Posted By : Chris Taylor, 19-May-2007,
08:21pm
Unless you really know what you are doing, I would NOT tinker with pinion preload. The preload alone should not affect the pinion ENGAGEMENT, and hence
cannot change any play between pinion and crownwheel. While you need enough to ensure the pinion bearings hold the pinion rigidly in the right place,
too much will overload the bearing rollers and lead to premature failure. If you adjust the shims on the pinion shaft, it adjusts the point of tooth
engagement on the crownwheel teeth, not the depth of engagement. To do that you need to adjust the shims either side of the diff carrier bearings, and
to do THAT you need a diff case spreader! Serious stuff and you REALLY need to know what you are doing. It MAY be possible to improve tooth engagement
between the differential gears by replacing thrust washers, but that is no small job and rather messy.
While play in the differential gears could cause a clonk, you should not get more play on one side rather than the other as a symptom of wear. Don't
forget that each output shaft is splined into the relevant sidegear. The crownwheel turns the diff carrier, (not the left hand output shaft) and in
turn this transmits power through the cross pin to the diff gear assembly. If the crownwheel (or pinion) is held firmly, and one output shaft turned,
any play apparent FROM THE DIFF gears should be apparent on either side as the play is "shared" across the diff "system".
While you may be convinced the clonk comes from the offside driveshaft, do your passengers agree? Such noises can play funny tricks on your sense of
location. It is possible that the root cause is play in the diff (not necessarily a big problem if it is not excessive) but the noise is hear
elsewhere; solid propshafts (which are tubular) can give a sort of "ring" if play in the drivetrain is taken up suddenly; the same sort of noise as if
you tap it with a hammer.
Before going into the diff (and a recon item from a reputable dealer is the most cost effective solution unless you can get a known good secondhand
one) I would thoroughly check EVERYTHING else, and on BOTH sides:
Are the bolts a firm fit in the radius arm bushes, and are the holes in the mounting brackets (on body and rear upright) round or worn slightly oval?
Is the bracket on the rear heelboard bolted on tight and is all the metal in the area absolutely sound?
You might have a cracked leaf in the rear spring, or play in the centre bolt or bush in the swing spring mounting "box", or worn/missing buttons that
separate the spring leaves.
I always suspect u/j's even if new! There should be absolutely NO play, and you need to be pretty brutal with a big bar to test this. If you are
unlucky, the play might be between the u/j cup and the hole in the yolk. If there is any evidence of the cup turning, revealed by shininess under the
circlip, then you do have a u/j problem.
Although more often heard on the overrun, did you fit (or try to fit) oversize circlips to the driveshaft u/j's? There should be zero endfloat on
driveshaft u/js.
Have you thoroughly checked the propshaft u/js?
Tightness and soundness of engine and gearbox mountings, propshaft (and driveshaft) coupling bolts, security of the gearbox output flange (need to
remove the prop for this) . And are the rear hubs properly mated to the end of the driveshafts?
Also worth looking at the diff mounting bushes (difficult to see the rear ones) and the bolts holding the mounting plate to the nose of the diff.
And completely off the cuff, are the rear brake shoes dragging at all, and sliding freely?
Does the same thing happen just the same in reverse? Are there any clunks when applying the brakes (perhaps just the handbrake) going forward or
backward? That might help pin down where any play in the drivetrain.
I am not saying it isn't the diff, but you have done just about all the realistic DIY jobs on that, so rule out all other possible causes before
embarking on the more serious (and expensive!) stuff.
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Posted By : Martin Bradley, 19-May-2007,
09:57pm
Many thanks Chris, I will remove the carpets over the heel board area and take my son out for a drive to see if he can pinpoint the source of the
noise any better. I have some time off over the half term week so bit more investigation is called for along the lines you suggest.
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Posted By : Martin Bradley,
03-Jun-2007, 08:53pm
And the answer was............ mangled u/j. The new u/j had only covered 350 miles but needle bearings had disintegrated into a paste
consisting of 2mm lengths of bearing mixed with grease! I hope this was not caused by some other factor like the outer axle shaft running ot of
alignment. The u/j's were supplied by Rimmers, I think I will get genuine items from Moss next time.
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Posted By : Leon Guyot,
03-Jun-2007, 10:15pm
Why not get some heavy duty items from Canley Classics?
I cannot understand what the fascination with Rimmers and Moss is?
Maybe it's their shiny catalogues?
Canley's and before them Kippings have never let me down!
Regards
Léon
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Posted By : Julian Saul,
04-Jun-2007, 05:54am
A slight diversification, but having heard so much about Canley's, I ordered several parts from them lately, not entirely to my
satisfaction though.
The postage costs, to Holland, were nigh on three times more expensive of the other big players , M & RB, the exhaust/inlet
manifold gasket I received had a foil coating on one side only, and when fitted to the studs left a fold in the centre of the gasket
preventing the manifold from being mounted adequately.
On approaching Canley with this situation, I was informed that they were unable to find any suppliers who could deliver gaskets with a
double sided foil coating, and I should fit the gasket with the fold in situ, as it would seal.
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Posted By : Colin
Wake, 04-Jun-2007, 12:48pm
The heavy duty ones are Freelander ones.
Not cheap.
I would suspect that the failed one was fitted with a skewed needle or similar to have failed so quick.
Cheers
Colin
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Posted By : Chris
Taylor, 04-Jun-2007, 10:58pm
U/J's may not be cheap, but how much do you value your time in repeating this job? And if you leave them too long before
replacing, or press new cups in too often, or get one skew while doing so, you can render the yolk useless. Not so bad if it is
the flange, but you cuold damage the driveshaft one, meaning a new driveshaft, and the DELIGHTFUL job of getting the hub off to
fit the bearings.
Not quite so bad on the prop (which deals with less torque) but I would suggest any extra spent on higher quality u/js was
money well spent! May not be necessary on a 4 cylinder car, but would not hesitate to fit stronger ones to a six cylinder car.
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Posted By : Leon
Guyot, 05-Jun-2007, 02:55am
The term 'cheap' is interesting.
At one time it only meant 'inexpensive' (British English), but over time it has come to mean 'cheap and nasty' (American
English).
Not cheap therefore could mean expensive, 'spendy' or pricey,
but it could equally mean 'well made', 'long lasting' or 'high quality'
Changing Universal Joints is neither a pleasant, nor a particularly easy job, and the longer between changes the better.
With standard engines, or 4 cylinder cars, or cars you intend to sell, use the standard UJ's.
With tuned/hi-output, or 6 cylinder cars, or cars you aim to keep for many years, use the good ones.
Simple
Best Regards
Léon
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Posted By : Brendan
Delaney, 05-Jun-2007, 01:16pm
Back in the 80's I accepted an offer from two guys who worked in the hospital where I was working to change the clunking OS
UJ on my 13/60 Herald.
That evening, whilst accelerating onto the M5 to drive back home there was a loud clunk and some serious 'kerfuffle' from
the back end. A cap had come completely off the new UJ and the drive shaft had bent - cost me about £250 at a
local garage to get fixed.
IMHO replacing UJs is a job for someone who knows what they are doing...........