Today made the call to Tom's Diff and ordered most of the parts for the upcoming 8 1/2 R&P change. Ordering parts these days is always a cross your fingers and hope adventure. Several time previous have bought rear end parts from Tom's, all good results.
To be prepared for a new buying experience at Tom's first I see he passed away several years ago and the business looks to not have changed. GOOD. Next i know Timken was always the preferred rear bearing and that's what i had got from Tom's several previous orders. I know Koyo is another premier Japan bearing manufacturer. I find Timken is sold and Koyo is sold, both to the same "group" and some China production is the norm.

With that tidbit of knowledge called Tom's and got a very polite women in an office in Idaho, Tom's home town. Better yet it's Tom's daughter on the phone and my order zips through her keyboard. We discuss the bearings, mostly Timken and anything with a big C get returned to Timken. My order was shipped today, no idea on the total invoice, it is what it will be.

A little 8 1/2 now in the car history.
It was a low mileage 87 Olds 442 rear, they came with the 3.73s and it was an open, non-posi. A good deal for 650 shipped cross country, disassembled, in two Fedex boxes. Only the housing, axles and ring and pinion would be used.

Tom's supplied a new Eaton posi, all bearings and shim kit, a 1350 yoke, and a LPW girdle and ARP bolts installed. All the misc stuff, stainless brake lines, alum drums, expensive shoes, big wheel cyl, backing plates, hardware, everything new. Just installing a posi doesn't require dealing with pinion depth if reusing the R&P. You are reusing a factory installed pinion, replace bearings and crush sleeve, set preload and done. Just do backlash and good to go. That was a little over twenty years ago.

One day a noise on the left rear turned out to be an axle journal. New bearings and a set of Moser axles fixed that problem.

About 6 years ago decided to change ring and pinion to a 4.11 because when drag racing at a 115 mph trap mph engine was only hitting about 5300 with the 3.73 and Hoosier 27" tall slicks. RPM about 10% higher to 5850 at 115 with the 4.11.
So when the Yukon 4.11 went in a 30 spline Truetrac, 30 spline Mosers and longer ARP wheel studs, all new bearings, a solid sleeve and of course now need to do a total setup install. Good thing is a friend has the expensive pinion depth setting tool, i borrow it.
That was my second total build of that rear.

So today parts with be #3 build happening some time before autox season starts again. When i installed the McLeod RST clutch they say no slicks to be used with it's organic discs. For years i suffered with an awful clutch in the car, an On-Offer, not forgiving but never slipped. An RST was desired for years and when I was lucky enough to install one I threw away the slicks and didn't abuse the RST yet.

So now current tire size is back to to a 25.7" for running autox. With that tire and my 2nd gear ratio of 2.07 engine is buzzing close to and sometimes off the rev limiter at 6200 on course We end up leaving the start in 2nd and shifting to 3rd to kill off rpm and torque. Running a course in 2nd my son has hit the rev limiter several times, that's 54 mph. Me when i run the course I'm much nicer and know not to beat on an engine with a 15 years old build that needs to be driven a hundred miles back home that day. The 3.73 allow the car to run in 2nd gear and be 10% lower rpm on course rpm. I think i will be quicker because my gut won't be telling me to hold the rpm down as much.

The parts ordered today will allow me to reinstall the 3.73's i removed years ago. Stopped and picked up some more gear oil and my friend with the pinion setup tool runs that NAPA, step two of gettin it done, borrow tools. When i removed the 3.73 I measured the pinion depth before taking it apart. So have a pinion depth number to start width, even think i know what the shim stack is. And when i did the 4.11 install i made up all the setup bearings needed. I'd like to say it'll be an easy job but i pull the rear and do it on the bench. The hard part is finding someone to pull the rear out of the car. Somehow never can find that person and it ends up being me.
O boy.
Bob

This post is Lance Approved!! You'll also find it'll be a bit better at not breaking the rear tires loose on corner exit with the 373s.

