triumph diff questions

[gibbon]

going to give the gt6 a birthday and part of it was going to be addressing the crappy diff. I went quite far down the r160 rabbit hole when someone mentioned they'd given up faffing with axles and "just bought a quaife instead". Sure enough the quaife unit and it's Chinese knockoff is still available and probably cost way less than hours of fucking around

But my question is, what part of the notoriously shitty triumph diff actually fails? would an aftermarket lsd unit address the weakness or would it just fail somewhere else? I just need something that's good for around 200hp and 150ft-lb 

[Alfashark]

@VitesseEFI will likely have an answer for you when he surfaces.

[locost_bryan]

51 minutes ago, gibbon said:

going to give the gt6 a birthday and part of it was going to be addressing the crappy diff. I went quite far down the r160 rabbit hole when someone mentioned they'd given up faffing with axles and "just bought a quaife instead". Sure enough the quaife unit and it's Chinese knockoff is still available and probably cost way less than hours of fucking around

But my question is, what part of the notoriously shitty triumph diff actually fails? would an aftermarket lsd unit address the weakness or would it just fail somewhere else? I just need something that's good for around 200hp and 150ft-lb 

Iirc the GT6 has the Herald "small car" diff, shared with the normal Dolomite and Marina. The Marina axle was used in the Caterham 7, the half shafts fail before the diff. The Group 2 rally Marina 1300 had 130bhp and a lsd in the standard diff and never broke one (and had class wins on the RAC and 1000 Lakes WRC rallies).

The Dolomite Sprint had the TR "big car" diff, plenty strong iirc.

@VitesseEFI will be your font of knowledge. 😊

[gibbon]

my understanding is that the diff was originally designed to go behind a 35hp Herald engine and the poms are the actual worst offenders for "if it ain't broke don't fix it" or rather "make sure it breaks, to help out the lads down at the Union"

[locost_bryan]

2 minutes ago, gibbon said:

my understanding is that the diff was originally designed to go behind a 35hp Herald engine and the poms are the actual worst offenders for "if it ain't broke don't fix it" 

Standard 8 before that iirc. 

More than 100bhp I'd be looking at the TR/2500 diff. Would be surprised if there wasn't an off the shelf kit for the upgrade over the years.

[HighLUX]

Id believe that, my trump 2000 paddock basher turned the spider gears into liquid with one clutch kick on grass.

The mig fixed it real good but thats not really good for a road car

[gibbon]

6 minutes ago, locost_bryan said:

Standard 8 before that iirc. 

More than 100bhp I'd be looking at the TR/2500 diff. Would be surprised if there wasn't an off the shelf kit for the upgrade over the years.

like with all things gt6, I think there's significant clearance problems that prevent fitting just about anything else. even the driver is an interference fit

[ahebron]

It all depends how the car is driven.
If you are hard on it then things will fail.
Plus remember the youngest GT6 is over 50 years old and the oldest is nearly 60, and still looking sexy.
If its a rotoflex back end then the brand/quality of the rotoflexs is very important. Original is best or CV conversion is an common answer.
UJs can break.
I broke an axle on my MK4 Spitfire going round the Basin Reserve back in 80s and that was a 1300cc.
I heard of a Daimler 2.5 V8 that was in a Spitfire running an almost standard back end. It did need almost weekly work on the back end.
There are strengthened axles developed for racing that are available for a lot of money.

TR/2500 diff wont fit though I have seen kits to fit modified big Triumph axles to the small Triumph.
Plenty of free info on the net regarding the Datsun/Subaru diff conversion but it doesnt address the axles.
I feel if you strengthen one component then you can stress another.
I used to treat UJs like fuses, when they blew I had put to much power through it.

Also beware of axles directional stress, problems of axles breaking when a left axle is installed on the right and vice versa.

