I have a leak in my transmission that is coming from the speedometer sensor in my 915 transmission. I have the style in the pic because its been flipped for a 914. It was fine on the bench but starting doing this once I got it installed in the car. Currently the back end of the car is up so its tilted down towards the bell housing. I'm now on the hunt for a new o-ring (the ones I had were too thick) in hopes that stops it but was wondering about putting some gasket sealer on it as well for added protection. Any other ideas on this? I just replaced all other seals on this transmission and want to get this one stopped too.

Click to view attachment

Anyone have any thoughts on this?

Well,
I suspect it's a issue similar to the one we made the cable drive bushings for. We added an extra o ring to help seal it. I do have a selection of viton o-rings, what size do you need?

The green one on the left is the one that came off the sensor. I didn't have any luck at auto parts stores but found the black one in the plumbing department at Home Depot. Its dimensions are 9/16" O.D x 7/16" I.D. x 1/16" but could not get the sensor to push into the transmission case when using it. The green one looks like it is just slightly thinner and I guess that makes all the difference in the world.Click to view attachment