Syncro front hub repair - anyone try knurling?

[Sodo]

Hope you all had a Merry Christmas and if not, a happy holiday I ate too much then slipped outside for a little mekkaniking (just a little).

Here's the blow-by-blow. Front wheel bearing was creaking and loose, sloppy, so I took it apart. When I put the wrench on the axle nut, got all ready to bear down on it, it was "loose". Nut turned with no effort. So this ruined my hub, and probably the bearing too. I had a shop service my axle (new boots) in 2009, 30k miles ago, I suppose either they forgot to tighten it (can't imagine that) or there was some problem wherein they DID tighten it to the 258 ft-lbs, but......it came loose over time.

Anyway, being loose damaged my hub, probably the bearing too. In fact I don't KNOW if the bearing was bad, but the wheel was loose & floppy. About 1/4" of slop at the top of the wheel. The bearing surfaces look perfect with lots of clean grease.

Recommend you fellas put a wrench on your axle, make sure you've got 258 ft-lbs. 258 ft-lbs is 200 lbs standing on the end of a 15 inch breaker bar. (258 ft-lbs ÷ 200lbs) x 12 in/ft = 15 inches.

This hub does not look good. Gotta pull this race off. Welded blobs so the puller can get a grip on the bearing race.

Puller moved the race just a little, but one of the blobs broke off (PING!) I half expected that (welding on a bearing race material) but I didn't like this puller arrangement anyway.

Decided to git after it a different way. Welded a pipe to the race and put it in the press.
I bought this 12Ton press at Harbor Freight for $109 the other day just to do this front-end rebuild.

Pushed the race off the hub.

Here's the ugly. Does anybody know if this hub can be knurled and re-used? Growing the diameter .007 is resonable for knurling, you can get to double that even up to 3x. Permatex bearing mount recommends for up to .015 of cylindrical clearance. This is better, it's knurled to zero, where the bearing mount fills the voids. So has anybody done this repair with success?
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[70coupyel]

What is the inside size of the race that goes on there. Do you have telescoping
gauge and a micrometer? Most press fits are .001 difference on the dia. So what was spinning on the hub to make the end smaller? Coming from a 2wd owner.
Also knurling the end can happen. I would bet that the steel of the hub might be a better steel. But I have no clue what it is. That means it's harder and the correct knurling tool is your friend.
What about sleeving it?
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[Sodo]

Here's a diagram of the hub and bearing arrangement.
I drew this up while xmas guests were talking about me so
I could listen to their comments and pretend to be self-absorbed.
I looked all over for this diagram (with my not-so great google-fu)
and couldn't find one so decided to draw one for TheSamba. I hope it's correct. Image was clarified Jan 1, 2017, added bearing driver dimension.

Bentley should have included this info, it's kind of important. You might print this pic and add it to your Bentley at P 40.23.

The double-row wheel bearing is assembled at the factory, all 3 races as one unit even though the inner race is 2-piece. Both inner races are a press-fit onto the (red) hub. Thus when you disassemble it, the (green) outboard race pulls out of the bearing with the (red) hub, I suppose destroying the bearing. The dark inboard race remains assembled with the (yellow) outer race.

This bearing arrangement requires that the axle nut is tight, really firkin' tight (258 ft-lbs tight) in use. I think you can see how - if the axle nut was loose - vehicle weight would cock the hub slightly and the (dark) inboard race would wear on inboard half of the (red) hub extension.

This is why they tell you you can't tow a Syncro without the front axles installed, or at least an axle stub tightened in there like a big nutted bolt holding it all together. Without an axle, you could use a large bolt or all-thread rod to hold the inboard and outboard wheelbearing races tightly together. Some people say you can't even put the weight of the van on it without an axle tightened. I think that might be overboard but exercising such caution would preclude you from forgetting, and perhaps towing it down the highway. Without a stub axle or a bolt holding the bearing together the hub could slide out and you'd lose a wheel.

In any case my van was driven many many miles with a loose axle nut, certainly worse than moving around the shop. I don't know for how many miles it's been loose, But I do know what shop serviced my passenger side axle on Sept 1, 2009 at 151,320 miles......grrrrrr.
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[rubbachicken]

to get the bearing shell from the hub, i put a grinder through it, not anywhere near close enough to mark the hub, once ground, a good sharp hit with a large chisel, they break really easily.
i've done 6 i think at least, everyone broke easily, after a touch with a grinder.
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[hans j]

I'm betting knurling won't support the weight of the vehicle. Nearly every single FWD vehicle and a LOT of the Quattro vehicles use this style bearing. I've done hundreds of them and yours is really bad rewelding and machining back down would be the best idea besides replacement.

I usually use an air hammer and chisel to remove the inner race. On the problem ones or hard to reach (mk4 VW), I will grind a slot like rubbachicken mentioned.
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[MarkWard]

Bummer. Short of a new hub, I think your idea of knurling would work. I would include Loctite bearing lock on the knurled surface, before you press it back together. Assembled and torqued you have a "sandwich" of parts sharing the load.

I would put some miles on it and recheck the torque and if ok, occasionally recheck it and the play. I don't believe it is dangerous to attempt this. At least less dangerous than driving with the nut loose. I would also check the r/s. Best of luck.
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[Sodo]

So you guys have been around these for many years and have not seen it repaired (or attempts) by knurling. Probably because nobody drives around for 30,000 miles with it loose.