Sounds like a good plan, as usual for Bob, and glad to hear the place you were dealing with previously (Tom's) is kept in the family and operating.

The posi unit in my SS's 8.5" is still working like a charm from you, think that's already 5 years ago now. I still have the stock 8.5" posi unit in a box from my 87' GN rear with about 200k miles on it. My rear end builder at the time offered to buy it from me since it's in good shape, but I decided to keep it. Sometimes wish I had 3.73's in the car but 3.42's have worked nicely.

I forgot that Eaton went to Paul's 8 1/2", someone else bought the 28 spline Mosers axles from that first 8 1/2" build.

One thing i will miss about the 4.11s is how outrageous the 1st gear multiplication of torque is. My T56 1st gear is 2.97 x 4.11 = 12.21 x the ton of torque the 427 makes down low. 50 years ago my 62 Nova had a 302 (DZ) with 2.20 Muncie 1st gear and 4,88s to get it moving. I thought that had a lot of gearing in 1st, it was only 10.73. Later pulled those 4.88s and install 5.38s so the car turned near 7300 in the traps with a 28" tire. And it still was only a 11.84.

Huge amounts of gear multiplication just makes the 86 easy to drive. But it's goota go now.
Bob

A box from Tom's Diff showed up on Weds. Timken, Made in USA, is on the two pinion bearings, pinion seal is Taiwan, a new pinion nut, cover gasket and yellow marking compound in the box. Somehow 10 ring gear bolts were on the invoice but not in the box. A call today to another nice person at Tom's and they are now on their way.
They say not to reuse ring gear bolts. When I did the 4.11 new bolts went in. In my rear parts stash is another set of used bolts, from my original 1st build of the rear. When I placed the Tom's order their was question if they had the bolts for an 8 1/2 ring gear. When they were not in the shipped box I then looked for other options to get a set. Ok, lets see 8 1/2 used both a 3/8-20 or the 7/16-20 and both are LH thread. My 8 1/2 uses the 7/16, let's see what a set of ARP cost, 89 bucks at Summit, OUCH!!!. Looking for less of a hit US Gear want $2.30 a bolt at Rockauto, so 30 bucks to the door.
On my Tom's invoice it showed 10 @.50 =5 bucks. The guy at Tom's today while talking to me put his hand into a box with a thousand of those bolts, stuck them in a small box and I have a tracking number already. His apology from Idaho and I'm waiting for another box. Thank you.

Three projects will happen at the same time on the car. First the trunk lid will be removed for some paint before the car goes on stands for the pulling of the rear.The rear get pulled and gears get changed in short order I think. While on stands the driver' seat will be removed for added bolstering and new factory appearing covers. Pulling the seat is easier when the car is on stands.
For the 25+ years of doing mods to this car downtime has always been a priority, keep it to a minimum. The goal for three projects is max of one month and thinking less than two weeks if everything fall into place.
I drove the car last weekend, maybe 40 miles, because my 02 SS needed some service in the bay the 86 rest in. The 02's rear Chinese rotors lost their machine surfaces from sitting and needed replaced, about 2 years and less then 10K miles, Not happy about that but that's life in the Chinese rotor market place. Also my Astro's 4.3L needed a new O-ring on the oil filter/oil cooler adapter and required the bay. Now my other junk driver's are good for a while and the 86 gets it's turn at being disabled for a short time. Just need to get my butt in gear and start some wrenching.
Bob

Sounds like a plan Bob! Wish I could find a good 8.5 10 bolt as it would make life much simpler but it's become a needle in the haystack.

Good luck Bob!!

A day of updates. With the painting of the trunk 99% done and the car driveable, the driver's seat well on it way to being improved with added bolstering and recovering, and the rear is on a work bench and 4.11s are out and 3.73 on their way back into the rear.

