727 Problems...

mcrivelli1898

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I have a 1968 Plymouth Fury 3 with a 383 and 727. The car has sat for the last twenty years until I purchased it. I had the car running great and have driven it a few hundred miles so far. The car has only 34xxx original miles, and I have replaced the transmission filter and pan gasket on the 727.

My problem came when I was driving home from work in the car. I came up to a light and on that particular day it was cold out, so to keep it idling while I was sitting at the light I shifted into neutral. When the light changed to green I shifted back into drive and heard a loud bang in my transmission. I got out of the car and looked under the car because the noise was so loud I thought at first the driveshaft came out. I got back into the car and went to put it into drive and the transmission would slip almost to the point that nothing would happen. I then went to manual 1st (low) and low works perfectly fine. When I attempted to shift from low to second it slipped exactly how drive did. Luckily I was close to home and limped the car back home. Reverse also functions completely normally and my line pressure recordings are as follows: P-0 psi R-30 psi N-0 psi D-30 psi 2nd-30 psi 1st-30 psi I have pulled the transmission apart in my garage and all seals and hard parts seem to be ok. If anyone can help me I would greatly appreciate it.
 
I agree. Sounds like the sprag clutch let go. I had one do that years ago. Broke the aluminum casting around the clutch and had to find a new casing.
 
I pulled apart the sprang and my finding are in the pictures below. Its harder to tell in the picture but some of the teeth on the spring retainer seem to have become misaligned. Also some of the springs have become distorted.

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You need a new sprag, I would buy a bolt in one yes they are more money and require more effort to install but 727 cases are not laying around like gravel anymore.
 
Just out of curiosity, what does it take to install the bolt-in model? Is it stronger or just more replaceable?

Thanks,
CBODY67
 
Just out of curiosity, what does it take to install the bolt-in model? Is it stronger or just more replaceable?

Thanks,
CBODY67

Im going to attempt it this coming week. From what I have read it looks like you just take a punch to take out the old one and then bolt in the new one through the four holes in the back. After I install it I can post some pictures and let the forum know if the over running clutch solved my problem.
 
The original is splined into the case, that's all that holds it. The bolt in works the same except before you install it you have to drill the threads out of the case that hold the governor housing then the new bolts hold the governor housing through the case into the sprag outer shell. The ultimate, 6bolt sprag requires two extra holes to be drilled but is really overkill on non high hp regular transmissions.
 
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