I know there are a million postings for leaky transmissions and I have read them all but I need some opinions. I have a four speed muncie in my 69 which seems to leak slightly (size of tennis ball) when parked. Its never been rebuilt, functions fine and holds the fluid level pretty well. I looked underneath at the tranny and the whole thing looks "wet".

Should I just keep checking the fluid once a year and drive? or should I have the tranny pulled and the seals replaced?

 

I have three Muncie cars and two of them leak. I think mine are leaking in the input shaft area.

Siphon some of the fluid to where it's about a 1/2" shy of the fill plug. You can test with your pinky finger.

This helps a lot.

 

A common leak source is at the tranny front and from the counter shaft (below the input shaft) on the bell-housing mating surface. If this is the source, it is an easy fix to stop. Find an o-ring about the diameter of the countershaft and a diameter that will fit into the groove that surrounds the shaft. You will more than likely need to snip the o-ring and cut to fit exactly in the groove around the circumference. Keep the cut part on the top side of the groove. After dropping the fluid level below the countershaft, clean the area around the shaft thoroughly with lacquer thinner. After it dries, use some black silicone sealer and lay a thin bead around the groove circumference. Place the clean o-ring into the silicone beaded groove, cut end up. Slide the trans back into position and tighten the four trans bolts. This will draw the trans tight against the bellhousing and compress and expand the o-ring. Bring the trans fluid level back to normal. This has sealed mine and completely sealed the leak. Of course, the leak has to be from the countershaft to work, but there it is...a simple fix. Good luck!

 

Mine stays wet too, but it's from the rear plate between the rear housing and the main case. I just check it refill as needed and drive. Next time I pull the tranny I'll fix it maybe. I think I've added maybe 2 tablespoons over that last 2 years. Not even a ull shot from my 90 gear oil pump.

 

Red69, I've used straight RTV around the perimeter of the countershaft. You have an interesting idea. What exactly did you use to as an "o-ring gasket".

Perhaps we could go into business.

 

Just an ordinary rubber o-ring with a tube diameter that fit into the countershaft groove. You won't find one the exact diameter to fit the grove, so you cut a larger one to fit. Keep the cut ends on the top when it is placed. Set it in a little silicone sealer and immediately bolt the trans to the bellhousing and presto....stopped leak. I've had the ocassion to pull this tranny to replace the clutch. In doing so, I observed the rubber o-ring and silicone sealer to form a beautiful gasket that I peeled off. Once cured under pressure between the trans and bellhousing, it makes a reliable seal against a leak in this area. I needed to reseal with a fresh o-ring and sealer to produce the same result after new clutch was installed. It reaslly is a simple fix and cost way more in time than materials. Be sure to lower the fluid level below the shaft, or tilt the trans, keep a plug in the tailshaft if you do this. Clean the area well with lacquer thinner or similar before applying the sealer.

Some readers might be thinking, all you need to do is stake the countershaft with a punch around the perimeter. That was tried and a waste of time in my case. One could spend a few hundred dollars to replace the counter shaft bushing, but not necessary if it isn't sloppy. This is worth a try if you are on a budget and motivated to stop that leak.