[PunchT37]

Set pinion preload by itself.

[dataway]

Update on the progress.

New bearings are here.

Couple of tips for people doing a similar job ... installing new bearings and using original gears and shims.

Purchase a bearing splitter/puller, or clam shell puller because it's helpful to pull off the old bearings intact so you can compare the total thickness of old bearings to new. I cut the carrier bearings off so I have no measurement of the old bearings. I'm continuing on the belief that the Timken bearings of the same part numbers will have the exact same dimensions.

This is of course important on the rear pinion bearing. My project will be delayed while I purchase a puller to pull the old one off intact. If you are confident that the bearings will be the same dimensions then you can cut away.

So far the bearing outer races I've measured the new bearing races are all about .002-.0025" shorter than the old bearings. However this is just the outer race ... the total of the stack of outer race, rollers and inner race is what matters.

So far all ID/ODs were spot on ... which of course you would expect.

The new carriers installed just using a seal/bearing driver with no unusual amount of pounding. They self aligned and drove on with a medium size soft face hammer (using the "hard" side). So I didn't have to roll out the press.

So now I wait for a pinion bearing puller to get here. If I was brave and really trusted Timken I'd just cut the old bearing off and press the new one on ... but, since this is my first time, don't want to have a variable I can't account for.

If I get the old one off and find more than about .005" in total height difference from the new one I'll have to make up that difference with pinion shims.

Here's a picture to hold your interest ... shows nothing important, but all long posts need at least one picture.

[dataway]

Here are some exciting work photos

My new $120 Amazon special clamshell bearing puller installed on the pinion.

A photo of it staring the pull.

A photo of the old and new bearing next to each other.

And a very close photo the bearing rollers old and new .. hopefully showing that the rollers on the old bearing are recessed into the cone more than the new bearing.

I compared the two and found that the new bearing is .010-.0012 thicker than the old bearing ... which is more wear than I expected to see even with the damage I saw on it. After thinking about the rollers looking recessed on the old bearing I thought I'd get online and check the specs on this Timken HM 89449 bearing.

Sure enough the old bearing was measuring about .010" below the spec for thickness, exactly the difference I was finding between old and new.

So the old bearing, besides the internal damage had decreased the pinion depth by at least 0.010" and lost all preload. Again, I'm not a diff expert, but it seems like that could be enough to create some noise.

I will be installing the new bearing, the factory 0.045" shim which should return it to factory pinion depth. How this will play with the worn pinion gear and ring gear I don't know. I don't know how much of the bearing damage took place on my 5 miles or so of driving on the original rear end after sitting 40 years, or how much was already there at the point I took it off the road 40 years ago.

With the new bearings in carrier and on the pinion and using the factory shims the pinion and ring gear should be in the same relationship they left the factory with ... BUT with a pinion and ring that have 100K miles on them, and ran who knows how long with the damaged pinion bearing.

Basically I'm saying ... cross your fingers for me Surely it can't be worse than it was before.

[dataway]

PS. Should I grease all these bearings on install to keep them lubed before the diff gets oil thrown around, or just lube them with some differential lube?

[mrennie]

I oiled mine with gear oil. I didn't want to use grease because I had a limited slip carrier and was concerned about contamination, an issue you wouldn't have.

I was going to ask where the Timken bearings are made, as tons of posts over the years advocate the best quality bearings are "USA made Timken bearings". I see they are marked India...not surprised. I bought an NSK pilot bearing from NAPA and it was marked China, so I paid extra $$ to have a Timken version shipped from Summit, only to find it marked China. I put in in anyway.

[Shiny]

You are making good progress rapidly! And acquiring some nice new tools.

Reading through your summary, I think you need to be open to the possibility of the bearings being manufactured with different "heights" and needing to adjust the shims. That bearing puller should make that easy if it needs adjusting!

Mike

[PunchT37]

Originally Posted by dataway

PS. Should I grease all these bearings on install to keep them lubed before the diff gets oil thrown around, or just lube them with some differential lube?

I`ve used white lithium grease many times as a prelube. Also, run the diff on jack stands for 30 minutes or so before running down the road. That will seat/ run in the bearings. They can generate a lot of heat when new.