Just my thoughts on the matter



 

[gibbon]

40 minutes ago, ahebron said:

Plenty of free info on the net regarding the Datsun/Subaru diff conversion but it doesnt address the axles.

yeah I did notice most of the threads petered out around the time axles were discussed. thanks for weighing in, I saw your post on the brit car pics thread and figured you were an old hand at triumphs and the like 

[VitesseEFI]

5 hours ago, gibbon said:

going to give the gt6 a birthday and part of it was going to be addressing the crappy diff. I went quite far down the r160 rabbit hole when someone mentioned they'd given up faffing with axles and "just bought a quaife instead". Sure enough the quaife unit and it's Chinese knockoff is still available and probably cost way less than hours of fucking around

But my question is, what part of the notoriously shitty triumph diff actually fails? would an aftermarket lsd unit address the weakness or would it just fail somewhere else? I just need something that's good for around 200hp and 150ft-lb 

Late to the party….. small chassis Triumph diffs are a bit shit.  Some are worse than others. For the purposes of this I’ll assume we’re talking about the later 3.89 /3.63/3.27 with round input flange. Theses suffer from
- Being too small for the 6 cyl cars
- Not enough oil capacity / no drain plug / leaks. So the oil gets cooked, is never changed and eventually turns to jelly or escapes and by the time the diff starts howling for help it’s too late.
- outright breakages are mostly either the cross-pin breaking or the carrier casting failing where the pins go through. The Quaife/Blackline copy solves this.
-It’s still a small diff though and you definitely can rip teeth off the CWP though being properly built and being full of decent oil helps.

2 hours ago, ahebron said:

It all depends how the car is driven.
If you are hard on it then things will fail.

Absolutely this. Go drag-racing /drive like a baboon on meth and it will die. Maybe not on the first pass, but soon. Though as also mentioned, you might well break something else first - driveshaft, UJ, diff output shaft, gearbox.

200bhp/150 lbft is pushing your luck pretty far even with the Quaife. Though a friend of mine does race a 2.5 Vitesse with a Quaife diff and CV shafts. That has 180 bhp and 180lbft and gets driven with aggression. He’s not yet broken the diff, though to be fair other components (notably gearboxes) have been acting as the fuse. He’s recently gone to a T9 so we’ll see!  200bhp is getting close to the limit for an R160 too I’d think.

I’ve not (yet) broken a diff outright. I’ve worn a few out though. Vitesse is only around 140 bhp /140lbft though.  I’m now running a Quaife copy as at last rebuild time all of my collection of standard carriers had problems. It seems fine - heaps traction without any odd clanking and snatching like the plate diffs.

I’ve also got a 3.54:1 viscous lsd R160 in stock along with a conversion kit from a guy in Melbourne. I’m procrastinating as I’ve been having trouble finding the right Subaru driveshafts (now solved) and want to beef up the spring hanger a bit as the Vitesse is fatter than a Spit/GT6.

@gibbon, is yours a rotoflex car, what engine/gearbox are you planning and how will you use the car?

 

[gibbon]

10 hours ago, VitesseEFI said:

Late to the party….. small chassis Triumph diffs are a bit shit.  Some are worse than others. For the purposes of this I’ll assume we’re talking about the later 3.89 /3.63/3.27 with round input flange. Theses suffer from
- Being too small for the 6 cyl cars
- Not enough oil capacity / no drain plug / leaks. So the oil gets cooked, is never changed and eventually turns to jelly or escapes and by the time the diff starts howling for help it’s too late.
- outright breakages are mostly either the cross-pin breaking or the carrier casting failing where the pins go through. The Quaife/Blackline copy solves this.
-It’s still a small diff though and you definitely can rip teeth off the CWP though being properly built and being full of decent oil helps.

Absolutely this. Go drag-racing /drive like a baboon on meth and it will die. Maybe not on the first pass, but soon. Though as also mentioned, you might well break something else first - driveshaft, UJ, diff output shaft, gearbox.

200bhp/150 lbft is pushing your luck pretty far even with the Quaife. Though a friend of mine does race a 2.5 Vitesse with a Quaife diff and CV shafts. That has 180 bhp and 180lbft and gets driven with aggression. He’s not yet broken the diff, though to be fair other components (notably gearboxes) have been acting as the fuse. He’s recently gone to a T9 so we’ll see!  200bhp is getting close to the limit for an R160 too I’d think.

I’ve not (yet) broken a diff outright. I’ve worn a few out though. Vitesse is only around 140 bhp /140lbft though.  I’m now running a Quaife copy as at last rebuild time all of my collection of standard carriers had problems. It seems fine - heaps traction without any odd clanking and snatching like the plate diffs.

