Th Dude

Hi All,
Please help me to understand some of the pros and cons of having a Limited Slip Differential.

Also, please advise ease of installation.

Thanks <img border="0" alt="[bigbye]" title="" src="graemlins/xyxwave.gif" /> D

Bryan

My '85 Euro 928S has a factory limited slip. It's hard to describe the pros and cons because I've never driven a 928 without LSD for any length of time. It's hard to imagine that a transaxle car with fat tires really needs it. And since the factory LSD is the clutch-pack kind, it'll eventually wear out. But, I do enjoy having excellent traction in all conditions. I remember having to make hard right-hand uphill off-camber turns in my old E30 and it would spin the inside rear wheel like crazy and hardly go anywhere. Not a problem in the 928. But I don't know how much of this is due to the heavier rear of the 928 vs the LSD.

Overall, I'm glad I have it.

Bryan

SteveG

If you are going to track the the car, you probably want it. Otherwise, like Bryan says, you really don't need it. Needs to be installed by a knowledgeable 928 mechanic, there are shims involved, I believe, need I say more.

heinrich

LSD is good. If you can get it at a reasonable price, you should. I have both. Without, there is wheel spin from takeoff, and sometimes I get stuck on my lawn with a spinning wheel. With LSD, the car powers out of any kind of slippery road, and it's nearly impossible to break a tyre loose. LSD basically causes power to continue to be transmitted to the remaining wheel once the other starts slipping. Conventional diff will transfer all power to the slipping wheel, thinking you're cornering and the slipping wheel is not slipping but just travelling farther, thus needing more power.

chris928

Is LSD good? The drug, no, messes up your head. The traction device, yes. Porsche engineers agree. Racers agree.

I almost got creamed pulling out on to highway 33 one morning by a semi truck who didn't feel obligated to slow down. As I was turning, the inside tire lost traction. I only had time to punch it harder and left a one wheel burnout about 100 feet long and a plume of smoke so big that I could hardly see the big rig in my mirror.

Wouldn't have been an issue with LSD.

The clutch style LSD's are OK. Definately not the gold standard, but are effective. McLaren has a nice design made in Santa Barbara, but they aren't available for the 928.

John..

The LSD is a must on my car...

Ed Ruiz

If all you intend to do is street driving, you don't need the LSD. If you intend to track or autocross it, it's a must have item. YMMV.

Th Dude

Thanks for the info, guys. I appreciate your input.

Bryan, "wear out" you say? Any idea after how many miles (approx)? Is buying one of these used a bad idea then?

Steve, Are you sure shims are needed in the installation if I purchase an LSD from a compatible year 928? I've been told '84-'89 are compatible. If you have heard (or know) differently, please tell me.

Heinrich, Thank you for your 1st hand experience with this. I would also like to take this opportunity to thank you for sharing your well written words about 928 ownership that have now found their way onto a beautiful plaque.

Chris, are you positive about that LSD messing up your head? That dude with the bugged out eyes <img border="0" title="" alt="[Eek!]" src="eek.gif" /> didn't mention that to me when I bought it from him. Well, I guess I'll just take your word on that one. <img border="0" title="" alt="[Wink]" src="wink.gif" />

John, "The LSD is a must on my car"...Uh, YEAH...you own the f'in "Bastard", man. I'm no expert on these matters (hence my original questions)but with the Twin turbo on that Bastard you probably need all the power management/control you can get your hands on. <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" /> to you.

Ed, I do not have any immediate plans to autocross or go to the track just yet. However, I am a fairly aggressive driver and have already added a few power enhancing mods (with more likely to follow). With that in mind what do you think?

D

Ed Ruiz

If you're not going to drive it in competition, save your money. YMMV.

drnick

jesus ed, you are too sober for words! i was pleased however to hear that you do take corners at more than double the posted speed..

my car was optioned with the LSD and yeah it does seem to work, gets the power down with minimum fuss. id say add it if you want it, i like having mine

there is at least one difference between the LSD options for the gt model which featured an electronicaly controlled unit. some people prefer the constantly operating mechanical kind and retrofit.

Ed Ruiz

Having done both Autocross and track events, the PSD on my GT has been put to good use. However, on the street, it hardly comes on. Back when I had a 86.5S AT without LSD, I missed not having it while tracking and autocrossing. Otherwise, it was not needed.

The way I see it, why pay for something that will not get used? YMMV.

BTW, here in VA a yellow sign with a speed on it is not enforceable. It is a recommeded speed, but not the speed limit. One can legally take a corner up to the official posted limit (in white).

However, even if you stay below the posted limit, but lose control and cross over the median, you can get tickets for: failure to maintain control, crossing a double yellow line, and traveling in the oncoming traffic lane. If you go off to your right you can get a ticket for failure to maintain control, and if you hit anything you can get a ticket for damaging public property. Also, your insurance company will likely raise your rates, not to mention the deductible you'll have to pay to fix your own car.

Have fun, but be careful. YMMV.

Jim bailey - 928 International

the limited slip is what the ring gear of ring and pinion is bolted to it replaces the carrier for the open differential . Although manufactured to very high close tolerances the setup of the ring and pinion is very important and typically requires shims to get it correct when changed . The late model slip is expensive , new over $2,200 used "worth" a $1,000 or so . All units after about 1984 for the USA market are "limited" limited slips able to transfer only about 40% of the drive to the tire with traction . The older units could be as much as 80% transfer ! If you get on the gas hard in low speed corners the slip is fun and helps get oversteer as the back end gets loose and trys to pass the front end !

AaronE

Besides the more powerful engine, the LSD is the thing I miss most about my Formula Firebird. There's something to be said for lighting up both tires to make a quick U-turn, or just for throttle-steering through turns. I've never tracked a car, yet I miss it a bunch. Of course, the independent rear would make the Firebird cower in shame...

WallyP

For city/suburban driving, LSD is a mixed blessing.

LSD makes the rear end reluctant to differentiate, and will increase rear tire wear. You are basically dragging one tire on every corner. (This is one of the advantages of PSD - it doesn't do that.)

While having fun in wet weather, if you don't have LSD, you spin the inside tire. If you have LSD, you spin the car. (PSD will do that!)

AaronE

What's PSD? Judging from your context Wally, it seems like it means "non-limited" slip (i.e. regular). Anyway, LSD really increases tire wear? My car squeals all the time on sharp turns with power (without LSD). My Firebird never did this, though your explanation makes sense for a simple, always active, "slip clutch".

Are there different kinds of limited slips? I always thought they had some sort of centrifugal clutch where it wouldn't grab until the difference in speed was above some threshold.