Ttalk Tech

Gearbox Rear Seal Modification

(Please note: the text below is taken from emails received from Jeff)

by Jeff Brown

I have been doing a thing--I guess you call it a fix--on the transmissions I have rebuilt; we machine out the rear of the rear gear case, where that boss is that faces the flange, and install a modern-day oil seal there, so that there is a second means of preventing leaks out thru the back of the gear case.  If you are interested in having some digital pictures of T Talk, I can take some and send them along, with the oil seal part number needed.  It is yet another way of preventing oil leaks!

I have to tell you that we rev this engine (an XPEG steel-sleeved, with forged crank, Carillo rods, Arias pistons, an aluminum flywheel, Chevy intake/exhaust valves, tighter valve springs... and more), to around 8,000 for short bursts, so I'm assuming that poor felt seal cannot take that kind of abuse!  The conventional seal just seems like a slight bit of insurance! 

I think the photos are really self explanatory.  Like you said, I do not think this mod is necessarily right for every street-going TD, but since I have fought a rear gear case leak in my vintage racer for several years now, we figured this might help cure that problem.  Note that we do still use the felt washer, in addition to this modern-day oil seal!

Rundown picture by picture:


 P5170011.jpg:  Shows the rear gear case boss machined to take a modern-day oil seal.  Yes, I know after machining that you're thinking that the structural integrity of that area of the gear case might, just might, be compromised, but I assure you that I have the dyno sheets to show a little over 135 BHP goes thru this gearbox!

P5170012.jpg:  This is the oil seal (from the local Carquest store, stock #710070) we use.

P5170014.jpg:  Here is the oil seal installed into the machined rear gear case boss.

P5170013.jpg:  Make certain that the machinist turns the shaft of the flange to fit the oil seal!

P5170015.jpg:  Here is how it all looks assembled!  Note that since I had to stand the rear case on its end in order to photograph it (not very well...let me know if you need me to re-take this shot), the flange has actually dropped down into the rear case more than it would normally be, if it were installed onto the rear of the mainshaft... In other words, the flange is too close to the rear gear case doesn't normally fit this closely.