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Wed Jul 23, 2014 6:12 pm

091 tranny

I'm in the process of replacing my CVs/axles and I just noticed that my driver's side output flange has a decent amount of up/down and side/side play - 1/8" or more. No play in and out. I pulled the flange and, while there is a little bit of slop between the output flange and shaft, most of the play is at the shaft itself. So it seems that the play is at the output shaft bearing. This seems, well, not so good. What are the chances that I can tighten up the giant adjustment nut to pull out this slop? There does not seem to be any slop at the passenger side flange.

I did replace the output shaft seals a few thousand miles ago, so maybe I didn't tighten up the nuts enough, but I marked the nuts in two places relative to the case and re-installed back to that point. I don't think (hope) I screwed that up.

Perhaps the clunking/rattling I was hearing from the rear end wasn't the CVs after all . . .

Any help/insight would be appreciated.

-Chris

Wed Jul 23, 2014 6:21 pm

Some good info here, but nothing conclusive about this issue I'm having (other than it seems to be bad):

http://www.thesamba.com/vw/forum/viewtopic.php?t=147264&highlight=output+shaft+play

Wed Jul 23, 2014 6:31 pm

The flanges can get loose on the splines, remove the cap in the center and try wiggling the inner shaft. If the bearings were loose it'd howl and both sides would be loose.

Wed Jul 23, 2014 6:38 pm

Aren't the output flanges kept in place by locking tabs inside the transaxle housing? And when the adjustment is made during assembly, this is to preload the bearings, right?

If so, would that much play as described indicate that either the locking tab is not doing its job (broken, loose or missing), or the bearing is failing?

Wed Jul 23, 2014 6:42 pm

The inner shaft wiggles with the flange removed (drivers side). The passenger side does not wiggle at the flange. The axle is installed on the pass side, so perhaps I haven't tried hard enough to wiggle it - the drivers side wiggled easily with the axle mostly installed, however (CV bolts not yet brought up to torque). Last trip I went on two weeks back - no howling, maybe 400 mi roundtrip.

I agree that if the sideplate/bearing was loose, both sides should wiggle, but that is not what I am seeing. The wiggle at the drivers side is very noticeable, nothing at the pass side. Is it possible that the diff is just preloaded up against the pass side right now?

-Chris

Wed Jul 23, 2014 6:50 pm

type11969 wrote: Is it possible that the diff is just preloaded up against the pass side right now?
Yes, could very well be. If the shaft wiggles that's not good, you can try tightening the preload nut but that's really a job that has to be done while it's apart with the correct tools, tightening one side and not the other may or may not change the gear mesh/backlash between the pinion and ring. You may solve a problem in the short term but cause new wear on otherwise good parts that will add to the rebuild you know is coming soon.

Wed Jul 23, 2014 8:26 pm

The differential side gears/ output shafts run in a bushing in each side of the differential case. The fit of either bushing can be loose independent of the condition of the other one. The differential side bearings can be well preloaded and the output shafts can still have slop, the bearings and bushings are two different things. The flanges can and will get loose on the splines. OEM transmissions seemed to develop slop in this area much faster than a rebuilt one. It wasn't unusual to see a lot of slop at only 40K miles on a Beetle tranny or 002 Bus tranny.

So long as the seal gives a decent life, then you can just live with the slop.

Thu Jul 24, 2014 5:13 am

Okay, I'm seeing in bentley that the diff is supported independently from the output shafts:

But I'm not seeing the output shaft bushing, is there another tear down photo of the differential housing that I missed?

I grabbed these stellar phone photos on my way in to work, so it is possible that I missed something.

It does seem like this slop is going to beat that output flange seal to death, the whole flange I'm sure flops up and back down every time I accelerate/let off. I guess I can run it for now to see how long it holds up, not thrilled about the prospect of a rebuild either . . .

-Chris

Thu Jul 24, 2014 8:13 am

There is no actual bushing, but rather the bore the shaft runs in that is likely worn. This probably isn't cause for alarm for the short term .. just something to replace at rebuild time. Replacement diff covers (#12) are available.

