Preload on posi C1

[Leon Brown]

I have a 3743833 P CASE for a 61, 4:11 posi. Where can I get info on the pre-load (inch pounds of torque) that the pinion should be set at. Also if the pinion nut has been torqued to tight previously will the crush sleeve need replaced. I'm not real confortable on how to properly this up and would appreciate your thoughts.
I referred to the st12 and my setup isn't the same as described in the manual. Thanks
Leon

[Roy B.]

Re: Preload on posi C1

OK when I was a mechanic in the 60's for a Chevy dealer I did to many rear ends on Car and Corvette , yes you can still use the old crush sleeve.

All we did back then was to use the in-pack gun witch was always at 175psi pressure , lay on the pinion nut for about three seconds, then hit the pinion using a 5lb. Hammer making sure the crush sleeve was set , then again it the nut with the in-pack gun again quick and that was that. I never had a problem doing them this way. ( and still do now)
But you do what ever makes you feel good!!

[Michael H.]

Re: Preload on posi C1

Leon,

You are correct. The pinion nut is to be drawn down to specs in one direction only. In other words, they can not be backed up. If you pass the rotational torque required to rotate the pinion after securing the nut, you can not reduce this value by backing up the nut. If you pass the torque figure, the crush sleeve will have been compressed beyond it's design length and must be replaced. If this is your first time at this, you may pass this figure a few times before you get it right so it may be a good idea to have a few new crush sleeves handy. It's easy to over torque the nut and fly right past the correct rotational torque spec. Very common.

Roy mentioned hitting the end of the pinion shaft with a large hammer but I don't think I feel comfortible with that method for a few different reasons. I've seen guys do this if they pass the torque value required to rotate the pinion but wailing on the companion flange or the threaded end of the pinion may not be a good idea.

I don't have the specs for the rotational torque required to rotate the pinion for C1 but it's probably in the 15 INCH lb range, with new bearings. I'm sure someone that has a C1 overhaul manual can provide the correct numbers for us. By the way, this spec is for rotating the pinion only, and does not include any additional torque required to also rotate the ring gear/differential case in it's preloaded bearings.

[Leon Brown]

Re: Preload on posi C1

Thanks guys.
According to the Chilton 58-62 corvette tune up guide (lol). It says to torque to 150-190ft pounds. I've done this and there is a tremendous amount of drag. I'm assuming I crushed the sleeve beyond specs and now crushing the bearings. I'm sure I will need to start over with a new sleeve. I don't feel good about taking the torque to 150# and will start low and increase until I get to the correct preload. So far Mike mentioned 15 inch pounds of preload, thanks. Another concern is did I hurt the bearings by torqueing to 150#
Questions:
Does anyone have the exact specs for the pinion preload?
Does the General carry the crush sleeves?
Thanks for your patience. Leon