gasket999
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| posted on 15/8/14 at 11:09 AM |
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Duplicating a TVR Chimaera/Griffith rear axle from donor parts?
I’ve read a lot of conflicting info regarding the original donors for the TVR Griffith\Chimera rear axle and it is driving me crazy.
Rear was a double wishbone set-up similar to the Haynes Roadster. I understand that the hubs were from a Sierra (not sure which model or if there is
any difference across the range). I know that the callipers and discs were also Sierra with 253mm discs. But I’m still drawing a blank on the
halfshafts and diffs.
I know that the diffs were all LSD and that pre 1997 they were a GKN unit and post 1997 they were BTR. I also understand that a BTR Hydratrak was an
option. But I can’t find a code for the diffs used anywhere – I would imagine a similar diff was used in other production cars, either in Europe or
Australia/the US but I can’t work out which. I’ve heard mention of Maserati but looking for more common sources such as
GM/Holden/Saab/Ford/Opel/Commercials/etc.
I’ve quietly heard that Vauxhall Omegas used a BTR diff and that the police ones were LSD – but not sure if this is true or whether it was the same
unit as the one fitted post-1997 by TVR.
Also confused on the driveshafts as I know they were equal length and that a Sierra hub was used so would it have been a custom halfshaft or would a
standard OEM shaft (eg Sierra/Granada) marry a Ford hub with a GKN/BTR diff?
Some articles actually say that a Sierra/Granada 7.5” LSD diff was used but I find this hard to believe and think they may be confused with the TVR S
models rather than Griffith/Chimera.
I've found this picture of a GKN rear setup but nothing of the BTR diff:
Heard plenty of rumours but a bit of fact would be very welcome.
[Edited on 15/8/14 by gasket999]
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gasket999
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| posted on 15/8/14 at 11:52 AM |
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Update - I've just been told that the BTR diff was the M80 as fitted to IRS Holden Commadores and Monaros. If this is right its exactly the info
I was looking for.
I've also been told that the GKN unit may have been used in a number of Jags but have also been told (again) that its a similar unit to the one
fitted to a 2WD sapphire cosworth. Still no code for it though.
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mark chandler
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| posted on 15/8/14 at 12:26 PM |
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Jags tended to use Dana diffs! Big heavy lumps with plated power lock diffs, you would be looking for XJS and XJ40 style XJR's, once they went
to v8 open diffs and traction control.
Police omegas, the v6 ones did have slippery diffs, but the miles a police car would have covered makes a second hand proposition questionable
assuming you can find one.
Sierra half shafts are only different lengths because the diff is offset in the car, you can easily get .
What you making, the standard sierra LSD is fine for a light car if on a budget.
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mcerd1
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| posted on 15/8/14 at 12:51 PM |
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what exactly are you looking to do that you need this info ?
the diff in your pic is clearly not a ford 7" or 7.5" one (at least the case isn't)
it does look a bit like the omega diffs I've seem, but I don't know the GM stuff very well....
in terms of what diffs you could fit without swapping the hubs - all that really matters is the type of CV joint (custom driveshaft's are easier
to get and cheaper than custom hubs  )
the 7.5" diffs in 2wd sierra cossie's used 'size 15' lobro CV joints (108mm outside diameter), these are fairly common across
a wide range of car makes including BMW and Porsche and I think its the same as a Vauxhall omega
the rest of the sierra's used 100mm OD joints (size 13 lobro I think) that's also common across a wide range of makes...
[Edited on 15/8/2014 by mcerd1]
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gasket999
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| posted on 15/8/14 at 01:03 PM |
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I haven’t decided yet but is likely to be a bit of a heavyweight – not a lithe little 7. Suspension will definitely be as per Haynes Roadster as I
already have Sierra bits. At this stage I can’t afford to give up the garage space to start fabrication but I can gather and recon the parts in
advance.
Basically working with parts I already have:
I have a hybrid V8 I built a few years ago as a blueprinting project. Basically the best of Buck/Olds/Pontiac/Rover (BOPR) bits to make a bombproof
little V8. Now has steel heads but still relatively light for a V8.
I have a WC T5 box out of a Firebird – just need a TVR bellhousing and may need to change the remote.
I have the running gear from a Sierra XR4i that I set aside a few years ago for a kit that never happened.
I have both Sierra and Mk2 Escort steering racks.
Effectively if I can work out the rear axle set up then I’ll end up with almost identical running gear to a Griffith/Chimera. That’s a proven set
up.
[Edited on 15/8/14 by gasket999]
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mcerd1
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| posted on 15/8/14 at 01:42 PM |
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quote:
Originally posted by gasket999
Effectively if I can work out the rear axle set up then I’ll end up with almost identical running gear to a Griffith/Chimera. That’s a proven set
up.
but the stock sierra rear end is also a proven setup in both seven style cars and tin-tops alike
in fact the only issue with sierra stuff is that the higher geared ratio's are a bit rare - but depending on your gearbox and the tyre size that
might not even be an issue....
the BMW rear end may be a good alternative now though due to the increasing rarity of sierra bits and they have a decent choice of ratio's
too
GKD use them in there cars and dax were starting to as well before they sold on the project - this is the last dax rush demo car - its running E46 3
series parts 
(couldn't find a decent pick of the GKD IRS setup)
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Sam_68
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| posted on 15/8/14 at 03:55 PM |
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I seem to recall that the BTR diff was also used in Maseratis (the 3200... dunno about the 4200 and subsequent models).
Not that Masers are exactly thick on the ground in scrapyards, so that probably doesn't help you much!
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britishtrident
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| posted on 16/8/14 at 11:26 AM |
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Jaguar used GKN Salisbury final drive units on all models for almost 40 years prior to the late 90s some models used plate type LSD you really
don't want to go down Jag route as the weight was huge.
Lotus used a smaller Salsbury unit on the 501 Elite and early Ecat I believe the later Eclat Excel used Toyota Supra unit but I am not 100% sure on
that.
More important than the final drve ratio the really important thing is to find a final drive with the correct ratio.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Lightning
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| posted on 18/8/14 at 11:21 AM |
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My TVR has GKN diff with drive shafts having 108 CV's 40mm thick 28 teeth. Had it reconned last year.
Don't know the length of shaft without crawling under.
Steve
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