Front and rear differential sizes

[chantz1991]

what up guys, gotta another question...for the 99 tahoe z71, is there a specific differential size for the front and rear, i have no clue, but what i do know is that i have 3:42 gears and im wanting to upgrade to 4:10's....

thanx, chantz.....

 

[blueflamed03]

I believe they are 8.5/8.6

 

[ravingmadman]

I believe they are 8.5/8.6

Yes, and You'll have to figure out if you have 28 or 30 spline axles. You just have to pull one out, and count it. If you're currently running 3.42 gears, the 4.10's are going to wreck your highway mileage, if you care. We don't care about mileage, but still. I've got 35 inch tires, and my new 3.73 diffs are working great for me. More important than your gear ratio, is getting rid of the gov-lock in your rear diff. That's a ticking time bomb. No matter what you do to upgrade your diffs, make that priority #1.

 

[chantz1991]

gov lock, wtf is that, haha, my rear end is free spoolin', but thanx guys

 

[swab]

8.25/8.5. 8.6 doesnt happen til nbs.

 

[Bad bow tie]

8.25/8.5. 8.6 doesnt happen til nbs.

Yup. The front is an 8.25" ring gear and the rear is an 8.5" ring gear. The gov lock is the factory Eaton locker that GM put in. It's a piece of crap and tends to explode and wreck the whole rear end. It is facory code G80 on your RPO code list in your glove box. 4.10 are a good addition but not really necessary if you're running less than a 35" tire. The lower the gears you go with (numerically higher) the more your fuel milage will decrease.

 

[ravingmadman]

What year is your hoe? If your diff is open, either your rig is old enough to not have come with one, or your rear end has been replaced once before. Drop a real posi in there, if you're going to swap the ring/pinion. Here's what a gov-lock does, when you need it the most:

 

[chantz1991]

1999 z71 lt, im kinda gettin pissed cause i really want to gettin posi units in the front and rear, i know how to do it, and have my college instructors to help, yet like everyone else money is tighter than a tics ass

 

[Bad bow tie]

Unfortuantly they don't offer a locker for our front IFS. For the rear I'd go with a Detroit or a Auburn. I've always heard good things about them but they expensive.

 

[swab]

the front dif is aluminum so its too weak to have any kind of lsd let alon locker up front. pair that with our front half shafts and youll get alot of wreckage.