85T/A

How do i do it properly? I have a 1990 Z71 and the spider gears were blown out of it, they chewed the ring & pinion up and cracked the carrier. Now Ive already bought a ring and pinion instalation kit , ring and pinion, and carrier, Im picking the spider gears up tommorow. I need to know how to set the back lash and shim it properly. Ive done transmission and engines, and have never built a rear, but IM on a tight budget this time around, REALLY tight and I absolutely need the truck.

junkcltr

iTrader: (1)

I have done a few rears with used gears. I found that factory GM (thirdgen body) gears use a backlash of .006" - .009". Order gear marking compound when you get the install kit.

Use the Richmond install instructions and http://www.differentials.com/install.html in terms of the pattern. I try to stay on the deeper side because it gives more resistance of breaking a gear. You need to be very meticulous if you do it that way or you will get a noisy rear. Since the gears already have a pattern worn in them you can't change the mesh too much from what is already there. Set the preload using using the instructions from the website above.
It took me about 4 hours of just messing with shims on the last POSI unit I installed with used gears. The time is worth it. It is both quiet and reliable. A few hours of swapping shims and fitting is less than doing it twice.

EDIT: What install kit did you get? Does it have all new bearings? Watch out if you use the pinion sleeve & shim kit instead of the crush collar with GM gears. The shim kit doesn't have a big enough ID for the GM gear to shaft radius. You have to file the shims to get them to fit properly. That is the Ratech kit with the problem. It took about an hour to hand file them. I wasn't impressed.

85T/A

yeah i got the ratech kit. But IM not working with a posi, just a stock open rear. I did buy the carrier ring and pinion used though. but how do i set back lash, what exactly is it? Ive never fooled around with the inside of the rear and I need this to work properly

big gear head

My first recommendation is take the Ratech kit back and get a good kit. The Ratech kit is junk. It will make the job harder than it has to be. Get a good kit from DTS, Tom's Differentials or Yukon. I've been building rear ends for more than 27 years and I've tried all of the kits. Ratech is the worst that I know of.

You must know how to set the pinion depth, bearing preload and backlash to get the correct contact pattern. You must know how to reaad the contact pattern so that you will know what adjustments need to be made to the pinion depth. I wouldn't recommend a used set of gears for your first try at setting up a rear end. It is much more difficult to read the contact pattern on used gears.

You are also going to need a few special tools. You will need a press with a bearing seperator, a dial indicator with a magnetic base, a preload gauge and some other stuff.

Patients is VERY important when setting up gears. You must be willing to assemble and disassemble everything many times until you get it right.

85T/A

Why DO I need a Press with a bearing Seperator? a Dial Indicator with a magnetic base and a preload gauge?
and HOW do I set the Back lash and everything?

big gear head

You will have to press the inner pinion bearing on and off each time you change the pinion shim. You will have to do this several times before you get the pinion depth right. You will need the dial indicator to measure the ring gear backlash.

Pinion depth and backlash are adjusted with shims. You will need a micrometer to measure the shims. You will have to start with a random pinion shim and assemble the rear end. You will have to set the backlash and then check the contact pattern on the ring gear teeth. You will have to read the contact pattern and then make another pinion shim selection based on what the contact pattern tells you. Then you will have to disassemble the rear end and press the pinion bearing off and change the shim. Then you put everytning back together and try it again. You do this until the contact pattern is correct.

85T/A

Cant I just assemble it the way it came out?

big gear head

Not if you are replacing any of the parts. If you replace anything then you have to set it up again the way I described above.

junkcltr

iTrader: (1)

No, just like big gear head said, you can't just throw in the new parts. Anytime you open the cover and pull the center section it is worth checking the pattern and backlash afterwards. It doesn't take long to do the actual measurement.

In terms of special tools you need:
marking compound for measuring mesh pattern
dial indicator (magnetic base or fixed base) to measure backlash
cut-off tool to cut off the old pinion bearing (I make a cut and pull the bearing, be careful) or bearing splitter
micrometer to measure shims
pipe to press on new pinion bearing (use a pipe and hammer, be careful) or even better is an actual press
extra pinion bearing for setting pinion shim (use 80 grit sanding roll in die grinder to open ID of bearing so it slips on and off the pinion shaft).
Torque wrench to set the crush collar (in-lbs)

I always install new carrier and pinion bearings. They are like $10 - $15 each and plenty worth it.

Make sure the dial indicator is exactly or very close to perpendicular to the ring gear teeth when making a backlash measurement. Make multiple measurements for backlash to check gear run out. Check multiple spots with the marking compound.

Measure your stock carrier and pinion shims and start from their for making shim adjustments. Keep everything clean to make accurate shim measurements. Once you get the pinion shim right then slide of the ground ID bearing and "press" on the actual pinion bearing. Set the crush collar / pinion load using a in-lb torque wrench. Do an oil change at 1000 miles or less. I run redline syn. oil for the final fill.

big gear head

This is the way you check the backlash with a dial indicator. I have other pictures of my tools on webshots if you want to look at them.

85T/A

All Rite. IM going to try this but I dont have a dial indicator. So I dont know what Im going to do.

junkcltr

iTrader: (1)

Try calling or going to Autozone. They do a loan a tool program. Maybe they carry a dial indicator as part of the program. You can use the tool for free with just a refundable deposit in case you break it.