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[cwill144]

Don't know if anyone can help with this one but I'm about to give up with my 3.0L MV6 Manual. it has been off the road for over a year have done a load of work on it, all new brakes, shocks changed engine etc. about 4 months ago thought I had finished it. I did about 10 miles in it and it drove great, then spotted the rear crank main seal was leaking.
so removed the engine & box and changed the bearing. all seamed ok. drove it again no leak, but now a horrible vibration above 20mph, like you are driving with a rear flat tyre!!! have looked it over can't see any obvious problem. Am going to change the prop rubbers, there is a little backlash in the diff but not excessive. as it drove ok before am baffled, wondered if anyone had a similar problem before? I'm getting to the stage of having to break it!!!

[GastronomicKleptomaniac]

All wheels back on the same corner they came off? Possibly some debris between hub and disc, or disc and wheel. Also what stste are the wishbone rubbers in?

[dave the builder]

clutch alignment ? or contamination ?
does the vibration go if you floor the clutch ?
prop center bearing ok and carrier ?
did you align the splines to the prop correctly and leave slack on the nut
prop rubber donuts judder as you first pull off if they are bad in my experience ,not at speed.

[456lbft]

Did the flywheel go back on straight?  You're not too far away from me (and other members too) if it was ok to bring it up to South Northants for a look see.  Bit difficult to diagnose via the forum.
I'd jack the back end up on a ramp and run it in gear to try and rule a few things out like prop centre mount etc..Don't give up yet!

[cwill144]

Wheels have gone back on same corners and was going to take off and check. it drives fine below 20mph then starts. Had no problems with clutch that I noticed on when I pit it back together. and it seam ok when you start it on axle stands.
I have ordered some new rubbers and centre bearing for the propshaft as that seamed an obviously easy fix. I can't drive any distance as not mot'd and the vibration.

[Doctor Gollum]

Flat spots on the tyres

[cwill144]

Also the problem seams to be coming from the rear/Diff which makes me think it could be the prop bearing

[456lbft]

Flat spots on the tyres

Having stood for a long time, tyres can cause awful shaking as the carcass gets mis-shappen.  Pump them up to 50psi and see if it helps with the vibration, then let them down again.

[jefflem]

Is the cardan shaft replaced exactly the same way it used to be? If it’s rotated along the hardy disc, you get awful vibrations too

Not sure if you already did it, but since you have a manual gearbox it’s easy to check: drive above 20mph/h and press the clutch. If the vibrations stop, you can check the engine, otherwise there’s a 99% chance it’s in the gearbox or beyond.

[cwill144]

Thanks for the advice, the car had wheels off most the time it was stood. will try the prop bearings and new rubber bushes and pump the tyres up to 50 psi and see.

[Doctor Gollum]

Wheel nuts torqued and rechecked?

[Nick W]

Also the problem seams to be coming from the rear/Diff which makes me think it could be the prop bearing

fitting refurbished diff mounts made my car a lot quieter.


But, as the problem only started after you did some work you need to investigate everything you touched BEFORE you buy or fit any new parts.

[456lbft]

Also the problem seams to be coming from the rear/Diff which makes me think it could be the prop bearing

fitting refurbished diff mounts made my car a lot quieter.

Slightly OT but regarding the above. Did you refurb them yourself? I understand that the mounts are no longer available and that too hard a Poly bush can make noises worse. I think I need to do mine to cure slight rear end rumble and tighten up the rear steering bump steer wandering, so I am interested in any feedback.

[Nick W]

Also the problem seams to be coming from the rear/Diff which makes me think it could be the prop bearing

fitting refurbished diff mounts made my car a lot quieter.

Slightly OT but regarding the above. Did you refurb them yourself? I understand that the mounts are no longer available and that too hard a Poly bush can make noises worse. I think I need to do mine to cure slight rear end rumble and tighten up the rear steering bump steer wandering, so I am interested in any feedback.

Like this:





and here:





and the jig, which will do a pair:

[Doctor Gollum]

Also the problem seams to be coming from the rear/Diff which makes me think it could be the prop bearing

fitting refurbished diff mounts made my car a lot quieter.

Slightly OT but regarding the above. Did you refurb them yourself? I understand that the mounts are no longer available and that too hard a Poly bush can make noises worse. I think I need to do mine to cure slight rear end rumble and tighten up the rear steering bump steer wandering, so I am interested in any feedback.

Mine were repaired in a similar fashion to Nicks, but were solid. No complaints of NVH, but it was an estate running plod springs/working self levelling and with rear subframe polybushes, front wishbone and arb polys, hd Monaro top mounts along with 18x8/245/40/18 wheels and tyres.