Thu Jul 24, 2014 12:29 pm

Lets get a few terminology issues straight here so everyone is on the same page.

Lets be sure exactly WHAT KIND of play you are referring to. There are a couple of details with this differential that many ignore. I have the same adjuster system on my 004 transmissions, same hub part #’s and same issues.

Definitions:

A. Axial play. This is the kind of play you get when you are pulling the flange…or the differential output shaft…straight in and out

B. Radial play. This is the kind of play you get if from the side of the axle flange or the splines on the output shaft with the flange/hub removed….if you pushed straight at the shaft perpendicular to its length and it moved up and down say between 6:00 and 12:00 position.

If after removing the plug, snap ring and adjusting ring shaft seal…you can rattle the hub on the shaft in any direction…getting either just axial play (it slips in and out easily on the splines) or radial play 9which generally gives you both axial and radial play)…..without any apparent movement of the splined shaft at all….then what you have is worn hub or worn splines and usually both.

Yes…there should be a little play after many miles….but not wholesale axial and radial play. There is a range of issues that cause excessive wear to the hub and splines…and even worse…once the hub and splines experience excessive wear…..IF YOU DO NOTHNG ABOUT IT…..will cause differential issues.

ISSUES

1. In the exploded view of the differential on page 23 you will note part # 5 (one on each side of the differential) which is the thrust shim for the side output gear shaft and part # 7 which is the side output shaft spacer. If either one of these parts is worn…you will get too much axial play on the side output shafts which will accelerate wear to the hub and splines and usually causes leakage to the seal.

Part #7 usually requires many many many mils before it starts to wear and cause issues. However, part # 5….can get prematurely worn…..if the next issue is not corrected

2. Figure 6-1….the exploded view of the differential casing. Note part # 15…one on each side. This is a spacer ring that fits between the differential housing and the CV hub, inside of the oil seal on each side.
This spacer is critical in maintaining proper tension on the hub and in maintaining output shaft axial play and tension against its thrust washers (part #5 on page 23). If that tension is not proper…the side output shafts move in and out crating accelerated wear of not only the spacer (part # 7 on page 23)…but thrust washer wear…and most especially early wear to the side output gears and the spyder gears.

This spacer ring #15…is very commonly left out or lost when unknowing owners change seals or hubs. Also….these spacer rings are designed as wear parts..to be replaced when necessary….which is rare….but if you have a leaking seal and run that way for a long time….the dirt that gets in wears out the spacer part or the hub or both.

Leaving this spacer out or not checking its wear level and replacing it with a thicker one is one of the main causes of excessive wear and slop giving both axial and radial play at the hub. If you find a lot of both…check that spacer.

Also….if you are noting axial play at the splined output shaft…be VERY SURE….you note whether its play of the shaft itself moving in and out of the housing….which means worn thrust washer and/or spacer (parts #’s 7 and 5 on page 23)….which means disassembly but is fairly minor work to replace…..or

…..if the whole differential housing is moving axially in the differential case. If that is happening….you either have a differential out of pre-load adjustment in its bearings (really you always have that if the differential housing is moving axially)….because someone moved one of the aluminum adjusting rings…..or bad bearings from wear (eventually you will always get bearing damage if you run with bearings un-pre-loaded.

DO NOT MOVE the Aluminum adjuster rings unless you have the gearbox out so you can really check what you are doing.. If you must do so….and you have a reason to assume that the ring gear to pinion gear lash has not been messed with….turn the passenger side adjusting ring only. The Driver side adjuster sets the gap/lash between ring gear and pinion shaft by not letting the ring gear back away from the pinion.

All moving the passenger side adjusting ring changes is bearing preload between the bearings….but turn it far enough outward and it will misalign the ring gear radially to the pinion gear. Everything will be wearing crooked at that point.

Just some thoughts. Ray

Thu Jul 24, 2014 12:54 pm

I know I should have read all of the above post but I only read the first few because they all seem to be dancing around what is going on and not quite addressing it.

