Okay, I cant find threads with all the answers, Perhaps someone can outline what is needed to do a RWD conversion, what LSD to use for road-course track events / street use, Installation guidance and parts that will need to be obtained ?

I have a Porsche dealer mechanic that is starting out on his own and would like to have him use my car as an example. So, he was questioning the installation alignment of a LSD, would there be anything special thats needed to setup a LSD, of course, tranny drop and such, but what about the unit itself ? Any shims or centering that is needed when installing ?

Thank you as always for the help

Dean W

 

I can comment on the rwd conversion, we did one for a customer. Pull the Panels down, remove drive shaft and remove front differential. Remove half shalfs and take them apart on the stub axle side. Clean stub axle from all the grease from the cv. Install the stub axle back into the wheel hubs on both sides. Put the panels back up into the car. Thats it for the conversion, you are going to want to put suspension on the car and maybe swap out the front hubs for the gt2 ones if your going to track the car so it will handle correctly but you can get away with just suspension with street use application.
And thats it am i missing anything guys?

 

Yeah, sell the TT and get a GT2....

 

Great info, i have a kw v3 suspension now, was also thinking of a quiafe lsd while my mechanic would getting into things. But i have not read about needing gt2 hubs for the front ?

 

I have had both. Not too much traction with RWD on high HP unless you run drags.

 

Yes i have read that the doesn't handle that great on the track with the turbo hubs, and its a lot better with the gt2 hubs, has to do with the position of the strut. Hey track guys can you elaborate for me please?

 

Subscribed. Always looking to learn something. I have a RWD conversion without GT2 hubs and no LSD...

 

Are the wheel speed sensors built into the hubs? if so gt2 hubs would deactivate the psm . . .

 

Here is a few things I found

[Quote Jean]
I apologize for the long post that follows, but I am not sure if I understand things correctly but if you are trying to make a decision on whether RWD is faster than AWD or viceversa, then we can look at this in two ways.

1) you go 2WD by removing all the components of 4WD, hence benefiting from weight loss, and you also do the suspension and gearbox modifications that are needed to make it handle consequent with the 2WD needs
or
2) you go 2WD by not investing any money in doing the changes (components and setup) and you keep the weight unchanged.

I can tell you straight forward that option number 2 does not make any sense, and it is better to stay 4WD, there is no debate!

I will comment on a few things I have seen written, and realize that most people know all of this, so I am not preaching anyone:

1) LSD. Yes it will increase push, however you need (and CAN) dial the suspension accordingly to neutralize as much as you would prefer, and even get oversteer instead of understeer at corner exit. Sway bar settings, wider front track, different toe-out, different compression in the front and rebound in the rear, different springs, different camber, tire pressures, and of course driving style (deeper braking into the turn)…among others. It is not all about camber!

The advantages of LSD in corner exit on a high powered 911 are not debatable! And this is where you win races.

2) Weight. The advantages of total weight savings are certain. A lighter car will reduce the polar moment while cornering, and the mass transfer under braking. All else being equal, it will go faster than a heavier car, I think it is no debate?

3) Front/rear weight bias in standstill. Myth. If you want to go faster make sure “load change” is top of mind, not the fr/rr weight balance at standstill!.

Weight transfer under braking is directly proportional to CG height, , long Gs, and overall weight and inversely proportional to wheelbase(in forward motion) or track (in lateral motion) To maximize cornering grip you must minimize load transfer. To maximize braking grip, you must minimize load transfer.

This is what happens under braking:

a- 996TT, 4WD, weight: 3,400 lbs
Under 1 G braking force: Load transfer from rear to front = 560lbs.
Total weight under braking:
Front: 1915lbs Rear: 1473 lbs. Fr/Rr weight bias under braking: 57%-43% vs. 40%-60% at standstill.

b- 996GT2, 2WD, weight: 3,168lbs,
Under 1 G braking force: Load transfer from rear to front = 515lbs.

Total weight under braking:
Front: 1703lbs Rear: 1465 lbs. Fr/Rr weight bias under braking: 54%-46% vs. 37.5%-62.5% at standstill.

So from the above it is clear that the Gt2 with its lighter weight, and lower CG (lower height) is better off, as the load transfer is 45lbs less than the TT , but more importantly, the weight distribution under braking is 54% front vs. 57% front for the TT. Therefore the grip on the rear tires is higher under braking and your long G in deceleration improves. I have not even talked about better suspension, stiffer springs, and geometry by changing to GT2 hubs or dampers. in reality the GT2 has an even better weight bias under decelration and cornering due to its suspension setup.

In acceleration it is the opposite, the lighter front and load transfer to the rear will increase grip on the rear tires vs a 4wd setup that has tracton in the front and minimizes load transfer to the rear..Win-win.

c- The GT2 has a wider track in the front and narrower track in the rear than the 996TT, this improves handling in corners and reduces understeer as well. You need to fit wider tires in the front in relation to the rear if you are going to 2WD.

d- The front differential is located in the middle of the car, so the polar momentum of inertia from the differential or (lack of) in turns, is almost inexistent ( in relative terms vis a vis the overall mass of the car on both sides of it.) The torque tube of the 4Wd is in the center, so the same applies, no effect on cornering. So both 2Wd and 4Wd are at par here.

If you re-read, I was not saying 73lbs is negligeable, I was saying the impact of those 73lbs in cornering or load transfer is negligeable, due to its location (below center of gravity and in the middle!)!

In summary, there is a reason that the GT2 handles better than the 996TT on the track, the 996GT2 Mk1 was ranked 8th. overall in cornering grip (lateral Gs) up there with the CGT, whereas the 996TT was ranked 30th. both on street tires, in Hockenheim by the same magazine and driver. This is independent from HP.

More examples, both on street tires, Sport Auto, Hockenheim, cornering speeds:

Turn 1
GT2: 128mph – TT: 122mph
Turn 2
GT2: 78mph – TT: 76mph
Turn 3
GT2: 108mph – TT: 101mph
Turn 4
GT2: 53mph – TT: 53mph
Turn 4
GT2: 78mph – TT: 74mph

 

wow, impressive, endless variables and no one thing will resolve an issue. Balance balance balance. .

 

A total noob question..
What is LSD?

I did look it up at Google..
Lysergic Acid Diethylamide ?
Lucy in the Sky with Diamonds by Beatles ?
Something else perhaps..?

 

I'm still considering doing the LSD AND keeping my AWD, after I do suspension...

 

Limited slip differential, google it

 

http://www.vividracing.com/forums/ga...p?i=3845&c=173

 

I have AWD with Manthey-Racing LSD 40/60 and after adding the LSD the car is excellent* on tracks!! (Of course some suspension adjustments had to be done as well)

*it still is too heavy