VNTGSPD

Here's what I was thinking last night driving home...

In around town driving and some of the tighter back roads, 2nd gear is very "flat" and uninspiring. Unless you are doing 45+mph second gear has a bit of lag to it before the engine comes on cam. So, I am looking to replicate the feel of my '69 with factory short gears in that every mid-rpm shift lands the car very near the power band. This allows you to drive the car through town with an effortless feel with the car always feeling responsive. Of course, when using all rpms, the next gear is always in the power band and the car just GOES!

So, I'd like a shorter 2nd to allow a maximum drop of 2500 rpm or so from 1st to 2nd. I think this would necessitate a change of the third gear ratio as well but was wondering if you could split the difference so that the leap to fourth would still remain "natural". If not, I think you could definitely split the difference with a modified 4th gear ratio. So you are looking at changing only 2 or 3 ratios (yet still "fixing" the 1-2 shift).

For someone like me that can do all of his own work, this could be a realistic option. I wouldn't mind opening the trans to change the gears and seals but not getting into a full blown rebuild. If I had to tear it down again in 20K miles I would not care because I have only lost my time. This would be different if I had to pay a shop to do the work, of course.

This would seem to result in a nice upgrade in real world driving performance and fun for a daily driver for what could be less than $3K. I realize some will poo poo an idea such as this and suggest that the only solution is a $7K upgrade and others suggest that such things should only be done after 401(k)s and college tuitions are paid. I'm looking to balance fiscal responsibility with LIVING a little while I'm still on this earth.

Bill - do you know if there are ratios available to change 2/3 to get the 1/2 advantage without ruining the 3/4 relationship? Or, add a new 4 to get a better 2-5 ratio? Remember that this is a road car and 6800 rpm shifts from 3rd are RARE and these shifts from 4th happen, well...never.

If I'm crazy, that's cool too.

Sorry for the winded post but thank you all for the great info and commentary on this as this has been a subject of interest for me for a long time now.

michel j

+1 (In around town driving and some of the tighter back roads, 2nd gear is very "flat" and uninspiring. Unless you are doing 45+mph second gear has a bit of lag to it before the engine comes on cam.)

Bill Verburg

Can't do w/o a new mainshaft and shouldn't do because of the cascade effect

VNTGSPD

I should have said that I have an early '95 so there's a very good chance that I "can". So, due to the "cascade" effect, you are saying that you would really need to do a 2,3,4 swap minimum or maybe even a 2,3,4,5 to avoid an unnatural rpm drop in the upper gears? But, if in normal driving I take 3rd gear 4K rpm before shifting to 4th, couldn't I find a ratio that might require an extra 500 rpm in 3rd to yield the same rpm when going to 4th.

I am familiar with this "unnatural" drop when you have gears with consistent spacing and get to an upper gear that seems "off". I put a freeway flyer "ZD" gear in my 911 and it does this. It works exactly as intended and I like it, however if you are going through the gears briskly and get to 5th, it seems like you might have missed a gear although the car still pulls well.

It seems that most of these re-gear threads seem to focus on a gearbox ideal for track or high speed driving (and perhaps rightly so). However my car spends 90% of it's time between 35 and 90 mph so the standard re-gear proposals as I read them don't address the area of biggest concern for me.

I'd just like to end up with a gearbox with a strong enough second to be able to use the power to rotate the car at lower speeds without screwing up the gear stack from 3rd - 5th.

I think I need to get a chart together and plug in some ratios to see where they fall...

chris walrod

to me 2nd gear is what makes the na car lethargic. I personally wouldnt change anything unless 2nd was lowered, much like the 2.048 gearset outlined above. I've autocrossed a car with that very ratio and it still doesnt seem low enough

Erik@GBox

Okay everyone, so if I understand everyone here, it looks like the first gear in the NA car is not the issue. It is more of a flat 2nd gear, which makes sense as the drop from 1st to 2nd puts the car off of the powerband.

I will try to rework a couple of things here to get what might work a bit better for everyone, I think that we can achieve what we are all after here, it is just going to take me a bit to put it together.

I appreciate the information and I will work on this right now. More info on this in just a bit.

