# Drive shaft yoke engagement



## 68Temp (Jun 20, 2012)

Recently swapped out TH400 with TH350, mounted to 400 engine.
Built up drive train with existing drive shaft and new yoke (for proper spline fit), I end up with a total of 1.75" engagement.
This is based on 5/8" of the shaft coming out of the tail housing and 1.125 of the yoke into the tail housing.

Enough? I have heard vibration if not enough, possible damage to tail housing if too much engagement. What is the rule of thumb?


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## Bensjammin66 (May 12, 2009)

Depends on what tail shafts are on the trannys but im pretty sure the BOP 400 is longer than the 350. So if you went from a 400 to a 350 id imagine you need to find the longer 350 driveshaft to avoid issues. Again, depending on the tail shafts. I'd call a local tranny shop and ask them how much engagement is safe on the output.


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## allpawl66 (May 9, 2008)

Push yoke all the way in trans. & pull out 1" then take your measurement to have shaft made , all 4 wheels must be on the ground .


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## 68Temp (Jun 20, 2012)

Thanks. That matches well with what others have said to me..."should be about 2 fingers"

I will measure and then have the drive shaft extended and balanced.


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## Pinion head (Jan 3, 2015)

A 68 Tempest/ LeMans 2 door would have a 56.00 inch length (center to center on the ujoints) driveshaft with the Super turbine 300 auto, or with a retrofitted turbo 350. 

With the correct length (medium length) turbo 400 yoke, a driveshaft for for the same car and shortail turbo 400 would be 5/8" shorter, so 55 3/8".

these measurements are with:
- stock 8.2 Pontiac rear, or 
-'67-70 type "O" Olds 10 bolt, or
-'68-70 BUICK 8.2 10 bolt, or
-any stock 12 bolt rear

IF, 8.5 A body rear has been installed in the car, subtract 7/8" from overall length.


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