Syncro drive vibration

[RichardF]

Last week my Syncro developed quite a bad vibration. It is most noticeable just above 80km/hr, also just below 50km/hr, but not so bad. It disappears at 100 to 110km/hr.

There has been a slight vibration around 80 ever since I bought the van 10 years ago, but never this bad. Mileage is 175,000 (280,000km)

My immediate though was that the CVJ bolts had come loose again, but they are still tight. The propshaft seems the next suspect, so I checked it today.

The rubber doughnut looks good, and the bolts are tight. The UJ flange bolts are tight and the UJs are not damaged. There is a maybe couple of thou's axial play on one leg of the rear UJ.

The propshaft has about 5mm rotational play, and there is a slight clunk from the gearbox when I turn the shaft back and forth.

Any suggestions, please? - dry UJ bearings, splined sleeve in gearbox, gearbox output bearing, front diff input bearing....?

[toomanytoys]

Drop the prop shaft off and see..
If vibration gone.. likely its either UJ's or the bush in the sliding part thats worn allowing movement.. Check for wear in the donut too along with signs of poss missing weights as these are just "tacked" on

Diff etc bearings would be noisey before vibration
Check diff and gearbox mounts

[HarryMann]

Yes, definitely have a good look to see if there are signs of missing balance weights as Simom has said, though it might be a guessing game
(you could try a jubilee clip at approx centre-length, moving it around the periphery in stages to see if vibration worsens or minimises, just as a test)

Unless the prop's UJs are really shot, checking whilst prop on vehicle for any play is very difficult to be sure.. (substitution with known good can be quickest, but remove and inspect UJs closely). I personally think the prop doesn't have to be replaced on flanges the same way it came off. (Each driveline component should ideally be in balance statically and dynamically)

Rotational 'knock' / slack is to be expected, they all have it to some degree or other and unless excessive should not be causing driveline vibration

Reasons:

Props UJ wear/ joint seizing/ roughness/ lube/stiffness

Prop 'dinged and bent', even slightly (test by substitution with known good one)

Engine mounts soft/misaligned

Ditto Gearbox mounts

Ditto diff mounts

Engine diff/alignment

Prop driveline alignment too straight (try shifting box slightly sideways, or packing diff mounts)

======

Worn rear CVJs (inner or outer)
Ditto front

Wheel balance, rear wheel, bearing wear (lateral/rock)

Bent driveshaft or gbox/diff drive flange (through joint coming loose?)

Blown Viscous Coupling (lost siloxane), low oil in front diff, knackered front diff bearings, rattling VC, loose on splines

====

Diesels sending enormous chunks of shock-torque up the driveline, exciting the prop when aligned in a certain way

(Diesel mounts may seem OK when levered about, but look for any signs of delaminating at all, not cheap but can have quite a big effect on clunk and snatch when changing gear/ changing form overrun to load or vice versa). Let's face it, they're nearly all 20 years old now, and that is rubber in a hot and oily environment, especially on the turbo side of TD diesels....

Kepe looking and changing things, you'll find the magic ingredient eventually, took me 2 years - don't underestimate effect of rear CVJs (all 4 ) and wheel balance. There is not one answer!

[silverbullet]

Don't forget to inspect all wheel bearings. If they're shot then you can get vibration at a variety of frequencies/speeds and can come and go as you drive at a constant speed. I've had this on two of the fleet, thought that it was an out of balance front wheel the first time around. When I took the outer bearing out the grease was black and rollers were breaking up

[RichardF]

Thanks for the suggestions. I didn't think it would be easy to diagnose

toomanytoys:- I can't get under the van at the moment, as I have another casualty over the pit, but I can't see a sliding joint in the propshaft.

I didn't mention it, but the gearbox/diff has been whining for quite some time, now more of a growl than a whine.
I checked the oil is OK, guess I'm just putting off the inevitable rebuild.

I don't know anywhere in France for gearbox rebuilds, and doubt whether the price would be attractive, after attempts to get the power steering rack rebuilt here. I sent it to UK eventually, much cheaper, even with the carriage.

