430Camaro

iTrader: (1)

I've been rebuilding the stock GM 10-bolt from my 91 GTA. I'm actually transfering all of the guts from that 10-bolt with a torn up housing to another 10-bolt housing that's not torn up(from a '83 camaro). This is the first rear end of any type I've rebuilt before but I'm taking my time and trying to get it right. I think I got the mesh where it needs to be but I'd like some opinions from those more experienced. :beer

Original parts used:
-auburn type carrier with original used ring gear still attached (3.42:1 ratio, ~100k miles)
-original used matching pinion gear (3.42:1 ratio, ~100k miles)
-original matching used axle shafts and c-clips
-original matching pinion yoke

Items replaced(full rebuild kit from RA Tech):
-axle bearings
-axle seals
-carrier bearings
-pinion bearings
-pinion seal
-all appropriate shims
-pinion nut
-solid spacer with shims instead of crush sleeve (RA Tech specific part)

So I started with cleaning everything and pressing on new bearings, etc. I set up the solid spacer with shims and got the recommended bearing preload. I moved onto getting the carrier wedged in with its bearing preload then started messing with carrier and pinion shims to adjust the pattern. I took some pics of the original pattern in the old housing as reference before I tore anything apart.

Pattern test 1:
In the new housing with the first shot at spacers the mesh pattern seemed high and was certainly near the heel for both the drive side and the coast side. (I didn't take a photo of this one)
So I did the following:
-moved 0.005" shim from the right to the left to reduce backlash.

Pattern test 2:
Pattern still seemed high but was now shifted to the toe on the drive side. The coast side still seemed high and heel.
I figured I went too far so I did the following:
-moved the 0.005" back to the right side then moved a 0.003" shim from the right to the left so backlash would be between test 1 and test 2 levels.

Pattern test 3:
Pattern centered but still high on the drive side; coast side still seemed high and heel.
I figured the centered pattern meant my carrier shims were good but since it was high I needed additional thickness to the pinion depth shim. So I did the following:
Added 0.002" to overall pinion shim thickness.

Pattern test 4:
The drive pattern was still centered and seemed maybe closer to middle rather than high or low. The coast side seemed just more spread out as apposed to a bulk shift one way or another.

I'm not too sure of the importance of the coast side. My service manual didn't seem too clear about it.
Please take a look at the pics and see if you agree. I'm thinking I've got it but would like someone to take a look! :grin:

Original Drive:


Original Coast:


Test2 Drive:


Test2 Coast:


Test3 Drive:


Test3 Coast:


Test4 Drive:


Test4 Coast:

big gear head

The pinion depth is pretty close. Try adjusting the backlash in both directions to see if the pattern will move closer to the center between the toe and heel.

430Camaro

iTrader: (1)

Are you talking about toe/heel on the drive side(IE: not coast side)? I usually painted two teeth pairs per test, sometimes two teeth pairs 180 degrees apart to get a look at the pattern. It didn't seem like all were totally identical for one single test. Is that expected for used gear sets? So on test 4 you're saying it's still a little offset from center?

big gear head

I didn't know that these were used gears. How used are they? Are they factory installed gears or are they after market gears that someone else installed?

430Camaro

iTrader: (1)

These are used factory 3.42:1 gears out of an original factory rear end with probably 100k miles on them. I'm moving it over to a new housing because welded on trac bars the previous owner has on tore up the original axle housing tubes and I decided to do a complete rebuild while doing the swap.

big gear head

So the first 2 pictures are of the pattern before you removed the gears from the original housing?

430Camaro

iTrader: (1)

That's correct.
Also, all of the pictures are patterns while I had the parking brake on enough to require ~45 lb-ft to turn the pinion yoke...that's what my service manual told me to do to get a good reading.

big gear head

It's always hard to tell with used gears, but the drive pattern on these gears doesn't look like it's from a used gear. You were smart enough to do a pattern check before removing the gears from the original housing, so you know what it needs to look like. Don't bother with what the book tells you it should look like because you are not dealing with a new gear. What you need to do is try to get the pattern as close to the original pattern as possible. Wear on the gears will cause the pattern to look different on a used set of gears, so the pattern shown in the book is useless to you. Did you check the backlash before you removed it from the original housing? If you did then that is what you need to set it to in this housing.