I`ve seen folks roast their new bearings with just a ride around the block. Too dry bearings and no run in. Especially on bigger trucks and such. Especially the pinion bearing. You would be suprised at the heat these things put out in the 1`st few miles.

[dataway]

What I found strange ... the inner race, cage and rollers were made in the USA, the outer race was made in India. Evidently precision has come a LONG way, these parts used to have to be manufactured together as a set. I sure hope Richmond Gear didn't get the parts mixed up before they shrink wrapped them.

Shiny, the new bearing is mic'ing at the same height as the spec for a new bearing of that part number, but yes I am assuming the height spec for that bearing number did not change in the last 50 years. And well ... you know what they say about assuming

Punch ... I recently installed some new spindle bearings on a big tractor mower deck .. yep, they got plenty hot the first hour or so and calmed down later.

Should have the pinion in tonight.

[Shiny]

Just for grins I looked up a Timken catalog (https://www.timken.com/wp-content/up...alog_10481.pdf) and find the total tolerance on the "overall width" of a tapered bearing is ~0.008" (+/- 4 mils).



So considering you are comparing two different brands, or at least two bearings manufactured a few decades apart, the 10-mil difference you found doesn't seem surprising.

But the real question is how sensitive the setup/gear pattern is to the pinion depth... anyone know how touchy this is? Does 8 or 10 mils matter when shimming the pinion depth?

???

Mike

[dataway]

That's more than I would have expected.

Basically I'm basing my decision on the fact that the new bearing measures exactly the width spec specified for that bearing number. The question is whether the OEM bearing of the same number also met that same width spec.

Over the years my experience with Timken has been that I rarely find a difference more than .001-.002 between bearings of the same number ... often dealing with tapered bearings produced in the 60's compared to new ( I replaced many tapered rollers on vintage motorcycles made in the 60's, both Timken and Japanese manufacture)

However .. yes, from what I've read, 0.010" would be a significant change in pinion depth. I think the OEM shims came in increments of 0.002" ... so I would assume that is the minimum significant measurement. How that applies to already well worn gears I don't know.

Probably wouldn't hurt for me to check the gear pattern at least and see if something is really wonky before I seal it up.

But I have no idea of the implications of setting up a good gear pattern on a set of gears with that many miles on it. Better to get a good gear pattern? Or better to have the same pattern it's worn into over the year?

Just ordered some setup compound, I have a full set of shims already.

[dataway]

Got the pinion installed with no seal, no sleeve and 20 inch/lbs of preload.

First observation is that it's completely silent spinning by hand, compared the rumbling sound of the previous bearing ...but this new bearing is greased so I'm sure that quiets it down.

I'm a bit surprised at the pre-load, 20 inch pounds is certainly movable by hand, but a LONG way from free rotating. Surely these bearings lose 10 "/lbs of that in the first 100 miles? I saw the service manual had a lower pre-load spec for used bearings.

The Pontiac Service manual specifies 25 "/lbs, I see numerous other sources saying 12-15 "/lbs (both for new bearings) ?? What would you guys use?

I notice the service manual says the pre-load sleeve keeps the front pinion bearing from spinning on the pinion shaft ... both the old an new front pinion bearing on mine are pretty much a press fit that have to be driven on or off (yes I mean the front bearing) ... no way it's spinning on the shaft, sleeve or not.

So to be on the safe side and for my curiosity I'm going to wait till my gear marking compound arrives and check the contact. At this point I have to remove the pinion again anyway to install the sleeve and seal ... so that would give me one free chance for a shim install.

Made the tool below to hold the pinion in place while drove on the front bearing, not sure if it's normal to use such a thing, but I don't know how one person would install the front end pinion parts without it.

[Cardo]

You could just use some white grease for gear marking....

[Shiny]

Sounds like you got this.

Smooth good, rumbling bad

Hopefully you've exorcised the demons and the depth setting will be easy to figure out.

[mrennie]

The problem with checking the pattern now is you will likely find it not ideal (due to having miles on it) and will not know if it is off because the bearings are different, or if it is off because of wear.

