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Best for diff rebuild/exchange?


Roger K
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I have a pronounced diff whine at around 40mph which is more than annoying.  Checked the levels etc., but this a CRP whine.

Who's best for a diff rebuild?  Are the main suppliers - Fitchett's, Rimmer's etc. any good?  Or is an axle specialist my best bet?

GT6 MkIII non-roto, 3.27 ratio.

Any advice gratefully received,

Roger

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It’s a typical diff whine, comes in gradually at 40 under mild acceleration, is pretty loud at 45-50 coasting and fades up to 60. It’s Intrusive under acceleration and coasting and vanishes on the overrun. 
Rimmers aren’t cheap for a rebuilt diff with new CRP - don’t know how good they are?

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if youve got a small surface table a height gauge and a verdict style dial gauge you can keep things as they were by replicating all the dimensions on rebuild 

you do or should use a diff case spreader to set the main bearing pre load by spreading the bearing  locations 

the overrun bearing  (outer )has no setting other than getting a preload  but the pinion thrust ( inner) bearing /shimmed position must keep the projected mounting distance very accurately or you get a howler 

Pete

 

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10 minutes ago, NonMember said:

I had a 3.63 diff done by Marcus (GT6M), which has been good second time (the first was a "funny" one that he wasn't confident of and exchanged when it proved noisy).

Hello Roger

                    I have one off Marcus as well and it has done at least 5000 mile if not more and is quiet

Roger

ps 3.63

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Diffs are a bit "luck of the draw"

Pete (Roger has met him!) did one for a local. It was a known howler. Pete was concerned, but set it up/shimmed etc and got lucky, near silent (certainly way better than teh one from Jigsaw that was new CWP that was deafening, jigsaw replaced with no quibble, second one better)

So a real lottery. I think Fitchetts supply most diffs now, but again, you hear good and bad. 

The 3.27 is a little different to the other diffs, but Mile Papworth is possibly your best bet. Pete simply can't find teh concave washers for rebuilds anywhere, and his "good used" stock has dried up.

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A few years ago, I bought one from Canleys, with new C/P, which whined slightly on drive, and quiet on coast, from square one. Dave Pearson had it back and 'couldn't find anything wrong with it' but swapped it as a gesture of goodwill. Unfortunately the replacement turned out to be even noisier after very few miles. At that point I gave up for a while. 

I've said this before, but I don't understand why reconditioned Triumph small chassis diffs seem to be a complete lottery in terms of noise/leaks. I know people say that some parts, shims etc, are in short supply, but surely reconditioners are aware of this and I don't believe the parts are prohibitively expensive to remanufacture. I'm not aware of MGB owners moaning about the quality of recon diffs in huge numbers. 

As things stand now - with the cost of recon diffs going through the roof - I'm very reluctant to throw good money after bad. Surely somebody can build qiuet diffs !

Gav

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Well, I asked in the hope that things might have changed since my last GT6 ownership in 1986, but clearly not!

Not a job I want to do myself, I wouldn't do enough to justify the cost of decent tooling and I suspect it's one of those jobs where you need to be 'in practice' to get a good result.  Triumph diffs have always been a weak point in my opinion - my GT6 got through two replacements in the six or seven years I owned it, and my two-year-old 1976 Stag needed a new one when it was three years old and had done 15,000 miles.  Warranty? Ha!

I'll try some of the suggestions above as I think they represent a better bet than throwing bucket loads of cash at Rimmers.  I like Tony at Fitchett's, so might be tempted to ask him, too...

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who wants to buy one of these   this will give you + - best run setting of the pinion  (this is etched on the end of the pinion) , but whine is most likely bearings rather than  mesh  

pre loads are there to maintain positions under varying loads , read the manuals about  heel and toe markings of the tooth markings 

it all gets a bit clinical in the settings , not a DIY job without some decent measuring , a good eye and strong tea 

pete

 

 

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Just now, Colin Lindsay said:

All being well then the whine is just a bearing? It's not lack of oil, anyway... it's got plenty.

That's the part of Pete's theory that I don't understand - i.e. whine most likely bearings rather than mesh. If you buy an exchange recon diff, I expect all bearings to replaced as a matter of course. Bearings shouldn't be wearing after a few miles.

Gav

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10 minutes ago, trigolf said:

That's the part of Pete's theory that I don't understand - i.e. whine most likely bearings rather than mesh. If you buy an exchange recon diff, I expect all bearings to replaced as a matter of course. Bearings shouldn't be wearing after a few miles.

Gav

That diff was reconditioned in 2012, went back into the car in 2013 but the GT6 was off road until 2015, covered less than 300 miles, just to local shows until 2018 - about 300 miles that year - then off road again until July this year. I'd estimate no more than 900 - 1000 miles in all. It's just started to whine but on the last run two weeks ago it was incredibly noisy at low speeds.

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In my experience, the whine from a diff is usually produced by damage or wear on the faces of the CWP teeth.  Worn bearings usually rumble or grind rather than whine - think of a worn wheel bearing.  Setting up the gear mesh is the 'black art' bit, in my view.

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1 minute ago, Roger K said:

In my experience, the whine from a diff is usually produced by damage or wear on the faces of the CWP teeth.

Precisely, so like Colin, mine had a brand new crown wheel and pinion fitted, but started whining almost from square one! Now it's bloody annoying and very intrusive in a convertible thats already noisy anyway, especially with the hood up ! I gather that new C/w pinions were made abroad - Turkey ? I'm suspicious about the quality control of said items !

Gav

 

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theres   three  noise contributors to diff noises   

the bearings    or tooth form     or mounting mesh 

we used to grade diff noise on a 0 to 10 scale    with 0-3 being ok  3 - 6 cause for concern     6 -10  its out for examination 

changes on drive to overun  

if it is noisy on drive but quiet on overrun then expect the mounting distance is wrong and the tooth marking is working at the ends of the 

tooth . also plagued by lack of pre load  allows the pinion to shift in and out of mesh  this might only be a few thou 

the frequency is a guide to whats the noise  , with bearings on the pinion they rotate  at  high speed  have many rollers and kick up a 

high pitched whine

tooth markings on the crown run at wheel rotation speeds and generate a lower frequency noise 

so theres whine  and there Howl     

pete

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Yes, I'd go along with all of that Pete!

Unfortunately the smaller Triumph diffs seem to be particularly prone to a whine.  That said, they're not alone - my '68 Mustang has a Currie Performance complete rear axle assembly, warranted to 1200bhp (although I'd have thought a torque rating would be more relevant...), and that's whined from new.  It's not loud, and it's got no worse in 45k miles, but still...

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