[QUOTE=Tom A;698753]Ok, so am just about at that point of taking out and throwing away. So have been recommended an Auburn cone-style LSD. Also an Eaton Detroit True-Trax. Any recommendations out there and why one over the other? They both are about the same price from Summit Racing.
Thanks.

 

Either of those is good. The Detroit has clutches and is rebuildable. The Auburn uses cones and is not. In real life, you'll probably never wear either one out. I've owned a couple of Auburn's, but have no personal experience with the Truetrac. I have lots of experience with Detroi Lockers, though, and they're a great product.

 

Hello again Tom...
OK so mulling this over...Not sure what the backlash and preload is. Have never gotten this deep before other than changing spider gears out. If I go to an Eaton or Auburn are these the same adjustments that need to be made when using the same ring gear or is there more to it? Can you hook me up with a link for this work? Was looking to take it to a shop but they want 200$ more for an Auburn carrier from their supplier than I can get it for from Summit. Plus the labor and all. Do you thing the extra cash is worth a shop warranty? They won't warranty the work if I supply the carrier. I believe I can do this if I have the right intel. This thing was supposed to be in working order when I bought it but I guess I didn't give it a thorough enough road test.

 

There are a few things you need to know when installing an after market 8.5 posi carrier into an 8.625 housing.

Most 8.5's used small ID/OD carrier bearings and 28 spline axles. Most 8.625's in our blazers after 2000 used big ID/OD carrier bearings and 30 spline axles. This is what you have.

First don't forget to put some paint on one of the carrier bearing caps to ID which side it is for.

After market 8.5 carriers these days are all made to use big ID carier bearings. Make sure to buy one with spider gears for 30 spline axles. To use them in an older 8.5, one has to use a custom carrier bearing (don't make a mistake and think that you need that one). What you need is standard carrier bearings for a 12 bolt rear end or for a 8.625 10 bolt - they are both the same size. If you have a good way to press off your old bearings and onto your new carrier, you can re-use your old ones (I would let an experienced shop with the clamshells and a press do this). Use new bolts for the carrier, and torque them with red loctite. The only adjustment you will need to make is setting the backlash. This is checked using a dial indicator on the teeth and you MUST have one AND get this exact. Like Tom says, just measure what your original backlash is before disassembly and set it to that by adding/subtracting shims from each side with zero preload (shims fit snugly without driving them in). Don't expect the shims on each side or the total number of shims to stay the same. Then when you have that correct, set the carrier bearing preload by adding 0.002 more to each side for old bearings (or 0.004 more to each side if you have installed new bearings). There is no real way to measure the carrier bearing preload other than how many more shims you stick in. Do not tap on carrier bearing races. under any circumstance. Be sure to recheck backlash when finished. If you buy any aftermarket shims to add (and you probably will need to), make sure they are for the big carrier bearings.

There are two strategies to getting the preload shims installed. One is to pound the shims into place with the races/carrier seated against the housing. For this case, you may want to use one of the shim packs you can buy that captures the shims with an internal ring - holding the thin ones securely between two thick shims that you can beat on with a plastic hammer. The other strategy is to put the shims into place (with thick shims against the races) and **** the races on the bearings just a tiny bit just enough to get them started (this takes more than two hands). Then beat back and forth on each side of the carrier with a large dead blow hammer until the carrier is fully seated.

Good luck!

 

Additional info

The factory 8.5″ carrier when installed in a factory 8.5″ axle uses Timken bearing part # LM501349 and race part # LM501314. The inner diameter of the bearing is about 1.625″ and the outer diameter of the race is about 2.890″.

The factory 8.625″ carrier when installed in a factory 8.625″ axle uses Timken bearing part # LM603049 and race part # LM603012. The inner diameter of the bearing is about 1.780″ and the outer diameter of the race is about 3.060″.

The after market carrier bearing inner diameter will be 1.780, so no changes in bearings are needed for you to do this with an after market posi carrier.