I have read many stories about guys trying to setup used gears and getting an OK drive side pattern, but coast side being less than ideal yet same as what was original in previous setup. The advice is usually to put it back the way is was rather than move the pattern for fear of creating more noise. Note: I have no direct experience with this, just repeating what I have read over the years.

You may recall I suggested getting a backlash measurement before disassembly. If the original side shims with new bearings still results in the carrier fitting tight in the housing, a noticeable change in backlash could indicate the pinion is not in the original location and with the results of a pattern check, may help guide you.

Regarding the pinion turning torque, I used the high (tight) side of the range when I built my 12 bolt. The purpose of the preload is to ensure a stiff assembly under all conditons so that the gear mesh is consistent, and building a higher horsepower car made me think this was the way to go. 20 in/lbs sounds good, I would not use 10-15 for new bearings.

[Shiny]

I mentioned my new gear set had a target depth stamped on the face of the pinion gear. Any chance your original gear has this?

I can't imagine a factory going through adjustments but my guesses are usually wrong.

Chasing down the original manufacturing adjustment method might guide you on matching the original setup.

[dataway]

I did a test assembly. zero noise that would indicate a major problem.

Backlash is .012" -- Pontiac spec for a new gear set is .005-.009", they don't specify any measurement for used gear set backlash.

Here is the problem, any original measurements for backlash would not help me since the pinion bearing was damaged and had no preload, so whatever backlash that was there would include whatever slop from the pinion not being held in place as it should be. If I had checked backlash BEFORE the pinion bearing got damaged it would probably have provided much more valuable information.

I'm shooting less for a perfect setup than I am for a setup closest to what it most likely had for the first 100k miles of its lifetime. I'm "assuming" that the pinion damage was mostly the result of the first few miles I put on the rear end after it sat for 40+ years (since it never made this whine while I was driving it 40 years ago).

The carrier with the new bearings, and original OEM shims seems to fit perfectly ... I had to lightly tap in the original shims. They were still snug when all the way in and square in the saddles. Carrier has zero side to side movement, rotates nice and smooth.

Cardo ... yes, when I was greasing the bearings with white grease the thought did occur to me that I could have easily used that as a contact marker

Shiny ... yes the OEM pinion should have a pinion depth stamped on it, at least that's what the service manual says. And mine does have numbers stamped on it ... which I of course ignored So when the pinion/carrier come back out to do a final install of the pinion I will have an opportunity to try to check pinion depth. Going to have to do some research there because the service manual specifies the use of all kinds of specialty factory tools. (I've seen the rear face of the pinion used .. but mine has a rough casting there .. no way it would be usable for any measurements)

Probably can't take much from it ... but the whole assembly rotates absolutely silently by hand. (and I did read in several good gear setup explanations that the primary indicator of a problem is strange noises when rotating by hand). Contact marker grease gets here on Tues so I'll have some pictures after that.

Thanks for the input folks, it's helping.

[Shiny]

Originally Posted by dataway

...Backlash is .012" -- Pontiac spec for a new gear set is .005-.009", they don't specify any measurement for used gear set backlash. ...

I'm sure you thought about this, but if the new pinion bearing was 10 mils wider than the old, have you considered reducing the pinion shim by maybe 5 mils? Not trying to create work for you, just curious what the backlash would be.

...Shiny ... yes the OEM pinion should have a pinion depth stamped on it, at least that's what the service manual says. And mine does have numbers stamped on it ... which I of course ignored So when the pinion/carrier come back out to do a final install of the pinion I will have an opportunity to try to check pinion depth. Going to have to do some research there because the service manual specifies the use of all kinds of specialty factory tools. (I've seen the rear face of the pinion used .. but mine has a rough casting there .. no way it would be usable for any measurements)...

That's good to know. I probably went down the same service manual path and improvised the measurement method I described before. Basically used a ground flat across the carrier saddles as a CL reference for the ring gear and my digital caliper to measure depth. Sketchy but it's what I had.

... Probably can't take much from it ... but the whole assembly rotates absolutely silently by hand. (and I did read in several good gear setup explanations that the primary indicator of a problem is strange noises when rotating by hand). Contact marker grease gets here on Tues so I'll have some pictures after that. ...

Woo hoo! Silent good. Rumble bad.

