[firechicken]

I'm attempting my first ring and pinion swap this weekend and am looking for any pointers from the rear axle pros on the board. I'm aware of shimming to achieve proper backlash, but am still uncertain of how to set proper pinion depth. I see the new gears come with a card with the checking depth and recommended backlash numbers on it. Any advice? Also wondering what kind of performance gain I could expect from the change to 3.73's from 3.23's in my 400/425hp 4-speed T/A.Thanks in advance.

[firechicken]

I'm attempting my first ring and pinion swap this weekend and am looking for any pointers from the rear axle pros on the board. I'm aware of shimming to achieve proper backlash, but am still uncertain of how to set proper pinion depth. I see the new gears come with a card with the checking depth and recommended backlash numbers on it. Any advice? Also wondering what kind of performance gain I could expect from the change to 3.73's from 3.23's in my 400/425hp 4-speed T/A.Thanks in advance.

[GR8ONE68]

This is a perfect question for Ol' Pinion Head! Has anyone seen or heard him lately?

[Tim Swain]

I'll tell ya it's a job. You may want to consider taking the whole rearend out, so you can work comfortable. Set it up on saw horses or sumpin. I made a puller out of 2.5 exhust pipe about 3' long. You'll need a powerfull impact wench to collapse the crush collar,Inch pound torque whench. The chassis manual is big help.

[TinInjun]

He's a few pointers. Use your old shims as a baseline to start from. Then check the contact pattern and start your adjustments.
You cannot swap 3.73 gears on a carrier that had 3.23 gears without using a ring gear spacer.
This is the Cliff notes version. I strongly recommend reading the shop manual before attempting this job.

[firechicken]

TinInjun,
Unless you know something I don't, A series 3 carrier will fit gears from 3.00-3.99 Can anyone confirm this for me.

[TinInjun]

I might have jumped the gun with the ring gear spacer. Assumed that this was a 8.2 inch 10 bolt. The carriers break down like this.

8.2 inch 10 bolt
2.56 - 2.78
2.93 - 3.23
3.36 - 4.33

8.5 inch 10 bolt
2.41 - 2.56
2.73 - 4.10

12 bolt
2.73 - 3.73
3.90 - 5.13

I'm sure OPH will poke his head in here and help me with any corrections. Earth to OPH,,,,, Come in OPH [img]/infopop/emoticons/icon_smile.gif[/img]

['ol Pinion head]

Tin's right, you can get away with same 8.5 carrier. Always smart to disassemble the carrier & ck the clutchs. I replace all the clutchs in 9 out ten 8.5 carriers that I get in as cores, most have clutchs that are marginal at best, but usually are wasted after 22+ years. In doing this, one will need an asst of special order GM clutch side shims to correctly shim the clutchs & side gear to spider gear tollerance.

A few pointers...
-With aftermarket 8.5 corporate gears, best to start with an .035 pinion shim. Don't use the .039-.041 stock GM pinion shim as a starting point.
-When installing new races in the housing, be extra careful not to raise a burr or ridge when removing the M802011 big pinion bearing race... doing so will effect pinion depth.
-You are going to have to do alot of plugging & chugging to get the pinion depth right without a good pinion depth guage. I always use 2 pinion depth tools (1 to ck the other), then confirm with patterns. During assembly, I use JT6 Mystic grease on the bearings. Also while doing this, use grease on the pinion nut to prevent galling of the pinion threads. At this early point, use an extra pinion washer or two to keep from running the new pinion nut on all the way, as you chase pinion depth. Only want to use about 2/3 of the nut's threads at this time. Using old pinion nuts can gall the pinion threads, even with grease applyed.
-Don't install a crushsleeve till you have the pattern dead nuts on. Randy's Ring & Pinion has the best understandable gear pattern charts. At this time, one can dissasemble, clean the grease off the pinion nut & pinion threads with solvent. Come back with blue loctite & carefully sneak up on 25 inch lbs of pinion drag as nut is tightened. Do not use airtols here. You don't want to tighten & crush the crushsleeve too much. Doing so will require disassembly & replacing both crushsleeve & pinion nut.
-When running patterns, will need someone with heavy leather gloves on to put drag on the pinion flange dust seal while you turn the axle with pinion flange tool. Wives or girlfriends don't seem to like to do this [img]/infopop/emoticons/icon_biggrin.gif[/img]
-Tools...At the very minimum, going to need access to a bearing removal tool, big hydraulic press, rigid pinion flange tool, & an inch lb torque wrench. Also I would not attempt this with rear in the car, unless car is on a lift & you have help. Typically, I bench build everything, Can't pay me enough to lay on my back & attempt this.

[firechicken]

Thanks OPH,
You'll probably call me stupid but after picking up my new 3.73 gearset today I went straight to a local tranny shop and had the gentleman there pull my old pinion bearing off the pinion and press it right on to the new one with the stock shims. Went home and replaced one carrier bearing that was flaking on the rollers. Had to cut the old one off. I used a cutting wheel in a die grinder. This worked much better than my cheap 2 jaw puller that stripped its threads almost immediately. Assembled everthing back together using original carrier shims and backlash is right on at .008 and the pattern looks to be good in my opinion comparing to a couple of charts including Randy's R&P. Could I be this lucky? I'm going to take it to the kind man that pressed my bearing (free of charge) and let him have a look for the peace of mind. Thanks to all for their input.

['ol Pinion head]

Firechicken,
What line of aftermarket gears did you buy/install?

While correctly setting up Richmond, US Gear Torqueline, US Gear-Strange, Precision, & Motive 8.5 10bolt gears, I've never used a pinion shim thicker than an .037, basically all of the aftermarket 8.5 gears that I've used, all set up between .028-.037 (that's over 400 new aftermarket gearsets). At the same time, all the factory GM 8.5 pinions we've pressed the bearings off of (close to a thousand of them) had .037, .038,.039,.040,.041 or even the rare .042 or .043 pinion shim (these not even listed in the parts book). The vast majority of these factory shims were in the .038-.041 range.

Side shims, have never had an instance when swapping in new gears where I could go back with the same exact thickness side shims as factory. I would never call anyone stupid, I just seriously doubt the odds of this happening & gears being set up correctly.

I mentioned starting with a .035 as it seems to best work for me & several of my protogee's. There are those out there that suggest using the same one off the old GM pinion. That is how I used to start with used GM gears when swapping into other housings. Problems... have a local GM dealership whose R/E "tech" seemed to enjoy using the exact same pinion shim as original. I have since rebuilt over a dozen Pickup/Blazer rearends out of that dealership's service dept...all of them were incorrectly set-up & howled.

Just trying to be helpful, I hope your install works out fine.

[ March 22, 2002: Message edited by: ol' Pinion head ]</p>

[firechicken]

The gears are a cheap set made in Italy. I wanted to do the swap as cheap as possible in case I screwed everthing up and lost my investment. I really just wanted to learn how to tackle this procedure for future gear changes and I think I've accomplished this to some degree. As for your remarks on the pinion shim,OPH, I know the backlash is within tolerance, and as for the shim I've arrived at the conclusion that if anything, I need a THICKER pinion shim. I'm sure I'm no pro at deciphering contact patterns, but the one I ended up with is near identical to the pattern on the 3.23 set I replaced. I'm going to put plates on the car today as the sun finally broke out here after a late snowfall last week. I'll post my road test results in case you may be interested. Thanks again,
Keith