mk1-forum.net

Hi everyone,
I'm working on my Mk1 race car and need to start thinking about the diff. At the moment, there is a standard 3.444 diff with Hardy Spicer's but I am thinking I am best to go to a limited slip diff while it's all stripped down. The car will be mainly used on the track but will do some sealed hill climbs. What would work best and what is strong ?

Al

Quaife ATB

Do you have any reasons why?

Al

It's just more "driveable", no trying to tug your arms out of their sockets, I'm sure some people refer to them as girls diffs, but I'd rather the car was working with me rather than against, another plus point is there are no plates in them to wear / set up, just fit and forget

Thanks for sharing your opinion. I have done a few laps in a friends car and you can't change gears sometimes, it needs two hands to hold the wheel.

Al

Im would reccomend a shorter diff than the 3.44.

Not sure what others use but I would think a 3.9 would be about right.

J

Al, I've got a sports sedan (Special Saloon) with big 13" slicks on it and an old Sailsbury LSD in it and it's a beast, don't lift mid corner, or you're off!

On the other hand, with the power down, say coming out of a hairpin, I can't get it to break loose, even with the long stroke 1412 ! 10 laps in that thing and I'm sweating like a pig!

I've heard talk of the Quaifes not being a true LSD if one wheel is off the ground, (this can happen at tight corners in hairpins) Yes easier to drive and all that but ??....

If I ever get it finished, I'm building a full race 1293 for hillclimbs and I've gone for the Minispares plate diff with 'race' settings, a good compromise?

Waits for comment............

with diffs, the grass is always greener....

a lady diff quaife is great, hardly noticeable and has the advantage of using a cheap std crownwheel and having the out puts built in (so a huge saving over a traditional lsd), but useless on the loose or in situations where one wheel will be off the ground a lot.

the plate diffs are great as they can be rebuilt and specced to suit the user, can really be tweeked to get the power down, but can really tug you around - the suspension can be tweeked to help with this, but a decent plate diff will always let your shoulders know when its doing its job properly.....

ive gone from a quaife, to a race plate diff, back to a quaife.

I cannot cope with a plate diff anymore, im sure my arms grew a bit from holding onto it!

Horses for courses really. If you're using it purely for competition then build it with a short competitive diff (3.9/4.1) and a 'proper' LSD. If it's a road going car used for the occasional track day / hillclimb then you don't necessarily need a set up like that as a 3.7/3.9 will suffice with a Quaife ATB and it'll still be drivable as Mark has suggested.

What Pete has described above is what I use mine for, road going, and Hillclimbs / Sprints through the year, I've even gone so far as to leave the 3:44 in it as I drive to the events, I don't want to start getting super competitive and loose the fun of owning the car and it being flexible enough to cope with different driving situations. If you are building something for competion only then you could afford not to compromise the build, and go for a full LSD and short diff.

I used a salisbury plate diff when i was competing, mainly tarmac stages and the odd loose event.
The torque setting was about 90 lbs and as mentioned above, the grip on any corner was really something to behold. It would literally drag you round the corner and by using said diff got me "out of trouble" many times.

On another note, Miglia race minis don't use an LSD and have a huge amount of grip through the bends which is all down to the carefully set up suspension. Something else to ponder, perhaps.

InimiaD wrote:
On another note, Miglia race minis don't use an LSD and have a huge amount of grip through the bends which is all down to the carefully set up suspension. Something else to ponder, perhaps.

the cost of the shockers and the lack of suspension travel is a serious compromise though!

How can it be a race car with a 3.44 diff? Do you plan on doing downhill hillclimbs?

so its part road going / part hillclimb sprints - youre not running big slicks and the majority of the time you wont be lifting a driving wheel in a corner, so for say 98% of the time you want the thing very drivable meaning theres no need to run a proper man type lsd which will slow you down till you really get used to it or pull it back out again - i would say spend the money and time setting up the suspension and tyres and brakes - properly set they will give you good results

the man type diffs are freekin horrible on tarmac, tugging you all over the show, snatchy heavy steering , clunking and clonking

no point having something that might help you on one occasion in a hundred but will hinder you the other 99 occasions !

pad

66S's car looks to be a race car, my car is a road car which gets used for hill climbs and Sprints throughout the year, so that's why I've stuck with the 3:44 diff and a ATB, driving a couple of hours on a SCCR box with SC drops is a compromise enough for me without having short gears, this year it's had some power improvements, the way I look at it the more power and torque it has the better it will pull the diff, last year it was an advantage at some of the sprints as the gearing was more suitable, I'm looking forward to seeing how much closer I am to the front runners after the winter improvements.

Anyway enough of the thread hijacking now, I've given my reasons for the ATB, which was the question the OP originally asked

Road going with occasional competition use = ATB

Full competition = LSD

Also agree with Pete above.

3.7 ish & ATB for fast road occasional track

3.9 - 4.1 ish & Plate Diff for track / competition.

A 3.4 would be embarrassing in most competitive events.

mk1coopers wrote:
Road going with occasional competition use = ATB

Full competition = LSD

full competition with pathetic upper body strength = atb

Thanks for your input guys. The car is a dedicated race car but it will do a few hill climbs in my hands. I don't think the 3.444 ratio is too bad on our local track and some reasonable times have been recorded by the previous owner. I don't think I will stick with it though but the ratio was not my question.

Al