Gt6+ Rear Suspension Upgrade For V6?

[Richard/SIA]

May as well throw this out there while I'm redesigning the Trick-6 suspension.

225" Buick V6 engine and T5 five speed OD trans.

 

The original real diff was taken before I got the car and would never work anyway.

Original rear leaf spring is gone and not missed, expecting to use coil-overs.

Being a +/Mk. III it had the roto-flex couplings.

 

I need to create an entirely new rear suspension.

Thinking of using Merkur XR4TI as it's fairly available and has the correct 4x108 PCD for my 14"x6" Enkei wheels.

 

Anyone ever fit the Merkur/Sierra rear to a GT6?

It's about 8" too wide in stock form.

Would also want to upgrade it to rear disc brakes.

 

Scrap everything from the original rear, or just the diff and axles?

Would like to keep as much as possible "Off the shelf".

 

I see lots of post on using Subaru diff's, why not the Ford?

I can also readily get Ford T-bird 8.8" diff's but they are pretty large and more than I need for a V6.

[Urge]

Most people opt for the subaru because a fixing kit has/was made for them.

With the fitting kit. Its a no chassis mod fitting setup.

[CHRIS211083]

Jango used a sierra type rear end with shortened shafts etc. There is also a coasworth powered gt6 and a Volvo powered GT6 which both have full 8" wider rear sierra back ends. I think the wider rear looks bad but each to their own. Good luck with the project. Pic are needed or it didn't happen!!! Ha Ha.

 

Chris.

[pomwah]

I've been going back and forth over my rear suspension setup. SCT diffs are old and, judging by the number of issues raised about them in these kind of fora, are not overly reliable. The transverse spring has some benefits but, by and large, these are outweighed by their disadvantages. I could use a live axle setup and cart springs but I don't think the car ('66 Spit Mk2) is suited to it. So, IRS, it is. Dual wishbones and coilovers seem to be the best, and easiest, option. Choosing a design is the tough bit, there are as many "variations on a theme" out there as there are ways to skin a cat.

I've come up with a number of different solutions which, when I start looking for parts and information, someone has done it before, both good and bad for me. Good that I can ride on the back of others efforts, bad because I didn't come up with a original idea and my "ego bubble" is burst .

I started with MGF rear uprights etc., may as well add disc brakes while I'm at it, but being a complete numpty jumped in and made some, irreversible, changes to them and limited my options. During one of my research forays into the rotoflex coupling I found a CV halfshaft replacement made for Lotus Elans and the early Lotus Elan uses a dual wishbone (ish) and coilover system.

 

Given the Mazda MX5 (Miata) used a similar setup to Chapman's design, I'm now looking at their solution.

 

 

The big question is: Do I massively modify the chassis to suit the lower wishbone or shorten the lower wishbone to suit the chassis? Also have to think about the PCD, 4x100 on the Mazda.

I think the Subaru diff is used for a number of reasons, they're common, they're cheap, they're reasonably light, there are a wide range of standard ratios and upgrades available and it's all been done before.

 

Welcome to Sideways!

 

I'll be following your progress closely.

Edited July 20, 2014 by pomwah

[Nick Jones]

MX5 rear end does have some attractions.  However, one negative is the lack of any sensible final drive ratios - all are too short for a large, torquey engine.

 

Sierra/Merkur diff can be made to fit and has been before.  Not sure what ratios exist in the US market but there is a decent selection in Europe. 

 

Nick

[Richard/SIA]

Who are "Jango"?

Is that a person or a company and where are they located?

Would like more detail.

 

I could use one of my Jag diff's but they are a bit large and heavy.

[CHRIS211083]

He developed a bolt on rear chassis with near perfect suspension geo and a sierra diff. Use the search function on this website and you will find his threads

 

Chris.

[Richard/SIA]

OK, I tried that search.

Found the person but it seems they are no longer active here and all their old post are gone.

 

Anyone archive the details?

I have a fair amount of machine tools and welders so could do this again.

Would be nice not to have to reinvent the wheel.

[Nick Jones]

It is this one

http://sideways-technologies.co.uk/forums/index.php/topic/1228-jangos-rear-end-kit/?hl=%2Bsierra+%2Bdiff&do=findComment&comment=15609

 

Extreme - but effective.

 

Nick

[Richard/SIA]

A great job, but nothing since Dec. '09, what happened?

 

Looked like it should have become the standard fix.

[RealWorld]

Jango binned the GT6 with the tubular rear chassis on a night rally in Holland a year or so back. Front damage only and the rear end survives. He's been 'distracted' by a brace of TR7s and Lotus variant big Vauxhall saloons recently and as a consequence the GT6 has languished of late.

 

The rear end worked well after a bit of road development - and another example exists that we're (Yorkshire Triumphs) about to start work on prepping and bringing to the road. I believe the supplier of the 'Jango' has jigs to make more - and essentially they bolt on to the chopped and welded chassis legs of a standard GT6 without body mods.

 

I could dig deeper if anyone's interested - Jango is a mate whose cars we work on as and when...

 

R

[Richard/SIA]

Very interested!

Been trying to locate him for a chat.

Seems just what I need for my "Trick-6" project.

Shipping to the U.S. is dear and we do have Merkur donor cars here.

So really just looking for the tube structure and any other parts that are special made.

Have to arrange some Marcos parts shipping too so might  try to consolidate.

No worry about welding we have plenty of certified welders.

[Richard/SIA]

Some actual progress of the "I bought another part" sort.

 

Got a Merkur complete manual trans complete rear today.

 

Open diff, not posi as the web info postings call for.

Aluminum carrier and a little smaller than a T-Bird 8.8 unit.

Some web threads I saw suggest that a GM 7.5" posi can be made to fit?

Ratio appears to be 3.65 which I believe is what the web claimed and should work well with the T5 OD.

Would really like to have more information from Jango.

 

I know I will have to fabricate uprights and "A" arms, the current trailing arms plus axles, are HEAVY and 10" too wide.

[Richard/SIA]

Got the Merkur/Sierra rear somewhat cleaned and stripped.

Looks like I am on my own for the engineering of it to fit the GT6.

I'm working from a bare chassis so it should not be too bad.

One item I REALLY do need to know are what axles to get in order to get the stock GT6 width when I finish?

If truly necessary I have a source to have mine cut and re-splined at one end but I'm not inclined to do that if it can be avoided.

I know I need two lengths, and there was mention of parts that may be correct in the Jango thread, but the inquiring post was never confirmed.

[esxefi]

if the Merkur diff is the same as the sierra type here in the UK then you are not alone.

 

I fitted one in my spit 14years ago.

I mounted it centrally in the chassis and had both drive shafts cut back and resplined to be equal lengths as you mention.

the original diff is offset anyway to allow the swing axles to be equal length(I know the trans tunnel is also offset to compensate) 

no vibration issues at all,best to have some movement in the ujs to prevent accelerated needle roller wear.all live axled cars have a constantly changing prop angle with no issues.more important is making sure the g/box and diff flanges are parallel to each other.

I had to cut off the handbrake cable guides to fit it with minimal mods to the bodyshell(had to remove a small section of the front of the tub which goes over the leafspring,covered by a plate made to fit) to allow the diff to go high enough.the top mounting boss on the casting hits there.if you want some pictures let me know.i'll have to take some.

[Richard/SIA]

Yes it's a Sierra XR something in the U.K, and "Merkur XR4TI" in the U.S.

2.3 Lima engine with a factory turbo.

Not a lot of them sold here but they are now at the peak of their being scrapped so not hard to find.

 

A couple of pics would be great!

My car is being extremely modified so a minor body cut is nothing.