Bill Verburg

I am finalizing the plans to regear my car for mostly track use. I have a Guard 40:60(freshly rebuilt), 25" 265/33 MPSC tires, stock 9:31 cwp. The lsd has been machined for clearance of other cwp but I don't think that is a direction I want to take.

I have been collecting info on this subject for a while, so one of these will likely be the choice


Any comments or suggestions?

also included in the plans are GT 1/2 & 3/4 billet shift forks, Gt reversing lever, RS linkage/ rod, and steel synchros(but I have to agree w/ Geoff that ~$1500 for the 2nd gear set seems just a tad steep )

Tom W

Mine are:
3.818 2.250 1.632 1.286 1.083 0.921
But I think I'd like the G50/31 ratios better. I saved money by using the stock 5th as 6th (a mistake for a street car) and I didn't swap the mainshaft to go to 3.154 (should have as I needed a new mainshaft anyway as mine came with both 1st and 2nd splined onto it). At the time I was very new to Porsche's and the track and let Rothsport determine which ratios to use.

viperbob

http://www.race-technology.com/WebPa...lculation.html

This will help you see a little better as to your drop off in RPMs from your intended shift points between gears with the speed associated at those RPMs. This is not the best calculator (I prefer to enter the I/O number of teeth and see the results graphically), but the best I could find on the web.

sonny1

Hey Bob thats a good calculator!.cheers,Sonny.

Bill Verburg

Yes there are several great calculators out there, wish I had the skills to do one like these

A good one

an even more useful one

But I can make my own so, thats not what I need

I am looking for feedback on the utility of the prosective changes

I do have a separate second and so could change 2nd, but besides the cost I really don't see why I should.

Tom, mine is designed around 5th going to 6th. Paul G. felt that was good because the gear would be quieter and I pretended 5th was the top gear last summer, didn't seeem to be much of an issue. Can you amplify on why the taller G50.31 or 32 gearing might be better.

Some more data comparing RSCS to the most likely choice for regearing


and the charts
993 RSCS G50.32 vs. proposed regear of G50.20 3 - 5

Tom W

Bill: I think my 2nd is too short. If you need it for a slow corner, it just feels like your out of revs too soon. In a linked series of turns like Thunderhill 11 and esses at 12/13, I'd like a bit taller gear so the shift point is a little later. I've never used 6th on a track out here so I think it's irrelevant. On the street, the normal 5th is too low for a highway cruiser. With your planned 5th, I would be topping out just before the end of most straights and I would not want to waste the time to shift to 6th for no real gain. With a bit taller 5th, like the RSCS gears, I'd still be in 5th until the braking zone. With stock valves and springs, I'd want to shift at 6500-6600 and the rev drops from that shift point with RSCS still would keep it in the power band.

Now, I'm sure you thought of all that. What attracts you to the gearing you're thinking of? Are the tracks out east that different?

Bill Verburg

Interesting, mine has RS cams, and will have the full RS kit eventually.

So your thinking is that a little taller 2 -6 will give you more flexibility.

I don't think that the difference between a 2 and 2.048 is worth changing, but I will certainly consider a taller 3 - 6 geared maybe to ~ 175 or so. Have to work on what that would look like.

Unfortunately the 2 main tracks, Lime Rock and Watkins Glen have very different gearing needs.

Any input on the noise factor, Paul felt that the factory gears would be quieter than his. This would be an issue only on the highway gear, 6

SteveG.

Bill,

I recently regeared with Guard's gears as well. The car feels much quicker and more driveable. Gear whine is minimal and doesn't really bother me at all, in fact I kinda like it. The sound is not intrusive, although I have heard some gears on other track cars that are rediculous. I also moved the stock 5th to 6th to save on cost mainly, not for gear noise concerns.

Since I regeared last summer, I have only had a chance to do a couple of track events on the new set-up. Overall, the car just felt much quicker and I found myself in one gear taller than what I used take a given turn in. I went from an open diff to a Motorsport LSD and the difference is amazing. That alone was worth a couple of seconds on my lap times.

My gearing is:
3.818 2.250 1.650 1.308 1.100 0.929

If you don't already have it, I have my spreadsheet with Paul's gear options in it and you can try different options and check out your splits.

Red9

Bill , I have done numerous gearboxes ( in every sense of that word ) and here are some numbers from a very successfull track car.
Diff Ratio 8/32 = 4:1
1ST 13-41 - 3.154 -- @ 7000 = approx 70 KMH approx 44MPH
2ND 20-40 - 2.00 " " 110 " 70
3RD 23-35 1.522 " " 145 " 90
4TH 29-36 1.241 " " 178 " 112
5TH 32-33 1.027 " " 215 " 135
6TH 35-29 0.0829 " " 266 " 167

Gearbox was G50/32 . I race some very fast circuits and this is moe than sufficient top speed allowance. On one circuit only the rev limit could be raised ( to 7500) . This was a big torque ,real HP engine . My view is the gearing can improve the lap time far more than dollars spent on chasing HP.
The lower diff is a cheaper way to fix a G50/20 or G50/21 of ridiculously 320 KMH top speeds.
Also worth noting it is better on the road ( as long as you dont mind changing gears.Road going GT3 is also far more pleasant to drive with 4:1 diff.
The noise some aftermarket gears make should not be there. It matters not on the track but a car that is any more than toy should not be making gear noise in general use.

Geoffrey

Bill, don't forget that I have a 4.0R&P (8:32) in my trans, so overall it is quite a bit shorter than what you have posted above.

Swapping the R&P does not solve any issues, it does not reduce the torque drop between the gears, it only changes the range in which the gears work. By iteself, it is not a cheap solution. The right solution is to change the gears which will reduce the torque drop between the gears.

Bill, as mentioned on the phone, I think you can have 1 versetile gearbox that will work with both LRP and WGI as you won't be using 6th at LRP, but the shorter gearset will solve the torque drop.

993RS

I installed this set (got them from Steve W.):

1.......3.818
2.......2.25
3.......1.68
4.......1.3
5....... 1.1
6........0.962 (my old 5th)

Bill Verburg

Noise is far down on the priority list, I only mentioned it because it was one of the first things Paul said was good about moving stock 5th to 6th(I was only trying to be frugal)

I only want to do this once and appreciate all the feedback. So the concensus seems to be that this will be ok for a car that will be driven to the track(I don't want to get back into the truck/trailer routine) and be appropriate for tracks that are sort of short/tight like LRP where 6th isn't used but still be ok for longer tracks like the Glen. Geoff I am sure has a good handle on this and recently did a similar trans(though w/ 4:1 diff)which his why I wanted to pick your brain.

Groffs suggestion was almost the same as Pauls and similar to what I see in some of the others here.
Steve that would be great. Ill send a pm w/ my email hope that is ok?

Bill Verburg

I guess that this is what I will likely do


Any other comments/ concerns?

Leland Pate

For what it's worth, I absolutely adore my new gearbox. It has multiplies the fun factor mayber 5 times.

Good luck with the gear selection, Bill.

Bill Verburg

After further consultation and review
V2