The cover plate for your differential housing is worn. specifically the bore that supports the drivers side, side-gear/trunion gear. The drivers side CV joint flange is the "drive side" that puts the power to the road. The drivers side will wear out first as a result. The diff bearings support the diff housing itself and not the spline'd output shafts the CV joint drive flanges mount to

If you can still get it to seal ok and the rest of the transaxle is operating ok you may be able to put off going through it for a little while longer but a gearbox is in your future.

Thu Jul 24, 2014 1:49 pm

Pretty much what sod said.

Thu Jul 24, 2014 3:15 pm

sodbuster wrote: I know I should have read all of the above post but I only read the first few because they all seem to be dancing around what is going on and not quite addressing it.

The cover plate for your differential housing is worn. specifically the bore that supports the drivers side, side-gear/trunion gear. The drivers side CV joint flange is the "drive side" that puts the power to the road. The drivers side will wear out first as a result. The diff bearings support the diff housing itself and not the spline'd output shafts the CV joint drive flanges mount to

If you can still get it to seal ok and the rest of the transaxle is operating ok you may be able to put off going through it for a little while longer but a gearbox is in your future.

Yes...you should have read it...because there are several items that it can 100% be...because they are more common than a worn differential housing which is what you suggested....and which it may only 10% be.

Also the items I described commonly cause a worn differential housing because they very quickly cause side loading at the hub and stub and loss of bearing pre-load......and the three items I listed must be checked either way, long before you get to verifying if the differential housing (trunnion as you describe it)....is worn.

Again...as I noted too many people skip these little detail items because they are in too much of a hurry looking at "whats" wrong...instead of what "causes" it.
Ray

Fri Jul 25, 2014 6:44 am

raygreenwood wrote: sodbuster wrote: I know I should have read all of the above post but I only read the first few because they all seem to be dancing around what is going on and not quite addressing it.

The cover plate for your differential housing is worn. specifically the bore that supports the drivers side, side-gear/trunion gear. The drivers side CV joint flange is the "drive side" that puts the power to the road. The drivers side will wear out first as a result. The diff bearings support the diff housing itself and not the spline'd output shafts the CV joint drive flanges mount to

If you can still get it to seal ok and the rest of the transaxle is operating ok you may be able to put off going through it for a little while longer but a gearbox is in your future.

Yes...you should have read it...because there are several items that it can 100% be...because they are more common than a worn differential housing which is what you suggested....and which it may only 10% be.

Also the items I described commonly cause a worn differential housing because they very quickly cause side loading at the hub and stub and loss of bearing pre-load......and the three items I listed must be checked either way, long before you get to verifying if the differential housing (trunnion as you describe it)....is worn.

Again...as I noted too many people skip these little detail items because they are in too much of a hurry looking at "whats" wrong...instead of what "causes" it.
Ray

Didn't even read all of yours because 35 years of VW aircooled Transaxle experience (learned using the factory tools and specifications) tells me otherwise. I choose to listen to my own knowledge my personal experience and my gut. Oh yea by the way, what caused it in the first place is age and wear. All 002 and 091 gearboxes do this to a certin degree. some more or faster than others. that simple.

Fri Jul 25, 2014 8:36 am

Good for you!

And none of that makes what I stated any less true does it?
35 years? is that all? I have more than that...just not all on transmissions.
:wink:

Also remember if you were doing this back in the day....or even 10 years ago....the vast majority of what you were working on had less wear than what everyone is working on now.

The parts I am speaking of have this problem COMMONLY...and if you worked on VW transaxles for a living you really should know this....and it costs nothing to inspect the parts I listed starting with what type of play/tolerance and exactly in what part area that play manifests itself before assuming what it actually is.

And lastly....the outer spacer for the hub to diff housing gap is one of the primary components that lead to wear and destruction of the spyder gearing.
Destruction of the spyder gearing is one of the main active problems leading to non ring or pinion wear related destruction of the differential. We all know what a shortage of non-destroyed 091 and 002 diffs there are now...dont we?

The gap between output hub and diff housing, thickness of spacer ring and possible excessive axial lash in the output shaft gear train......takes minutes to check....and is non-invasive.

You will notice that I stated that this is a common problem.....not this "IS" the problem.

