Jman69

Everytime we pull the Corvette out of the garage theres a big puddle of trans fluid on the floor. It appears to be coming from the transmission pan, we've replaced the gasket and the filter but it still keeps leaking. We tried over torquing it and under torquing it but still keeps leaking, any advice?

Jman69

On the instructions to install the filter it said that in 1986 the filters got taller so you might need to get either a bigger pan or the older filter, has anyone else had this problem?

87 vette 81 big girl

TRANSTAR USA sells a special 700R4 & 4L60E Fiber material transmission oil pan gasket.
Its pricey at around $10.00.
I used it on my 1987 C4 Vert 700R4 rebuild & blueprinting back in 2010.
10,000 miles later I have ZERO transmission fluid oil leaks from the trans pan to the main case sealing joint.
You can purchase the special TRANSTAR fiber material trans pan gasket direct yourself.
Its coated with a similar Flourestomer material like Fel- Pro Racing headgaskets are.

Brian R.

joeld

The grommet on the dip stick fill tube where it enters the transmission will get old and brittle and allow fluid to seep out. It then drips down onto the edge of the pan and looks like the pan gasket is leaking. Clean the area good and check for leaks there.

Joel

Cliff Harris

Clean the pan area thoroughly and then check to see where the trans oil is coming from.

My prediction is that it's coming from the front cover (the one with the little hole in it). The front cover doesn't seal at the bottom and it will leak there. Roughly 100% of the early 700r4s will develop a leak at the front pump seal. This is a very well known problem and it was fixed late in '87. Right now I've got a water heater leak catch pan under my car... ...and a freshly rebuilt '89 trans waiting to go in -- a present from a friend who put a ZF in his car.

One other possibility is that you've got a cork pan gasket. They ALWAYS get saturated with oil and eventually leak. Just thought of one other possibility: I've found that you need to retorque the pan bolts about 5 times before they'll finally hold their torque. The heat/cool cycles and gasket compression cause the bolts to loosen.

383vett

If the pan bolts are overtightened, the pan rail will warp and will have difficulty sealing. When the pan is off, turn it upside down and tap the raised areas around the boltholes with a block of wood supporting the pan rail from the bottom.

cadmaniac

I just changed the trans on my '86 700r4, and it leaked only when parked....a lot. Changed the pan gasket twice....still leaked.
Finally I got a mirror and a good flashlight and it was the TV Cable. I put a new o-ring and some "right Stuff" on it and it doesn't leak now. It really looked like the right front corner of the pan was leaking....


It's difficult to diagnose leaks when you can't get up in there to see where it's leaking. Take your time and diagnose it properly. It's frustrating to fix something and have it not be the problem.


Good luck.

pricesgarage

probly the kickdown cable gromet or dip stick all i use is the fiber gaskets

burnout88

If you need a really nice transmission pan gasket go with a Lubelocker. I use them all the time on my Jeep and Silverado and they are leak proof and awesome. They have a new one for a 700r4 that I am going to install next week on my 88

http://lubelocker.com/products/products/9-gm