[Essex Nige]

Richard, i have the exact same problem, but i dont have a gearbox whine, just the vibration at between 55-75 kph

[Aidan]

so essex nige what's yours like prop off ?

[toomanytoys]

Gearbox rebuild... Only one person I trust...

Deffo one of the french Syncro club has got Aidan to rebuild their box... with the current exchange rate its a lot cheaper, sure he has supplied a good few parts over there too.

My prop comes off and on, on a regular basis and it never goes back on in the same position at each flange as when I bought it 5 years ago.. no vibration issues..

You've done the cv joints recently so assume they are ok (worth giving a good wriggle etc though..) so prop off.. see what happens..

IIRC the donut has a second part sliding inside it with a bush (My prop doesnt have a donut as its a lowly 1.9 DG wbx, the only engine fitted with a solid prop) the bush wears and then it doesnt hold in alignment.. Clive/Aidan etc will have to confirm that I think...

[RichardF]

I'm beginning to think it's about time to at least replace all the wheel bearings and the UJ spider bearings.

I'm also going to be looking at the cost to ship a gearbox and front diff back to UK, and talking to Aidan about rebuilds.

Then again, I might just keep on driving and see what goes first. I have a pretty good recovery service.

I also enjoy a challenge (so long as it's not in the middle of winter). Many the times we've camped in odd places in Europe while I fixed the waggon.

[toomanytoys]

I'm beginning to think it's about time to at least replace all the wheel bearings and the UJ spider bearings.

I'm also going to be looking at the cost to ship a gearbox and front diff back to UK, and talking to Aidan about rebuilds.

Then again, I might just keep on driving and see what goes first. I have a pretty good recovery service.

I also enjoy a challenge (so long as it's not in the middle of winter). Many the times we've camped in odd places in Europe while I fixed the waggon.

Drop the prop off and see if anything changes..

On the "drive it and see what goes first".. not clever.. do you have deep pockets? as when the gearbox is fubarred and nothing is salvagable, you have to go find another box/parts for aidan to rebiuld.. and he has seen quite a few of the "it'll be ok, so I'll keep driving it".......... " oh dear how totally buggered is it??" I've seen some of the bits that have come out.. and when a good used part isnt available its a VW only job.. IIRC a new crown wheel and pinion was £450 last time he had to order one...and depends if actually available too

Much better to do something about it while its usable....

Mmm.. gearbox fix will be a lot more difficult away from home.... but if thats the challenge you are after

[Essex Nige]

so essex nige what's yours like prop off ?

This weekend's project, but on the way to work tonight i coasted for a bit just to see what happenede and it went away.

[HarryMann]

I'm beginning to think it's about time to at least replace all the wheel bearings and the UJ spider bearings.

Syncros aren't famous for running wheel bearings, and play in rears more likely to be the hubs ovalling then the bearings themselves ... as a general rule

Yes, power on/off (load/overrun) can drastically affect driveline vibration

[syncroandy]

Surely its gotta be worth getting the wheels balanced ? Could have lost a weight.

[RichardF]

Surely its gotta be worth getting the wheels balanced ? Could have lost a weight.

I did. Unfortunately (or maybe fortunately ) they haven't.

Just remembered, lying in the garage I have a 2.1 engine with a good 5 speed 2WD gearbox from an accident damaged van which I bought 10 years ago, for the engine. I have a big garage, so there's a lot of stuff in it.

As I have never really needed the 4WD I'm thinking of fitting that. Remove and store the Syncro box, propshaft, front diff and driveshafts. I should also use less petrol.

I can even drop the petrol tank and finally fix the vent valves, so I can get the last 10-15 litres in in less than ten minutes.

I just need two old front outers, so I can have the stubshafts machined off to put them inside the front bearings.

Can anyone help with two otherwise unuseable front outer CVJs?

[toomanytoys]

Christ, thats a lot of trouble to go to to cure a vibration...

Better off selling the van and buying a 2wd if you dont want or need 4wd...

Saving fuel.. I doubt you will..

Macjineing the stub axles for the front.. why? they wont be in the way.. + made from some tought stuff.. not wortht he effort..


Have you dropped the propshaft off yet and tried it??