About to s**t-can putting an LSD in the S!

About to s**t-can putting an LSD in the S!

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Kitchski

Original Poster:

6,514 posts

230 months

Friday 15th August 2014
quotequote all
On the verge of giving up on this one. I'm used to pulling TVRs apart and putting them back together on a daily basis, but the world of Sierra differentials is too painful!

So, originally I decided to replace the 7.5" 3.64 ratio open diff with an LSD, while I was doing the body off. Managed to find a decent 7.5" LSD with the same 3.64 ratio from a Sierra Cosworth (a 3dr one, it turns out). I then pay to have it refurbed.

Fit the diff, before realising it has the 108mm output flanges, and the S uses 100mm types. Bugger. No matter, I'll put 108mm CV joints on one end of each driveshaft, so run 100mm one end and 108mm the other. Don't fit - different splines on the shaft! Bugger again.

Think about converting entire rear end to 108mm, but they won't fit in the trailing arms (and it's expensive). Bugger again.

Think I'm only a winner when someone suggests changing the output flanges over from the old diff. Pull old diff apart, remove output flanges in minutes. Even think I'm onto a winner when I realise I can remove the output flanges of the Cossie diff while it's still sat in the chassis. Result! Then crumble into a heap of self-pity and torture when I realise (and immediately kick myself for not thinking it through previously) that the LSD output flanges have deeper shafts than non-LSD, meaning they aren't interchangable.

Try to find Granada 24v diff (that's the one I really needed, same as fitted to V8S) but with no luck. Try to find Granada 24v output flanges. No luck.

Currently in comms with GKN to see if they can do a custom driveshaft or CV joint with 108mm outer and 25 splines. Not holding out much hope of it being cheap, or even possible.

Very close to thinking screw it - no LSD for me. But I was so excited about it! laugh

Ceejay73

489 posts

227 months

Friday 15th August 2014
quotequote all
Another possibility for output flanges is Sierra XR4x4 LSD. The diff is 7" in that model but the flanges are 100mm and may fit. Would recommend getting them measured before shelling out more cash though.
Just a thought.

Carl.

Kitchski

Original Poster:

6,514 posts

230 months

Friday 15th August 2014
quotequote all
Yeah I'd considered the XR4x4 flanges too, but they're equally scarce. The diffs are more common, but then I'll have fitment issues with one of those.

Ceejay73

489 posts

227 months

Friday 15th August 2014
quotequote all
Think the 7" has been fitted to an S by somebody on here but can't remember who. Can't see it being too difficult and don't think there is a great difference in reliability/strength between the two sizes.

ETA: It's TopGearTVR what done it recently.
Another edit: He may have a goosed 7.5" diff with 100mm flanges for sale too.

Edited by Ceejay73 on Friday 15th August 11:40


Edited by Ceejay73 on Friday 15th August 11:42

magpies

5,129 posts

181 months

Friday 15th August 2014
quotequote all
I may be wrong but try mailing Alan Whitaker - I think he fitted larger drive shafts and 'opened' out the trailing arm to suit - looked an easy cut and weld job

Kitchski

Original Poster:

6,514 posts

230 months

Friday 15th August 2014
quotequote all
Ceejay73 said:
Think the 7" has been fitted to an S by somebody on here but can't remember who. Can't see it being too difficult and don't think there is a great difference in reliability/strength between the two sizes.

ETA: It's TopGearTVR what done it recently.
Another edit: He may have a goosed 7.5" diff with 100mm flanges for sale too.

Edited by Ceejay73 on Friday 15th August 11:40


Edited by Ceejay73 on Friday 15th August 11:42
I'll try and get him on FB, cheers!

The 7" diff isn't any weaker.....truth be told I'm not sure why they made so many different bloody types! But to fit a 7 means shims & washers etc. Can't be dealing with all that.

Kitchski

Original Poster:

6,514 posts

230 months

Friday 15th August 2014
quotequote all
magpies said:
I may be wrong but try mailing Alan Whitaker - I think he fitted larger drive shafts and 'opened' out the trailing arm to suit - looked an easy cut and weld job
You probably could, but they've only just been refurbed so I'm reluctant to muck around, plus it would mean getting new shafts made.

Alan Whitaker

2,054 posts

181 months

Friday 15th August 2014
quotequote all
Hi
You do know not all the 3 door and 2wd had LSD, some had traction controll with a open diff, have you opened it up. converting to 108mm flanges is not hard but takes a bit of time and money to get right.

Alan

DamianS3

1,803 posts

181 months

Friday 15th August 2014
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Isn't that the Granada ie LSD through to bug eye 95 model which switched to TC.

I thought all the sierra and escort cosworth variants had the LSD.. 7.5 on 2wd and 7" on the 4x4 iirc..

Could be wrong mind.

Damian s3

Alan Whitaker

2,054 posts

181 months

Friday 15th August 2014
quotequote all
Hi
Just thinking your on 4 stud wheels, I changed to 5 which added the extra work, with 4 wheel studs all you need is the complete hubs and shafts and it should bolt to the trailing arms, may need a spacer re the cv joints.


Alan

mikel003003

1,084 posts

165 months

Friday 15th August 2014
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I got a 7 inch lsd from a sapphire cosworth.

Kitchski

Original Poster:

6,514 posts

230 months

Tuesday 26th August 2014
quotequote all
LSD back on - custom driveshafts being made at Berrisford. 28splines one end, 25 the other. That way I get to keep the proper 3.64 ratio in the diff, but have the Cosworth LSD with it. I'd already refurbed it, so didn't want to give up on it!

Means for future work I can still just buy standard CV joints and not have to worry about having them custom made. I {i]nearly[/i] found some 108mm CV joints with a 25spline, but gave up eventually. It was the prop coupling on the front differential on a Jeep Grand Cherokee if anyone decides to pick up the ball, but I'm not convinced they're the answer. They're £100 a pop too, so too much just to try out for me!

Loach1

431 posts

140 months

Thursday 28th August 2014
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I think you made a wise choice there with custom shafts, that will make it a tidy solution with long-term support. Funny you mention the Grand Cherokee front prop because 15 years ago or so I worked on that project in the GKN assembly plant here in North Carolina.

The plunge joint internals are slightly different to a normal halfshaft joint because there are higher RPM's and lower angles required on a propshaft. It might work just fine, but that depends on the angles that the S suspension requires of the joint.

I'm back with GKN now, but in the machining plant so I'm not sure what size VL joints are being used in propshafts at the moment. If there is any further interest I can ask one of the guys in the assembly plant if they have a 25T/108mm OD VL joint in production.

Alan Whitaker

2,054 posts

181 months

Thursday 28th August 2014
quotequote all
Hi
Ont the CV's I think Porsche or one of them is a 108mm X 25 splines but not all 25 splines are the same cut.

Alan

Kitchski

Original Poster:

6,514 posts

230 months

Thursday 28th August 2014
quotequote all
I wondered if the Jeep's joint would have been suitable anyway, due to the angles it's designed to work at like you say. They're £100 a pop (on eBay, not main stealer), so I'd be £200 down for something that may or may not work. And if it did let go, it'd likely make a mess.

Chased the Porsche one up and found there were some cataloguing errors, and couldn't actually find a 25sp 108mm joint. There's a lot of talk from Porsche owners about using 108mm joints on the 930 over the 100mm, but they change the shafts too, so if beefs up the drivetrain in general.