Rear wheel bearing? - 99 Suburban C2500

[stutaeng]

??? OP has a 9.5" axle...

 

[Pinger]

??? OP has a 9.5" axle...

Yep, and...

Random thought... If the G80 carrier does end up being worn out, personally I wouldn't spend any time or money trying to rejuvenate it. IMO they weren't a great design to begin with. If one of mine ever fails I'm putting in a Detroit Locker or TrueTrac, unless I just end up swapping the entire 8.5" axle for a 9.5" semi-floater.

... limited options being in the UK.

At worst, it looks like clutch packs - which I'll replace if I have to.

 

[df2x4]

??? OP has a 9.5" axle...

Whoops! Not sure how I missed that...

... limited options being in the UK.

Out of curiosity is it more of a price markup issue or just availability? I figured you could probably get Eaton carriers over there fairly easily. Shows what I know I guess...

 

[Pinger]

Whoops! Not sure how I missed that...



Out of curiosity is it more of a price markup issue or just availability? I figured you could probably get Eaton carriers over there fairly easily. Shows what I know I guess...

Availability - no 'treasure yards' packed with GMT400s here - unfortunately. However, pursuing parts via Eaton and/or checking if any officially imported vehicles had the same components is worth considering now you've mentioned it.

So far, unless something catastrophic has happened inside my diff (unlikley at 45,000 miles and it being so quiet) parts from Rock Auto should sort it. New parts - always good.

Just trying to see if I can tell if it's shaft and C-clips or clutch packs causing the problem which I may be able to do if I've correctly figured how it all works and, can gauge if the extra play is in the inward or outward direction. As ever, waiting for Schurkey's (Shurkey the shovel - digging me out of another hole) comments and then order some parts and get stuck in. Reluctant at this point to order clutch packs until I know absolutely they are required. I'll open it up to replace the shaft and C-clips and again if it needs clutch packs. Or that's where my thinking is at the moment.

 

[Schurkey]

Thanks Shurkey - much appreciated.
I kinda figured there must be a block with the pinion cross shaft running through the middle of it.

While I appreciate the thanks...that wasn't me.

That was Stutaeng.

When there is more axial play than there should be, it isn't obvious whether the additional play is in the inward or outward direction - or both. For the C- clip to become dislodged, there has to be sufficient inward travel (as per the standard removal/refit method). Would the drum contacting the brake shoes' edges prevent that extremity of travel?

I wouldn't count on that. Too many folks have the axle shaft walk out of the axle tube to rely on the brakes to save the day.

As the clutches wear, the side gear moves farther outward. When it moves outward enough, the C-clip falls out. So it's not "just" a matter of the axle shaft moving too far inward, the side gear can move too far outward. It's the relative position of the two parts that matters.

I'm still a bit freaked out that my G80 clutch packs could be at the root of this. If they are so worn as to be the cause, do you think the locking facility would still be functional?

I don't have enough experience to answer that, except to say that clutches that worn aren't doing things any good.

Do you know for sure that your Gov-Lock is actually working? Mine did, when I first installed it. In fact, it was really aggressive, causing a noticable lurch around corners when I had the throttle applied. After about a month, I had no indications that it still functioned. Changed fluid a couple of times to remove all the Amsoil (with included friction modifier) gear lube, and now it seems to work again...I think. It's no longer aggressive at all, but it does seem to engage--smoothly--on low-traction corners. (Makes for easy U-turns )

I've been digging into G80s (including a how-to replace clutch packs on an 8.0'' unit) and am struggling to understand how correct meshing of the axle shaft gears with the spider gears is achieved and maintained.

Axle shaft gears = side gears, splined to the axle shafts
Spider gears = pinion gears

The mesh is sloppy to begin with. I have believed for years that some of these side gears/pinion gears are not even machined--they're forged (perhaps from powdered metal--near-net-shape) with only the most rudimentary geometry to the gear teeth. But I don't know that for sure.

I'm assuming that despite there being 'substantial differences with differently sized units, that the operating principle is the same across them all.
What I'm seeing when the locking is activated is the LHS (viewed from the rear) axle shaft gear being pushed rightwards and this motion is transmitted to the RHS axle shaft gear via the thrust block. Thus, the distance between the gears doesn't change - but that the two gears shift rightwards in relation to the spider gears (the hole in the thrust block being large enough or elongated to clear the cross pinion shaft). How does this not mess up the meshing?

