Okay, I have a 2 series carrier with 2 series 4:10 gears in my stock 10 bolt now. However, no posi, but I have an aburn unit sitting around. I believe that this posi unit I have is a 3 series carrier, so how do I get my stock 1991 RS 10 bolt to accept the 3 series aburn posi unit, then do I have to switch to 3 series gears to fit that?

Also, with my set up should I go from 4:10's to 4:56's or do you think that is too much?

Mods:

388 stroker
carbed
3500 RPM stall
B&M street/strip shift kit
700-R4
280/280* duration WITH 530/525* lift Crane cam

Thanks for the help/advise...

 

You need 3-series gears to run the 3 series carrier.

What is your RPM through the traps with your current setup? What is your shift RPM? What size tires are you running (height)?

 

no trap times yet, still working on it for this up coming season. Shift RPM is around 6000 RPM's, when racing will be running 17" wheels in frot (my daily driver wheels) and 16" BFG drag radials in back (just for racing), when daily driving it will be 17x8" wheels on the road all around (4).

 

Trap RPM is what really determines what the best gear would be. If you're already going through the traps with the engine buzzing at redline then stepping up the gear won't help, and may make the car slower, especially if you have to shift at like the 1,200' mark.

I'd get the car together and see what the trap RPM is, and then worry about a gear swap if you aren't at redline going through the traps.

 

I think 4.10 is too much for a F-body unless you are running pretty tall tires. I would never go any lower than 3.90, and even that is kinda pushing it.

 

I agree 100%

 

Why is that? It's all in the particular setup.

 

I think 4.10s are too much for a stock motored car. The stock TPI doesn't have the RPM capability for gears that steep. The 1st gear will also tend to be very short, and this can actually hurt dragstrip performance. Back when I used to race my 5.0 you could always tell the guys with the 4.10s becuase you could see them shift right at the 60ft mark. What they didn't realize was that cars with 3.73s and the exact same setup were running several tenths quicker than they were.

If your car isn't stock, and you've got a motor with 6,500 RPM potential then the 4.10s may not be all that bad. As mentioned it does depend on the setup.

Without a T56 though the 4.10s are going to really raise the RPM on the highway, which burns more gas and is harder on the engine.

 

I went with 4:10's which is perfect, and by the way my car is not a stock motor by far...

Thanks for the help