LimeyBoy

I vaguely remember a topic where this was discussed but am struggling to now find it.
There are a few lucky RLr's that have taken the plunge and fitted shortened ratio gearboxes Aside from the fact that all gears would effectively be shortened, what are the negatives of regearing the differential to improve acceleration instead?

NYC993

With re-gear you are trying to reduce certain gaps between gears not just shorten all of them.

To be honest, unless the gearbox needs to come apart, the benefits seem pretty small (given the cost). You got to be driving to the redline pretty hard to see the benefits of better ratios.

I was following a regeared 993 on the track and he would pull away in 4th gear slightly only for me to catch up and pass in the next turn.

race911

More correctly, you're contrasting the regearing of the any/all individual ratios with the regearing, usually shortening, of the final drive (aka ring and pinion).

The differential is just what allows the drive wheels to turn at different speeds when cornering. (We'll ignore the effects of traction controlling differentials in applying power, or assisting with braking stability.)

That's going to be nearly 100% driver dependent. Proper gearing will be under 1 sec/min lap time, on limit.

NYC993

Exactly

Martin S.

You may have been passing a driver lacking your experience and talent. Get a stop watch, you drive his car....once you hit 3rd gear, and then 3rd into 4th, you won't be able to pry the grin off your face. I drove my car, about 6 to 8 track events a year, since 2001, with gears in the car only in the past 2 years. I congratulate myself for the decision to go with 3rd through 6th gear, steel synchros, forged 1-2, 2-4 shifting forks and a Guard repacked LSD. Best money spent on the car

NYC993

Yea, my "talent" or lack thereof is not there. I'm sure the car pulls better with better gearing but there are many other things for 10k+ that will put smile on my face.

Bill Verburg

regearing is expensive but is also one of the best mods out there, as w/ a great suspension a great regear transforms the car onto what it should have been from day 1.

sander97C2

+993regear^^

Have been enjoying my regear immensely and agree with Mr. Verburg that its a great mod. Its very unfortunate U.S. 993's were geared long. Look at the GT4, its geared long but at least has the power to help overcome that. For some the stock gearing is just fine and is actually better for certain tracks but for me I'll take my regear/lwf combo over stock any day.

JB 911

Bill, or others with regear and upgraded engines I have a hypothetical question for you; So for guys with an upgraded engine, i.e. Rennsport built, 9m built etc to 325-350hp specs, can a re-geared transmission ever become 'too' short? Or is it more like putting gas on an open fire, it just gets even better? (If you are into fire) For extra credit, What about something as crazy as the (almost) mythological sounding engine Mr Linton is working on?

Bill Verburg

yes, the exact gearing you want depends on the torque curve and rev range
A stock engine has a fairly wide flat curve

The things I found most irritating about stock gearing w/ stock engine
1) 1st is too low, which contributes
to
2) 2nd is too far from 1st, not too much wrong per se w/ 2nd otherwise
3) 3rd is too far from 2nd
4) 4th & 5th are ok,
5) 6th is too tall

one of the biggest potential pitfalls of re-gearing is too close, when the gears are too close the tail of the lower gear crosses the succeeding gear before redline, factory gear stacks are very good at avoiding this issue, unfortunately for most street transmissions since the 90's EPA fuel economy was a more important input than strict performance criteria, hence the g60/20 seen in US 993s. There is one time when you might want the above and that is where aero limits come into play



RoW got the g50/21 whose main failing was too low 1st but which otherwise was a close match for the g50/31 in the base 993RS

Of course the other reason to dive into a gearbox is to get rid of the plastic bearing shells that melt and break w/ severe track use and to upgrade to steel syncros and billet shift forks. For street use only the re-gearing is really that desirable

Martin S.

stuff from Bill, once again.

race911

And to pile on, for those of us who use data--my great for Thunderhill and Sears gearing costs me probably 2 sec/lap at Laguna. If only a G50 (or 901 or 915) had EZ swap out gears like a Hewland.........

earossi

I was fortunate to pick up a Motorsport G50/32 tranny. The car was totally transformed for street use. Shorter gears and proper spacing of the gears makes the car a delight to drive. The best money ever spent on my hobby. The car is faster simply because you can hold the engine in the power band so much easier while accelerating.

But, the best feature is the wide grin on my face everytime I drive the car. I hated the OEM gearbox.....especially the 1-2 gears. The Motorsports tranny fixed all of that.

mgerber

^This. As a machine it just feels so much better, and as stated above now feels like it is working well together. Yes, a lot of money for making it feel better, but if you have the cash...

LimeyBoy

Thanks Ken.
I fully appreciate the benefits to overall gearbox ratio shortening - and while you are in there - upgrades. But at a cost.
So is just shortening the final drive possible/worthwhile? Has anyone on this board done this?