3B Gearbox mount question

[gmac78]

Evening all

I have a question regarding gearbox mounts that I'm desperately wanting an answer for.

Today i replaced my gearbox mounts to find that the new ones are not much better than the ones that came out when driving. I still have lots of movement in the gearbox when on/off throttle.

I think i have stumbled across the problem where the cup that fits onto the mounting does not seem to sit flush on the four rubber sections that protrude from it. When all bolted up nice and tight there is a gap of 5-10mm. Should there be a spacer washer between the mounting and cap?

The mounts on the diff look correct where this cup is held tight against the mounting itself.

This gap is allowing a fair amount of movement and surely can't be right.

Could someone please shed some light on how this cup fits on your gearbox mounts.

Look forward to your help.

[Zeus]

On my car the disk and rubber don't or almost don't touch... Don't know if it's normal though...

[gmac78]

Hi

Yes i'm a bit confused about this one as cups on the rear mounts seem to touch the rubber but the old and new gearbox mounts i fitted today have a gap which i think could well do with a spacer to reduce some drivetrain movement. Again, i don't know which set up is correct- with or without a gap?

Any more thoughts/advise guys?

[Error404]

the gap is normal. The driveline shunt you are experiencing is mostly lash in the centre diff

[gmac78]

Centre diff? Theres no centre diff just front and lockable rear. Surely this excess play in the mounting will lead to a fair amount of driveline shunt. Has anyone ever fitted spacers to these gaps? If so i can easily get some made up to try the difference.

[WidowmakerS2]

All quattros have a centre diff as far as I know. It's mounted on the back of the gearbox.

Try twisting your propshaft using your hands, the play you feel there is the 'shunt' you're feeling when driving. As error said, the play is mostly in the centre diff, not so much in the rear diff.

[Error404]

All helical diffs have lash in them by virtue of how they work. The later Type III diffs I think used a spring plate to try to stop the on/off power shunt you get as the planet gears in the diff load & unload, but basically unless you want to fit a late 01E quattro box with a later diff, there is only so much you can do. Try fitting solid mounts, even this has not real effect on the shunt.

[Mikes2]

A worn propshaft centre bearing can also allow excess movement

[gmac78]

My mistake on the centre diff.

Having had a closer inspection today at my rear diff mounts, i noticed that both side mounts are facing the same direction, I think i read somewhere on the forum that the side mounts have a right and wrong way to be mounted, can anyone confirm this? And if so which way round should they be?

Also, having filmed the mounts with a camera whilst rocking the car in forward/reverse i noticed the passenger side has loads of movement but the drivers side with the cup flush against the rubber mount has next to no movement. Again this makes me think that these cups should fit flush , and by footage taken today also function better.

This raises the question- why would my drivers side old diff mount with cup sitting flush have very little movement in it, and the new gearbox mounts fitted yesterday have around 5mm gap between mount and cup? Surely there should be consistancy with these mounts, cup flush or not?

Hmmm the mind boggles....

Any more thoughts?