LSD...Welded...opinoins!

This is my first year in IT, and my first year road racing. I picked up a ITS prepped 77 280z.

It came with a welded diff, and after a interesting discussion with an experienced road racer, and engineer, I am confused. He says we should swap in our open diff for the welded diff, and he also says to NOT upgrade to an LSD.

He feels that we should spend more time with our suspension setup, perfecting it, and we won feel a need for an LSD, at IT-S power levels.

Anyone else feel that the z platform can be setup in a way that the open diff wont be a limitation?

Thanks,
Josh

I can think of no instance where his advice to run an open diff would be well advisable.

Anytime traction at maximum acceleration matters you will notice it, arguably even more so with a well dialed in suspension. In stock form it matters for an even ITC car.

I would have him clarify.

I have raced ITS and E Production Z cars since 1992, beginning with an ITS 280Z with an open rear. In most corners the 280 would light up the right rear and be crazy loose. We soon welded up the rear and the car was at least 2 seconds a lap quicker at sebring short course. The car would push somewhat in some corners, however the trade off was well worth it.

Several years late we built a 72 240 Z ITS car beginning with a locked rear. The car handled well and was very quick. We installed an LSD and the car was about 1/2 second quicker at sebring short and had no push.

I agree with Turbo, I can think of no instance where the open rear would be beneficial in road racing.
My experience is the welded diff's can work just fine in Z cars, however, a properly set up LSD would be better.


"Bosco"

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I can think of no instance where his advice to run an open diff would be well advisable.

Anytime traction at maximum acceleration matters you will notice it, arguably even more so with a well dialed in suspension. In stock form it matters for an even ITC car.

I would have him clarify.
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Quote:

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I have raced ITS and E Production Z cars since 1992, beginning with an ITS 280Z with an open rear. In most corners the 280 would light up the right rear and be crazy loose. We soon welded up the rear and the car was at least 2 seconds a lap quicker at sebring short course. The car would push somewhat in some corners, however the trade off was well worth it.

Several years late we built a 72 240 Z ITS car beginning with a locked rear. The car handled well and was very quick. We installed an LSD and the car was about 1/2 second quicker at sebring short and had no push.

I agree with Turbo, I can think of no instance where the open rear would be beneficial in road racing.
My experience is the welded diff's can work just fine in Z cars, however, a properly set up LSD would be better.
"Bosco"
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This is the same argument I had. Somehow by the end of our conversation he had me sold. I believe he basically said that when re appling throttle the weight if dampening/rate is proper the weight should trasnfer and traction would be sufficiant. I know we are talking simple suspension stuff, but it seems as though he has some point and I am not understanding it completely. He has so many wins, and so many big teams under his belt its hard to not to weight his suggestions heavily.

I am going to call him tonight and ask him to write me an email.
Josh

Josh - I agree w/ the others, I've driven my 300's w/ a NISMO LSD and an open diff, same ratios. The open diff was a pain. Smoked the rear tire out of NHIS #3 even w/ a really crappy motor. Had to loosen up the rear to help keep it from doing this & change my line. Just get your hands on an R200 w/ the LSD set up. Late '87 and on 1st Gen 300zx turbo came w/ this standard w/ a 3.70 ratio. Poke around on Z31.com they turn up for sale from time to time there. They are moderately coveted by the 300zx guys. The Z31 page has all the info on what diff's were in what cars (for the first gen 300's). You'll have to do some work to install the output flanges as the 300's use stub shafts that poke into the diff, yours has the u-joints that bolt on.

Or you can deal w/ the joys of a locked diff.

Matt

The only time I can think of that an open diff might work in road racing is with a small, underpowered formula car like a Club Ford. Otherwise, nyet.

Welded diffs on 240Z's eventually break stub axles. Go LSD.

When funds allow, I run an ITC Datsun 510 and needed an LSD (spinning inside tire out of the corners) at my first drivers school years back with a motor out of a "Fred flinstone car" - Foot brake option available due to lack of floorboards, with 200,000+ miles and spun the inside out of EVERY corner under 45 or so mph. I next went welded and it really works fine unless you are running a track like Hallett with a lot of tight corners and I felt the welded made the car push on tight turns. Some folks say welded always push and maybe it does a tad on real fast corners, but you are normally drifting (not in the "drifter" sence) the corners anyway at speed. I currently run a LSD and am happiest with it as most all tracks have a tight corner or two, LSD's vs welded are especially nice when moving the car around the shop as you cannot push and turn the wheel as it will only go straight when welded.

Open should not be considered at all as stated by others.

Matt
ITC 13

Thanks for the advice, I am going to run welded until I found a good LSD.
Josh

I'll throw in my 2 cents. I have run both in a 240Z ITS. I've had overheating problems with LSD during endurance races so usually run the welded. Probably has more to do with the exhaust running unshielded right under the diff, but that's another story. I have a brand new 110mm LSD for sale if you're running 110mm ring gear instead of 115mm.

Dave Ciufo
ITS 240Z #34

Dave, I'm interested in your LSD if you still have it. If you know of a 115mm LSD please let me know.

Thanks Terry Miller