With new-ish (fairly tight) clutch packs on both sides, the overall movement wouldn't need to be very much. As the clutches wear, the movement of the ramps on the one side gear and the ramps on the mating piece would travel farther, increasing the separation between them. So some of the additional travel would be used to lock the left-side clutch pack, with the rest being used to lock the right-side clutch pack.

As the right-side clutch pack requires more movement to compress the worn clutches, the side-gear travel would increase. But as I said--side gear mesh with pinion gear mesh is pretty sloppy.

Or does the cross pinion shaft have enough play within the diff cage to allow for the motion?

The cross-shaft should be a slip-fit in the case, but with no obvious "slop".

The shaft where it slips through the case would have very little wear--there's no intentional movement there. But the areas of the shaft where the pinion gears spin, and to a lesser extent, where the axle shafts bump against it, do wear.

If so, is the force to move it in the direction of the axle shaft gears transmitted at the gears or, is the cross pinion shaft snugly fitted within the thrust block and moves in concert with it (but still within the constraint of its clearance in the diff carrier)?

I have to think the thrust block has an oval or oversize hole that allows the block to move relative to the cross-shaft.

How worn clutch pack(s) can affect axial play: only in the outward direction?

Yes. Extra movement in the "inward" direction can only be due to wear on the inside tip of the axle shaft, or on the matching face of the cross-shaft. Those parts do wear...but not very much.

Inwards, the axle shafts are restrained by the cross pinion shaft - which can only move within its clearance in the diff cage.

The clearance between the cross-shaft and the differential case is not enough to be concerned with. Might as well think of it as "zero". In reality, I suppose a slip-fit of about a thousandth of an inch.

Outward play is restrained by the C-clip acting against the axle shaft gear which in turn bears against the diff cage with the clutch pack between its and the diff cage's thrust faces. Thus wear at the clutch pack increases outward axial play.
Have I got that right?

Yup. On one side, there's the matching-ramp part that causes the clutches to apply, but if you just consider that as part of the "clutch pack" you're correct.

About all that's left to consider is wear or distortion of the C-clip, and the C-clip groove in the axle shaft. I don't think either one is normally a big concern--but worth looking at.

It'd be nice to find that you've got a couple of worn C-clips, and not have to dig into the clutches at all.

Random thought... If the G80 carrier does end up being worn out, personally I wouldn't spend any time or money trying to rejuvenate it. IMO they weren't a great design to begin with. If one of mine ever fails I'm putting in a Detroit Locker or TrueTrac, unless I just end up swapping the entire 8.5" axle for a 9.5" semi-floater.

Far as I know, the 7.5" and 8.5" Gov-Bombs are marginal to begin with. So I would think twice before rebuilding one. I'm not saying that I absolutely wouldn't, especially if it were in a lighter vehicle. But if I didn't already have a rebuildable core, sure, I'd be looking for an aftermarket differential case.

But I don't think that's at all true with the 9.5 and 10.5 axles. I'd have no moral dilemma gathering parts to rebuild one of those, if I had a good core to start with. My plow-truck has the 10.5" axle, but with an open carrier. (Who orders a truck to put a snow plow on, but doesn't spend the money for a locking diff???) so there's a Truetrac ready to be installed in a couple of weeks.

I don't know what the OEM Gov-Lock parts-supply looks like. No doubt GM has discontinued every service part they possibly can. But what the aftermarket has, what dealerships have old stock, and what pleasant surprises GM may have...I don't know. Haven't researched it.

Just trying to see if I can tell if it's shaft and C-clips or clutch packs causing the problem which I may be able to do if I've correctly figured how it all works and, can gauge if the extra play is in the inward or outward direction.

Almost certainly "outward", but you'll find out when you open it up.

As ever, waiting for Schurkey's (Shurkey the shovel - digging me out of another hole) comments

"Schurkey the shovel." Well, better than the usual "Schurkey the turkey".

Reluctant at this point to order clutch packs until I know absolutely they are required. I'll open it up to replace the shaft and C-clips and again if it needs clutch packs. Or that's where my thinking is at the moment.

