Tas Diff Ratio's

[ctsdave]

Hi all,

We currently run a 3.54:1 LSD diff with an MT75 box in the racer (24v Cosworth V6 engine), and for next year needing more power and more accelaration! I'm going to conentrate on the latter first - hoping to fit a T5 box over the winter (better 1st gear and more direct change too), and was hoping to put a different diff in too. What ratio's are available? Hoping for about a 3.7 or there abouts if possible?

If not, is there any other complete diffs I can fit with minimal problem?

Thanks in advance

Dave

[Wedg1e]

Not sure the Salisbury 4HU (Jaguar) diff was available in anything higher than 3.54:1... certainly it went down to 3.09 and maybe 2.88:1 but dunno about anything higher.
Google search? That diff's been around since the dawn of time, must be some info out there.

Maybe you could adapt to a newer diff like the later TVRs did, with CVJs instead of UJs... then you could go for the fabled top link as well and maybe have a wedge that goes round corners

[TVRleigh_BBWR]

We are getting 1.5G's + round corners so there not as bad as some think, also these are trailing arm cars.

As for higher diff's There are about, but very rare, I know Dave Chant has a 4:1
Also Graham has fitted Quaiff internals to his, and this way you can get any ratio you want, but can be expensive esp if you want it LSD.

Also there is a more detailed thread here
http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Oh and I sent you a message on FB.

Edited by TVRleigh_BBWR on Thursday 23 September 17:08

[barrington]

hi leigh did you get your email

[NTEL]

ctsdave said:

Hi all,

We currently run a 3.54:1 LSD diff with an MT75 box in the racer (24v Cosworth V6 engine), and for next year needing more power and more accelaration! I'm going to conentrate on the latter first - hoping to fit a T5 box over the winter (better 1st gear and more direct change too), and was hoping to put a different diff in too. What ratio's are available? Hoping for about a 3.7 or there abouts if possible?

If not, is there any other complete diffs I can fit with minimal problem?

Thanks in advance

Dave

Dave, your better off sticking to what you have already but, seriously, unless you can get your engine to rev above 7200rpm you may be taking a step backwards. Lets have a chat at Oulton.

[grahamw48]

If you're really determined to do it....have a look at this lot:

http://www.limora.com/index/lang-2/lkz-195/markeni...



The 2.8 XJ6 could be had with the lowest diff ratios (I used to have one of the gutless things years ago)

As Dave says, probably not necessary if you can develop enough power and torque to pull the current diff.

Enjoyed watching you all on the Telly yesterday, but definitely intend to be at Oulton.

[ctsdave]

Thanks for the replies guys!! Seems that there isn't a diff out there around 3.7 then...

Mr Chant - I know I need more accelaration just by the way you were able to pull away out the coreners I couldn't go to 4.1 - when I've done some calculations around a 3.73/77:1 would be great - some slight top end loss (though a slight increase in revs will keep this) and better accelaration by far!! I know I can get the motor to around 230-235bhp fairly easily next year (maybe even the same as you with proper ECU haha), but I'll still be on a back foot out the corners.

The option could be a smaller flywheel I guess, though not sure how much benefit that would give...

Cheers

[adam quantrill]

Can't you play with the tyre diameter too? Reduce the rear tyre diameter by 10% and 4.1 is perfect.

[ctsdave]

Adam - would I not need to increase the diameter (and therefore rolling radius) to make a 4.1 diff work? It's currently running 17s rear - and for next year, assuming a little test at Snett next weekend works, will be running 17s all round (makes tyres easier to get - ex touring car slicks, far cheaper than new ones )

[grahamw48]

I was going to suggest different rear rim/tyre size too, then thought you might need the top speed, which normally would be slightly lowered.

To lower the overall gearing the rolling radius would need to be smaller of course, but should be possible with the right tyre profile.

I'd have thought your 17" wheels will have RAISED the gearing over the original spec, considering that originally the car was fitted with 205/60 x 14 tyres. and that must be making the car more sluggish out of the corners, even with your lower profile tyres.

[TVRleigh_BBWR]

Most of the Rolling radius of all the Dunlop slicks we use are about the same.

I'm running the 3.54 Diff but very rarely get into 5th, so I could easily run a 4.0

[ctsdave]

I've needed 5th on a couple of occasions this year (Cadwell, Pete at Snett I think, and no doubt Oulton Pk). Could maybe look at 16's all round, but couldn't really go any lower, and not sure if I'd gain much either?

I reckon if it had been possible, a 3.7 or 3.9 would be ideal, given the max revs possible would be 6500rpm. 4.1 would be too short - we don't have the revs to use that unfortunately! Might see what it's like once the T5 box goes in (and lighten flywheel while I'm on) and look at alternate diff options later... Shame a GKN/BTR wouldn't fit in there - that would be ideal!

[adam quantrill]

Yes sorry, increase the radius by 10% to use the 4.1. You may run into problems fouling the wheelarches though (at least for the first few races ;^)

Or keep the same diff and reduce it? But looking where you are going with wheels this probably won't work.

[ctsdave]

Yeah Adam - thought that's what you meant! We couldn't go any smaller than 16" wheels as I don't think 15's would fit comfortably over the brakes. Plus as I say for next year I've found a source for some tyres so ideally looking at 17s all round.

Looking at Quaife - assuming their ATB could be done in a suitable ratio - it's £800!! I can get Emerald ECU and more power for £600... I think for the moment I'll be looking at T5 box installation and a lighter flywheel for next year...

Thanks

[NTEL]

ctsdave said:

.

Looking at Quaife - assuming their ATB could be done in a suitable ratio - it's £800!!

Thanks

Dave, its £800 just for the ATB. That fits onto the existing crown wheel. For a new crown and pinion as well, it will cost mega bucks!!!!!!!!