If anything rebuilt diffmounts complete the package as they keep the rear end fixed and allow the suspension to do its job

[Doctor Gollum]

For the OP, failing/failed diff mounts are unlikely to be your issue.

When they fail, if you throw the car into a corner, if feels like the back end just fell off, made worse if only one has failed as the weight transfer is highlighted one way... Also worse with estates due to the higher CoG.

[456lbft]

Also the problem seams to be coming from the rear/Diff which makes me think it could be the prop bearing

fitting refurbished diff mounts made my car a lot quieter.

Slightly OT but regarding the above. Did you refurb them yourself? I understand that the mounts are no longer available and that too hard a Poly bush can make noises worse. I think I need to do mine to cure slight rear end rumble and tighten up the rear steering bump steer wandering, so I am interested in any feedback.

Like this:

What is the white goo? Self mixed Polyurethane perhaps? Any links to material sources and properties would be handy. Thanks for all info, it sounds as though that would help to stop the rear end wandering on undulating roads.

[Doctor Gollum]

That sounds like a shock issue... Diff mount failure doesn't show up under those conditions.

Easily checked. Support (not lift) the diff (gearbox support if using a lift) and remove the mount bolts from the chassis cross rail. If the cage falls off, the mounts need work.  Remove/refit one side at a time. Upto half inch drop with the bolts removed can be considered normal.

I used this... https://www.ebay.co.uk/itm/Black-Fast-Cast-Polyurethane-Liquid-Plastic-Casting-Resin-1kg-Kit-/283326020756 to do mine.

[Nick W]

Like this:

What is the white goo? Self mixed Polyurethane perhaps? Any links to material sources and properties would be handy. Thanks for all info, it sounds as though that would help to stop the rear end wandering on undulating roads.

It's 2part polyurethane from HERE. 150g of the main component will do a pair of mounts. Don't buy a bigger kit thinking you'll keep it in stock, as they aren't kidding about the six month shelf life! Scales that are accurate to at least a gram are needed, I bought one from Ebay for about £5.


They look a lot better if some black pigment is added; you only need a couple of grams, and it's cheap from the same supplier. They do other colours, but black always looks best - white is the natural colour.


These were done for another forum member, so I put a bit more time into the cleanup, and a squirt of black paint:

[456lbft]

Thanks for all the advice,  I might well give that a go if they are falling apart.

[Nick W]

Thanks for all the advice,  I might well give that a go if they are falling apart.

My jig is way over the top, you could make a one-off from a few scraps of ply/thick cardboard and a glue gun. Vaseline works well for mould release.

[456lbft]

Thanks for all the advice,  I might well give that a go if they are falling apart.

My jig is way over the top, you could make a one-off from a few scraps of ply/thick cardboard and a glue gun. Vaseline works well for mould release.

Does the refurbed mount transmit more diff noise to the car? 85 shore PU is quite hard.

[Nick W]

Thanks for all the advice,  I might well give that a go if they are falling apart.

My jig is way over the top, you could make a one-off from a few scraps of ply/thick cardboard and a glue gun. Vaseline works well for mould release.

Does the refurbed mount transmit more diff noise to the car? 85 shore PU is quite hard.

It got quieter. Actually connected to the car


I've fitted lots of polyurethane bushes in all sorts of locations. None of them has ever created more NVH. The main reason I use them is for durability(wishbone front bushes, Capri TCAs, etc) or rebuilds like these diff mounts.

[456lbft]

Thanks for all the advice,  I might well give that a go if they are falling apart.

My jig is way over the top, you could make a one-off from a few scraps of ply/thick cardboard and a glue gun. Vaseline works well for mould release.

Does the refurbed mount transmit more diff noise to the car? 85 shore PU is quite hard.

It got quieter. Actually connected to the car


I've fitted lots of polyurethane bushes in all sorts of locations. None of them has ever created more NVH. The main reason I use them is for durability(wishbone front bushes, Capri TCAs, etc) or rebuilds like these diff mounts.

Thanks for the feedback

[Doctor Gollum]

Thanks for all the advice,  I might well give that a go if they are falling apart.

My jig is way over the top, you could make a one-off from a few scraps of ply/thick cardboard and a glue gun. Vaseline works well for mould release.

Does the refurbed mount transmit more diff noise to the car? 85 shore PU is quite hard.

It got quieter. Actually connected to the car


I've fitted lots of polyurethane bushes in all sorts of locations. None of them has ever created more NVH. The main reason I use them is for durability(wishbone front bushes, Capri TCAs, etc) or rebuilds like these diff mounts.

Significantly improves the overall driving experience too. Which is nice.