3B Diff output flanges vertical play

[gmac78]

Evening chaps.

My rear diff is leaking and need to get round to sorting it. However due to the vertical play in the output flanges, I would say somewhere in the region of 2-3mm, is there any point in replacing the seals. Surely they will just start leaking again with this amount of movement?

Also I seem to have a slight vibration on overrun at around 30-40mph. Not sure when it started, only recently I noticed it. Hard to say where it's coming from but would this play be a contributor? If I apply the slightest of throttle the vibration seems to smooth out. Strange!

What is the fix for for this, is this amount of play excessive?

Cheers lads
Gordon

[gmac78]

Infact this vibration is getting worse. Just been out for a thrash and you can feel a strong vibration though the car. It wasn't to bad whilst just cruising around, a vibration could be felt around the 30-40mph zone, however after a spirited drive it was a lot worse. It feels like the back end, I think this diff might be suspect. I just don't like the amount of play in these output flanges!!!

Anybody else have vibration issues from the rear diff?

[Tractor Dave]

I think there is a tapered bearing in there that might have failed. One on each side according to 7zap. I have no idea how you would change them mind

[gmac78]

I've no idea either, not something I've looked into. I'm wondering if this is a common problem on these cars, my car just ticked 150k a few days ago so not excessively high mileage. If my diff has this amount of play I would think most others with similar miles would be the same.

I changed my prop bearing a couple of days ago and the shafts are nice and straight. Everything was returned to the position it was in previously. I felt this vibration for the first time one night before I replaced the prop bearing so the problem lies elsewhere.

The flanges must be rattling around in there causing the vibration surely?

[Tractor Dave]

There was no noticeable play in mine when I overhauled it during my 're build. Play as you describe needs urgent attention. It's probably run out of oil at some stage in its life. These diffs are normally very durable.

[gmac78]

I drained and refilled with oil a few years back, however looking on the outside of the diff it's been leaking for some time. Might not be much oil left in it now actually. The play in these flanges is too much though and needs addressed one way or another.

[Bowie69]

The drumming/vibration noise is the driveshafts moving eccentrically because of the play in the bearings, essentially it puts them out of balance.

Much the same as when a CV gives out.

[gmac78]

The drumming/vibration noise is the driveshafts moving eccentrically because of the play in the bearings, essentially it puts them out of balance.

Much the same as when a CV gives out.

Yeh I guess you're right enough there, makes sense. I had to drive the car 15 miles today to it's resting place for the next few weeks and the vibration the whole way was not nice!!! Again, at it's worst around the 30-40mph zone but present the whole time now.

[JariP]

Mine has 479 000km on the original rear diff. It has had a very noticeable vertical play on the right side output flange for at least last 200 000km maybe 300 000km. Does not leak, does not make noises. I can't remember how it is on the left side. These are tough units. You may want to check for other sources for that drumming before attacking the diff.

[gmac78]

Mine has 479 000km on the original rear diff. It has had a very noticeable vertical play on the right side output flange for at least last 200 000km maybe 300 000km. Does not leak, does not make noises. I can't remember how it is on the left side. These are tough units. You may want to check for other sources for that drumming before attacking the diff.

Well that's interesting I must admit!!! If you've covered that amount of mileage with noticeable play and no vibration it maybe good news for me. I've not had a chance to put it on a ramp yet but will do over the next few days. It should be quite obvious where it's coming from if I spin the wheels whilst on a two poster.

[JariP]

When those kind of bearings start to go bad, they usually start with a whine. If it has oil, it will whine a long, long time before anything major happens. When it gets to vibration and drumming, then it's ready to blow up. Maybe you should put your car on a lift and have a listen with stethoscope while turning the wheels by hand. It's easy to spot a bad bearing like that just poking around with the stethoscope and listening.

[gmac78]

Alright gents. To update this thread, I fitted a spare rear diff I had from a Coupe Quattro which had much less play in the output flanges, also I found a notchy rear inner CV joint and some play in an outer one so replaced both inner and outer CV's on both sides whist the diff was being changed. I thought the notchy CV joint would be the cause of my vibration, however after putting it all back together my vibration is still present!!!!!!

On installing my propshaft to diff input flange I've tried the 6 different orientations and managed to get the vibration down to better than it was previously, however it's still noticeable from around 25-45mph. I did the same for the gearbox to propshaft flange and again managed to find a position that vibrated less than the others.

This vibration is doing my head in and wondering if the slight rotational play I found in the propshaft CV joints is likely to be the cause of it? Both propshaft CV's were found to be nice and smooth to move with ample grease that hadn't dried out. I regreased them anyway but wondering if anyone else has had vibration problems from slightly worn propshaft CV joints?

One thing to note is I changed the prop centre bearing last year but marked it up on removal, however I'm wondering now did i install it in the exact same position it was in originally. I've already tried turning the propshaft halves 180deg to see if that would fix my vibration but that made it worse. It's possible it could be a a spline or two out on the yoke though?

On a positive note though fitting the new rear diff and inner/outer cv joints has made a big difference to the shunt/clunk felt when coming on/off throttle, so I'm pleased with that result at least!

[gmac78]

Also the propshaft is correctly aligned straight and found that it vibrated the least with no spacer washers installed so all good in that respect. I hate being defeated but the amount of times I've jacked the car up and down over the last few days is taking it's toll on my jacking points, the front ones are starting to split and bend now!!! Oh the joys!!!

[s2driveruk]

I would get it off the car and get it balanced they try again.

[Bowie69]

I feel your pain, got the same sort of vibes here, but not yet been on your marathon of attempted fixes....

I am hoping to get mine balanced, is that something you have considered?