Limited slip diff SOLD

[one-two]

New and unused Guard Transmissions 50/80 switchable limited slip diff suitable for a late 901/911 and/or an early 915 gearbox. £SOLD ono. Many thanks, Robert

[ChrisW]

I believe that the '72/'73 911S would have an early 915 gearbox, but can you offer the gearbox number range for which tit would be suitable ?

Is this the item that would be the option code 220 ?

Thanks,


Chris

[left4dead]

... which tit would be suitable ?

[one-two]

Hi, my understanding is that the part is suitable for the 1969-73 range of late-901, 911 and early 915 boxes. I'll double-check that. It is a regular limited slip diff from a well-regarded manufacturer, but it's not original equipment - I would guess that a car fitted with a limited slip in period would have had a ZF component. Hope that helps, Robert

[smallspeed]

50/80

thats a lot of lock!!

[one-two]

Agreed - you can back it off to 40/40 or something similar if you choose. From memory, and someone else will know better, that is roughly where the road car optional item might have been.

[smallspeed]

i guess porsches do a lot more braking with the rear wheels than most cars because of the weight distribution.. 15% is normal on a BMW i think, normally 30% for road/track and 30/45 for track only cars i think!
presumably it is adjusted by increasing the pre-load rather than somehow adjusting the ramp-angles as they will be under loads of pressure?

sounds like an interesting unit, glws!

[sfl993t4]

Hi
I think that the original diff was either 40/40 or 80/80 and it was swapped by changing the four plates around so that only two of the four (for 40% locking) or four of the four (for 80% locking) were acting. The originals ran with very little pre-load much like the latest road porsches whereas the guard runs with more pre-load (more like a racing diff). I think that the locking ratio can only be changed from 50/80 by obtaining new ramps from guard, but I could be wrong.
Looking forward to seeing the pics
Steve

[smallspeed]

sounds interesting!
i've just been through rebuilding a zf lsd for my bmw, so went through many restless nights thinking about how many clutches/plates to run and how much preload! i think it might be a case of the more you think about it the more confused you get

[one-two]

Will post some pics later today if I can - here's what the blurb says about changing percentages:

"Your LSD is set at 50/80 using our unique asymmetrical ramps. This means 50% lock-up on acceleration [and] 80% lock-up on deceleration. The standard 80/80 ramp percentages are selected by rotating the cross shaft/spider gear assembly 45 deg within the pressure rings, placing them into the symmetrical ramps.

The asymmetrical locking percentages can be reversed by switching the pressure rings (installing #1 pressure ring first), thus making the higher percentage lock-up on acceleration [and] the lower percentage lock-up on deceleration (although this is rarely done on Porsches.)

The locking percentages can be halved by the standard method of replacing two of the four friction discs with plain plates (or by placing the two friction discs on each side back to back.)"

Sounds vaguely ZF-ish, no? Best wishes, Robert

[johnM]

Mike Bainbridge has experiance of these LSD's in competition. Might be worth giving him a bell for info.

Good luck with the sale.

Kind regards.

[smallspeed]

Yes all makes sense.. Much like a normal diff but with two sets of ramps which is pretty cool
Switching pressure and clutch plates around is fairly standard, and adding a spacer plate in the place of a clutch and pressure plate to reduce lock is kind of backwards of what the bmw boys do

If anyone buys this and wants a spacer let me know; I have one in my garage I just took out of my diff

[ChrisW]

... which tit would be suitable ?

oobs

[ChrisW]

Hi, my understanding is that the part is suitable for the 1969-73 range of late-901, 911 and early 915 boxes. I'll double-check that. It is a regular limited slip diff from a well-regarded manufacturer, but it's not original equipment - I would guess that a car fitted with a limited slip in period would have had a ZF component. Hope that helps, Robert

Thanks ... I'll keep my eyes open for a ZF then ...

[johnM]

Chris
Not sure if I am teaching you to suck eggs or not but it might be worth bearing the following in mind.
I have a ZF LSD in my car, most ZF have been run with the incorrect output flanges and this damages the casing. Correct out put flanges are almost impossible to find. My LSD case required repair and the re machining. As I couldn't find the correct output flanges I had to buy a pair of modified sun gears £350 to fit allowing the use of standard output flanges. The diff then needed a pair of conical washers and a number of clutch plates. Once I had these it can be rebuilt and fitted. The gearbox needs to be out of the car to be fitted. If Roberts diff accepts standard output flanges and requires no setting up it may be a lot less hassle.
After saying that I think the ZF is properly the perfered choice for most folk.

Hope that helps and good luck with the sale.

Kind regards.