I’ve also got a 3.54:1 viscous lsd R160 in stock along with a conversion kit from a guy in Melbourne. I’m procrastinating as I’ve been having trouble finding the right Subaru driveshafts (now solved) and want to beef up the spring hanger a bit as the Vitesse is fatter than a Spit/GT6.

@gibbon, is yours a rotoflex car, what engine/gearbox are you planning and how will you use the car?

 

thanks for the reply, I'm pretty confident that the Blackline would end up miles cheaper than building adapters and getting half shafts etc machined for the R160, as you say the other half of the equation is getting in there and replacing the oil, i guess welding a drain plug boss in at the same time etc

My car is a rotoflex (probably needs new donuts come to think of it). Plan is a supercharged mx5 engine and box. (although the bridgeported 12a and starion box languishing in the garage got a long hard look too) I doubt it'd be anywhere near 200hp but I'm playing it safe. Likewise I'm a placid driver, but I don't really want to leave an obvious weak link in the system, especially if it's fifty years old. If the LSD unit replaces the traditional first points of failure then that's what I was hoping to hear

[VitesseEFI]

Ok. Driveshaft UJs are probably the weakest link with the Blackline fitted.  CV shafts are a nice solution. I was selling conversion kits for a while which used MGF/Rover 100 outer CVs and shafts with Volvo 340 CVs at the inner end also replacing the hubs and wheel bearings with Rover 100/MGF parts, but Rover 100s and Volvo 340s are basically extinct now.  There are shafts available in the UK that bolt right up using the standard hubs and bearings but fairly pricey. There original rotoflex arrangement can reasonably reliable but only with DECENT donuts!  It’s very scary when they give way in service. 
 

The diff rear casing has a boss already in the casting which can be drilled and tapped for a drain plug.

[gibbon]

7 hours ago, VitesseEFI said:

Ok. Driveshaft UJs are probably the weakest link with the Blackline fitted.  CV shafts are a nice solution. I was selling conversion kits for a while which used MGF/Rover 100 outer CVs and shafts with Volvo 340 CVs at the inner end also replacing the hubs and wheel bearings with Rover 100/MGF parts, but Rover 100s and Volvo 340s are basically extinct now.  There are shafts available in the UK that bolt right up using the standard hubs and bearings but fairly pricey. There original rotoflex arrangement can reasonably reliable but only with DECENT donuts!  It’s very scary when they give way in service. 
 

The diff rear casing has a boss already in the casting which can be drilled and tapped for a drain plug.

if you don't mind giving up trade secrets, was there much involved in putting your kits together? There's a couple of MGFs for bits on trademe and Volvo CVs are still available.. 

[VitesseEFI]

No secrets…. Last set done was for my own GT6 in 2019 and there won’t be any more (though younger son is agitating for a pair for his Spit). But note that this particular route involves machining the vertical links to take the Rover/MGF bearing pack. Which is quite involved.  If you are up for this (I can supply a drawing) then you need 2x front left driveshafts from a non-ABS Rover 100/Metro (not the Mini based one!), 2 x CVs from a Volvo 340 (4.4, 1.6D or 1.7 - not the 2.0 360 which has different splines) and 2x CV/UJ adapters (drawing available).

Note that although the MGF LH shaft is a match for CV and splines it’s 20mm shorter. Potentially you could make the adapters 20mm longer but I think this will lead to chassis/inner CV being extremely close, if not interfering.

Alternatively, my mk1 version involved Ford Escort (Euro!) mk4 1.6 manual driveshafts and again the Volvo 340 at the inner end with adapters. This used more or less standard hub/bearing and vertical links to take apart from a hub mod to alter the shim location and clamp the bearing properly (the original designer had some strange ideas).

more on this here (my embarrassingly ancient site)

https://www.shadetreegarage.co.uk/Vitds1.htm#top

This last really just to present the idea that there are various OE part combinations that can be made to fit without huge effort.

A further demonstration of that is that if you have the Rover 100 based conversion there is an existing Subaru CV that can be swapped for the Volvo one that allows use of the R160 diff with no further mods….

I should maybe also mention that there are a few examples of people using the Rover shafts with the Rover (FWD) vertical links to and also with the MGF vertical link….. which also gives rear disc brakes. Many possibilities - just got to find them.  The other fairly common route is to get the outer part of the rotoflex shaft turned down and fitted with a UJ flange and making up a sliding spline shaft with UJ at each end.  The was a UK specialist offering these but dunno if he still is. There was even a story about someone using off the shelf PTO shafts from some piece of farm machinery but I’ve never managed to discover if that’s remotely true!

