Experiences with Locker (welded) Diff?

[scca_ita]

I know street driving will be funky (inside wheel dragging)

Other driving? Braking, AutoX, Tack?

[jluetjen]

You mean a Spool right. A locker is a pretty blunt instrument that alternates between open and locked causing a racheting feeling when cornering. I had one in an IT car that I raced and I didn't like it too much.

A spool would be the same as a welded up diff and I haven't tried one of those yet. I did reread an article about the Turbo RSR (ca 1975) and they said that they used a spool on faster tracks which didn't have tight corners. On tracks with tight corners they used a LSD.

[Thunderbolt]

I believe that the 935 used a locked diff. I remember reading about Brian Redman driving a 935 for a vintage race. The car 10 yr old rubber on the front. When he got to the first turn that thing plowed right through the corner into the grass.

I saw those cars run a couple of times in the early eighties and they seemed to be basically throttle off in the corners or very big lag. Anyway when the boost hit (hopefully with the car pointed straight) the car would absolutly rocket away. They were nasty fast in a straight line. It would be really cool to stand on the bridge on Riverside's back straight (which is about 1 mile long) and watch the car stretch it legs, absolute rockets.

[scca_ita]

Yes, I am talking about a welded spool. I would expect this configuration would be a handful at an autoX

[addictionMS]

I have driven a locked rearend in a 911, it is fine on the track, but it will kill you on autocross or street driving. The car really becomes a point and shoot, get the car rotated before the power or the car will not rotate and will push.

Jim

[scca_ita]

This is what I was anticipating, I will wait till I can affort a ZF......

[wevoid]

scca_ita

We tested our 915 spool for a long period in our road / track / autoX car.
This is a 170 hp, 2200 lb car. Either 205's all round, or 205 / 225 depending on our activities.
On the street the spool was no problem, but we did see more front tire wear.
On the AutoX it was all or nothing. Very high levels of commitment required and often 170 hp was not enough to maintain a balance of oversteer on the throttle. For an experienced driver there were times when it was good (TTOD at one event) but for a less experienced driver without the range of driving skills at her disposal, it was often too much inherent understeer to overcome. Both drivers always left foot brake and this is a major advantage with the spool.
On the track, we started with a balanced car and found we had to lower rear ride height and stiffen front ARB to restore the same balance as the car had with the 40% ZF diff. The advantage with the spool was very significant, more stability on the brakes, more entry and mid corner speed. I like to have the car with a mild US (at the limit) in the exit and this was easily maintained with the spool - same feel as the 40% ZF.
On the track the spool was definitely faster.
Some of the fastest PCA GT4 cars in the country are running with spools, these are 300+hp cars with 12" slicks, so their package is much different to ours.
After we completed testing the spool we returned to the ZF diff, this time set at 80% - hoping to take advantage of what we learned from driving the spool. I did one AutoX like this and removed it, and set it back at 40%. At 80% the ZF Diff was less predictable than the spool.

For track work I would not hesitate to use a spool, even if I drove to the track (in fact we did at that time) but for a track / AutoX car I would go for a 40% ZF diff.

Regards

Hayden

[CamB]

Did someone say titanium spool



http://www.gunnarracing.com/project/rsr/stage4.htm

[scca_ita]

Gunnarracing - very cool link- wish I had the time and facilities. Oh, and $$$$$$$ to do start from scratch.

[scca_ita]

wevoid,

Thanks for the info, I will be mostly tracking, Stadium AutoX and TT. My car will be around 2100lbs and have a 300 hp 3.6 ( I hope will see once it is installed over the next two weeks)

I think I will give it a try - the price is right.