You could very well be right...or wrong. My humble suggestion is to not tell people you KNOW EXACTLY what it is when no one would have no way of knowing EXACTLY what it is from the fairly crude description of symptoms in the original post.

Not trying to be an asshole....even though I really am an asshole.......

but you do a bit of a dis-service by showing up with the preface that ...."I have been doing this for 35 years".....that basically causes people with less experience to skip simple diagnostics. ray

Fri Jul 25, 2014 8:56 am

raygreenwood wrote: You will notice that I stated that this is a common problem.....not this "IS" the problem.

You could very well be right...or wrong. My humble suggestion is to not tell people you KNOW EXACTLY what it is when no one would have no way of knowing EXACTLY what it is from the fairly crude description of symptoms in the original post.

Not trying to be an asshole....even though I really am an asshole.......

but you do a bit of a dis-service by showing up with the preface that ...."I have been doing this for 35 years".....that basically causes people with less experience to skip simple diagnostics. ray

This is what it's all about. Teaching diagnostic skills is FAR more usefull than giving someone an answer which you don't KNOW to be true. By asking questions and teaching us to dilligently inspect, we can actually teach people to diagnose and repair issues, rather than just replace parts at whim.

type11969 - Sorry I can't help with the differential issue, but I will reminisce; VW had more inspectors than any other auto manufacturer at the time, maybe in history. It's your job to become all of these inspectors. Measure. Measure again. Ask questions. You're on the right path- but make sure you know how to find the answer, not just read it on the internet. Your bus will thank you.

Sat Jul 26, 2014 4:36 am

Awesome, thanks guys. To be clear, the issue I am having is radial play at the output shaft with the hub/flange removed - the play is not between the hub and the output shaft splines. The output shaft does not seem to have axial play, only the slight amount that allows it to radially move.

Does item #15 end up between the hub/flange and the diff bearing or housing? I did replace both oil seals within the last few thousand miles, so it is possible that I somehow misplaced this part. Without item #15, I can see how the output shaft would rely on the diff bore for alignment/support, with it, it seems that the output shaft, once the hub is installed, is supported by the engagement between item #15 and the diff-facing side of the hub. Correct?

I did remove both aluminum adjuster rings to replace those oil seals . . . marked the alignment beforehand, however, and returned them to the same spot.

-Chris

Sat Jul 26, 2014 11:24 am

type11969 wrote: . . . marked the alignment beforehand . . .

Does that mean both the clocking and the depth of the adjuster rings? I'm tending to think gross misadjustment of the adjuster ring(s) is the
cause of your output shaft wobble. Normal clearance between outshaft shafts and diff housing/cover is .001-.003 inch, it's hard to see how
even extreme wear there could result in the kind of movement you describe.

The #15 thrust rings sit between the flange and output shaft shoulder, you can see where they go in the diagrams on p.43, Trans&Rear Axle chapter
in the Bentley manual. They should have no effect on output shaft movement. If you have the flange removed, you should be able to see them
at the base of the output shaft.

You can pull the clutch housing and see what's going on when you move the output shaft.

Sun Jul 27, 2014 5:14 pm

Clocking and depth were verified.

I can get a .005" feeler gauge between the output shaft and the bore in the diff housing, and considering the stiffness of the feeler gauge, I'm sure the clearance is even larger than this. When I move the output shaft (without the hub). all of the movement is due to taking up this clearance. So bore wear seems like an issue as sodbuster mentioned

But

The thrust ring is missing, at least on the driver's side. A PO used what looks to be a CV joint spring shim between the hub and circlip on the output shaft. I never questioned it because I figured the joint had never been apart. The shim does seem to effectively take up the gap, but I'd rather be running the right parts (and this setup could be the cause of this bore wear).

So, does anyone have a spare thrust ring or two? Or recommendations for where I can find em?

Thanks for all the help!

-Chris

Sun Jul 27, 2014 9:48 pm

Try this outfit: http://longenterprises.com/, or anyone who messes with bus transmissions has
gotta have a line on those dealios. FYI: VW p/n 002-517-281 for the 002 trans, don't know if
the 091 uses the same.