Looking into buying a Quaife ATB diff for a Busa powered MK Indy.
On the quaife web site there are 3 options
Standard
15Deg Helical angle
23Deg Helical angle
I assume the angle increase makes the diff more aggressive?
Whats the best option for mostly fast road work with odd track days?
Is this for a sierra diff?
I thought they were all the same, hance the automatic in automatic torque bias in ATB?
Their website doesnt explain anything either, will be interesting to know!
Yes it has a standard 7" Sierra diff 3.38 ratio with push in shafts.
My other question is wether to install the ATB diff with a 3.38 ratio or a 3.14 ratio as I have a spare crown wheel and pinion of both ratios.
That's new, when I got my diff a couple of months ago I had no options.
http://shop.quaife.co.uk/caterham-de-dion-quaife-atb-helical-lsd-differential
It's there, but what does it mean?
As if these things weren't complicated enough!?
Phone them and ask... then explain it to us.
The decision whether to fit an ATB (automatic torque bias) or a Limited Slip differential may be assisted with some further info on the
"function" of the two types.
The ATB supplied by Quaife and Ashcroft have 6 planet gears on each side but the Truetrac only has 3 on each side.
The diff is fitted with sets of "helical" gears sitting in pockets within the diff, the helical gears are unsupported so as they work
together they generate friction against the sides of the pockets, the amount of friction is determined by the helix angle and preload on the gearset.
In a situation where one wheel has less grip than the other there is a tendancy for this wheel to spin. Due to the friction within the internal
gearset and the configuration of the gears the wheel which has retained grip can still drive "but" the torque transmitted to the
"driver" will be proportional to the torque transmitted by the "slipper" this is the ATB effect and can be up to 2:1 ratio.
The only down side is if the "spinner" has no grip ie torque transmitted is zero the ATB will effectively multiply this by 2 giving zero. If
the car has some form of traction control there will always be torque applied to the "spinner" i.e by traction control which is then
enhanced by the ATB giving double the torque to the "driver" . We stock the Quaife Diff to fit the Rover type 24 spline diff.
Note : Due to the nature of the ATB diff we do not recommend the vehicle is brake tested on rollers, ask for a decelerometer to be used instead.
This is my take on the Zero torque transfer which is only likely if 1 wheel is on ice or possibly wet mud
An option is to fit a break pressure retaining valve to the rear which will hold a few Lbs of pressure just enough to drag the rear breaks another
option is a click or 2 of handbrake or a dab of foot brake
[Edited on 10/11/14 by snapper]
I sent an email to Quaife and here is their reply.
Hello,
Hello basically the different angles give you a different torque bias ratio however we do not use or quote TBR figures as they don't really mean
much to anyone. The TBR is a very difficult thing to measure (we know this from our work with OEM diffs) and actually not very useful.
Essentially the TBR is a complicated way of comparing the helix angle of the internals (sun gears and pinions) and the vast majority of our diffs have
the same angle internals although some of the very large and very small diffs have different angles. A few diffs have options (e.g. QDF9U) as they are
used in different applications, i.e. QDF9U (31dg) in a Honda Civic Type R or QDF9U/23dg in an Ariel Atom. If you put a standard QDF9U (31dg) in an
Atom (very light mid engined car) the diff would push too hard for the amount of grip at the front.##
So for your car I would recommend the 23dg.
If you have any further questions or I can be of any assistance in the future please don't hesitate to contact me.
Kind regards
Dave King
Technical Sales
[Edited on 10/11/14 by hkp57]
Are we to take it from that that the "standard" angle is 31 degrees?
Thats how I read it.
So have I just spent £x,xxx on BGH building the wrong diff for my car 
I really don't remember seeing these options earlier in the year and its not mentioned in the catalog I picked up at Autosport in January.
I guess I best ask them but I am dreading the answer....to be honest if I have the wrong diff I am now stuck with it as I have no money left in the
budget to change it 
I would doubt it would make a huge change and if even noticable in daily driving, maybe if your looking for that last 10th of a second on a qualifying
lap??
quote:
Originally posted by peter030371
So have I just spent £x,xxx on BGH building the wrong diff for my car
I really don't remember seeing these options earlier in the year and its not mentioned in the catalog I picked up at Autosport in January.
I guess I best ask them but I am dreading the answer....to be honest if I have the wrong diff I am now stuck with it as I have no money left in the budget to change it
I emailed Quaife and asked they said;
The standard sierra one is 31dg. To be honest unless you do back to back testing on a racetrack you will not notice the difference in
performance.
So i'm happy that for me my 'standard' unit will be fine 