choice of LSD, + better gears ratio

[alex']

Hello, :grin:

I have to rebuild the gearbox on my Puma,
and i think it's a not bad idea to buy and mount an lsd :grin:

this is for fast road use the week end, and little trackday not competition or rally build.

wich is the best choice of lsd in that list:

- escort rs turbo lsd
- genuine racing puma lsd
- quaife lsd
- or a better idea, i see other type of ib5 lsd on ebay

i want a longlife system, i don't want to open the gearbox and rebuild the lsd every year :lol:


and for the gearbox ratio,
i want to use an genuine ST 150 gears ratio for 1/2/3/4th (buy 50€ some years ago), i know it same as 1.7,
but maybe it's stronger ?? what do you think ?

and for the 5th and final drive, i want to use an puma 1.6/fiesta zs ratio

good idea ? or not ?

 

[Wild E. Coyote]

I won't comment on the ratios as I think the stock ones are suited prefectly to the car.
The escort RST and racing puma LSD are both viscous units and de facto the same.
Quaife is the torsen type. Both types are maintenance free. The difference is in operation. Viscous type has a certain type of oil inside that as it heats up changes viscosity and sort of bonds the friction plates together and thus closes the diff to a certain, preset torque value. For FRP it is 35 Nm.
The quaife has three pairs of sun gears of worm type which can turn in one direction, but are blocked in another (we call that effect self braking, don't know how it is called in english; the same phenomenon is with metric threads which, when under stress, won' undo themselves). So when a wheel spins (the sign of lost traction) this worm gears will be in effect be pushed by the driveshaft and they can't (because of the phenomen described above) and there you have your limited slip effect.
In theory the quaife is clearly better, BUT! For this worm gears to work, both wheels have to be on ground. If a wheel is in the air (a pothole, runing over a kerb and similar) the limitation slip effect is lost and it becomes effectively an open diff.

PS. I will be selling my gearbox which was overhauled and has RST LSD inbuilt. The LSD was serviced by Bara motorsport and rerated at 120 Nm. Not to dilute your thread, if you are interested, PM me, please

 

[alex']

Hi !

This a good response !
Very complete, thanks you ! :grin:

But in my opinion ... 1th Gear IS too long, and 5th too short on the 1.7 Gearbox

1.6 Gearbox IS better ... Just the 5th too short on autobahn ... I know Puma smiede.de has sold some year ago a kit to upgrade the Gearbox but nothing available on the website now