Installing 4.10s and a Posi- the easy way
 

You don't see me in this forum much. That's cause trannys and rears really aren't my bag. I've done a few and they've worked decent, but never quite as good as I hoped. Just did my first gear/posi install that went dead-bang-perfect. And it was easier than I ever imagined.

Subject in this case was the wife's 92 Camaro with the stock 7-5/8" 10 bolt rear. Most GM rears are laid out very similar to this one. Mine had 2.73s and an open diff. It had 200K miles on it, although it looked well maintained when we took it apart. Lube looked fresh, all the bearings looked like new. Only the pinion seal leaked a little.

Not wanting to spend the $350 all the local shops wanted to install the Auburn posi and 4.10 gears in this rear (many shops won't even touch the littlest 10-bolt and turned me down flat!), I decided to do it myself.

I won't bore you with the gory details. Y'all know more about this than me, so I'll get to the "secret."

My neighbor, Bob, who owned his own shop for decades and also raced Pro Stock back in the 60s, was enlisted to help out. He asked 2 questions:

1. Is the rear all original? No gear changes, no internal work done at all? Yes, it's all original far as I know.

2. Does it make any noises, whines, vibrations, clunks or any signals that it might have problems. Answer was no.

OK, he says, then we'll have this done in a few hours.

Bob, I say, perhaps you misunderstand. We're changing gear ratios AND putting in a posi- this will require extensive set-up time.

Damon, we're not GOING to set it up. We're going to take out the original stuff, swap all the original shims onto the new parts and put it back together.

Come again? Bob, I don't want a "whiner" when I'm done, I want it set up RIGHT.

Trust me, he says- I've done this many times. The stock shims will get you VERY close. In fact, you're more likely to make an error in measuring clearances and putting in the wrong shims because of it than you are of having a problem with the stock stuff not being close enough to cause problems with the new parts. Well, he's got a LOT more experience with rear ends than me so I shut up and trust him- fully expecting it to turn out disappointing. Whining, clunking, etc.

Long story short, in 4 hours we had it all put back together with the new stuff, re-using the original shims, and dropped on the ground again. I pulled out of the driveway and gently laid some throttle to it. 20 MPH, 30, 40, 50 (that's as fast as I went since I am breaking in the gears). DEAD FREAKING SILENT!!! I let off the throttle and let it coast- still dead silent. Went around some turns, no noises. The thing may very well be QUIETER than the stock 2.73s! And remeber these are Richmond gears- well known for being "noisy" on the street. STUNNINGLY good results for how little effort this took- and how little brain power! In a million years I would never have thought to try it this simple way.

A few odds-n-ends I happend to remark on during the install....

Stock pinion shim thickness: .036"
Stock driver side carrier bearing shim thickness: .243"
Stock pass side carrier bearing shim thickness: .234"
Quickie backlash check with the new gears revealed: .008-.011" depending where I measured. Spec is .008" for the gears, but it was within Richmond's .004" tolerance range.

Also, the Richmond install kit SUCKS....

1. The supplied pinion nut and washer are a joke. The washer won't even fit over the pinion threads. I reused the stock pieces.

2. The Richmond pinion shims DON'T EVEN FIT ON THE PINION SHAFT!! There's a little radius where the pinion gear joins the pinion shaft. The supplied shims don't clear this radius!!! Remember these are Richmond gears and a Richmond install kit. No mix-n-match. The pinion gear will NEVER seat fully against the rear pinion bearing with the supplied shims. This could definitely give a funky, unstable pinion depth reading. The stock shim DID have a little relief in it for this radius and laid dead-flat between pinion gear and rear pinion bearing. Stock stuff was definitely better thought-out than the Richmond parts.

3. Ditto the carrier bearing shims. The housing requires a shim (or stack of shims) that has a slight bevel to it's outter edge to seat fully into it's receiver on the sides of the housing. The supplied Richmond shims have no such bevel- they don't stand a chance of lying flat against the sides of the housing. Again, thank goodness we were using the stock stuff over again or there WOULD have been problems. Plus it's a lot easier to install ONE shim of the proper thickness (stock-type application) rather than a STACK of shims of various thickness like you would with the kit.

you pretty much showed what not to do and what you don't know ,but you said that at the start.

good job bro!!! i bet your excited to have that done huh??? Does it feel different than your 2.73??? more torque or what. fill me in cause i want to do my rear from a 2.73 to a 3.73. thanks

It's a LOT stronger out of the hole, even though I still have the stock stall converter in the trans, which isn't really well matched to the engine combo I'm running (haven't gotten to the trans yet). 1st gear is done before you know it. With DRs on the back traction is still not much of a problem- I can nail it from the line and it dead-hooks and goes. On street tires it would probably spin pretty bad. Previously with the 2.73s and open rear it was very weak coming off the line unless you torque-braked it and let the right rear tire haze a little as it got rolling. Even then it wouldn't come close to how it launches now. It's really a different car.

My previous best with this car (with the 2.73s and open rear) was 13.6 @ 104. That was with some really bad 2.2 and high 2.1 second 60 foot times.

I expect this gear/posi upgrade is going to drop about 4 tenths and I might even pick up a little MPH by getting the engine into it's power band more quickly. We'll see.

Glad that setup worked for you, b/c I have done numerous installs in the 3 years where that wasn't the case. I have done mine 2x, and each time the stocker shims were totally wrong.

Just shows you got better luck than me I guess!!!

he is right where you start with the stock stuff. (thats how I always start , I almost always have to do some fine adjusting but, it seems like it gets you in the ball park)

I was reading the yukon gear install instructions and they pretty much say the same. they say to start with the stock stuff, make sure backlash is where it should be and then set the pinion depth as your final setting. after you have it all done. go back and double check you backlash and pattern

84 camaro rear end
 

Does anyone know what size my rear is 7.5/8.5??
It has a 10 bolt cover with the following # on the bottom of the differential. (22522676) Any idea on the gear ratio? According to the vin # it was a 305 Z-28. I think it was original automatic.

Thanks
jmarc

If it's a 3rd gen Camaro or Firebird, and there's 10 bolts holding the cover on, it's a 7½". They never put a 8½" rear in one of these cars.

I'd like to hear back from ya in a year about those gears....a friend of mine did something similar with my rear, and had trhe same "perfect" results....a year later, not only was the pinion gear missing teeth, so was the ring gear! The next rear blew too, and so did the next, then I read building a better 10 bolt and followed that to a tee.....now if only the pinion seal wouldn't leak....why didnt I use cheap easy to get oil, then I could keep refilling until I could get the seal replaced, but instead I had to use that redline shockproof oil :)

IMO the best thing to do to one of these rear ends is to get rid of the crush sleeve. Use a solid bearing spacer instead.

be careful about re-using the stock pinion nut. I had one back off on my 5 spd formula and almost wiped out my whole assy. If you are re-using this part, use RED loctite on the threads!! Trust me, it will still come back off. I know some drivetrain guys that even snap a tack weld (gasp!!) on the end of the nut after its been torqued. They say better safe than sorry! Best to go to the store and buy a new one that has the Nylock stuff thats unmolested. Use your old nut to set tolerances and when you're done, torque down the new nut in its place. Just my 2 cents.