what would be causing the pressure loss

[77 cruiser]

I put a guage in the car tonight and drove it. The pressure was at 220 thru 1st did a blip on the 1-2 and at about 4000 rpm it dropped to 170 and didn`t recover. After the rpm is up to 4000 or more in any gear except 1st press drops to about 170. It didn`t lose press in park with TV maxed and rpm up to 4500. The fluid is a 1/2 quart + overfull. Any oter tests I should do before going into surgery.

BTW Is this and the no 3-4 at WOT have anything to do with each other?

Thanks
Jim

 

[MeanBuicks]

Sounds like you may have a leak in the second gear circuit somewhere. What does it do in Reverse and Manual Low/Manual Second?

 

[77 cruiser]

I was afraid it wasn`t going to be easy. I think man. 2nd was down a bit too. Lo was OK. Where do I start looking? Prolly drop the VB or what?

Jim

 

[MeanBuicks]

I'd start by pulling the second-gear servo from the side and examining the pistons and seals. If you don't see anything there, pull the pan and look at the 1-2 accumulator housing and piston. (It's the aluminum housing under the pointed section of the pan.)

If you still don't see potential problem, yank the valve body for inspection. Take a good look at the VB gaskets as well to be sure they haven't failed.

 

[77 cruiser]

Thanks Greg I`ll take a look.

Jim

 

[77 cruiser]

pressure retest

Did another press. test on jack stands. Press seems to drop the most in D about 50 pounds loss. In 2nd maybe 20 pounds loss. When I put it on the stands I pulled the TV out to max and run it up thru the gears, it seems to take a few seconds for it to drop.

Jim

 

[87GN_70GS]

My guess is the pump slide primer spring, seeing as how it's rpm related. Best thing to do is replace the whole pump.

 

[77 cruiser]

That`s not the news iI really wanted to hear, but thanks.

Jim

 

[77 cruiser]

I think the prob. is fixed for now, I`m not really sure what it was.
I flat sanded the accum. housing, (it didn`t look bad a few spots maybe high)
Put in a new filter & put in 8 quarts 424 (old filter only had about 3000 miles on it, but maybe it was bad) or
My one guess was the fluid was foaming(thats only a guess)
If it hangs in there for a couple more months I`ll pull the pump & look at that.

Thank for the replies.
Jim