Im working on a friends powerglide out of his s/c dragster, it worked fine one weekend and then at the next race, unloaded out of the trailer and nothing works. He puts in his spare trans and same converter and all is good. I've torn down the bad trans and see nothing wrong, with any of the internals. I start looking at the hydraulic systems, take the front pump apart and find the priming valve stuck in the open position. After some effort I get the valve out, spring is not broken. I polish up the piston and have it moving freely in the bore. Question is this, would this being stuck open, cause no pressure in the trans, if not what else should I be looking for?
Originally posted by topfuel: Im working on a friends powerglide out of his s/c dragster, it worked fine one weekend and then at the next race, unloaded out of the trailer and nothing works.
This sounds like a pressure regulator valve stuck. We had one do the same thing. Qualified in a heads up class on Saturday night, got up the next morning to race and the pressure guage on the dash reads zero, nothing.
They have been know to stick open. Caused NO pressure. Dead Trans.Some do the 3/16 pin deal. Some do the tap/flip the valve around/pipe plug deal. Total elimination.
Posts: 1421 | Location: Under a Truck | Registered: August 23, 2013
I have the priming valve issue solved, but we don't have the trans back together yet, to verify the pressure issue is solved. After watching some FTI video, and talking with other trans experts, I'm convinced this was not the root cause for no pressure. I will be looking at the pressure regulator in the valve body today. We already went down the Hughes convertor and input shaft investigation, and ruled that out. I appreciate the reply's we have got so far, this forum has a wealth of knowledge. When I find the smoking gun, I'll post up the results.
Kinda of thinking the same thing. On the BV's the sleeve wears from constant oscillation, therefore reduces line pressure. There are different size boost valves. Also see what color spring is in it. Mine has the.489 valve in it with the white spring. And at 265 Psi. But that just me.
Posts: 1421 | Location: Under a Truck | Registered: August 23, 2013
TD3550 thanks for that input, this BV is .445 and has two yellow springs (spring inside a spring)I don't know if this is good or not. One thing I noticed when removing the BV snap ring, the pistons would not come out of the bore. Once I started unbolting the two halves of the vale body, it popped out on it's own, makes me think the valve body when torqued together is distorting the bore. When I took the pressure regulator snap ring off, all the pistons and springs came right out.
Originally posted by topfuel: TD3550 thanks for that input, this BV is .445 and has two yellow springs (spring inside a spring)I don't know if this is good or not. One thing I noticed when removing the BV snap ring, the pistons would not come out of the bore. Once I started unbolting the two halves of the vale body, it popped out on it's own, makes me think the valve body when torqued together is distorting the bore. When I took the pressure regulator snap ring off, all the pistons and springs came right out.
Install the Coan adjustable pressure regulator I gave you a link to on FB, It solved allot of problems for me.
Posts: 2556 | Location: Moving back to the door side | Registered: April 30, 2010
Big Steve, thanks for the link, I looked at it. It's not my stuff I'm working on, a new valve body may be in the equation with the adjustable regulator option.
Originally posted by topfuel: TD3550 thanks for that input, this BV is .445 and has two yellow springs (spring inside a spring)I don't know if this is good or not. One thing I noticed when removing the BV snap ring, the pistons would not come out of the bore. Once I started unbolting the two halves of the vale body, it popped out on it's own, makes me think the valve body when torqued together is distorting the bore. When I took the pressure regulator snap ring off, all the pistons and springs came right out.
The first valve in (PR)must float. Stand the VB on end, hole up.Drop the actual PR valve in. With a magnet, pull up on the valve, pull magnet, Valve must freely drop on it's own with no restrictions to the bottom. If it hangs, check the bore for burs.Finish boost valve assembly. The sleeve will be the last component in followed by the clip.The sleeve removal will be tight until you split the halves in a lot of cases. Like you stated above. Sounds line an older VB. Non pro brake.Sometimes it's just better to update. Food for thought. With a Pro brake application, single spring. It's a mother to get the last clip in. lol
Posts: 1421 | Location: Under a Truck | Registered: August 23, 2013
TD3550 thanks again for the response. I've been out in the garage all afternoon polishing all the valves/pistons and cleaning the valve body bores. I have to admit in my earlier post I misidentified the Boost Valve in the valve body. I've since learned the Pressure Regulator (PR)valve and Boost Valve (BV)are located in the same bore, separated by a large spring. You mentioned a white spring, I checked Sonnax website and don't see any offerings, they do have the oversized BV. This is and older TCI Pro tree valve body, probably 20 years or older. I've spoken to the owner about possible updating the VB.
Don't know what kind of power you're working with but this is all the spring you need 2500hp. We put 125 laps on a PG between service @245psi-2,000rpms 3400 lb doorslammer with 2500hp plus F3 ProCharger big chief 632. For pin bias lower than 255psi is the better option. If I was worried about pressure I'd run a ratio or Super Servo and 255psi tops. All ya need pretty much any power level.
