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Posted: 5/10/2003 1:22:51 PM EDT
I've searched and searched on the net for this answer, this is my last resort before professional help. anyways...

I blew the ring and pinion gears up in my truck a few weeks ago, I have the replacement parts, I rebuilt the whole thing, bearings and all. Last night I finished putting it all together. My problem is getting contact like they show in the little picture. It's really close, but not quite. Everything I read on the net says I have to use a dial indicator to measure backlash and pinion depth, then shim them. The thing is the total overhaul hkit I bought has no shime. So I assumed the design of this rear end didnt need them. I looked online for hours trying to find out if thats what i'm missing, but cant find specific info on my rear end.

It's a chevy 7.5" out of a '89 S-10 Blazer. Does anyone know if chevy 7.5" rear ends use shims? It has two large ones to the left and right of the ring gear carrier, so I dont see how I could even adjust backlash if I needed to. The only thing I can think is mabye my Pinion gear needs shims. And how the hell do I set preload? it calls for about 2ft lbs, but the big nut on the end of the pinion takes way more than that to tighten?

Anyone know anything? thanks..

Link Posted: 5/10/2003 1:44:01 PM EDT
Your kit should have come with shimes.
There should be a set of diferent thiknes shimes.  If you know anyone who has dune a rear end thay will have some shimes left over.  
You have a thing called a crush sleev, it must be preloaded just so. You might want to get some help.
Link Posted: 5/10/2003 1:52:30 PM EDT
Damn...its been years.

You should hump that bad boy down to a qualified mech who does those for a living.  They can be tricky.  I never did one because I was just too impatient and unskilled to set it up right...but I did watch a few go together.  They were the old heavy duty racing units from the '60s.  I blew out a set of spider gears and some other odd parts in my race car a long time ago.  The mech assembled the unit using the shims to "dial in" the proper clearance and used liberal amounts of bluing on the pinion gear to check the alignment and finish the setup.  The blue liquid transfer from the pinion to the ring gear had to be dead in the middle if my memory serves me right.

I'd take it to a pro.

Good luck!
Link Posted: 5/10/2003 1:59:40 PM EDT
Falcon2, the best advise I can offer is to either go to Autozone and get a Haynes Manual, or seek a skilled friend to help you do this.

I have done one and also had to have other shims to set backlash.

I set the pre-load on the pinion bearings first then move on to proper tooth contact. IIRC, the turning torque on the pinion is what is most important measured in inch pounds. Do not confuse this with what is required on the nut itself. Shims on the pinion itself may or may not be needed for proper tooth contact with the ring gear also.

The shims for the side carrier bearings are a similar story. The shims not only control the gear lash, but also must load the same bearings somewhat.

It's difficult not being there with you and has been 10 years since I did one like you have.

Don't rush it, you could ruin your new gear set.

Where are you located?


Link Posted: 5/10/2003 2:11:07 PM EDT
Liz Taylor's doctor?
Link Posted: 5/10/2003 3:16:56 PM EDT
Link Posted: 5/10/2003 3:31:59 PM EDT
Looks like i'm gonna make a few phone calls tomorrow...

"Hi, i'm a dumbass who thought I could rebulid my rear end, how much do you charge to fix it?"

oh well, live and learn. at least I didnt try to drive on it and blow my new Richmond gears up. thanks for the advise.
Link Posted: 5/10/2003 3:37:25 PM EDT
If you've never done one (several is better), find adult supervision.  Certain areas of an automobile can be repaired by a trained monkey, but the diff isn't one.  I've had my hands in several, but I still would ask a friend (who has set-up dozens) for assistance during the set-up phase.  

Don't forget the break-in procedures.   Good luck.

Link Posted: 5/10/2003 3:49:24 PM EDT
No, but I've torn up the rear ends of a few buxom models.[;)]
Link Posted: 5/10/2003 3:53:17 PM EDT
I can do some liposuction.  But thats the wrong kind of rearend!
Link Posted: 5/10/2003 4:00:00 PM EDT
A GM 7.5" is a good one to practice on as they blow easily anyhow.  The pinion depth is set with shims, just tighten the pinion nut enough to take the slop out of the bearings.  The ring gear is moved left and right by swapping shims from side to side.  Take you time, you can do this at home if you take your time.  If the contact pattern is right on the edge of the teeth, it wont last 50 miles.  If you are on the middle of the teeth and not perfect, it will whine somewhat.  Move one adjustment aat atime, and use the proper manual to get it set right.  Done properly, the rear end should last about 200K.  Its not hard, just a PIA.  
 The inch-pound requirement is the torque required to turn the pinion after the nut is tightened.  It will require a LOT of torque on the nut to get the pinion bearings tight enough to drag at 10 to 20 in/lbs.  Get the gear mesh set, then remove the ring gear again and torque the pinion nut.  reinstall the rign gear and carrier and reinstall the shims as you had them when everything meshed properly.  Torque the carrier bearing caps and recheck the gear mesh.  Dont be surprised if you have to move a shim or two.  TAKE YOUR TIME!!  Ops
Link Posted: 5/10/2003 4:07:36 PM EDT
shims dont come in the rehab kit.

Shims are part of a huge set that is meant to be used over and over again.

Rear end building is the hardest of ALLLLLLLL things truck and car to master in rebuilding.
NOT KIDDING !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Sometimes the rear end will melt together with some new parts. Most of the time is you change everything ,bearing, pinion shaft and ring gear it will not match up well and will need to be adjusted with shims or tourqe.

BRING IT TO A SHOP THAT SAYS THEY DO IT ALL THE TIME or get a junkyard pumpkin like everybody else.
Link Posted: 5/10/2003 4:54:41 PM EDT
I've learned this the hard way too.

There is no margin for error in setting up gears in a rear end.

Link Posted: 5/10/2003 6:24:03 PM EDT
I have friends that are life long Chevy fiends,that have switched to Fords(god they hate them)!    Only because of these shims,under extreeme loads these  shims can be undone,bad juju!

  Bob [:D]
Link Posted: 5/10/2003 6:24:34 PM EDT

All the info you need at this site.

I watched a driveline mechanic change the gears in my buddies Jeep. He just pounded everything in with a dead blow hammer and checked everything by feel. Granted he has done thousands of gear sets but I figured if the mechanic could pound one together that I could do it with the proper instructions and the right tools. I have now done three sets including installing a Detroit locker. It's no big deal. Just take your time and follow the directions.

If your carrier bearings need shims then an assortment of shims should have been included in the rebuild kit. You can order a shim kit from several suppliers. Randy's Ring and Pinion is one source.

You might have problems finding an inch pound torque wrench to set the pinion pre-load. If you can't find one set the tension so that there is no slop in the pinion but you should feel just slight resistance when you try to turn it by hand. There are two types of setups for pinions. One takes a crush sleeve and the other takes shims.

The backlash is the critical setting. You MUST have a dial indicator and magnetic base. Get the backlash set within spsecs.

The gear contact pattern is difficut to read by using the dye method. It is easier to use white grease and use a screwdriver to put pressure on the ring gear while you turn the pinion to get a pattern. Another method is to tear a thin strip of newspaper and run it between the ring and pinion gear. A pattern will imprint on the paper strip.

You probably will not get a perfect pattern but shoot for full contact near the middle of the gear tooth.

It's real easy to tell if you did everything right. If you didn't the rearend will whine and then selfdestruct within a few miles.

Good luck.
Link Posted: 5/10/2003 6:37:51 PM EDT
Shit, and here I thought this was about "extricating" hemorroids...[rolleyes]
Link Posted: 5/10/2003 8:01:55 PM EDT
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