C4 Mainshaft leak

[bcgofo]

Guys, I noticed a significant leak coming from the front seal on the C4 (or OC4) gearbox. I pulled the cover and sure enough the seal is bad. Mainshaft bearing is in great shape. Easy fix.

Question I have relates to the amount of play, specifically pistoning of the shaft is within spec. I appears that the shaft is recessed enough that the seal was “sealing” on the splined portion of the shaft rather than the smooth part.

I was able to pull the shaft out (with a little persuasion) about a half inch before it wanted to pull the bearing. When looking through the fill hole on top of the gearbox, no movement of the gears was seen when pulling shaft “back out.” Everything still shifts fine and normally.

This position would allow the seal to interface with the smooth part of the Mainshaft. What would keep this from simply working its way back in and ruining the new seal (since it’d be back on the splined part of the shaft)?

 

[bcgofo]

Here’s pics of the 2 conditions: pressed fully in and pulled out

 

[bcgofo]

Part #2 shows mainshaft locating snap ring. Seems this may only prevent pullout?

I’ve had the cover off gearbox a few times already, hoping to not have to again.

 

[Snowcat Pat]

If you orient the box on end (shafts up vertical) you can pull the input shaft straight out with the front bearing and snap ring (if its there). Don't move any of the gears while its out and it will go back in with ease. You can see what might be wrong with the shaft when its in your hands.
-Pat

 

[bcgofo]

Just wanted to close the loop here. I was able to press the new seal deeper into the cover plate, basically right against the main shaft bearing. This seems to keep it from articulating with the splines of the main shaft. After driving a bit, everything seems to be staying put and no leaks.

 

[turbinator62]

That's what I did. I got a new seal from Snowcat Pat, and machined an install tool from Delrin to install it deeper so it doesn't contact the spline. My Trans hasn't leaked a drop in 9 years.