240Z leaking front tranny seal

the front tranny seal on my 240Z is lasting about one to two races before it starts to leak. (more than the ocassional drip) The shaft is smooth where it contacts the seal, no burrs or grooves. (I am using a Nissan dealer seal for the repairs) I have added and extra vent on the tranny, in case I was building up too much pressure. I am running Redline MTL, so I don't think that's the case. shaft run-out is withing specs and I use a new pilot roller bearing at each change out. I have replaced the seal 3 times and a Nissan Master Tech has replaced it twice, in the last year. In the previous four years, I never had a problem with the seal. any ideas?

This is a trick that I learned when I raced a 240Z in CProd back in the good old PL Newman days. If you replace the front bearing (the bearing before the input shaft) with one that is "sealed one side" (it will have a ring seal that sits against the ball bearings), if you look up the bearing number in a timkin bearing catalogue it will be an optional choice. Since the oil can't pass the seal, the normal seal will keep all of the minor oil out. It made a world of difference cause I fought that same problem for 3 years.

Good luck
Tom Blaney
(old cat was CProd # 26)

[quote]Originally posted by js:
[B]the front tranny seal on my 240Z is lasting about one to two races before it starts to leak.

I to had mystery leak in front of tranny,I had not been replacing the paper seal of cover plate. siliconegasket sealer did the trick.
David

Couple of things here.

Make sure to run the oil level about a 1/4 of an inch from the top. The other one is to use thread sealer on the front cover bolts. Some case the threads go all the way in to the oil.
Lastly make sure the seal surface of the imput shaft is clean with no burrs and use a light film of white grease or seal glide on it during assembly. often times seals fail early because they are not properly lubed during assembly. Oh and also make sure the seal is not being snagged by the front bearing snap ring. These are all the things I have found in these gearboxes over 15 years of doing them.

thanks for all of the great ideas. I have been racing this car for 5 years, with this problem showing up in the past year. I will probably pull the tranny today to see what exactly is leaking. will post the results.

May as well throw this into the mix to. The pivot for the clutch fork is bolted into the front cover and can leak if its loose. That one got by me once but it won't happen again.