscosity.Slight scoring of the pump pocket doesnt cause a 50 psi drop either .The transgo or sealed power pump rings always cause minimal pump scoring especially with large boost valves and heavy pr springs.

I agree with you Chris. I don't think the slight amount of normal wear that's commonly found in the pocket is going to be his main problem. Unfortunately, I predict the number will be higher than eight.

 

[77 cruiser]

Weak pump slide spring maybe?

 

[Alky V6]

Weak pump slide spring maybe?

I've never come across a weak pump slide spring. I think it would cause low line overall. Not just a hot/cold condition.

 

[DorianL]

Thanks fer compliment on car and there are red -see part of foot next to tire- jackstands under the rear.

Number will be higher than 8? Yeeesh!!!

As I say, there is some grooving on both faces... much less than there was on other used pump that I have. Again there must be only 2000 miles on this pump and those bolts seemed to be too tight on there. It used to see 240, now I am happy to get 200.

Could this kind of wear produce low max TV pressure, <200 ? Should I be looking elsewhere other than the pump for low pressure? I really am not in the mood for 9 drops.

Could something somewhere else in the case or the VB do this... pressure maxing out at 180? The rebuild shop here is supposed to be very good. I am expecting the guy to fix all issues in the pump.

 

[DorianL]

Again - if you guys think there could be another source for this pressure drop external to the pump... I am a listener.

I just called up the trans shop here. They can rebuild and/or replace the pump. I'll drop off my pump tomorrow. I'll ask them to check the condition of my valves. If possible, it would be nice if they could dyno test.

 

[Yedi]

Here's my experience I've had w/ pressure problems. I had my pressure regulator spring go on me 2 times ( it broke, found pieces in the pan, and in the pump) ) That caused my pressures only to only go so high @ Full TV, still shifted good, but made a whinning noise, and the pressures on the gauge were down.


I give you credit, I've only had my Current transmission out 3 times, all fairly close together, it gets VERY frustrating, but like you said it's hard to go back to a Non-Overdrive....

But, If this happens again this summer, I don't know what I'll do, I built the car to drive, not be on Jack stands for the summer....

 

[DorianL]

I hear ya!

One more bump - other than the pump, are there any other possible sources of low pressure? Again - since I have the trans out...

The pump is grooved. I used to get up to 280 in R and 240 in D. Now across the board I get 180.

No other thoughts?

 

[quickt]

I've never come across a weak pump slide spring. I think it would cause low line overall. Not just a hot/cold condition.

Been there done this. Had one that was 250-260 testing. Drive car as RPM goes up, pressure would fall to around 200. Pump slide spring was the problem. I have also seen about 10-15 psi drops hot.

 

[Alky V6]

Been there done this. Had one that was 250-260 testing. Drive car as RPM goes up, pressure would fall to around 200. Pump slide spring was the problem. I have also seen about 10-15 psi drops hot.

Was this a temperature related condition?

 

[DorianL]

Just came back from the Trans repair shop. I doesn't think that the wear is significant enough to lose 70+ PSI.

He think it might be something in the VB. He said the most common issue is the Acuator Feed Limit valve. As far as I know 200-4R's don't have these.

This leaves me in a pickle... put back together the pump and look for issues in the VB.

BTW - he vacuum tests the circuits. 10 inches acceptable 20+ very good.

 

[DorianL]

Ok... NEWS

I discarded the local trans shop's advice. Basically, I was not satfsified with the answer the my pump was not worn enough to result in such a pressure drop and that the VB should be checked.

I came to this conclusion by examining two other pumps I have: the wear seemed minimal there.

After chatting with Bruce, I ordered a pump from PTS. Aaaaaaand, drum roll please...

The pressure shot up... easily to the HIGH 200s PSI.

I guess we can safely say that it was the pump and not the VB. I'll be tuning over the weekend but so far, I can feel that things have definitely changed.

THANKS BRUCE!!!!!

D.

What I don't understand tho is how I can lose a pump with only 1000 miles on it.