How to know if driveshaft too long for t5 swap?

sap · 09-06-2009, 11:10 AM

I've searched this topic with no luck. I've completed the swap and need to know if my old c4 driveshaft will work. I've got the driveshaft mounted in the car. There is about 3/8" of yoke showing between the shaft seal and yoke joint. I can push the driveshaft into the transmission another 3/4" or so and it does not seem to bottom out, but the seal is scrunched a bit. How do I know if the yoke is bottomed out in the tranny? will it hit something hard? I don't want to push it too far in for fear of ruinning something? Is the 3/8" of yoke showing enough? First time doing this, so any tips are appreciated. Thanks.

C7ZZ-F · 09-06-2009, 01:18 PM

the yoke will not bottom out on the inside of the trans. it will hit the outside first. 3/4 to 1" of yoke outside should be a good figure.

sap · 09-06-2009, 01:31 PM

So the squishing of the seal is no big deal? Is it normal?

fireplug · 09-06-2009, 09:48 PM

i bought a 63 fairlane in 1973 with a 260/2sp auto. a few years later i put a 66/289/3sp manual from a mustang and the drive shaft worked fine. eventually i got a toploader to replace the 3sp and the drive shaft worked fine. a couple years ago i pulled the toploader and replaced it with a t5 and the drive shaft worked fine. but if you will notice i have not worked with a c4 so i cannot say for sure but in my opinion it will work fine. i did have to change the yoke with some swaps but not all of them. measure the overall length of the c4 and then the length of the t5 plus the bell housing. i used the same trans mount and crossmember until i changed to the t5. i had to have a new crossmember for the t5 but the same mount worked.

nzabka · 09-06-2009, 10:08 PM

I had my driveshaft cut so that 1 inch of the slip yolk was showing between the seal and "knuckle". Some say 3/4" is enough.

I think you will want at least 3/4" so the slip yolk knuckle doesn't hit the seal during driving conditions and damage it.

3/8" is not enough.

JohnnyK · 09-06-2009, 10:25 PM

I have about 1/4" at best showing. What I find funny though is when I run the rear suspension through it's travels, the clearance increases. I would think as the suspension raises up, the hypotenuse would get shorter (Err, you know what I mean), however, it seems that the distance is the shortest at full droop. So I might be good. But we'll see!

eyster · 09-07-2009, 10:17 PM

I did this swap with my '67 convertible. Went from the stock C4 to a T5. I used my original driveshaft and slip-yoke with no problems whatsoever.

66Restomod · 09-07-2009, 11:53 PM

You need .750 to 1.000 inches of freeplay with the cars weight on the suspension. You can put jack stands under the rear axle to give you room to get under the car to measure.
Too little free play and you risk driving the slip yoke shoulder into the transmission case. Too much free play can cause vibration and damage to the bearings in the transmission.
I took some pictures and have some information from when I did my T5 conversion on my website: http://chris66dad.tripod.com/id34.html
I also got an aluminum drive shaft from Shaun at Street or Track rather than cutting my old one. It was $299 and made to the length I needed. Great deal!

Good Luck and Be Safe
Ron

ALEBEAU415 · 09-08-2009, 08:32 AM

I think 3/8 is fine if that is that closest it gets. Need to put the rear suspension through it's travel to measure that. Typically on a car, 3/4 to 1 inch is with suspension drooped.

blkfrd · 09-08-2009, 12:17 PM

I have about 1/4" of gap from the yoke to the rubber seal plus the rubber seal can be pushed in another 3/8" or so. An angle gauge, a tape measure and little math showed that I would be just fine with 5/8" total gap with room to spare. I've gone to a road course with the car with no problems. I also have a rigid chassis and all new bushings, etc. An older "loose" car would require more gap.

66Restomod · 09-08-2009, 12:29 PM

The Coleman aluminum drive shaft from Street or Track I am using said it requires 3/4 to 1 inch of free play.

From website: http://www.streetortrack.com/Custom-...-pr-16159.html

Measuring Procedure:

The most important dimension in ordering a drive shaft is the length. This length is expressed as the distance between the centers of the front and rear u-joints.

To arrive at this dimension, first raise the car off the ground, being very careful to insure that the normal vehicle weight is being supported by the rear suspension. (The suspension is not at full droop or unnecessarily compressed.)

Take the slip yoke that the driveshaft will be assembled to and insert it all the way into the tailshaft housing of the transmission. Now pull it out 3/4" to 1". This will be the free play that all driveshafts need when the suspension moves through its full range of travel.

Carefully measure the distance between the centers of the front and rear u-joints. Double check the 3/4" to 1" free play in the slip yoke and measure again. Measure twice, order once!

This is the length for your new aluminum drive shaft.

Good Luck and Be Safe
Ron