Rear transmission leak

My '69 SII OTS has developed a leak around the rear transmission flange (tail shaft?). This has started after about 20 minutes of driving after a total engine rebuild and seal replacement on the transmission. The leak is considerable, not a flow but many drops over a short time period.

Today, I dropped the IRS and backed out the drive shaft so I could remove the tail flange and seal retaining ring. The seal, which i replaced two years ago (maybe three) while the engine/trans was out of the car look fine. There is no noticeable wear on the output flange where the seal rides on the flange, and the flange diameter measures 1.750" (best I can do with my calipers. Will bring a mic home from work on Monday for a more precise measurement).

I did replace the seals on the speedo, it’s dry.

Could oil be seeping by the splines on the output shaft? What seals the splines? Am I missing a seal somewhere?

I had a similar problem with my XJ6 - removed the old seal and replaced it with a double lipped viton oil seal. Problem solved. Expect you could get one of these at a bearing shop. Paul.

Thanks Paul, I’ll look into this. Still wondering what keeps the oil from running down the splines though…

There is an internal oil pump located at the back of the tranny that circulates the oil. Right at pump outlet there is a tapped hole with a little hex screw and supposed to have a copper washer to seal the hole. Check to make sure the screw is tight and has a copper washer. It is on the top of the tranny output housing. You can’t see the screw or washer from below.

Kris,
Found the hex screw and copper washer - both are in place, tight, and that area is dry.

I think the leak is coming somewhere around the output shaft itself because it’s throwing oil as the drive shaft spins (I’m driving the car around without the transmission tunnel cover on). I wonder if I received a bad seal for the output shaft, the wrong seal, or I installed it incorrectly.

That shaft seal sounds reasonable. If the Speedo drive it’s also dry not many options left. Rework sucks…

Yes, hate rework. No doubt. Going to buy a double lip seal, as suggested by Paul from McMaster and polish the gland on the shaft before install. Will also make my own gasket for the end plate that retains the seal out of Aramid fiber impregnated gasket material. The stock paper gaskets from the usuals seems really weak… Finally, going to purchase some Allen counter sunk screws to mount the end plate because it’s impossible to tighten the slotted screws with the transmission in place. These will be secured with a little red Loctite…keeping my fingers crossed that this is the issue.

I would recommend not using red: blue would be adequate.

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Update: I dropped the exhaust and IRS, drained the gear box and removed the rear transmission mount. Cleaned all the gear oil off of everything. Pulled the output shaft, made a new gasket for the seal retaining plate and purchased a new, double wiper gasket. Also made a gasket to go under the washer behind the nut that retains the output shaft as without that, I can’t under stand what keeps the oil from running out the gaps in the splines. Put everything back together, took the car for a drive. No leaks…initially. However, after about 10 miles, it’s leaking again!

After a lot of sifting through the internet reviewing radial lip seals, I think my problem could be the surface finish of the output shaft that the seal is riding on. While restoring the gear box I’d run the output shaft through my wire wheel - it had a lot of surface rust. It’s possible that the surface finish of the gland on which the seal rides is too rough. SKF and Parker both recommend an Ra of 8-14, which is nearly mirror smooth (but not quite, as mirror smooth will actually diminishes the lubrication of the seal).

I’m also going to check the runout of the shaft. I can’t believe there should be any significant runout else I would expect vibration while driving. But, it’s an easy check so I’ll do that after the drive line is disconnected (again) and before I pull the output shaft.

Then, I’m going to pull the seal and output shaft, polish the gland to an Ra of 4-8 on a lathe using various grits of paper, ending at 400. Then, a new seal from SKF and put it all back together again and test it a third time.

Will report back once I know more.

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Is this a situation where a Speedi Sleeve would help?

I really don’t know - that is just the approach that comes to mind when having difficulty getting a shaft to seal properly.

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Thanks for your reply Ahwahnee.

I’ve thought about that - I mic’d the gland and it’s still at 1.750", and the seal allows -0.003 inch tolerance. So, I think I can polish without losing the diameter spec. The gland is in good condition and wasn’t rusty when I cleaned up the shaft. I’m thinking (and hoping) that I damaged the surface finish when I went at it with the wire wheel…that’s all I can come up with. Failing this, I’m really stuck.