Warmest Regards,


Erik Johnson
GBox Sales Manager
(303) 895-4828 cell

Erik@GBox

Okay everyone, so if I understand everyone here, it looks like the first gear in the NA car is not the issue. It is more of a flat 2nd gear, which makes sense as the drop from 1st to 2nd puts the car off of the powerband.

I will try to rework a couple of things here to get what might work a bit better for everyone, I think that we can achieve what we are all after here, it is just going to take me a bit to put it together.

I appreciate the information and I will work on this right now. More info on this in just a bit.

Warmest Regards,


Erik Johnson
GBox Sales Manager
(303) 895-4828 cell

axl911

Yes. For a daily street driven car, I would like a higher 2nd gear and 3rd. I actually like stock 6th for cruising.

Erik@GBox

Okay everyone,

See what you think of this.

RPM Redline (lowered from original chart posted here) 6500
Tire Dia = 24.732
Final Drive = 4.0 or 8:32

1st gear made slightly taller then stock, raised to 2.538 or 13:33 = 47.120 MPH
2nd gear changed to 1.895 or 19:36 = 63.128 MPH
3rd gear stock = 84.987 MPH
4th gear stock = 107.021 MPH
5th gear stock = 129.864 MPH
6th gear stock = 154.338 MPH

This should allow the 993 to stay in the power band on hard acceleration throughout the gears at you will never drop below 4800 RPM. It should also allow for easier starts from stop lights and rapid acceleration.

Does this look better?

I look forward to your comments on this.

Erik Johnson
GBox Sales Manager
(303) 895-4828 cell

NineMeister

Personally I would never use an 8:32 R&P in a road car because of the 1:4 wear pattern of the teeth - putting it bluntly they wear out a lot faster than the standard R&P which constantly varies the mesh of the teeth.
My advice would be similar to Bill's in that I would definitely change out 1st & 2nd to be more active, then look to achieve sequentially reducing rpm drops through the rest of the gears. In practise this usually means that you get approximately even mph changes through each gear. Around 50mph in 1st gear is ok for street use, it's approximately what Porsche fitted to the 993RS as standard with either the dual mass or lightweight flywheel.

brucec59

I like VNTGSPD's idea. Can we take it one step further? What if we change ONLY 2nd. Just make it a bit shorter, so the RPM drop from 1-2 is more manageable, but not so short that 2-3 becomes a problem? I'm fine with 3 thru 6 as they are. Leave R&P alone. Is this possible?

GTgears

The problem there is as VNTGSPD suggested, the rpm drop on the 2-3 shift is just going to be too big. You'll want to move 3rd as well, and preferably 4th. You could arguably get away with just 2 and 3 if you only cared about 0-80mph. If you ever track the car and want something in that 80-110mph range you'll need a different 4th.

Also, once you are in there, the labor is what it is. Adding or subtracting gears is the only change in cost for those sorts of things. If you get it done with just a 2nd and hate it, you're going to pay the labor all over again, which is about the cost of a gear, so why not do it first time through and be sure it's what you want.

Erik@GBox

Well it would appear that we are exactly where I thought we would end up LOL.

Different drivers have different desires for their gearboxes. I would be happy to discuss each person's ideas individually, but the thought of this thread was to try to find a solution that would appeal to the masses sort to speak.

Don't worry I will keep on trying. LOL

Feel free to give me a call to discuss your personal thoughts and needs though. I am always here to help.

Warmest Regards,

Erik Johnson
GBox Sales Manager
(303) 440-8899 work
(303) 895-4828 cell

Red9

Cheapest most effective way retains original R&P
-- New 3rd gear at about 1.65
-- existing 3rd becomes 4th
-- New 5th gear at about 1.117
-- existing 5th becomes 6th
Gives best spread and makes the ratios closer and more usable. Not to tall a 6th for cruising and you are never going to run out of top speed on the track-- but the gear becomes usable.

okindao

Bill ,your last example where you keep 1 and 2 and move 6th to 5th is great only wondering if i have 275- 40 -17's in rear versus your example of 265 35 18's if 6th will drop even more ,,cause if so think i need to make it slightly taller for track such as VIR ? would you aggree ? Thanks for all the information very enlightening ...everyone knows i need that