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Transmission Leak - C4 1966 Mustang

2K views 1 reply 2 participants last post by  Ivy66GT 
#1 ·
Hi,

I have a 66 Mustang C4 (200 ci) with a transmission leak.

After replacing the oil pan(brand new), the transmission still continues to leak. I've narrowed it down to one possible source from the passenger side of the transmission which appears to be coming from this bolt that is sticking out right below the transmission oil cooling line.

I'm not sure what that bolt is, and whether its as simple as pulling it out and replacing/buying a new gasket? I checked the dipstick tube and re-placed the O-ring, and I also replaced the transmission oil cooling line fitting (brand new) as well as replaced the oil pan(also brand new), so i don't suspect that these are the causes of the leak.

In terms of leaking, I really only suspect this bolt as the culprit given I haven't seen oil from the driver side part of the transmission in addition to running my finger right under the bolt and finding transmission oil. I've attached two pictures (again, passenger side of transmission) for reference.

Any insight or any diagnosing advice would be great. Thanks in advance for your help.
 

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#2 ·
That is a lock nut for adjusting the rear band; there is another one on the other side for the front band. Its not likely the source of your leak unless you have been trying to adjust that band a lot more than most people. Otherwise, that nut never moves so why would it suddenly start leaking? I am going from memory but I think the photo below shows what the rubber seal looks like on the back side of those lock nuts. There is no need to take the adjusting stud out of the body, just remove the nut and see if there is any seal left. (DO NOT take that stud out or parts can fall out of place inside.) You also can't let the square-ended adjusting stud turn more than just a small amount while doing this or else you have to readjust that band afterwards. Mark it so you can tell if its turning or not and return it to the same rotation angle it was before you started.

Those nuts come in a C4 rebuild kit (that's where I took this photo) but I don't know that they are for sale by themselves. While you are doing a rebuild the nuts get replaced since they are cheap and easy, not that they are parts that leak often. Unpressurized oil has to work its way down the threads of the adjusting stud before possibly leaking out from there.
 

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