Confused now?

[Alfashark]

Bit of Lego trickery there - The worst part of it is a distinct lack of 340s, Rover 100s and Mk4 Escorts in this part of the world.

Having just finished work for the week and after 20 something hours awake, I haven't looked at any measurements but would an MX5 diff/axle assembly be close to the right dimensions for a GT6?

[gibbon]

16 minutes ago, Alfashark said:

Bit of Lego trickery there - The worst part of it is a distinct lack of 340s, Rover 100s and Mk4 Escorts in this part of the world.

Having just finished work for the week and after 20 something hours awake, I haven't looked at any measurements but would an MX5 diff/axle assembly be close to the right dimensions for a GT6?

on the triumph experience site a guy has just shared his project of fitting a complete mx5 rear end which he concludes was way too much work, I can only assume he fitted the entire rear end because just fitting the diff and axles was even more difficult 

[VitesseEFI]

2 hours ago, Alfashark said:

would an MX5 diff/axle assembly be close to the right dimensions for a GT6?

No.  Too wide for a start, and the ratios are hopeless, at least on NA/NB cars. 

The transverse leaf spring layout is unhelpful when it comes to alternative schemes.  It makes things difficult without chassis mods and that (in theory) means going through an SVA certification process here in the UK, which is somewhat less enlightened than your cert process from what I can see.  This is fairly widely ignored but I prefer not to.

In the USA it seems anything goes!

Edit: https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/gt6-project/57420/page2/

[VitesseEFI]

2 hours ago, gibbon said:

I can only assume he fitted the entire rear end because just fitting the diff and axles was even more difficult 

Quite likely true - though I can't imagine what level of hackery it took to to get the whole thing in there.  There's a "thing" in the UK loosely based on a Spitfire which has a mid-mounted Audi TT 1.8 lump stuffed into it.  The engineering quality is dire.  It has not been SVA'd and yet somehow has an MoT (tester forgot his guide dog?).  Though ISTR it failed first time as even the blind tester thought his homemade front suspension components were sketchy.  The pictures of those seem to have been removed from the internet but they were uggerleeeee!

https://engineswapdepot.com/?p=83157  (do not click if easily offended/prone to nausea)

Back on the topic of fitting Mazda parts to Triumphs.... I have an MX5 g/box in my GT6 mated to the Triumph six.  It was a bloody mission getting it in there and I won't be doing another. Mazda really didn't consider my future needs in their design.  Undeterred by my suffering, my older son put one in his Spitfire, complicating his life even further by mating it with a 1.6 Ford Sigma.  It's now in daily use, but it took a while and development continues.  This has (just) sufficient points in the assessment system not to need an SVA.  More relevant to this thread he has a Triumph diff in 3.63 ratio with a Blackline Torsen centre and suspension is mainly rotoflex, but with CV shafts (my second to last set) and a twin arm bottom link.

 

[gibbon]

9 hours ago, VitesseEFI said:

 have an MX5 g/box in my GT6 mated to the Triumph six.  It was a bloody mission getting it in there and I won't be doing another.

I feel like I should be more concerned about this than anything... I thought the mx5 setup was considered as close as anything is going to get, as far as fitting in without major butchery?

I would also be interested in your axle drawings, although they will probably have to be in crayon for me to make sense of them. I keep running into this circular argument where I want to use the blackline centre to avoid having to mess with fitting up an r160, but then I want to eliminate the rotoflex, which means custom axles which means I dont need to keep the triumph diff, so I could run a datsun diff, but wouldn't I like an LSD? well in that case just get the blackline centre for the stock diff, oh but the axles.... maybe I get an lsd subaru r160 and build custom axles for that? 

As for this ominous word "machining" - I have a lathe, a welder and a drill press, how much more technical do I need to get?

[gibbon]

for context I have avoided brakes, diffs and suspension almost my entire life because they are so, so shit to work on

and the way those yanks build their cars, looks like they could have started with just about any vehicle as it's all hot rod butchery by the end. seems to be a culture that never stops to think "surely there's an easier way of doing this"