You are close to nailing this and being whine-free. Sorry you had to go through this but you're putting another notch in your restoration belt. Your car is beautiful and the work you do is impressive.

[dataway]

I'm sure you thought about this, but if the new pinion bearing was 10 mils wider than the old, have you considered reducing the pinion shim by maybe 5 mils? Not trying to create work for you, just curious what the backlash would be.

I didn't want to do that because I'm fairly confident the old bearing lost that .010" during its failure. The new bearing measures exactly to the width spec, the old bearing reads .010" below the Timken spec. Yes the Timken info says that's just about within the factory width tolerance ... but it would be hard to believe that it was on the very edge of the tolerance 50 years ago, and the new one is close to dead on.

My guess is the back lash would have been considerably more with the old bearing still installed, how could it not be with the pinion .010" farther away from the ring, or allowed to move around because of the bad bearing. Although ... jeez the way those gears mesh is very complicated, and I certainly can't say from experience what it would do to backlash.

I was thinking about your pinion depth method, going to try something similar ... I'm sure I have some suitable stock lying around. My problem is what am I going to indicate off of? The rear of the pinion is very roughly machined, varies by easily .030" and has all kinds of dimples and stamping. The OEM tool set didn't even use the pinion I don't think, it had a gauge tool that was inserted into the diff case and tightened into the bearing races and had some kind of weird build in mic that would read pinion depth based on where the tool sat in the races, then you would add or subtract shims to equal the number stamped in the pinion.

I'm almost enjoying the process, it's not like I'm pulling an engine or something I even bought several cover gaskets and a load of diff oil in expectation of multiple disassemblies.

Close up of the end of the pinion.

[1968GTO421]

Thanks to you for this thread, extremely informative. You've inspired me to get under my "68 and check out the condition of my 8.2 rear. With a 428 up front my 8.2 is not a keeper but I should try to keep it up until the budget calls for something better. Appreciate it.

[Shiny]

Originally Posted by dataway

...I didn't want to do that because I'm fairly confident the old bearing lost that .010" during its failure. The new bearing measures exactly to the width spec, the old bearing reads .010" below the Timken spec. Yes the Timken info says that's just about within the factory width tolerance ... but it would be hard to believe that it was on the very edge of the tolerance 50 years ago, and the new one is close to dead on.

It's as good a guess as anyone's. I am skeptical the bearings wore, just pitted from corrosion, but that is just my guess too. Regardless, impossible to know where it started, let alone how much it changed.

I expect the assembly was designed to maintain some preload for life, otherwise I think it would be noisy. In my experience, rolling element bearings will not wear when lubricated and operated within their load range. I can accept and would expect some preload relaxation but not wear.

My guess is the back lash would have been considerably more with the old bearing still installed, how could it not be with the pinion .010" farther away from the ring, or allowed to move around because of the bad bearing. Although ... jeez the way those gears mesh is very complicated, and I certainly can't say from experience what it would do to backlash.

I think geometry predicts a change in pinion depth will affect backlash. The gear geometry is complex, but the basic conical shape is not so much...

I also expect the backlash was in spec when new. So if out of spec now with the new bearings, why? Pinion depth change or gears worn? Or ???

I was thinking about your pinion depth method, going to try something similar ... I'm sure I have some suitable stock lying around. My problem is what am I going to indicate off of? The rear of the pinion is very roughly machined, varies by easily .030" and has all kinds of dimples and stamping. The OEM tool set didn't even use the pinion I don't think, it had a gauge tool that was inserted into the diff case and tightened into the bearing races and had some kind of weird build in mic that would read pinion depth based on where the tool sat in the races, then you would add or subtract shims to equal the number stamped in the pinion.

I'm almost enjoying the process, it's not like I'm pulling an engine or something I even bought several cover gaskets and a load of diff oil in expectation of multiple disassemblies.

...Close up of the end of the pinion.

Yes, that does not look like a high-confidence surface to measure! I agree it might not help you.

I think the best you can do is set it up in spec for backlash with a good pattern (pinion depth and side shims) and assume that's as close as you can get to original. The challenge with this IMO is the pinion depth and carrier shim adjustments are NOT independent. Hopefully your pattern oija board cooperates!

Mike