Leak from seal at the back of TH700 Raptor
 

I bought a TH700R4 transmission from PATC (Raptor stage III with upgrade) few years ago but is has only been used for around 200 miles.

I have been having a problem from the start, if I give the engine some gas, some transmission fluid seemst to get out of the transmission at the rear. I have changed the seal but the leak does not change.

The Y-pipe is just under there so I alwais have a huge cloud of smoke when that happens. If I stop (but dont shut down the engina) there is a smoke for some time afterwards.

If I am just driving normally or have been and stop there is no smoke (at least so small that I dont notice it).

Should there be a pressure at the rear of the trans and what can I do to get rid of this problem?

Jon H.

P.s. I contacted PATC and told them I was only looking for solution (not a warranty issue) but it seems like they have no interests in helping me at all (I paid $2500 for this transmission so I though I deserved to get at least some help) and the tech support guy was not helpfull at all.

Re: Leak from seal at the back of TH700 Raptor
 

Make sure the drive shaft yoke is not worn where the tail shaft seal rides. There shouldn't be any fluid under pressure back there AFAIK.

There's also a bushing in the tail shaft housing that the drive shaft yoke rides in (it's behind the seal). I wouldn't expect this bushing to be worn out in 200 miles but you should check it anyway.

Some drive shaft yokes have a kind of vent hole in them, in-line with the transmission output shaft. You can see the hole if you look between the universal joint on the transmission side of the yoke. Fluid is known to leak out of this hole. This hole is sealed with an o-ring that fits around the transmission output shaft. To access this o-ring requires the tail shaft housing to be removed. Some people just seal the hole in the yoke with a glob of silicon sealer. There is also a "band-aid" seal kit that fits inside the yoke.

http://www.teckpak.com/lpgm.cfm?id=KT3507&type=L

I can't comment on how effective this seal kit is.

Re: Leak from seal at the back of TH700 Raptor
 

Thanks, I will look into this :)