489 big yoke to 318 small yoke drive shaft

Sonny · Jan 9, 2020

I am swapping my 8.25 rear end with a 8.75. I bought a 489 case, axles, and housing but the 489 has the large yoke and my ‘70 Belvedere (originally came with 318) has a driveshaft for the 8.25 rear with small yoke.
Question 1. What is the u joint conversion number I need or
Question 2. Is the 8.25 driveshaft the wrong length and I need a new driveshaft with large yoke anyway?
Thanks!

Darter6 · Jan 9, 2020

Moog #347 conversion joint. Rule of thumb to check length, the weight of the car has to be on the axle.With jackstands under the axle install the driveshaft and push it as far into the trans up to the boot of the seal. Some have a dust boot some don't. Pull it back out 1''. Check the distance from the rear u-joint to the rears yoke. You should have about 2'' center line of cap to center line of yoke.That will give you a working distance for the slip yoke to move with the suspension. I use the 8.25 driveshaft from a 70 Coronet in my car hooked to a 8 3/4.Works for me since 2004.

Sonny · Jan 9, 2020

Darter6 said:
Moog #347 conversion joint. Rule of thumb to check length, the weight of the car has to be on the axle.With jackstands under the axle install the driveshaft and push it as far into the trans up to the boot of the seal. Some have a dust boot some don't. Pull it back out 1''. Check the distance from the rear u-joint to the rears yoke. You should have about 2'' center line of cap to center line of yoke.That will give you a working distance for the slip yoke to move with the suspension. I use the 8.25 driveshaft from a 70 Coronet in my car hooked to a 8 3/4.Works for me since 2004.

Thanks man!

PurpleBeeper · Jan 9, 2020

Yes, check for sure and the c9nversion u-joints work just fine. However, you might want to check online for the lengths of the two driveshafts.....your original & whatever would come behind a 383/440 car. There is a good chance the lengths are different...but check. I ran a driveshaft that had my trans yoke out abou 3" and it seemed to work but screwed up a transmission driving the car aggressively....check

489 big yoke to 318 small yoke drive shaft

Sonny

It’s all fun til the rabbit gets the gun.

Darter6

Well-Known Member

Sonny

It’s all fun til the rabbit gets the gun.

PurpleBeeper

Well-Known Member

Similar threads