Transmission / Overdrive: leaking seals

[Ron Dame]

Sometimes the simplest jobs frustrate me.

When I rebuilt the transmission, I installed a Redi-Sleeve on the output flange because the surface was pitted and grooved. A new National seal was installed. While looking at the driveshaft last night, I noticed it was dripping from the seal. A month ago, I installed a new pinion seal on the differential because it was leaking. I polished the flange, but there were no grooves or pits. It's still leaking as well.

I was very careful to make sure the lips on the seals were not rolled under, the flange surfaces were lubricated, and I used a block of wood and light taps to seat the seals so as not to distort the metal part of the seals. Come to think of it, the seal for the overdrive solenoid (new) is dripping as well. What on earth am I doing wrong to screw up three simple seal replacements?

[StudeRich]

What Transmission do you have? Is it the T-85 3 Speed Overdrive, for which NO Seal is available?

[Ron Dame]

T-90 overdrive.

[JohnM15]

Sometimes the leak can be from where the seal mounts to the case. I clean both the seal and the case with denatured alcohol and apply a thin coat of high temperature silicon (RTV) adhesive to the seal or that before mounting the seal.

[Neal in NM]

Check your runout. If the shaft is not running true it will wear the seal unevenly and prematurely fail. Neal

[radiotech]

In addition to what Neal said in post #5, the bushing in the tail shaft of the trans could be worn causing the yoke to 'flop around' in the rear of the trans and tear up a new seal.

[Dwain G.]

The backside of most seals has a spring-like tensioner to keep the seal lip tight against the shaft it supposed to be sealing. During new seal installation that spring can be knocked out of its groove. Pack the backside of seals with a light grease to prevent this.

[Ron Dame]

The seal was installed with thread sealant, since my tube of RTV had dried up. I posted yesterday, but it's not shown up yet, that I don't recall a bushing in the back of this trans (maybe I forgot already) but the rear bearing in the overdrive was replaced. In either case, the shaft has no movement. I will check the runout of the yoke though. I would be surprised that I had bent shafts and or excess runout in both the transmission and the diff though...stranger things have happened.

In addition to what Neal said in post #5, the bushing in the tail shaft of the trans could be worn causing the yoke to 'flop around' in the rear of the trans and tear up a new seal.

[Ron Dame]

Next time I'll try that. I was careful, but who knows what happens once that side it out of sight.

The backside of most seals has a spring-like tensioner to keep the seal lip tight against the shaft it supposed to be sealing. During new seal installation that spring can be knocked out of its groove. Pack the backside of seals with a light grease to prevent this.

[JoeHall]

Unless it is puddling overnight, I'd leave those seals alone. Studes are like old Harleys, they only stop leakin when they are out of oil. The Shop Manual Lube Order says to check the tranny & rear end oil every 1000 miles, so they were aware of some leakage. Mine all leak from the same seals as yours, and I check them every 5000 miles. They seldom need more than a few onces to top up. The standards as to what constituted a leak were different 50 yeares ago.