Been near 7 years since i installed the 4.11s and us old guys needs to relearn stuff. Like dealing with pinion depth, the tooth contact patterns on the R&P.
Initially I bought new bearings and a seal for just the pinion, thinking the carrier bearing at 14k miles would be OK. Well ended up ordering new carrier bearings yesterday and now need to wait to do the final install of the old gears. Can do the complete setup of the gears using the old bearings, Just need to swap carrier bearings and recheck, adjust backlash and carrier bearing preload if necessary.

Being a lot of the parts in the rear suspension had been installed in the car for a long, long time. The Edel UCAs and the Spohn LCAs and the rear's HR products bushing were all removed, taken apart, checked for wear, joints readjusted, lubed, arm length measured and reinstalled in the car. Can say that all 8 joints are in very good condition, this says something about delrin and it's ability to live in nasty places.

Being a stick shift car when the 8 1/2 rear was installed in 2002 new GM e-brake cables done. I felt it was time to refresh them. Every time I exit the driver's seat the e-brake is applied. Over the 20+ years that is thousands of times. My daily drivers are automatics, rarely use the e-brakes. So from Rock ordered new Delco cables, a L and a R, of course they are now China made. The R side has a clamp to hold it to the frame above the tunnel. The new clamp was the wrong, wrong location, and wrong configuration to bolt in. Had to remove the clamp from the old and install on the new cable. Minor detail, but!

Rear brake are stockish original drum brakes with alum drums, expensive HP brake linings and the 7/8" wheel cylinders. If you have ever bleed the rear wheel cylinders it's a nightmare getting a wrench on the bleeders and a hose to do a manual bleeding of those cyl. Many years ago made a special 5/16" box wrench to fit into the recess and loosen the bleeders, but always cussed when the hose popped off and fluid was all over the place.
What would help would be a longer than stock bleeder. Stock is about 23mm, about 7/8", and of course a metric 8 x 1.25 thread. Shopping for a longer bleeder and found getting a 35 length can be had easily in Europe, but no one in the US has them. I did find that Pegasus sells a speed bleeder that is 30.3 mm and bought two. Not crazy about them being a speed bleeder. Many moons ago bought Russel speed bleeders and ended up trashing them because the check valves in them got stuck closed. Don't care about the speed bleeding capability of the bleeders i bought, may end up drilling them out to remove that valve in them.
https://www.pegasusautoracing.com//productdetails.asp?RecID=6234

So painting is done, seat is in progress and rear gear swap well on it's way to being done. Three Winter projects nearing completion.
Bob

Bob, glad your getting your winter goals checked off, hopefully I'm right behind you on the gearing.

Progress!! Good luck getting things swapped out and wrapped up Bob!!

Trying to wrap up two Winter projects so i can go play in a parking lot very soon. Just posted that my driver's seat will be picked up on Mon, added bolstering, recovered and a third belt is being added.

Progress on swapping the 3.73 back into the 8 1/2 had a few things slow it down. Life events the big part of it.
And when you do a R&P swap every 6 or 7 years you need to educate yourself again. And when learning stuff takes longer because you don't take PREVAGEN, and you only get a couple hours here and there to play with it.
It just drags out.

The 3.73 going back in are my used set i ran for many years, Original GM set, from an 87 open rear Olds 442 rear. I installed an Eaton posi and all the internals the first time i did the rear. Pinion depth setting not necessary. Just change bearings, use the original shim, a .039".
Second rebuild of this rear i installed, Yukon 4.11, a 30 spline Truetrac with Moser's all the remaining parts. Pinion depth had to be adjusted, a .010" + the .039 was used. I used a T&D pinion depth tool to determine that. Fortunate to have a friend who has one. At 14k not the easiest of miles those Yukon 4.11 made zero noise and wear pattern on the ring gear when I remove it was very good.
https://tdmach.com/product/td-pinion-depth-checker/

Now for the third time the pinion depth needs to be checked cause it an old gear set. So the T&D has been used way to many times just trying to figure out why i think i need to adjust from the .039" original shim originally installed on this pinion, in this housing.

