I have a 3.08 gear from a 1978 Camaro..posi unit. Anybody know if it will fit in in a rear from an 1985 442...8.5?

Thanks,
Ted

 

pretty sure it will, asumming the gear you have is also from a 8.5 GM rear

 

Although I can't say for sure . I just put limited slip carrier and gears from a 85-86 grand national in 74 omega.
Railguy

 

It should fit as both should be 8.5" 10 bolt rears. If you post the casting numbers on the posi carrier we can say for certain if it will fit or not.

 

85 442 is a 3.73:1 ratio, right?

 

Yes

 

3984829 13:40 GM. 6E

310 1978.....pinion

Casting...410408N......carrier

8

 

so the goal is to end up with a 3.73 posi?

or swap it all and have 3.08 posi?

 

3.08

 

410408 is the 3 series posi carrier so it should work with either the 3.08 or 3.73 gear set.

I would just put the posi in with the 3.73 gears as all that would be needed is setting the backlash instead of an entire ring and pinion gear installation. Plus I would prefer 3.73s over 3.08s, but that's just my preference.

 

Yeah, what he said
why lose the performance ratio?

I found this in the PN database

"You have the 8.5 inch "corporate" 10 bolt in your car, so you can use a limited slip diff from another 8.5" 10 bolt with no problems.
The 410408 is a 3-series carrier, for 2.73 & numerically higher ratios, and the 410409 is a 2-series carrier for 2.41/2.56 ratios.

This site gives the years and applications for a lot of vehicles with the 8.5" 10 bolt: http://www.richmondgear.com/01pdfs/page10.pdf -

Chevy & Chevelle 70-76; Chevy II 70-75; Camaro 70-81; Z28/TransAm 72-81; GTO/Firebird 70-81; Olds F85/Cutlass 70-76; K10/K20 Front 77-87; Blazer front 77-91; C10 K10 Blazer Rear, C1500 K1500 Rear 80-02; Suburban Rear 80-96; Suburban Front 77-91; G10 G20 Van 79-96; Elcamino 73-76.

"Posi Carrier numbers 410409 or 410408 for c-clip axles will work in your non-c-clip axle. '409 would need a ring gear spacer to use gears 2.73 and larger numerically. There are also carriers numbered 725 and 726 which are the non C-Clip application carriers which would work fine as well."

 

Thanks for the input👍
I am taking your advice and sticking with the 3.73 gearing....

 

Ted, here are some pics of the 410408 Series 3 that I put into my 72. I opted for 3.42:1 gearing. This came to me from Jim Mitschke (aka Monzaz). If you need any help setting it up, he's your go to guy.




Bearings pressed, ready to install





Casting part number





Just as it should be - 10 bolt

 

Welcome back Allan! You have been missed. Hope to see more posts from you, A.

 

Everything Adam said! Good to hear from you Allan👍