Which Diff ?

[ChrisC]

I am currently thinking about fitting a LSD to H15 SVN, however I cant find a copy of What Diff in the newsagents so, can you enlighten me to the pros and cons of the various types of LSD on the market, and there likely cost 🤔 I know that some LSDs need to be setup, so I am assuming I will take my current diff unit to be rebuilt and setup by a specialist, so what type of cost will this service set me back 🤔

 

 

[Chelspeed]

27 views and no-one brave enough to reply?

 

There are plate type lsd's, aka ZF or salisbury. These have clutch plates between the two sides of the diff. The clutches are forced together by the action of slip between the two sides causing pins to run up ramps. You change the speed of lock up by changing the ramp angles and the point at which it first locks by shimming the clutch packs.

 

There are two types of "torque sensing diffs", one is made by AP and called the Torsen diff and one by Quaife. These work by magic. You can look inside and have no idea how or why they work but they do. Some sort of worm gears sort of thing.....

 

Finally there is the viscous coupling diff, these were standard fitment on the XR4i Sierra that Ford sold to caterham so some have found there way onto Caterhams from scrappers. Never supplied by Caterham I don't think. They work by having sets of alternate plates full of holes attached to each side of the diff. The gap is filled by a fluid that displays rheological, non-newtonian properties, the faster the plates spin relative to each other the stiffer the fluid gets and resists this movement, lets just say these work by magic too shall we?

 

Finally II there's the locked diff, you weld the two halves together and it's not a diff any more it's a...... thing that turns drive thro 90 deg I guess. A completely prevented slip diff rather than a limited slip diff.

 

All types are within the diff, replacing Fords standard crown wheel mounting thingy with a new one. So they all need the diff totally stripping and rebuilding which means loads of measurement, shimming and stuff like that, so all are a job for a specialist to build into your diff assembly. For you it would have to be Paul Stewart at Road and Race near Brands Hatch.

 

Pros and cons:

 

Plate type can be noisy and need periodic rebuilding to replace the clutches, this is very infrequent and dependent on use, unless you're a real hooligan doughnutting all the time they'll last a good few years. Allegedly they can cause understeerthrough hairpins but I forget the mechanism and I've never seen it myself. So may not be ideal on the road due to noise but the best choice for hard sprint and race use. I'd still choose this one though for any use and live with the noise on the road.

 

Torsen diffs are quiet and never wear, but they never totally lock so if you lift an inside wheel thro a corner they will still spin all your power away. For this reason they also got a bad reputation from racers for breaking transmission, ride the kerbs on a tight bend and a wheel will lift, spin up to some horrendous speed then when they land the shock loads break driveshafts, diff, propshaft or gearboxes. So not recomeneded for racing but OK for fast road and light speed use.

 

VC diffs, can be cheap from scrappies but no real experience in a Caterham.

 

Locked diffs, OK for drag racing (no corners) or grass tracking (no grip) absolute nightmare on tarmac with corners, don't even think about it.

[ChrisC]

Hi Chelspeed

 

Loads of info, thanks

 

Do you know what type and make was used in the VX HPC spec?

 

From your info I think I would be looking at a plate type, ZF or Salisbury, my car has very little tendency to understeer (helped by widetrack, ACB10's and a lump of iron called the VX XE). I am not worried by noise. What type of cost am I looking at for the ZF or Salisbury diff.?

 

Chris....

H15 SVN Get it !

[STEVE GILBERT]

I built in my own Tran X and while not exactly easy, twas not hard either. The unit is of the same type as all Power Lok Thornton Axle Co Patented Plate types but can be set Ramp and Pre load correctly for this vehicle. No Case mods needed or machining of the ramps. Mine is totally silent in use despite the 190 Zetec and lots of track days.

This would be my Diff of choice given the noise reported on this forum from ZF owners.

I did a quick write up here:http://www.blatchat.com/T.asp?id=22446 but am happy to answer/assist in any Diff building as it was a most satisfying job.

Reading Ammos reply to that posting made me laugh out loud, how did I miss it first time round? He summed me and my attitude to all things Caterham up in a couple of sentences.

 

HTH

 

Steve (Dial Gaugue ready 😬)

 

See My Old Zetec Power 7 Here. Caterham Fireblade update soon

[scooby dooby doo]

the torsen is just about unstandable - it works cos a worm gear can drive a normal gear but not vice versa. They allow approx 3 times as much torque to go to one wheel compared to another. so, as Graham says, if you lift a wheel it doesn't help. it also means that man hole covers on the inside of a wet roundabout can cause you to spin. allegedly of course....

 

if you get a plate diff it also needs setting up as a caterham isn't much like the sierra or whatever it came off.

 

I think we forgot a pro as well - they make doughnuts a lot easier (that works by wiping the sugar off your lips as you eat them BTW 😬)

 

HOOPY

R706KGU Hoopylight R

[ChrisC]

mmmmm donutsvoice>

 

So assuming a plate type diff, the Tran-X is the recommended choice then. Any idea on cost, because prices are not listed on there website.

 

Chris.

 

 

Chris....

H15 SVN Get it !

[I reply to every thread]

On a VX you want a 3.92 ZF with low load ramps. That slips off the tongue nicely because I bought one yesterday. Speak to Phil Stewart at Road & Race Transmissions. Not only does run a VX, support a race VX, & know his stuff but he's also a very nice bloke.He has one on the shelf too.

01959 525105.

[I reply to every thread]

Cost? - depends if you're running a 3.92 already but you're looking at £8-900

[STEVE GILBERT]

The TranX is not THE recommended diff it is A recommended Diff. YOU make your mind up as to which one to go for.

Every person on this forum probably has their own opinion. Mine is based on my experience of this unit in use and the fact that I have had it dismantled to single component level and built it in myself and that I like the fact that the Ramp angles and pre-load are correct from the factory plus no case mods.

Cost is £519.75 + delivery and VAT, then you need it fitting.

 

Good luck with your decision

 

Steve

 

 

See My Old Zetec Power 7 Here. Caterham Fireblade update soon

[ChrisC]

Steve - I appreciate your comments, but it is nice to know other have had good experience with a product and also the customer support should a product fail.

 

AVES - I am going to stick with my 3.62 CWP ratio, because my car was fitted when I purchased it with 13” and the Caterham 6sp. Even with a windscreen it can hit the limiter in 6th on the long straight at Bedford aerodrome (my fav track), so I see no point in changing it at the moment. My main problem with the car is traction out of the tight bends, when the inside wheel is spinning off all the power, even with warm ACB10’s, hence the thread.

 

From all this info, I know what type of diff I am going for, clutch plate type, make well ZF or Tran-X, and have a good Idea of the cost, budget say around £1K. (£600 if Mrs Collins is reading )

 

Look like I have a winter project.

 

Thanks All

 

Chris....

H15 SVN Get it !

[simonbell]

Chelspeed

 

Thanks for that........so we just need to become magicians to understand this stuff 😬

 

S2 8ELL

Birkin S3 2.0 Zetec 170bhp