The T&D tool in it's round about way using the thickness of the pinion's head.will determine the pinion shim necessary. A problem for me was the 3.73 pinions head thickness is + or - .005" so when you check using the T&D that will effect the depth number produced by the tool. The 4.11 Yukons gears I did prior were uniform thickness and had an install depth number, setting pinion shim thickness was easy.

The 3.73s tooth faces have a fair amount of "run in" wear, with a new inner bearing, different backlash, different carrier preload, , all factors to consider in making this a permanently successful reinstall of a used 3.73 set of gears.
After playing with a lot of pinion shim thicknesses to see how it effected the patterns the .039 original is going back in.

When the first batch of small parts to do the swap were bought i failed to buy carrier bearings. Thought the carrier bearing being just 14K miles could be used again. After inspecting the races I ordered new Timken from Tom's.
I used the old carrier bearings for all the carrier test installs, to do patterns way to many times. That way if they got beat up no loss, new were going on for the final tweaks and install.
Last night i pulled the two bearing off the carrier, no easy feat. New carrier bearing now ready to be installed, inner pinion bearing with it's 039" shim ready to be pressed also.
Back not a decade ago I just walked into the rear entrance to the automotive machine shop two blocks from here and gave the owner a couple bucks for a couple pressings, they are gone now. Today tried 6 people for a quick and easy pressing and had 6 strike outs. And tomorrow is Sat, car repair shops are like doctors, short weeks. Will find a hydraulic press somewhere over the weekend, need bearing on for the final assemble this coming week.

Gear marking compound. Got a itty-bitty tube of it from Tom's. Used that up and had to find someone who had a little so i could waste it on my setting up. Not many people have a little gear market compound laying around. Even my T&D owner didn't have any. I bought two tubes of GM 1052351 compound off ebay the other day. One tube will to the owner of the T&D so he won't have an excuse. The other will go to the guy who had enough compound to help me.

Goal is by the end of next week rear reinstalled in the car and done. Driver's seat reinstalled in the car.
Bob

Bob, I understand the issue of only having a few hours too work on the project. With me working out of a 22'×22' attached garage that my wife and monte park in every night I spend 20-30 minutes dragging everything out work for an hour then 20-30 minutes to put everything back up. Just hard to get much done unless you have half a day or more.

I've ran into the same issue in the past about needing a press, everyone says drop the part off and I'll try to get it in a week or 2. When it comes to my axle bearings I might finally just buy a press.

Glad to see both seat and gear projects coming to a close.

Back in the day within a few miles we had 4 automotive machine shops that sold parts out the front doors. Drop a pair of drums or rotors off to get cut, stop back at lunch time and pick um up. When i installed the RST clutch a few years ago had to drive a 1/2 hour back and forth two times to the only place with the needed tool. Two hours of my travel time just to Blanchard surface a flywheel.

Last year needed to have the delrin bushings ID for my new three piece sway bar opened up a little. Took me a week to find someone with a lathe. 20 years ago had numerous places i could have that done.
Times they have changed.

I will have bearing pressed on Monday, just need to be as persistent as always to get things done.
Bob

I left my hydraulic press in KC when I moved away but bought one once again after I got setup out here. You don't use them much but when you do need one, you need one.

Good luck getting the time to get things finished up...racing season starts soon!!

The last time I needed marking compound the Chevy dealership had a big tube (2-3 oz?) in stock.

Bernie off Ebay bought two GM tubes, 1052351 for reasonable, like 31 delivered. Yesterday gave one tube to the guy I borrowed his last little round container off compound from. And he has a press, and I didn't have time yesterday to use it but later today will bother him for press time.

Have you been to Harrisburg yet? We are hoping for June 17 as our first trip.
Bob

Progress, pinion bearing and carrier bearings now pressed on late this afternoon. The press is in the back of the shop and everything was happening out front, the other side of the wall, lucky me. Best part, free. NOT! Best part done. Happy with both outcomes.

