TH350 Swap: Leak at Tailshaft

Posted: April 13, 2015 in Automotive
Tags: , , , , , , ,

New tranny shifts great and you’re feeling pretty confident that your huge custom aluminum driveshaft will get the job done, then you park on an incline and the next morning it looks like your oil pan fell off.

While there are several common places for leaks on the Turbo 350 Transmission, you may discover that you have a driveshaft yoke problem versus a transmission problem.

What are the signs?

  • Your leak occurs only when you park on an incline (front of vehicle elevated higher than the rear).
  • The most forward evidence of the leak is near the tranny tailshaft area, or at the driveshaft yoke itself. You may only see the oil running down the driveshaft.

Is there a part for this?

The answer is yes, there is a slip yoke sealing kit for the TH350 and 700R4. The issue seems to be that what appears to be the “right fix” isn’t necessarily the best fix.

You are an internet search away from understanding that these kits are usually sold with extra yolk seals. So if you are into having it done the right way, plan on getting a hold of several seals and probably go ahead and get a few output shaft drive gear clips as well.

Here’s an example of what to look for.

Atlas Concepts LLC_Shop Talk Blog_Yoke Seal Installation Kit

image credit Techpak-Fitzall

My suggestion.

Simply fill the hole from the outside with RTV.

Atlas Concepts LLC_Shop Talk Blog_TH350 Drive Shaft Yoke

photo credit Atlas Concepts LLC

Realistically there are a few fixes that work. For instance, it’s a great reason to pull out your mig welder, just remember that auto-settings don’t work well when spot welding.

Other alternatives are JB Weld, a machine screw, or using silicon in combination with a “homemade plug” such as a thumbtack.

Now that you’ve taken care of that problem, keep your eye on the oil pan and the dipstick tube.


Atlas Concepts LLC_Jordache Williams_Shop TalkJordache Williams, of Rock Hill, South Carolina, is the Program Manager for Atlas Concepts, LLC. He understands that sometimes a small piece of information is the difference between success and failure. His contributions to the Shop Talk blog are purposed with sharing relevant information based on his own experiences.

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