[pontiac1981]

What is this and will it work with 3:42 gear's in a second gen? I was told by the guy I bought it from that it would work, now i'm being told it won't by someone else.

[67gtospud]

Yes that is a posi unit, you can Identify this by the spring in the center and the clutches at each side. I'm not sure what it will fit.

[max 93]

A quick search shows that is a posi for a 8.5 rear with 2.56 gears and down.

[Dr.Corvette]

No it will not work with 3.42 gears. Your case has a casting no. 410409. That is a 2 series carrier. You need a 3 series carrier. Casting no. is 410408

[pontiac1981]

Thanks guys. It looks like I got taken on that deal.

[Skip Fix]

You can try a spacer plate, but sometimes they can have issues.

[firechickenman]

I put a spacer on my wife's 2 series carrier in her 76 T/A to install 3.42 gears. No issues yet after a couple years. Might not be the best choice if you have lots of torque and sticky tires.

['ol Pinion head]

Built with a ton of #9 posi carriers in the early-mid 90's. At the time was buying Mr Gasket ring gear spacers kits, 10 at a time, at $23 each. Times have changed, the GM 8.5 clutches are discontinued, but replacement clutch kits can be bought aftermarket (expensive). The one thing that has stayed the same, the aftermarket ring gear bolts in the 8.5 spacer kits are too long, they will bottom out & strip the bottom few threads.

Besides a $40 ring gear spacer kit, make sure & buy a small pkg of hardened machined washers. Mr Gasket sells the right size washers in their traditional Small Block Chevy head bolt washer set... about $10. Without the hardened washers, the supplied grade 8 LH thread bolts often will strip the bottom 2-3 threads of the new bolts. This isn't good! 2-3 less threads for the ring gear bolts to work with. Don't forget the Locktite upon assembly & correctly torque the new bolts to spec in 2-3 increments. Follow the above & you shouldn't have probs with a properly installed 8.5 ring gear spacer in a 15-14-13- high 12 sec auto car. Planning on running quicker, esp in stick car with slicks, I'd sell the high ratio carrier off & upgrade to a HD Eaton prob in 30 spline variety.

[Skip Fix]

Back in high school with a clutch side step I ripped all the ring gear bolts out in my 409 Impala-it had a spacer plate I didn't know it had. Next unit used a thick gear for it.

I did use a spacer plate in the 79 Camaro that got my 78 TA's original rear but it was autocrossed and not side stepped.

[pontiac1981]

So if I use the right spacer I can use my 3:42s with this unit? What gauge of a spacer would I use?

[Skip Fix]

Mr. Gasket makes one specific for this use. And yes you can use the 3.42s. Like OPH said you need all the components he listed.