I suppose if it's driven far in a failed bearing the hub can be ruined. Or if the hub is destroyed removing the bearing race. How ELSE do these hubs 'fail' (such that replacement is required)?
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[whip618]

if you are going to knurl the hub I would suggest that you install the splinned stub axle into the hub and run it between centers in your lathe, this would maintain concentricity and add support while knurling, knurl the hub oversize and then turn down to the required press fit dimension.

I am in the process of replacing the front wheel bearings on my syncro at this time and the measured diameter of the hub at the bearing seating area is 1.655 (this is in inches) and the ID of the bearing measures 1.653 so about .002 press fit would work.

Phil
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[bluebus86]

heating the race with an oxy acetylene tourch or the slicing method previously mentioned wpuld have prevented hub damage note that for next time.


if hub is impossible to replace, consider spray metal and remachining, or machine to correct size for a sleeve both shpuld be better than knurling for longitivity. some folks do make repair sleeves for tnis kind of thing
.

also if the nut was loose, make sure the hub splines wnere not messed up, as oftennhappens when tbe nuts is loose, the splines rock back and forth, widening them, at which point all the torque in the world wont stop them from rocking and re loosening.


if splines are undamabed, consider a sleeve to refit the bearing race if ypu cannot obtain a new part.
and next time heat the race or slice it to remove it. I have done both or either and never had a race damage the shaft on removal, it works

goodluck
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[Syncrozilla]

I have a nice used hub for a benjamin in the classifieds. I'm down to only a couple left. Just sayin.
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[Syncrozilla]

I just looked at theres one on there for $50.00. If it's good thats a steal. I'd be on that if I were you.
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[Sodo]

I'm surprised too by the lines from pulling the (welded) race off but I think they are inconsequential. The method I used was chosen because of the available tools, and it was efficient. I could have cut it with a grinder and split with a chisel too but saw other pics of someone cutting too deep and simply chose the welding method for forum variety.

[vanonimous]

Doesn't it look like in the picture that inner bearing race was walking on the hub even before you used the puller? Because of this damage pulling the race caused additional perpendicular scraping.

In other words it looks to me like it was already damaged and binding.

I have never done this job on my syncro but I am just about to. (wanna sell your press when done? ) I have removed various other non VW bearing races off hubs and they would come off fairly smoothly with some heat from a regular map gas torch.
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[hans j]

The galling on the outer portion of the hub for the inner race is definitely not normal. I'd say metal got transferred under extreme heat and pressure.

The hubs only get this much wear when the bearings have been bad for a very long time, or the axle but was left loose.

I've never had an issue with not using the loctite on the threads.
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[Sodo]

[IdahoDoug]

I agree it looks like the inner race also spun - I see lines under the removal marks from the race spinning. In operation, things got hot and loose and some unlubricated spinning happened.

I think you should clean it up and use the latest generation of bearing adhesive and see what happens! I've heard some great stuff about this stuff - the Loc-Tite bearing stuff.

Doug
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[Syncrozilla]

[IdahoDoug]

Agree, guilty as charged. I know its not going to last, but I also know Sodo's the one to do it and get some data safely, because he's the type to embrace this foray into the unknown. And he'd do it right by having a spare hub/fresh bearing ready to go and the knowledge to swap it out the minute it started squawking - using only a Leatherman, the spare tire, and some sharpened sticks on the side of the road!

And, it might surprise us all and last for 10,000 miles!!
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1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[Sodo]

Those marks on the outer bearing land are stains on the surface, not a spun bearing. Notice how the scratches cross them straight, and smear them, theres no depth. I can't imagine what caused them.

When I heard the wheel creaking, I was 200 miles from home. I felt the hubs and they were both slightly warmer than ambient. So I kept driving. Checked a couple more times, no heat. Drove home at 70 mph. No heat. This 183,000 mile bearing was running cool and happy. The inboard bearing land (worn away by movement allowed by the loose nut) is the problem.

Still surprised by the scratches, maybe the circumferential weld on that far end of the bearing shrunk it.

I think knurling a bearing land should generally be considered a temporary repair that you might run until you can locate the proper parts. This situation is not like others, as its tightly compressed by 258 ft-lbs, with no relative motion allowed. If any knurled repair has a chance to survive, this case, tightly preloaded, zero off-axis forces is a poster-boy case for knurling success. If you guys have heard of bearing adhesive performing well, how could it be a better situation than this? Also you seem to be favoring Loctite over Permatex. Any reason or experience?

Main problem with this as a 'test' is "the work", and you have to destroy a $50 bearing to disassemble it. Surely its better to assemble it with a good replacement but would not have a catastrophic failure. I predict the failure mode of a knurled repair might be; a re-creation of what I heard a couple weeks ago - creaking and a loose spindle nut. Another PITA.

This bearing land was damaged by motion allowed due to a loose spindle nut. There can be no motion between parts while theres 258 ft-lbs on that spindle nut. If it failed it would not be catastrophic or leave you stranded.

Also, "my sources" tell me that Syncro front wheel bearings run a long time, giving hundreds, maybe thousands of miles notice as they are "going out". Same as the rear wheel bearings you have to be absolutely clueless for a long long time to have catastrophic wheel bearing failure with a Syncro.
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[GoWestyYoungMan]

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