ok im new to this, but I need some help. Im swaping the 3rd member out of an 80 pickup ito my 86 toyota to match the gearing in my front axle because I did a SAS. But I put it in and there is a funny vibration. Any Ideas why this would be. The bearings look ok, does the nut on the companion flange have to be a certain torque. . . Any help will be appreciated. Thanks

 

I'm assuming you took the flange off and swapped it with the newer thirdmember so the driveshaft would bolt up properly?

The companion flange tightens against a crush sleeve to set the pinion preload. You don't just hammer it down to a certain torque
http://personal.utulsa.edu/~nathan-b...35differen.pdf

 

ok so how does one set the preload on the rear diff. I thought it was as simple as just swaping it out. . .

 

and could that be what is causing the vibration, or could my driveshaft be out of balance. but I dont see how it would be my driveshaft cause I never altered my driveshaft except for sliding it in on different teeth.

 

Did you slide the slip yoke apart? If so, you gotta put it back just like it was ...

 

"Sliding it in on different teeth"?

It was balanced for the way it was. You can't just pull it apart and put it back any way you want.
You might need to go to the driveline shop and let them re-balance it.

 

as far as the yolk, I assume your talking about the flange. I just slid it back on there. so yeah im gonna take the drive shaft to a shop and have it balanced and see what happens then