I've torn down a factory 4.88 to install a lockright. I wasn't changing the gears themselves, so felt that I would not have to mess with the actual gear setup. I did install a solid pinion spacer, and took quite a few tries to set up the 10 lb/in torque for the pinion bearing preload. After re-installing the carrier, I checked the pattern and it looks like the picture I have attached. Now from my reading (first time doing a third) it looks like the pinion is too deep. Can someone confirm this for me? It looks like I have to re-shim the pinion bearing (remove) to get the pattern closer to the middle of the ring gear (away from the toe). My backlash was set at 9 thou, which is what it was when I disassembled it. Am I correct in thinking that opening the backlash will not move this pattern toward center, that only re-shimming the pinion bearing will do it?
This makes me mad, cuz I thought I wouldn't have to deal with this with a factory setup. Now I need to source shims, and maybe bearings while I'm at it.
Hopefully ZUK will chime in and steer me in the right direction...

 

I don't know much, but yeah, your pattern is WAY off.

I thought the backlash was supposed to be 5-6.

x2 for waiting for ZUK. (did you PM or email him the link to this thread?)

 

Too tight on the nose of the ring gear teeth, pinion is too deep, add shims to back it out.

 

Once you back the pinion out, you'll also have to move the ring gear in towards the pinion a smidge too.

Now the reshim/test pattern, reshim/test pattern, crapola begins.

You'll get it just don't call it good enough and let it go.

PATIENCE is the name of the gear game now.

 

sorry I took so long...had some things going on. It does look deep but that could be just a backlash adjustment. Try 7 or 8 thou on BL. You shouldn't have to touch the pinion depth.

edit---I re-read your post and bl was at 9 already? Confusing.

 

shoot me some pics of the coast side....and the tools you used to set BL. Did you mark the spanner adjuster rings before removing them?

 

Thanks for the replies, guys (especially gear master ZUK!)
I'm an East coast guy, so wasn't up late enough last nite to reply then.

I don't have any other pics of my dial indicator setup, I wasn't really planning on documenting everything with pics, I only took that pic of the pattern at the end for the purpose of this post.

I did my best to get the dial indicator at a 90 degree angle to the ring gear. I did check the backlash before I tore it down, and it was at .009. I marked both of the side adjusters, and put them back in the same spot without adding any CBPL to check the pattern. The backlash was the same at this point as when I started, .009.

Like I mentioned, it is a factory 4.88 diff, I don't believe it has ever been touched based on the fact it still had the white paint on the pinion nut, which was still staked. I did press off the inner pinion bearing, there is only one shim back there with a thickness of .078.

I guess I'll be looking to get some shims to shim the pinion bearing, am I right in thinking I need to remove shims to move the pattern toward center?

Note to self: take more pics along the way.

At this point I don't know if I should reassemble it to get better pics of the tool setup and coast side, or remove shims and then do it...

 

Removing pinion shims will take care of the fact that your contact pattern is too deep (too close to the root of the tooth or too far to the left in your picture), but will do little for moving it away from the toe (moving it up in your picture). To move the pattern up to get your pattern centered between the heel and toe (top and bottom of tooth in your picture), you have to move the ring gear away from the pinion (increase backlash), which is surprising if you actually have the .009" you say you have. Are you sure you're measuring it correctly?

Start by removing shims to make your pattern a bit more shallow (move it to the right in your picture), then check your backlash again and adjust as required.

Once you get the pattern depth right, you may notice that you have a pretty good competition pattern (good depth, and concentrated more towards toe of tooth (bottom of picture), under load, your pattern will tend to move up towards the center of the tooth anyways.

 

Is that typo Ringmaster? He need to instal thinner shim to move pinion back...