Transmission Leak?

[Tribalmonkey]

I have a pretty significant transmission fluid leak from the speedometer cable connection on my 1931 roadster. I currently don’t have a speedometer cable attached. The speedometer is rusted solid anyway. After each drive it makes a pretty good puddle. I can see it leaking directly from where the speedo cable would attach on the torque tube. This is different than the engine oil leak from the big cotter pin bell housing area I had on my coupe. I’m also wonder if it could be coming from the rear end through the torque tube. Same 600 fluid in both. Opinions? Suggestions? Thanks!

[Bob Bidonde]

There is a seal at the front end of the torque tube which has a dry side towards the differential. I suspect the seal in your car is wornout.

Replacing this seal is a work intensive job because the rear axle assembly needs to be disengaged from the universal joint. It is best to have the rear axle assembly on a work bench because removing the drive shaft bearing race is a tough chore. All of this to replace a $2.30 seal!!!


Wile the rear axle is out, you should also consider giving it a thorough inspection for gear & bearing wear. Also replace the axle shaft seals, and adjust for excessive play in the axles.

[Tribalmonkey]

Thanks. Sounds like it would be easier to replace the transmission. :-/

[Brentwood Bob]

That probably won't fix the torque tube seal.

[Tribalmonkey]

Ok. So the torque tube seal not the transmission seal is what is suspect? Do you not think it is a transmission leak? Differential leak? Just making sure I understand.

[Bob C]

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The way the torque tube seal is installed is to keep the trans and u-joint lube from migrating to the differential so I don't think that will stop lube from coming from the speedometer drive.

[katy]

You could replace the rear transmission bearing with one with a seal on one side.

[john charlton]

The paper gasket between the drive "cap" and the torque tube must be in good condition and the two 7/16" bolts are tight . Take care when you check tighten these as they can easily strip . I have had this problem and fixed it by finding a cap with the right thread and sealing the cable output . Plastic or metal either will work . Trans oil is leaking past the output bearing. If the torque tube neck seal is OK the leak will stop after everything finds its common level . Make sure your trans is not overfilled .

John in sunny Suffolk County England .

[Tribalmonkey]

Thanks everyone for your quick responses. I will go with the cap solution until I have time to dig in further. I was concerned that if I cap the speedo connection I would just eventually fill up the torque tube with tranny fluid. I think I understand now that there is seal in there to prevent that from happening.

[john charlton]

You can also make a cap by using the female threaded "collar" cable connector off a speedo cable . A suitable coin or blank with some thin gasket material on the inside will also work . If the bearing in the torque neck is good the seal is normally good too .

John in the same place same weather .

[Tom Endy]

Oil from the differential does not migrate that far forward to reach the transmission. The grease seal at the front end of the torque tube is there to prevent the grease intended for the U-joint and front roller bearing from migrating down the torque tube.

The oil leak is probably coming from the transmission. It can leak down the main shaft spline under the rear bearing. It is normally stopped by the special washer on the bolt that attaches the U-joint to the end of the main shaft. An incorrect washer could have been installed, or the bolt has backed off. Some amount of oil does come through the bearing itself, the majority of oil is blocked by the oil baffle. Most people today install a sealed bearing to prevent it.

Tom Endy

[1crosscut]

Check to make sure the vent hole on the back side of the shift tower is not plugged.