Worn rear wheel bearing or something else?

[BDA]

No. You must adjust the crown/pinion backlash as well as the bearing pre-load with the tranny out of the car. These adjustments are not something you can do by just snugging the diff nut.

[Adde]

Ok, thanks.

[EuropaTC]

I think John is the most knowledgeable of us on this topic and as I've never pulled this type of gearbox apart I think I'd wait for his input before making your final decision on what to do.

Personally I would be tempted to fit shims and see how it all feels (play and backlash) before stripping the gearbox.  If there is serious wear present then I'd expect it to feel rough or noisy even when shimmed correctly. Then I wouldn't feel so bad about having to remove the gearbox from the car. 

I'd suggest that because it's easy and can be done in an hour or less whereas removing the transmission is a much bigger job.   Drive out the roll pin (make a punch tool if need be from steel rod) and with the car supported on axle stands on the chassis and the suspension free you should have enough movement to slide off the yoke and drop a few shims in.  Don't rotate the stub axle or yoke so you keep the holes aligned and know that the new roll pin should fit perfectly. 

My method of shimming was crude;  I guessed the first attempt and looked if the holes line up with the yoke pressed hard against the gearbox. If they don't, add or remove shims until it looks right. It's always been a tough job to drive the roll pin back in place with no play present.

As an aside, yet again I'm impressed with  the technology we have today and this interweb thingy. Even 20 years ago there would have been email debates over what was actually wrong and yet your phone video sets it out clearly.  I think this computer thing might just catch on y'know.....   

[jbcollier]

Typically there is NO perceptible axial play on the output shafts.  You have a lot of play.

Have a close look at the image you posted with the arrow to the diff.  The arrow points to the diff side and spider gears. Immediately to the left of the left side gear is the shim which controls the output shaft's axial play.  Here's another image:

http://www.rdent.com/manuals/europa/tcparts/transmission/FM.gif

The diff housing (incorporating the ring gear) is a solid assembly.  The external nuts set the ring gear's position and bearing preload but would have NO effect on the output shaft axial play.

The shimming people are talking about is the placement of shims between the pinned half-shaft yoke and the collar which the seal runs against.  The seal collar presses against the very large diff housing and its bearings which have no problem carrying the suspension's loads.  Without these shims, the suspension load goes to the internal side and sider gears.  These are not up to the task and quickly wear giving the excess axial play you are experiencing.  The play develops first, then complete failure.

Myself, I would remove the transaxle and repair the problem.  This may involve just replacing the diff side gear shim, or fitting another unworn diff housing.

Mr E. TC is suggesting that you properly shim the half-shafts.  This will correctly apply the suspension loads to the diff housing from the internal gears.  The internal shim/housing/gears will not get "better" but they will stop getting worse.  This may be worth pursuing and provide a lasting fix.  Unfortunately it is impossible to know for sure without stripping the transaxle and checking the diff's condition.

So, now it is your decision which way to go.

[SwiftDB4]

Or go to a twin link set up and not worry about pins, shims, and diff loading. Did mine 10 years ago.

[EuropaTC]

(part quote)
The internal shim/housing/gears will not get "better" but they will stop getting worse.  This may be worth pursuing and provide a lasting fix.  Unfortunately it is impossible to know for sure without stripping the transaxle and checking the diff's condition.

Can't argue at all with that John, whatever damage is done won't be fixed by externally shimming it correctly.

I have been puzzling over the video this afternoon while fixing my bike because to me there's a heck of a lot of movement and I kept thinking with that amount of potential wear on a gear or bearing we were into grinding bearings/gears that were shouting "fix me" very loudly.  I had a failure on the diff of a Scimitar many years ago and although it sounded like the axle was about to explode, when I replaced it I was surprised how little misalignment made so much noise.

Which got me thinking along a different tack, could this have been assembled incorrectly at some point and not driven much since ? The lack of loctite on the splines got me wondering because that's a well known item so perhaps there's an element of improper assembly here as well. I'm curious if there has ever been any shims fitted, internally or externally ?

[BDA]

Thanks, John! It's always an education when I read your posts!

[Adde]

Hi

I removed the UJ today today to see if I could pinpoint the axial play to the output shaft.
But, with the UJ removed I was not able to recreate the axial play through pulling/pushing on the output shaft.  I could feel some minor axial play,  but not close to what was seen on the movie before. However I could not apply the same amount of force now, but I tried by both hand power and through putting a screwdriver through the pinhole to get better grip.