430Camaro

iTrader: (1)

Yup, backlash was 0.011" which is a little wider than the spec of 0.005"-0.009". I had thought that I'm basically changing the wear pattern on these used gears if I try to bring them back into spec, which may not be a good idea...unless they wear back into one another. I took just about every measurement I could think of before I took it apart: backlash, pattern, all shim thicknesses and positions, crush sleeve length, pinion and combined bearing preload lb-in measurements, and I bought the RA Tech pinion depth measuring tool so I have that measurement as well. Although it seems hard to use on these stock gears because the back face of the pinion gear is not flat and the tool rocks on it making the measurement a bit subjective...

The backlash right now is around 0.009"-0.011". I get variation depending on the angle at which the dial indincator is sitting on the tooth. It's a bit tricky to get positioned right. But I tried to measure the original one in several places around the diameter and got 0.010"-0.011". So maybe I'm pretty close?
One other thing is, the pinion preload is ~20lb-in (using a small bar-type torque wrench) and the total (with carrier and axles and all seals) is ~22-23. The spec with new bearings is 15-30 on the pinion and 32-55 combined. So I'm wondering why the total isn't adding much. Original measured 16 and 17 so maybe there just isn't as much jump as the book says...

big gear head

Total bearing preload is a bunch of crap. The pinion bearing preload is the only one that you can measure. Don't worry about the total bearing preload. This number will change with gear ratios. The total preload will be much higher with a 2.73 gear than it woudl be with a 4.10 gear, so completely disregard this number. You do need to preload the differential bearings, but you can't measure it by using the pinion.

If you are using the old bearings then you have the bearing preload set way too high. If you have new bearings then you are doing good.

Don't try to reset the gears. Go back to the original pattern and try to copy it. If you try to reset the gears and wear them in again you will be making a mistake. These gears were set up at the factory to the correct settings and then they got some wear on them. They need to continue to wear in the same place, not a new place.

430Camaro

iTrader: (1)

Yup, all new bearings and seals. I was mainly using the total preload as just a double check but not putting a whole lot of weight into the reading, so I guess I was thinking right. That's a good point about it changing with different ratios. I made the diff preload pretty close with a feeler gauge to see when it started to drag and added that amount of shims, and I have to really work it to get it all in there so I figured I'm at least close.
After looking closer at the pics of the original last night and looking at the current pattern I think I'm pretty much there. The drive side looks simular with maybe slight "fingers" in the pattern extending out and maybe just slightly shifted to heel. And the coast pattern is also kind of hatchet/wedge shaped like the original too. So I think I'm going to call it good from here. I'm going to weld the housing/tube joint for whatever it's worth, install a new pinion nut, button everything up(w/ a TA cover), and paint.

Thanks for the help!

big gear head

You need to shim the differential tight enough that you have to tap the shims in, but not tight enough that you damage the housing or shims. You should have to pull very hard on the differential to get it to come out.

Welding the tubes on a 3rd gen Camaro isn't needed. The torque is transmitted into the torque arm and no twisting force is applied to the axle tubes.

430Camaro

iTrader: (1)

That's pretty much where the diff is at now. I can get it in with a combinatin of using an aluminum block to knock them in(since I don't have that cresent shaped tool) and pulling it out partially and jaming it all in together. I certainly have to get down in there and pull pretty hard to get it out.

What about loads on the tubes from the other suspension mounts like the pan hard bar? If anything I guess it would prevent sepage of fluid through that area if it decided to leak later.

big gear head

If you weld it you need to do it right. You are welding mild steel to cast iron, so you must use nickel rods or wire to do the welding. Read this. http://www.nastyz28.com/forum/showth...ing+axle+tubes