Blackline helical LSD?

[NickW71]

I came across these yesterday and as I'm in the process of rebuilding my Stag from the ground up I was wondering if this would be a good upgrade. You essentially replace the internals with this plus new seals and bearings. I can't find a review anywhere though. Has anyone on here used one? I would love to hear your thoughts.

https://www.rallydesign.co.uk/product_info.php?products_id=25099

[wilf]

Can't comment on that specific piece of equipment, but why do you want a LSD on a road car that rarely spins up its rear wheels anyway? Unless you are fitting a much larger engine or tuning for racing?

[richardthestag]

fancies treating the car to monumental understeer

[dasadrew]

Can't comment on that specific piece of equipment, but why do you want a LSD on a road car that rarely spins up its rear wheels anyway? Unless you are fitting a much larger engine or tuning for racing?

+1

Based on my own experience of an LSD (different car), I think you might find it more problematic to hear thoughts whilst you're driving with an LSD.

[NickW71]

Yeah I'm fitting a 4.6 Rover Efi and might do the odd track day. The the whole BMW rear end option is a little cost restrictive. Doesn't the understeer issue depend on how the particular diff distributes the torque? Also conversely wouldn't it help with potential oversteer and maybe help to remove the 'twitch' aspect of Stag's handling that many talk about?

[Motorsport Micky]

Nope, the limited slip diff IMPOVES the grip at the back wheels varying it from one side to the other that's why the slip is ...limited. If you gain grip at one end (the rear) then it overcomes the grip at the other end. Which means the understeer lovingly crafted in by Triumph (because understeer is safe) now is fed steroids and becomes UNDERSTEER, certainly it will help reduce oversteer. It's useful you are rebuilding the car from the ground up because you need to do something with the problematical drive shafts that stick and the rear hubs that thought they had an easy life these past 40 years and may well be problematical as well as regards shearing and the stub axle which has microcracking which you can't get checked.
These cars have the Innsbruk rear suspension drive system fitted and it's shared with the big Triumph saloons and very helpfully with the TR4a/5/6 series sports cars (think canary in the mineshaft) with the same IRS suspension. Here try a copy of a recent thread from the TR Register Forum.

https://www.tr-register.co.uk/forums...comment-759918

I'll give you a taste

These rear hubs are fitted upon TRs, Stags and the big Triumph saloons. The TRs are the canary in the mineshaft, many of the drivers in their near past used to drive them like Jehu (ie furiously) and as the pendulum of time swings every year we reach the limits of what these parts can stand.

(There are other photos of TR hubs and stubs which fail...but I thought we'd use Stag units which many have seen on this forum before).

You've probably seen these photos before, they are Stag units which were swapped as a pair from one of the main Stag and big Triumph suppliers, within 4 months one hub broke through the stub axle.


After returning the hub and receiving a replacement with apology and a further 15months driving had the other original replaced hub do this



Now the hub has snapped take the opportunity, look deep within, ...see the fretting marks on the matching surfaces, this hub has been cracked INSIDE and continued to hold together for some distance, over weeks and maybe months, until tested and driven to destruction by...the driver...could have been you. The problem with these parts are they are very inaccessible, built up components with difficult processes to split them apart which often means a 20 ton plus press and a oxy torch, if they weren't cracked before hand, they stand a good chance they are afterwards.

We have the resource within the forum to have catalogued these failures... and many have and are available to read from our own forum search facility.

A) ...Regarding your squeak, I wouldn't drive it until you get to the bottom of the cause, my 6 had an annoying squeak from the rear audible at low speeds, when I took it to Enginuity for them to have a look at, the cause was as per Mick's photo, my hub had cracked 3/4 of the way round the flange, so the wheel was about to part company with the car. When I had the car rebuilt I went for these http://www.vessey-classic-car-servic...m#.XzEOLC2ZMwc not cheap and they do come with their own issues but at least I know that all the wheels should stay on the car.

