PatColclough · Apr 26, 2015

Sorry guys, I know this is done to death but....

The prop shaft bearings have gone on my '03 TD4. I've just taken ff the prop shaft and removed the old bearings so I now have the VCU on the bench.

If I clamp one end in a vice I can turn the other end with a 30 cm lever with one finger - VERY SLOWLY. If I use both hands and heave it will turn SLIGHTLY faster.

From all I've read on this forum about what it does, this would seem to me to be about right; but I've no experience with the things. So, simply, would you guys with experience tell me if that seems like a sound unit? Can I replace the shaft 'cos I really can't afford to replace a smashed transmission!

gareth123 · Apr 26, 2015

I know of no way to test these on the bench. Your best bet is to put it all back together and do the One Wheel Up test (do a search on here). There is also a lot of stuff about reversing on full lock and seeing how easy it/difficult it is but that is more by feel than science ....

Hippo · Apr 26, 2015

Yer can bench test them. Put a weight on a bar. I've done it at 38cm bar length.

lenny1234 · Apr 26, 2015

PatColclough said:
Sorry guys, I know this is done to death but....

The prop shaft bearings have gone on my '03 TD4. I've just taken ff the prop shaft and removed the old bearings so I now have the VCU on the bench.

If I clamp one end in a vice I can turn the other end with a 30 cm lever with one finger - VERY SLOWLY. If I use both hands and heave it will turn SLIGHTLY faster.

From all I've read on this forum about what it does, this would seem to me to be about right; but I've no experience with the things. So, simply, would you guys with experience tell me if that seems like a sound unit? Can I replace the shaft 'cos I really can't afford to replace a smashed transmission!

Sounds about right to me. As I said elsewhere, all they do is stop the transmission winding up when you are cornering - on a straight run assuming the same tyres front and rear they dont actually do anything at all much.

The aim is really a 'solid propshaft, except when it isn't' so to speak.

PatColclough · Apr 26, 2015

Thanks guys.

Lenny1234; I agree entirely, (although I know jack). It would seem to be able to slip easily enough to stop a transmission lockup, but should transmit a respectable force to the rear diff. Anyway, you've helped a great deal in the decision; it's going back on.

Now if I could only solve the random knocking from the rear

I've jacked up the rear and tried to move the diff and it does move a bit. Doesn't seem excessive to me but I've ordered a set of mounts and will swap them out before I put the shaft back on.

GrumpyGel · Apr 26, 2015

I'd agree that that does sound exactly right for the characteristics of a VCU in good condition. I would add though that it could also be the characteristics of a VCU that's to tight - it all depends on what exactly is "very slowly" and "slightly faster". So it should be qualified with tests you can compare to.

There is info on here and youtube for how to test on a bench - but I'm not sure if there's any data on what timings you should expect - so without that - its a pointless test! There is though quite a bit of data for the 1 wheel up test, so I'd say that's you best bet.

Also, take it from someone who's learnt the painful way - it doesn't matter how well your VCU is working, if you don't keep a careful eye on your tyre pressures - it will be that which smashes your transmission a lot faster than a tight VCU.

Oh and have a search for "cracked chassis" to see if that's your knocking sound.

PatColclough · Apr 26, 2015

Thanks Grumps, that's the rear subframe cracks I take it.

GrumpyGel · Apr 26, 2015

PatColclough said:
Thanks Grumps, that's the rear subframe cracks I take it.

Yeh, basically at the bolt onto the chassis. Not sayin its that, just something to have a look at.

guineafowl21 · Apr 27, 2015

Have a look at this (purportedly from Bell Engineering):

https://m.youtube.com/watch?v=0jkvamLKorc

Nodge68 · Apr 27, 2015

PatColclough said:
Sorry guys, I know this is done to death but....

The prop shaft bearings have gone on my '03 TD4. I've just taken ff the prop shaft and removed the old bearings so I now have the VCU on the bench.

If I clamp one end in a vice I can turn the other end with a 30 cm lever with one finger - VERY SLOWLY. If I use both hands and heave it will turn SLIGHTLY faster.

From all I've read on this forum about what it does, this would seem to me to be about right; but I've no experience with the things. So, simply, would you guys with experience tell me if that seems like a sound unit? Can I replace the shaft 'cos I really can't afford to replace a smashed transmission!

I'd say that it's working as it should.

PatColclough · Apr 27, 2015

Well thanks everyone for their advice. I'll refit the VCU and forget it, hopefully.
The video was interesting, mine would do that, but it would turn, slightly slower, with very little force, one finger in fact. Two hands on a 30cm lever, maybe 20 + kg, would turn it about that speed. So there you go, 70,000 miles and 11 years old. Maybe they aren't all bad. Trouble is you only hear of the ones that break. The thousands that don't are never reported, except mine

.

Thanks again everyone.

PatColclough

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gareth123

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Hippo

Lord Hippo

lenny1234

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PatColclough

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GrumpyGel

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PatColclough

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GrumpyGel

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guineafowl21

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Nodge68

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PatColclough

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