Slip yoke 4 speed. How much tolerance

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Mopar92

Mopar92

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What’s about the most you guys feel comfortable with the yoke flat surface to the boot seal?
 
The the boot seal means very little because boot length sometimes vary. How much spline engagement is what really counts. I push the yoke all the way in and pull it back out 3/4-7/8"
 
Yeah I understand. If I bottom the yoke out up in the boot.... mines backed out 7/8. The drive shaft shop came up a little shorter that I wanted. I measure U to U with the yoke shoved into the boot then take off .75”. This shop was insistent to take off 1”. I don’t want to kill the tail shaft bushing.
 
IMO, you're good at 7/8"-1" from bottoming the yoke regardless where it contacts the boot. I'm thinking you should have plenty of clearance for removal of the shaft from the rear yoke and plenty of clearance for any rearward engine / trans assembly motion and combined axle motion. Some seals have no boot I believe.
 
I’m giving that as a reference. The boot. Touch the boot and back off an 1”. That’s where I am. Wish he’d have made it like I wanted and not by his standard 1” shorter than bottomed. Sounds like I’m ok.
 
The measurement is not taken from touching the boot. It is taken from bottoming the yoke all the way into the tailshaft with the boot (if a factory style seal) collapsed. You then slide the yoke out 1" (this is the standard that I always use and what I have typically seen recommended) and measure center to center of the u joints. If you can slide the yoke more than one inch into the transmission your driveshaft is too short. Be sure to have the rear suspension loaded when you measure!
 
Well I crammed and collapsed the boot as far as it would collapse and my buddy took the measurement. Well we took it 3 times to verify. I know on my dirt late model the slip yoke moves in and out around 4.5-5” per lap. I just don’t want to ever bottom this out but I wasn’t sure about only 1” out from completely bottomed out. There probably isn’t much movement with leaf springs like there is with our 4 links.
 
It’s pretty scary knowing what goes on in our dirt cars. We also run an 8” yoke too.
 
I have measured the movement on a couple cars (stock suspensions) and they never moved more than 1/2". I also measured my 68 Cuda with Caltrac springs and they didn't move more than 1/2" in and out either so you should be fine at 1". Driveshaft makers typically use the 1" rule so there is very little chance it'll bottom out and wreck your trans. They don't want to be liable for that
 
fishy68 said:
I have measured the movement on a couple cars (stock suspensions) and they never moved more than 1/2". I also measured my 68 Cuda with Caltrac springs and they didn't move more than 1/2" in and out either so you should be fine at 1". Driveshaft makers typically use the 1" rule so there is very little chance it'll bottom out and wreck your trans. They don't want to be liable for that
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But too much out is hard on the tailshaft bushing too.
 
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