Trans line psi low 70psi
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From: Houston TX
Trans line psi low 70psi Had trans built up lasted 2000 miles started slipping in 3rd and 4th. Took it back they changed some parts charged me 200$ and said it was fixed. Drove the car 100 miles seemed ok but soft shifting from 2nd to 3rd. Then tried flooring it while at 45mph it downshifted good but when it shifted back it flared up deep into the redline then rolled into the gear. Put gauge on it found line psi around 70-80psi while going through the gears. Car just got new 3.73 gear in the middle of all this b/s and i cant even tell its back there. Car feels weak. Car has been down with this problem since March getting fed up!!!!!!
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From: Ann Arbor, MI
First, it is good that you have a pressure gauge on the trans; that will help determine the problem.
If the line pressure stays at the same 70psi at all throttle position then you either have a very bad tune or a defective EPC (pressure control solenoid). I would start by replacing the EPC. Perhaps your local trans shop could "lend" you one - the least they should do.
Another "test" would be to remove the trans connector - this will force a "working" EPC to max pressure - 175psi+. If it stays low, the EPC is almost certainly at fault. Since the trans connector can be very difficult to remove due to tight spaces, this might not be realistic.
Ask what they did for $200; perhaps they only installed a bigger boost valve, which is a good idea, but obviously didn't fix the underlying problem. (With a stock boost valve, idle pressure is in the 50-60 range, with a bigger boost valve it is in the 70-90 range at idle.)
If the line pressure stays at the same 70psi at all throttle position then you either have a very bad tune or a defective EPC (pressure control solenoid). I would start by replacing the EPC. Perhaps your local trans shop could "lend" you one - the least they should do.
Another "test" would be to remove the trans connector - this will force a "working" EPC to max pressure - 175psi+. If it stays low, the EPC is almost certainly at fault. Since the trans connector can be very difficult to remove due to tight spaces, this might not be realistic.
Ask what they did for $200; perhaps they only installed a bigger boost valve, which is a good idea, but obviously didn't fix the underlying problem. (With a stock boost valve, idle pressure is in the 50-60 range, with a bigger boost valve it is in the 70-90 range at idle.)
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From: Houston TX
Its still on the rack at the trans shop. It burnt up the clutches for 3rd and 4th they replaced them and still slipping feel. He replaced the epc sol. and no change? Has shiftkit and blue clutches. corvette servo, next stall up from stock.
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From: Ann Arbor, MI
You are going to replace the 3/4 clutch every week with only 70psi pressure at WOT. They need to figure out why the pressure is so low. They should know that removing the trans connector will force the EPC into max line pressure (Zero current).
You mentioned shiftkit - what year is the trans? What shift kit?
A boost valve for a 2006+ trans installed into a pre-2006 trans will give extremely low pressure. Same if the "spacer" on the boost valve in the Transgo HD2 kit is left off. Perhaps also if the boost valve is very loose in its bore. (The Sonnax boost valve has o-rings to solve that.)
What is the pressure in Reverse - it should go up automatically quite a bit (even +125psi) due to the hydraulics around the boost valve.
You mentioned shiftkit - what year is the trans? What shift kit?
A boost valve for a 2006+ trans installed into a pre-2006 trans will give extremely low pressure. Same if the "spacer" on the boost valve in the Transgo HD2 kit is left off. Perhaps also if the boost valve is very loose in its bore. (The Sonnax boost valve has o-rings to solve that.)
What is the pressure in Reverse - it should go up automatically quite a bit (even +125psi) due to the hydraulics around the boost valve.
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From: Houston TX
Not sure about ps in reverse. I will find out monday more info. The trans that i had blew up last year input shaft snapped. So i got a trans was told it was out of a 98 ss. It was burnt up but the trans guy said he could use the case. So i got the next size up tq converter too.
Then it made it 2000 miles and 3rd and 4th started slipping. I took it back and 2-3 flares in the redline. trans go kit with sunshell upgrade, shaft sleeve. This guy has been doing my transmissions for 20 years first time i had one mess up.
Then it made it 2000 miles and 3rd and 4th started slipping. I took it back and 2-3 flares in the redline. trans go kit with sunshell upgrade, shaft sleeve. This guy has been doing my transmissions for 20 years first time i had one mess up.
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From: Ann Arbor, MI