Strange behaviour from GT6 differential that otherwise seems fine.

[Jim-GT6]

49 minutes ago, Pete Lewis said:

yes they should be    its wear and tear upsetting the very accurate dimensional settings that makes them noisy 

there is a lot of critical settings to control bearing preloads  crownwheel and pinion mounting dostance and backlash all need to be right 

its not any DIY job without special tooling and experience  

as for noises  howls and growls is meshing ,   whines would be more down to  bearings 

maybe  its time to check the gearbox oil as well !!!!!!!

Pete

 

If they can be quiet, then that's my new goal, because with a quiet diff, my car would be a very different experience.

It's just gone round the clock, but had a full engine about 10k miles ago (circa yr 2000) and its in really good overall condition. It could easily have the original diff at over 100k.

Gearbox is topped up. I changed the hydraulic system completely last year, so had the tunnel cover off. I overfilled the gearbox a bit (I think) as the overdrive went loopy for about 300 miles. In and out constantly. It settled down. Which might mean it leaks quickly .... but it doesn't seem too bad from the underside

So ... I've been looking at diffs. Looks like round about £850 inc vat from Rimmers with new crown wheel and pinion. Where can I get a great diff with a good setup? I now realise it's a better investment for my car than a stainless sports exhaust! (which was top of the list, and daft, given the sound of the drivetrain)

Best route to a quiet diff?

 

[Dick Twitchen]

9 hours ago, Jim-GT6 said:

Best route to a quiet diff?

Talk to Mike Papworth; details are in the back of The Courier.

[Pete Lewis]

=+1 for mike papworth

also look at  td fitchets  prices in the courier 

dont forget a recon is just that  some new some old parts 

its all down to utopia or compromise  

always take your expected usage into account costs of any rebuild 

most diff noise is down to pinion bearing wear which in  turn upsets the mounting distance (mesh) 

crown wheel and pinions are a matched pair run on a Gleason tester to find the best running settings a used CW set if un scuffed is quite re useable

planet and sun gears are re useable and dont cause any noise 

so adding new bearings correctly set to a used good  CW & P can be fine 

 

[Jim-GT6]

8 hours ago, Pete Lewis said:

=+1 for mike papworth

also look at  td fitchets  prices in the courier 

dont forget a recon is just that  some new some old parts 

its all down to utopia or compromise  

always take your expected usage into account costs of any rebuild 

most diff noise is down to pinion bearing wear which in  turn upsets the mounting distance (mesh) 

crown wheel and pinions are a matched pair run on a Gleason tester to find the best running settings a used CW set if un scuffed is quite re useable

planet and sun gears are re useable and dont cause any noise 

so adding new bearings correctly set to a used good  CW & P can be fine 

 

Thanks chaps!

Mike Papworth hasn't been in the last 6 issues (I only joined in June this year). That said, he could be in October. I can't find October. I did a search online and found contact details. Nice interview on YouTube too! 

I'll give T.D.Fitchett a ring tomorrow as well. They've had the same stock list in every issue I've got, so I assume it's not kept current. No listing for a GT6 diff. Decent price on a Spit mkIV one though.

On driving today, it's better than before I filled it, but it can still howl at speed.

As for expected usage, the GT6 is my only car. I've only had it a year. I do about 100 miles every week. All year round. More if I go on a proper drive instead of just commuting. I hope to keep the car for a long time. I have no plans to raise into the 'special' category. It's a lovely, tidy example, and I'd like to make it incrementally better every time it needs attention. 

Pete - are you saying I may get a quiet diff if I had the pinion bearings replaced? That is if my CW&P is 'good'? I suspect it might not be! You haven't had the benefit of hearing it. 😬 - but I can appreciate an offset in the mesh distance from bearing wear would make a racket

Or, are you saying a refurb unit can be fine if the donor had good gears but shot bearings?

Either way, mail order delivery or collection is likely the way I'll need to go, rather than take out and send away for refurb.

Thanks again

[Pete Lewis]

12 minutes ago, Jim-GT6 said:

are you saying a refurb unit can be fine if the donor had good gears but shot bearings?

Yes thats about it 

as you have run with low oil  teeth may be scuffed  , they are tough bits of kit but do transmit all the load to the wheels 

triumph ( and all the others) design is to be quiet  more so with a hypoid as the tooth contact is longer  so quieter 

and a new CW&P does need to be run in to add a final polish the the tooth form , early life hairy driving will make a noisy unit for life 

front wheel drives eliminated bevel gears  so you dont hear of the problem with moderns 

in the 70s/90s we had a noise grading 1 -10  it was easy to get a 7-8  reject 

Pete

 

[RichardS]

Just to bring this thread up to date ...... the balanced propshaft with new UJ bearings plus the new output bearings and seals in the differential finally sorted out the vibration. I also changed the gearbox output seal whilst I had the prop shaft out so she's finally oil tight.

Even with the balanced prop shaft, she still wasn't pulling well above 70mph so I've also had to replace the brake servo which was letting air in an weakening the mixture and replace some dodgy wiring (a 12V coil and 12V electronic ignition unit was fitted by a previous owner but the ballast cable was still being used) but I took her out for a test run yesterday and she reached a genuine 90mph without too much difficulty.

I still need to get the mixture spot on but I reckon that she would have reached 100 if the traffic were lighter but once you get above 80 then it all feels a bit "sketchy" and definitely not relaxing. However 80 is comfortable cruising speed and means that I can keep pace with motorway traffic.

Anyway, I'm feel ready for another trip to "Caffeine and Machine" but a bit faster this time. I wonder if I'll be invited to park her up on one the the show plinths again this time. 😉

Richard