This makes me unsure about where the real play is, i.e. in the axle or in the UJ?. If it is not in the axle I can not really understand how the UJ should be able to move on the axle whit the pin properly installed through the axle and the UJ. (The pin fit is tight in both UJ and axle, but maybe the pin spring when the UJ don't have a solid support against the differential house? Probably just a wishful thinking of me but I will start by buying some shims and add these between the UJ and the nut on the differential to see how that works. There don't seems to be any shims on the UJ right now, see fig)

"The external nuts set the ring gear's position and bearing preload but would have NO effect on the output shaft axial play." Ok, then I will not touch the nut.

I will return with the results and most likely further questions, too. (for sure if I decide to disassemble the gearbox)

All your support is so appreciated!

 

[BDA]

If you replaced the u-joints, the movement is not coming from them. From your video, it seems very clear that the movement is coming from the output shaft moving.


jbcollier is the expert in this area (and most others, too). I would prepare myself to follow his advice.

[jbcollier]

Wrap the output shaft with a rag and grip it with vise-grips.  That should give you enough grip.  Rotate the diff and try in several different places.  Hard to believe it is gone but you can't fix what isn't broke.

I quickly checked with my long-suffering wife and she assured me that I'm invariably wrong in all matters great and small.  Seriously though, we are diagnosing over the "phone" so to speak, and it is not always easy to understand what is actually occurring.  Lots of discussion and investigation is a good first step in any repair.  As I tell my students in the mechanical classes I teach, I have just been making mistakes longer than they have.

[buzzer]

OK, to my mind its the shimming of the output shaft on the gearbox. In looking at the video that is your issue (assuming you have not shimmed the driveshaft yoke onto the output shaft but just fitted the roll pin, if you have shimmed correctly then its gearbox output bearings and the box has to come out)
The splined gearbox output shafts do have end float as the output bearings ride on the diff crown wheel which control the crown wheel backlash and bearing fit. The splined output shafts are a clearance fit inside this crown wheel housing and will have backlash from the internal differential gears.
IF there was no end float on the gearbox output shafts the shims would serve a different purpose. i.e. after fitting the roll pin there could be a gap behind the driveshaft yoke and the gearbox and you would feel no play. THIS IS NOT THE CASE! there is end float on the gearbox splined output shaft which the shims take up to ensure any load is taken on the output bearings and not on the internal diff gears and the roll pin and allow excessive driveshaft play, all of which are bad....very bad...

When fitting the shims follow the manual.
However, if after shimming the yoke onto the output shaft properly you still have float then its must be in the gearbox output bearings, which if this is the case you will find vertical movements too as these bearing are tapper bearings

hope this helps

[jbcollier]

Generally diff side gears and spider gears are set up to be a "stiff" or "snug" fit.  This means the diff gears will be a bit stiff to rotate (not the diff itself, but the internal gears).  This will wear into a nice fit with minimal drag, good tooth contact, little stress to the gears and shafts and hardly any play.  In and out play as shown in the video means that gears are moving around under load and during load/no-load transitions.  The gears are under going considerable stress and tooth contact is not ideal.

In Europas this is caused by incorrect half-shaft shimming.  Instead of the suspension loads being applied to the large tapered roller bearings supporting the diff housing, the load is going through the diff side and spider gears first.  They were not designed for these loads and they will wear and fail.

Now the question is: Can he get away with just shimming the half-shafts correctly?

I don't know myself though, again speaking for myself, I would open it up and repair the diff.

[314159td]

Similar situation here, abusive PO didn't have the output shims fitted and the differential has ~0.010" of axial play in the sun gears on either side. Intuitively that's probably from all of the gear faces wearing, and the thrust washers under the satellite gears. There is some light scoring on the faces of the sun gears but only facing in one direction. Strangely the wear isn't on the faces I'd expect, though maybe it's shock loadings from engine braking that causes it to show up on the "non-driven" faces. Not sure if I should swap them to the opposite direction. Satellite gears look fine.

It seems like shimming the sun gears is the consensus to deal with that output shaft play? Shims are blue, the Bakelite 2mm spacer is red.

[jbcollier]

I'd feel happier if you had equal shimming on both sides.  I would keep the gears in their original locations.

[314159td]

Yeah, would be doing both sides. Need to find the correct ID/OD shims, I'll post part numbers here if I do.