Hi there ladies and gents, I was after some more ideas please because this is driving me mental!
I have a late non roto gt6 mk3, i have virtually rebuilt the very tired back end:
New leaf spring
shockers
poly bushes
half shaft assemblies (from diff flange to hub)
Also new balnced propshaft
I had this vibration before i did the work but also had bearing noise, I thought the vibration was connected with this but alas not! It drives wonderful
now except for this vibration!
I have had the wheels rebalanced swapped them round, tried another set of wheels, and this still has made no difference.
Approaching 55+ there is heavy vibration from the back end of the car so much so at 70 I think shes coming to pieces!
I have stuck the back end on axle stands and the wheels are running true when the car is run up. Someone has told me it is possible that the brake drums
being oval could cause this is this true?
Any ideas will be greatley appriciated as most of the components have been replaced except for: engine diff gearbox
Thanks, Den
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Posted By : Philip Charlton, 25-Nov-2006,
10:11pm
i really reckon its your diff.
my old diff was ace, super silent, but one day it started to rumble, then going round corners an odd noiuse would happen.
Then BOOM! blew up on the A64. the case broke into several pieces!
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Posted By : Chris Taylor, 25-Nov-2006,
10:34pm
Despite what you say about a new one, I would still point the finger at the propshaft. Try changing end to end and see if the vibration "moves". You
could also try changing the relative position of shaft/pinion flanges by "moving round one bolt hole" and see if there is any change.
If you take the shaft out, check that each joint moves freely and with equal resistance in ALL planes, that circlips are properly engaged, no grease
nipple has been left in, that the alignment of the two joints at each end of the shaft are correctly aligned with each other, that there is NO play in
any sliding joint, nad that there is no deformation of the flange faces, either on the shaft or diff and gearbox flange.
If the shaft is slightly out of balance, you can balance it in situ using a pair of large jubilee clips at each end. Tedious, and sounds alarming, but
it DOES work.
With regards to the diff, see if there is any play at all at the pinion. As for brake drums, is it any worse when applying the brakes? And have you
double checked for WHEEL balance, and any deformed tyre?
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Posted By : Peter & Mick Lewis,
26-Nov-2006, 09:16pm
is it noise or vibration ??? does the problem persist with it out of gear ?? is it on drive or overun ?? do you have overdrive ??
we have a problem on our vit6 with a new prop/ diff/ drive line & o/d bearings still feels like prop as uping the diff ratio moved it up the
speed range , had prop check twice its ok need to put dial indicator on the gearbox flange to check spigot runout as
not much left to change now,, dont foget clutch disc damper springs can cause loads of vibration and noise when stuffed but generally under drive
not coasting ,,,just some thoughts Peter
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Posted By : Nigel Gibbins, 27-Nov-2006,
10:23am
I would normally say - propshaft and rear wheel balance... but you say you've checked that (unless they are all out of balance).
So may be bent drive shaft ? bent propshaft... all doubtful but may as well check.
So let's try some 'silly' stuff.... gearbox mounts - are they good and/or tight? Likewise diff mounts?
I've heared of diffs being the problem sometimes although not experienced it myself.
It's definately speed related? always come in at 55mph regardless of which gear you're in? If so then it's definately after the gearbox.
Are the tyres out of shape?
You'll notice the rear drum thing when you brake as you can feel it through the pedal - or you could pull the handbrake on a few clicks (so you can
still sping the wheels by hand) get the rears off the ground and turn them to see if they bind... gradually add clicks until you can't spin the wheel
anymore.
... running out of ideas now... anyone else?
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Posted By : Mark Hammond, 27-Nov-2006,
11:30am
Hi, I had this problem on a Vitesse 1600, and later on a big 2000 saloon. Both cars were non-overdrive. I sold the Vitesse because I couldn't cure the
problem, but on the 2000, it turned out to have a hairline crack in the gearbox tailshaft housing which I have subsequently heard is not unusual. Check
this and also the nose of the diff casing which equally could produce the same effect if there is a crack in it.
Regards,
Mark
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Posted By : Paul Dearing,
31-Jan-2007, 09:54pm
I've had similar problems with my GT6 Mk1. I bought it with several problems.
I had an off centre brake drum which was replaced. It was original Stanpart so must have been a manufacturing fault.
Rear offside half shaft was bent (probably jacked up by garage Yoof when changing wheel,) which was replaced.
Prop shaft was knackered and was reconditioned by Reco-Prop in Luton. Fine job.
Vibration was reduced but still there. I had a good look at the rear nearside halfshaft and found that although it was not bent, the universal
joint was not centred so the shaft wobbled. It also didn't help that it was a long halfshaft whereas a short one is required for the Mk1 GT6 (about
an inch difference). Replaced the shaft with a spare from Colin Wake. Ta.
The reason this is possible is that the modern UJ circlips are thinner than the originals and the refitting process is normally to push the UJ cup
up against one circlip to make space for the opposite clip.
I used older thick circlips and checked the centering. No more problems.
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Posted By : Keith Marsland,
01-Feb-2007, 06:54am
Interesting! Look like there are so many things to look out for! I had massive vibrations on my GT6 starting at 50mph until I had the gearbox
replaced and further vibs were reduced by balancing the prop done by reco-prop in Luton. However the vibes speed have risen to about 75mph so
it''s not too bad. I can take the wife out on country roads at up to 70 without her feeling nervous lol.I think my UJ's might have gone dry
with little use in the past and can see some shiny metal in the joint which I will investigate later as it appears my 2 ton jack was nicked in
the side passageway along with my wheelbarrow.
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Posted By : Vin Poonwassie,
01-Feb-2007, 08:30am
2 ton trolly jack, ALDI supermarket are selling them for a tenner! (as mentioned last weekend on this board) in a plastic carry case
too.
I got one to complement my large twist handle trolly jack and my mini trolly jack....
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Posted By : Keith Marsland,
01-Feb-2007, 10:25pm
Oh thanks Vin re the trolley jack offer from Aldi.
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Posted By : Peter & Mick
Lewis, 01-Feb-2007, 10:35pm
Luton Aldi trolley jacks are sold out of....have to be quick in these shops to get the bargins peter
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Posted By : Peter &
Mick Lewis, 01-Feb-2007, 10:45pm
dont forget the viration frequency difference between propshaft speed at 55 being at 2500/3000 rpm and the much slower
rotation af drive shafts and wheels aprox 780 rpm the feelings are very different zoom zoom or wobble wobble in simple
turms
vibro massage or the shakes peter
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Posted By : Peter &
Mick Lewis, 17-Feb-2007, 06:52pm
Dennis dont know where you have got to with the vibration we have been chasing a similar propshaft frequency vibration
for ages last resort was to take off the overdrive and the planet gears were incorrectly timed
dont know if you have an overdrive but its cured our persistent 70 mph banshee
took od off the back without removing the gearbox, Peter
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Posted By : Dennis
Bailey, 10-Apr-2007, 00:41am
Hi there, sorry i havent posted in a while, ive been out the country!
Running the car up on axle stands and witth all else looking good, I am going to take the plunge and replace the
diff.
It seems to be rather noisy and is leaking also it is the last mechanical component to be replaced on the car!
Thanks for all the help for my invest it is greatley apreciated, wil let you know i've gone on.
Also anybody got any reccomendations for a good supplier for a diff?, I think canleys will probably be getting my
business.
Thanks