I'd open it up to INSPECT the cross-shaft and C-clips, and the matching grooves in the axle shafts. Replace parts as needed. But other than that, I think your process is right on.

 

[Pinger]

Here are the photos I meant to take yesterday. The center block is actually not solid as I assumed...

I did find this source for axle endplay, but it's listed for the 14 bolt 9.5" GMT 800/900...

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.canadawideparts.com/downloads/AxleComponentsInstallersGuide2015.pdf&ved=2ahUKEwjupsPx-tj3AhX4kGoFHWfVBOoQFnoECCQQAQ&usg=AOvVaw0kydQHWW6i9I3iFPcpDPyz

Thanks stutaeng - I mistakenly thanked Schurkey for this post.

Did you pull the pinion and side gears out of that unit with the ring gear still attached?

 

[Pinger]

Seems to me that there's a "special" C-clamp looking tool, for Gov-Lock "bushings" or some such. The service manual would tell all.

It has been years since I had one apart other than for gears/bearings, so memory is a little fuzzy. aI do remember the governor shafts/bushings being a pain to remove, cue expletives. There is a special tool, but you can improvise.

I saw that in the GM manual - whereas a 'how-to' on an 8.0'' G80 punched the pins out with punches.
Any more info on 'improvisation'? Does the C clamp have a forked end (to engage with a groove)?

Past the governor, I sure don’t recall anything difficult. I just did a quick net search and there are a couple videos out there that can show you how it is done.

Link to one of them? Can't find one specific to a 9.5'' one of appropriate age (1999).

 

[stutaeng]

Thanks stutaeng - I mistakenly thanked Schurkey for this post.

Did you pull the pinion and side gears out of that unit with the ring gear still attached?

No worries!

Side gears? Spider gears? No, I just removed the carrier and pinion because I was re-gearing it. I didn't mess with anything inside the G80.

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[Pinger]

Again, thanks Schurkey.
Quoting your post but heavily edited as most of it answers my questions fully.
A few more questions though.

Do you know for sure that your Gov-Lock is actually working? Mine did, when I first installed it. In fact, it was really aggressive, causing a noticable lurch around corners when I had the throttle applied. After about a month, I had no indications that it still functioned. Changed fluid a couple of times to remove all the Amsoil (with included friction modifier) gear lube, and now it seems to work again...I think. It's no longer aggressive at all, but it does seem to engage--smoothly--on low-traction corners. (Makes for easy U-turns )

As far as I know it is - or was relatively recently.

Axle shaft gears = side gears, splined to the axle shafts
Spider gears = pinion gears

Will stick with that terminology - ie, side gears and pinion gears.

It'd be nice to find that you've got a couple of worn C-clips, and not have to dig into the clutches at all.

See below.

I'd open it up to INSPECT the cross-shaft and C-clips, and the matching grooves in the axle shafts. Replace parts as needed. But other than that, I think your process is right on.

I think what I'm going to do is open it up before ordering parts (though maybe order cross shaft and C-clips in advance for the outside possibility of the clutch packs being OK).
To assess the condition of the clutch packs before pulling the diff out of the axle casing what am I looking for? Rattling slack thrust block? Uneven gaps between the plates (signifying excessive wear on some)? Actual axial movement on the side gears?

I'm probably dependent on Rock Auto for clutch parts. Here's all they have listed for a 9.5''

More Information for GM GENUINE 12471390

Listed as a 'right' fitment, 5 plates in total. How many plates does a G80 need in total for both sides and are they the same each side? (Guy rebuilding his 8.0 said they are but also mention of one thicker plate in the left hand pack).


GM manual talks of 'spreading axle casing'. Guy with his 8.0' just popped his out and back in without. What am I facing? And, as per Mr 8.0'', if I refit the bearings exactly as they were (including spacers/thrust washers), no problems with gear meshing etc?

One other thing that has me confused - though I'm maybe attaching too much importance to one guy's experience. Mr 8.0 found his LH pack shot but his RH pack OK. Would that be typical (given the initial actuation is from the left)? And, wouldn't it give rise to excessive play on the driver's side wheel - not the passenger's side where mine is? It doesn't however, seem plausible to have 2-3 mm of play caused by wear of the cross shaft and C-clip alone - agreed?

 

[Pinger]

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