1991 GMC 1500 atf leak

Tiny
1991 GMC SIERRA
  • MEMBER
  • 1991 GMC C1500
My 1991 GMC sierra 1500 2wd 350ci developed an atf leak behind the flywheel cover 2 years ago. When driving, it would suddenly dump fluid out creating an oil slick on the undercarrige and up the tailgate. I just had the 700r4 tran rebuilt with the master rebuild kit/seals and a new torque converter. I was told that the pump looked good, ie no scoring on the input bushing.
After re-installing the transmission, it ran fine with no visible leaking for 55 miles, over the course of 3 days and 3 start-stop cycles. On the 3rd day, I noticed that part of the pan was wet, and there were drips from the flywheel cover pinhole.
I checked the level of the fluid to find that it read 3/4" above the full mark.(I was very careful when re-filling however having only put a total of 11 1/2 quarts total into the trans) Despite having my doubts that the trans was overfull, I lowered the pan and drained about 1 quart. After letting it cool overnight, I drove it up the street about 2 miles when it started smoking(dumping fluid over the hot exhaust) I looked under the truck to find a half/dollar size puddle forming at a rate of a drip per second.
The leak seems to be behaving exactly the same as it did before the rebuild.
I dropped the flywheel cover and located the drip to be coming from the seal at the torque converter input to the pump. Could a new seal be leaking? Could the pump be bad even though it passed a visual check?
My truck has 145000 miles, but the trans was new 100000 miles ago.
The fluid I'm using is pensiol ATF "for vehicles formerly serviceable by mercon/dextron atf"
I also put a bottle of Lucas trans in with my atf.
What should I look for now?
I'm sure its not leaking from the pan, and nothing was found in the pan. The fluid is dripping from the tab surrounding the torque converter seal.
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Tuesday, October 23rd, 2007 AT 6:06 PM

2 Replies

Tiny
MERLIN2021
  • EXPERT
Are you sure it's not leaking from the pan?If a pressure test was not done a worn seal that looks good to the naked eye, can be worn enough to leak! When you dropped the pan, you did'nt find a spring in the shapr of a circle did you?
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Tuesday, October 23rd, 2007 AT 6:18 PM
Tiny
1991 GMC SIERRA
  • MEMBER
Im sure it is not coming from the pan. All gaskets are new except for the pump. I was told that there is no replacement bushing or seal for the pump without buying a new pump.
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Tuesday, October 23rd, 2007 AT 6:35 PM

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