Jadz928

I'm looking to put together a list of specs for a custom-made aftermarket LSD.
So the question is: What would be the perfect LSD setup/Final drive ratio for your 928??

I used to work for Eaton Corp as an product engineer. My main focus was developing aftermarket differentials at higher volumes. I have experience with lower volume, special apps runs as well (ie. Mustang SVT, Lightning SVT, Toyota TRD).

I have a good connection with the engineering/marketing manager at Eaton . My objective is to propose the concept to said manager, give him specs and an estimate on volume. Hopefully we can come to an agreement on options and cost/price.

At this point this a study. Based on demand, there is potential to become a lower-volume group purchase. So, I would like to get my "ducks in a row", with your help of course, to spec out what we want in a custom LSD for our 928s.

Let me know what you think. Thanks!

Regards,

PorKen

Can anyone speak to the difference in dimensions between the 78-82 LSD and the 83-89?

Mark Anderson

"Can anyone speak to the difference in dimensions between the 78-82 LSD and the 83-89?"

There is a difference in the offset mating surface for the ring gear (about 4mm) but you could make just one and have a spacer to make it work for both aplications.
Also the earlier LSD uses more friction plates than the later.

Jadz928

If the offset is only 4mm, then the same casting of the housing could be used, then machined to required specs bases on model/year.

SteveG

Well, I'd be interested in adding LSD to mine, but concerned about after market testing product "durability", etc. Who is going to stand behind this thing, pun intended? In your defense, at some point "after market" is all we are going to have, so I'd like it to succeed. Could you provide some more details of the production/test process for those of us who could lose our investment ($500 ??) w/o recourse? I have two Pcar shops nearby that could be considered for the installation, but I don't know if they would undertake installation other than on a "no responsibility" basis.

I'd like to hear more.

Gregg K

Hey, wasn't it Eaton who designed the Govlok?
I had one of those. Not what you want on a 928.
I just put a Powerloc in one of my rearends recently. Love it.

You've got a job on your hands. I'd suggest going to 928int'l and throwing down some rulers and photographs. I would guess there aren't any major dimensional differences. Right. Sounds like fun.

Jadz928

Eaton would take responsibility for reverse engineering a 928 LSD. The inner assembly w/Eaton proprietary engineering would be fit within the usable package.
Testing would be conducted by Eaton and units would be sold with their aftermarket differential product warranty.
Service/labor (and warraties thereof) for installing the differential would be between you and your mechanic.

General Eaton differential specs: Carbon clutch pack, forged pinions, up to 400lbs preload.

Gregg,
Is the GovLoc a form of locking diff? I would say a locker is not what we want for a 928.


Edit: If it comes down to a substantial saving in providing Eaton w/ the diff housing specs. I have the resources available to spec it.

Gregg K

Oh, yes. I forgot it was a locker. Weird thing. A little injection molded spinning piece, that would tell when to lock up. Or break.
Yeah, truck only stuff.
Diffs are a lot of fun.

I've always wanted to met a factory engineer. I'm surprised they even entertain ideas of producing smaller quantities of parts. Cool.
I'm just taking up space here, as my newer car has posi. And I'd probably not be inclined to mess with my other car. However, if I got rid of the new car, the old one would definitely get a posi. That doesn't help you now though.

Jadz928

Eaton has a factory production line, but the aftermarket group is mostly lower volume product. For instance, people who want to retro fit the 69 Chevelle and the like. Eaton also reproduces the old Moroso LSDs.

The engineering for the lower volume is run seperately, but concurrently to the production engineering and manufacturing.

tuk_928

Jim D,
Good luck with your ambitious project. I'm interested as my diff is open. Please keep us posted here on your progress. I come from a family of engineers so I'll enjoy following "Projekt - Eaton Custom 928 LSD"
Tim/TUK

Brent 89-GT

I'm not a potential customer for this product either but I wanted to comment on durability. I have an Eaton posi in my Buick. That engine puts out a dyno verified 550lb/ft of torque. It puts that torque to the ground repeatedly via a 3200rpm stall convertor and 9 inch wide drag slicks. That particular diff has proven to be super strong IMO. I think they are perfectly capable of providing durability at stock 928 levels of torque. I woundn't question the reliability for a second. I am sure it will be over engineered to avoid having problems. I hope you guys can work it out. I think all 928's should have a LSD

Jim bailey - 928 International

Jim how small is a small run ? I think the market is actually pretty small We have used slips for the early cars for $500 so unless the Eaton is less or much better . The late slips are more expensive and have only 40 % power transfer so the Eaton slip would probably be a better alternative especially for high power cars . Interesting topic .

Jadz928

Jim,
A small run could be 50-200. A casting could be made from prototype tooling (alot less expensive), the casting would be machined to 928 specs, and if all goes well, Eaton will use off-the-shelf internals. The price will skyrocket if they need to make custom pinion gears though.

Eaton makes one heck of a differential. Like I said before, I has first-hand experience with Eatons being used in the high HP Ford Lightning SVT, and Toyota Tundra TRD. These are trucks with LSDs.

worf928

Jadz, what final drive ratio are you contemplating? If you start talking about something higher than the GT 2.73 you may get some of the track crowd interested. A while back a couple of folk had a small run of 3.09 gears made - they liked them. Kim Crumb was trying to generate interest in a run of Quaff <sic?> diffs.

Jadz928

I would be interested in a ratio over 3.0. I would imagine it would give my S2 a little extra zip-snap.

Anyone on the list have experiece with the higher ratios?

Like I said, this is a study. I'm very open to all ideas and suggestions.