B)...get new hubs and axles and if you can't afford them park the car until you can. It may not just be you who suffers but other road users. Refurbished are just old high mileage ones cleaned up and could break before you get out your driveway. The L/H stub axle broke just under the edge of the outer bearing where it couldn't be seen. It felt like a flat tyre, slowed down to about 80kph and there was a loud bang, the car (TR4a) went sideways and rolled 1 and a half times, lucky I had a rollbar or I would not be writing this.
Spent 7 weeks in hospital and now have two hands that are not a lot of use any more and a car that is going to take some time to repair. My brother has purchased a TR6 which he immediately pulled the hubs off and found 1 hub flange with the boss broken off like in the photo and the stub axle cracked and ready to part company on the right sides its off the road now until new hubs can be obtained. I have already purchased new C/V joint driveshafts and hubs from Rimmers which are waiting for my hands to start working.

C) We had a local member turn up an one of our meetings and we all laughed at the very obvious "squeak" every revolution of the back wheel as he slowly drove up - he is an engineer by profession and had searched high and low for the cause and even asked his local garage to investigate, all to no avail.
None of us were laughing a week later when we learned his nearside wheel had overtaken him at 70mph on the A12 in the outside lane, and by the grace of god, he managed to avoid a massive accident. The hub had sheared just as in Mick's photos - guess what, it was a reconditioned hub from a well known TR parts supplier less than a year and 1500 miles previously.

D) Some of the replacement panels on my car came from a club member’s TR6 which rolled on the racetrack after a stub axle failure. Her roll bar saved her life. She did not buy another TR.

E) Years ago when I worked in the OEM motor components industry, some of the senior managers had Triumph 2000s and some did very high mileages approaching 100K in under 3 years. This problem with broken rear hubs was known then!!! and that was in the 1970's!! We had a couple of 2000's become 3 wheelers which meant a change in policy...then the 2000's went to auction at 75K.

And from a TR owner whose career has been spent Non Destructive Testing of aircraft frames and engine parts.

F)...if you are going to rebuild a unit then seriously consider a new shaft item 42 Shaft
This is one of two things that can snap and you lose the wheel. The old shaft can not be positively crack tested.
It goes from good to broken in very short order.
some of these high strength steel alloys do not help the NDE (NDT) inspector as the period from star of cracking to failure can be very short.
Also many of these steels allow micro cracking (un-inspectable) to exist for long periods before going bang.
Aircraft parts that use these materials are usually 'lifed'. I think our original hubs are at the end of their life.

G)...,due to the nature of the steel and its heat treatment crack testing will do no good.
If there is a crack then you may find it. But. you will not find a crack that has not started yet or is very very small.
Similar steel on aircraft is often life'd as once the steel structure starts to 'go' it will be rapid.

H).The rear hubs are nigh on impossible to detect prior to failure.



There are at least 3 different CV driveshafts available for our IRS cars, if you buy a set with new hubs including Timking bearings and new stub axles it will cost about £1100, I had a new set for my Stag which makes it easier to sleep at night.

Your cars your choices.

Mick Richards

[NeilR]

I think your £499 + VAT could be better spent.

[Dorian]

I have the full BMW rear chassis and the limited slip and the car feels really balanced. On the front, adjustable drag links and arms allowed for a lot more Castor and a bit of negative Camber though which together with a thicker roll bar may have helped but it was all done at the same time so I don't know the individual effects. The Rover engine is quite a bit lighter than the Stag so might offset some of the original understeer?
I guess once you start changing things and catering for the manufacturing tolerances on these cars, being able to try different suspension settings can transform the cars when things don't feel right.

[Matt Cook]

It is a copy of the quaife atb automatic torque biasing differential. I fitted a quaife unit to mine, did I need to? No. I did the rebuild myself and thought I would put the money I saved towards a lsd. Really pleased with the results. No rear end squirm or drama in the wet or gritty roads when your floor it off a roundabout or similar!