8.5 open to posi swap ???? help

[florr23]

ok fellas i need some help or some re assurance i'm changing out my carrier in a 86'442 rear 8.5 that had an open diff ,now going to a factory s-type posi c-clip and keeping the same ring and pinion that came out. My question is do i need to reshim the pinion or can i just put it back together in reverse of the way i took it out . if i do need to reshim and adjust what all will i need never done this sort of project before..any help is greatly appreciated

R.Flores
Sgt./USMC

 

[t5montecarlo]

I have never had to reshim the pinion when reused in the same case, even with new bearings.

 

[luv2xlr8]

i just changed from an open carrier to a posi and did not have to reshim. put something on the teeth and spin the carrier around and make sure the wear is in the middle of the teeth if not then you may need to reshim

 

[florr23]

ok that sort of what i thought i just wanted to get some second opinions
thanks

 

[monzaz]

The only re shimming needed MIGHT be the carrier left to right which is referred to as the BACKLASH. This is the slap of the gear from coast to drive side of the gear. Your pattern will NOT change. Caps to 60 FTlbs. torque. Ring gear bolts get lock tight and 60-65 ft lbs. TIP: (left hand threaded bolts )

CArrier preload : If you can pull carrier in and out with out some sort of pry bar you DO NOT have enough pre load on the carrier bearings.

Good luck, Jim

 

[florr23]

monzaz,
Iclickedon your link and man you got a lot of useful info on there great stuff , anyways i'll keep that in mind when I'm putting this bad boy together, i had one more for question for the gear heads out there before i tear out my old rear and put in that 8.5 86' 442 rear i noticed the pumpkin is just a tad bit longer than that of my 7.5 rear in there now about 1-1 1/2 inches inches longer. I don't mean by width but from the back of the pumpkin to the front where the yoke comes out . Now about a year ago when i took out the th250 the car had and slapped in a 700R4 i had to shorten my driveshaft now i'm gonna have to do it again of course i'm gonna let the machine shop do it cause i want it balanced and all, but i wanted to ask yall guys to get the correct measurement how do i measure it on the driveshaft it self after i get my measurement from the trans to the new 8.5 rear after it is installed..
thanks for all the help

 

[t5montecarlo]

If you are replacing a 7.5 with an 8.5, the driveshaft will need to be 1 inch shorter.

 

[monzaz]

PLEASE....please...Install the rear first...Load the rear with the weight of the car on jack stands then measure. I have seen this measurement vary some. So please so you do not waste time and money do it this way. Jim

 

[StreetBu]

Just installed mine this spring. Went from an open to a Detroit Tru-Trac. Didnt have to change a thing. BUT.....that doesnt mean you shoudlnt recheck it after its back together. Only takes 5 minutes and is VERY easy to check your pattern.