Tomorrow should have a few hour to do what should be the final round of checks before final assemble. Carrier bearing preload with now new bearings changes that a few thousandths of an inch. That carrier preload method using the GM's method is add .004" per side after zero preload. A simple method, add shims to ring gear side of carrier until you have zero lash, then add shims to the opposite side to obtain zero preload. Zero backlash at zero preload, a tedious but precise way to find zero preload.
You mike the shim stacks on each side and add them together, that total number becomes your reference total which now .004" preload per side adds .008" to the total.
So .250 one side, .220 the other = .470 + .008 = .478

When you do final drop in and backlash you are pulling a few thousandths off one side to the other. The trick is to keep the "total" of both side shim stack the total number with the added in .008" preload, .478. It's a dance doing the couple thousand thick shim flip flops. Why 478 is so special, like a wild card, you hope to get it right away.

Hate to say it but one advantage to a 9", backlash and preload gotta be a lot easier.

With limited time currently to play with the car things that only took a week not that long ago now take a month.
Once the R&P are in there final resting place the rear can go back under the car. All is ready there. Probably should get the RT660's out of Winter storage and put them on now.
Bob

Just a short update.
The axles are still laying on one bench, the girdle another and the housing still sitting on stands on another bench.

When, weeks ago, the new carrier bearings were installed, by me, on a press I had never used before, in a dark corner of a shop, not mine, I found they didn't bottom out on the carrier, about .005 to .010" each bearing.
When I got the carrier back in my shop. I pulled the new Timkens just installed, ordered another new set of Timkens, waited a week again for delivery, made my own install tool using 16" of 5/8-18 rod and pulled, not pressed, the new bearings onto the carrier, in my shop. Preheated the bearings to make install less stress. A 5200 watt dryer heating element run on 120 with a hanger was used as an oven for preheating. Worked great.

Now have the carrier sitting in the housing, pinion depth set and good patterns, pinion preload solid spacer thickness known, back lash at zero carrier preload known using known shims and ready for final shimming side to side to dial in backlash and carrier bearing preload.
Finally, now 5 weeks into this I can see soon the rear end finding it's way back under the car.

Trying to remember why a perfectly good 4.11 R&P I removed to reinstalled a used 3.73.
Oh yea, that will allow my son to run a slalom in 2nd and not hit the rev limiter.
Bob

Bob, glad you are making some head way. We are pretty much running parallel but the one advantage I have is mine is a separate project that does not add downtime. Me and you are the same on keeping downtime to a minimum so I feel your pain. You are ahead of me though on your setup.

Last night I pulled all the external pieces I had bolted on off, put the alignment bar through one last time to check. I left all the old races in while doing the fab work so I didn't have to worry about damaging their seat area and drove them out so I'm down to bare housing. Plan to go home to do a thorough scrub inside and out on the housing tonight. Drive in new races, put ring on diff and torque and hopefully get everything setup to start installing when I have a larger block of time as I want to do it in one shot with not a lot of stop and go.

Keep us up to date.

Fri afternoon found the carrier is now permanently bolted into the housing. Very happy with all the final install numbers derived. Because this 3.73 GM gear set was used, by it's original install in an 87 442 rear and then by me for 15 years behind my T56 spending the extra time to try to duplicate it's old install was done. Once back in the car and highway speeds will hope for zero gear noise. Third time I've had this rear apart and set back up, third time a charm?
With all new bearings ended up with good patterns on the coast and drive, just the pinion's preload set at 19-20", backlash at .0065" and total with carrier bearings preload of 20". Good numbers for this 8 1/2"

Tomorrow is Father's Day. My daughter asked what would I like? Four hours at the shop to finish assemble and bolt it back into the car.
Bob

Get 'er done Bob... Me bets that you are going to love having the 373 back in there, especially on the autocross course.

Rear is hanging by the shocks back under the car. Everything bolted/torqued back together except the rear drums brakes are yet to be reinstalled. Rear brake line get flushed, wheel cyl bleed and will also need to adjust the ebrake which has new cables.
The rear brake parts on this 8 1/2 are all good stuff, upgrades and work very well. Just need to dial in the amount of play on each side and know they do the rest. The 7/8" wheel cyls, expensive linings, alum drums and a Steward valve makes for a good cheap rear brake with a very good E-brake.

