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Which LSD to go for?


Old 18-08-2015, 09:01 PM
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Default Which LSD to go for?

Winter is coming and I have decided to tackle a few more of the issues with the Escort.

The main issue it has at the moment is the clutch ; it is a Helix 4 paddle where I plan to use a normal pressure plate. After having a go in another owner's car and from reading up it seems this setup should work well with my car.

However, the other issue remaining is the small matter called traction. My power graph is looking like this with around 225BHP and 278lbft:

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However, it does like to wheelspin in 2nd, and sometimes 3rd (when wet) if the tyres are not quite warm enough. On the previous tyres it would spin in 3rd in the wet as well.

While my father's Mondeo 2.5T is a less dramatic affair the torque steer does not seem that bad in this car, despite having some of it; in the bends I can use it to tighten the line of the car .

However, I am beginning to wonder if the car has an LSD. It is running a Mk5 Escort BC5 'box where I suspect the following:
  • The 'box has an open Ford diff
  • An RST diff has been fitted but it is tired.

Upon spinning the front wheels it feels like any other FWD car with an open diff, with no real resistance felt when turning the wheels over on the axle stands.

I have seen the odd unused FRP viscous coupled diff come up cheaply but I am debating fitting a Quaife ATB (basically, a helical LSD. The lack of maintenance and need to run a gearbox oil that is not necessarily the best of one of the gearbox are the big plus points but I can appreciate that a plated LSD can have advantages elsewhere.

But for the reasons about (in addition to the chatter and knocking present with a plated diff) I have decided not to go with one .

My question to you is which would you go with and why, and have I not considered some options? Have any guys tried a Quaife ATB on an RST or had an RST with an open diff? If so, how did they all compare?

Also, is it possible for me to tell what diff I am running without dissembly or is it a case of pulling a driveshaft out?
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Old 19-08-2015, 09:04 PM
Karl @ FPT
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I find the Quaife ATB to be a little harsh on your box, it's a great diff but IME helps get through box's a little quicker.
A non refurbed RST diff will not be performing well 25+ years down the road.
The FRP diff is what I would go with if you can get one at a good price.
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Old 21-08-2015, 06:45 PM
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if your content with staying b5.ib5 then i would fit a re jelled rst diff.... as said the quaife is a nice piece a kit but the grip just smashes the box....

or you could fit a front starter mtx and a Frs mk1 diff. conversion its self cost more and a little more involved but it is pretty much fit and forget!!
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Old 25-08-2015, 06:52 PM
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To be honest, my gearbox has probably seen enough abuse from the Helix 4 paddle it has fitted . The previous owners tried having the biting point right on the floor in order to attempt to use it!

Is the BC5 really that weak? I would not say that I am running as much power as quite a number of cars on here. I was also under the impression that unlike other diffs the ATB acted as an open differential most of the item, unlike plated differentials.

It is food for thought mind you. After ringing one or two places I was informed that only certain RS Turbo LSDs can be regelled. Is there any way to tell and which cars came fitted with them? From what I gather the FRP diff should just go in fairly simply.

After looking at the FRS 'box I guess a different gear linkage and gearbox mounts would be required, in addition to potentially cutting away metal on the car?

Last edited by Chas; 25-08-2015 at 06:57 PM.
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Old 26-08-2015, 11:56 AM
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no problems on my box with a quaife lsd
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Old 21-09-2015, 08:57 PM
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Well, cheers for the help. I think I have decided what diff I want .

I had a chat to CTS about rebuilding the 'box and fitting an LSD (if I sourced one to be regelled or if he supplied one) and he suggest that my car wheelspinning could be down to the springs being too hard up front. I doubt this is the case (it does hop up or down, it just 'smoothly' spins a wheel on the move), but I shall investigate this before getting the diff done.
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