Slip Yoke Confusion
Thread Starter
Ancient Olds Lover
Joined: Mar 2007
Posts: 261
From: Connecticut
Slip Yoke Confusion
I have a question about TH400 slip yokes, it's a stupidly long and boring story, but I'll make it as short as possible.
The car in question is a 1969 Cutlass S. I swapped in a 455 and its matching TH400 out of a 1969 Delta 88. The trans is a longtail that required a new drive shaft, so I had one made for it. I ran this combo for a couple years, including a few passes down the track at Lebanon Valley for Musclepalooza. No problems whatsoever.
This trans has 120K miles on it and while it performed well, I realized is was actually slipping.
A friend of a friend of mine had a TH400 built for his 71 Cutlass. For health reasons, he wasn't able to build the car he was planing to, so he offered me the trans for a fantastic price.
We swapped out my 1969 Olds longtail TH400 and installed the new trans. This new trans is a 1971 Buick TH400 and is a shorttail. Now I needed a longer driveshaft.
The drive shaft builder explained how to obtain the measurement he needed from me; Insert the slip yoke all the way into the trans, then pull it back 3/4" and measure from the center of the front u-joint to the center of where the rear u-joint will be (at the pinion).
I measured as directed and he made a new drive shaft with all new components.
The new shaft is too long. I discovered where the problem lies. When the slip yoke I used for my initial measurement was inserted all the way into the transmission (for a fixed reference), the center of the u-joint was located 1.5" from the rear seal. When the new slip yoke is placed in the same position, the center of the u-joint is 2.5" from the rear seal.
It would be easy to simply put the slip yoke I used for measuring onto the new shaft, however it's rather pitted right where it meats the rear seal.
I don't know where my old slip yoke came from, but out of the 3 or so random TH400 slip yokes I had lying around my garage, it's the only one that goes in so deeply.
Logic tells me that for multiple reasons, the u-joint should be located as close to the trans as possible.
My drive shaft guy can't seem to find a new version of my old slip yoke so he would need to shorten the new shaft by an inch to make the new shaft fit.
My ultimate question is this:
What is the correct, proper slip yoke I should be using?
Thanks for any help with this!
The car in question is a 1969 Cutlass S. I swapped in a 455 and its matching TH400 out of a 1969 Delta 88. The trans is a longtail that required a new drive shaft, so I had one made for it. I ran this combo for a couple years, including a few passes down the track at Lebanon Valley for Musclepalooza. No problems whatsoever.
This trans has 120K miles on it and while it performed well, I realized is was actually slipping.
A friend of a friend of mine had a TH400 built for his 71 Cutlass. For health reasons, he wasn't able to build the car he was planing to, so he offered me the trans for a fantastic price.
We swapped out my 1969 Olds longtail TH400 and installed the new trans. This new trans is a 1971 Buick TH400 and is a shorttail. Now I needed a longer driveshaft.
The drive shaft builder explained how to obtain the measurement he needed from me; Insert the slip yoke all the way into the trans, then pull it back 3/4" and measure from the center of the front u-joint to the center of where the rear u-joint will be (at the pinion).
I measured as directed and he made a new drive shaft with all new components.
The new shaft is too long. I discovered where the problem lies. When the slip yoke I used for my initial measurement was inserted all the way into the transmission (for a fixed reference), the center of the u-joint was located 1.5" from the rear seal. When the new slip yoke is placed in the same position, the center of the u-joint is 2.5" from the rear seal.
It would be easy to simply put the slip yoke I used for measuring onto the new shaft, however it's rather pitted right where it meats the rear seal.
I don't know where my old slip yoke came from, but out of the 3 or so random TH400 slip yokes I had lying around my garage, it's the only one that goes in so deeply.
Logic tells me that for multiple reasons, the u-joint should be located as close to the trans as possible.
My drive shaft guy can't seem to find a new version of my old slip yoke so he would need to shorten the new shaft by an inch to make the new shaft fit.
My ultimate question is this:
What is the correct, proper slip yoke I should be using?
Thanks for any help with this!
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