The Falken RT 660 have been sitting here at the house, staying warm during the Winter. Tomorrow will load them in the Astro for the trip back to the shop. Made the decision today that the BFG Comp 255/50x16s on the car now will make the trip to my tire guy. They now are well past prime and have aged out, 7 years old and just need to get trashed. A shame because they are just getting into that tread depth left that make them better handling. It's just the rubber has given up and aged out.
The Falken 17" RTs will live their final days over the next 10 or 12 months mounted on the car.. And, will need to survive next Winter sitting in the shop. The 35 degree temp thing is a problem when you have expensive, sticky Summer only tires. Sure wish fuel oil was still 49 cents a gallon.
Bob

The 8 1/2" finally has got maybe 50 miles of driving on it now. First quick drive around the block noted a 1 sec very subtle gear noise when going from the drive side to the coast side transition on the gear teeth. Several subsequent drives noted the same noise at the same time at various speeds from 40-60. I'm not happy but will drive the car for a few hundred miles to see if there is a change. Zero gear noise on hard acceleration on the drive side and zero noise on the coast side, it's just that 1/2 sec transition noise.
I knew because the R&P was well used, and I did not bother to check/write down the backlash when I pull that set of gears. So I was shooting in the dark when that set got reinstalled. Backlash was probably on the looser side, maybe .009" when i pulled the 3.73 in 2016, I reinstalled at .0065". Hindsight now say should have set the lash looser.

I will live with the very slight noise for a little while. If it doesn't clean up sometime before the snow flies the carrier will be pulled and backlash will be loosened up a little. The rear can stay in the car, carrier pulled and already know what the shim thicknesses side to side will need to be to get to the "loose" backlash setting. Biggest PITA to that is the dripping gear oil that will happen and constantly be the PITA.

Noticeably reducing the rear's ratio by 10%, 4.11 back to 3.73, I can tell when driving the car. The ton of torque the engine produces at the low rpm range is effected by the reduction in ratio, and i can tell it's gone. I drove the car for decades with the 3.73s, just need to now readjust.
Bob

I think it'll help a ton in autocross...both with more speed in 2nd and less likely to spin the tires on corner exit.

Have had the car numerous short trips now, might be 150 miles. Just not happy with that little bit of gear noise. While I still have the interest in possible fixing it today stopped at Napa and picked up a new gasket for the 8 1/2". Drive to the shop and the Lincoln, and a pair of jackstand, and then a clean bowl to catch the gear oil was in process.

Because i'm now a 72 year old, laying on his back, under an 8 1/2, sliding a truetrac out far enough to get the shim packs out, thing move a long a little more carefully, can't get cut, hurt. Reinstalled the bottom carrier bearing cap bolts, took care of the carrier even needing to be removed, the bolts allow the carrier to nicely sit on them.
Once the shims stacks are out you play with the dozen or more of shims to get the new stack thickness you think you need for each side. The gear noise i hear is during the transition from very light drive torque to just the start of coast. Under 40 not really noticeable, rear hot maybe a little less.

Hindsight says I was probably wrong to set up a well used, old GM 3.73 R&P on the tight side of the spec. Spec is .005-.009 and I setup at .0065". I set up that 3.73 gear set once before, back in 2002, when I installed an Eaton and all new bearings in the 8 1/2". It never made any noise.
Now my thinking is back in the day when it made no noise and had lot of wear it was over the .009" just because of age, use and abuse.

Today i pulled .004" from the right side shim stack and added it to the left side of the carrier. A pretest of the backlash before disassemble was .0065". All back together with the .004" adjustment and it's now .009". The girdle is torqued down, the fill plug on the housing has spewed it's full, lug nuts torqued.
Tomorrow, should be able to find a little time to see if the noise has disappeared. I hope, I hope, I hope.
Bob