hockenheimr

Thanks guys for all the info....this is amazing

The car should put out 350-380 Hp, around 300 lbs of torque, above 7,000 RPM limit, Rothsport Big Bore kit, 3.8L, 993 Heads, RS Valves....etc. Should have a similar curve as a Singer I guess. I noticed the 'average' Singer just changes the R&P to 4 and keeps all the same gears but I believe that weakens the system. I plan to keep the 17" cup rims just because I like the stock look.

Someone mentioned on a forum, why not just replace 3rd with 1.65, move 3 to 4 at 1.41, mover 4 to 5 at 1.12, and move 5 to 6 at 0.93. This would put me out 2 gears (since 5 is broken) and labour.

Something likes this:
1: 3.82
2: 2.05
3: 1.65
4: 1.41
5: 1.12
6: 0.93
R&P 3.44

Looks good on paper

Bill Verburg

Here's one way to compare the various options all at 7000rpm, a;; w/ 24.5" OD rear tires
g50/03 is stock for US 964 thu '91, the later g50/05 have taller gearing
g50/20 stock for all US 993 n/a
g50/21 early RoW n/a, uses 993RS g50/31 upper gears and /20 1st
Singer g50/20 w/ 4.0 cwp otherwise stock
regeared /20 as described in previous stock 1 & 2, 5 moved to 6, custom 3, 4, 5(i'd prefer a taller 6 for this one


I dislike the short 1 on all of them, the /21 would be my choice of these

GTgears

Well for starters, you can't get there from here... 3&4 are swappable. 5&6 are swappable. You CANNOT put 4th into 5th.

Beyond that, the stock 3rd in 4th like that is just way too tight of a stack down low. And even if it wasn't, that 3rd is too short for the kind of engine you are building, so if you go with a taller 3rd, your stock 3rd becomes even more useless. You are really going to want something like a 1.579 or so in 3rd.

You said above your 5th is bad. You want to get the gearbox apart before you go too far down the rabbit hole. Not only may your 5th gear be totally shagged and need to be replaced, but often a bad 5th in these gearboxes is indicative of a broken center case. If the center case is cracked it is a throw away and finding a replacement could take some time and will cost $1000 or more these days.

hockenheimr

It's already apart, I'm pretty lucky but only a small piece is missing from 5th.

Does a 997 GT3 maingear fit into a G50/20? If so, that would fix the 2nd gear issue.

I'm all over the place with this



Sorry for the GBox plug

Bill Verburg

Those sorts of data views don't show you much

I prefer this if you have torque curves



or these w/o torque curves, but at least you can see the rpm drops

hockenheimr

Thanks Bill! I'm debating if I change the R&P to a 8:32 and go the singer route, or change the gears to what you recommended a few posts ago.

Anyone know the reason why they gave the RS America a 3.33 R&P?

hockenheimr

Ok, so thanks to a few guys I kept the 3.44 R&P and I went with these ratios:

1st - 3.82
2nd - 2.26
3rd - 1.64
4th - 1.29
5th - 1.06
6th - 0.92

I used Guard gears where the supplier had them.

Will let you guys know how it turns out

GTgears

That curious since the only gear on that list I was asked about was the 6th, which I supplied. Did you get some used gears?

hockenheimr

Two of the gears are yours, 4,5 or 6. Someone who knew someone who knew someone had some race gears in stock.....which I assumed are new. Some of the other gears are used GT3 gears, but I will try and get some pics before installation.

GTgears

I wouldn't normally say something like that but the shop where you got that gesrchsrt you posted is not a Guard dealer and in the past they have sold people gears they claimed were mine and actually were not. If you aren't dealing with them you are likely fine.

GTgears

Something occurred to me overnight. That 3rd gear you bought is a stock GT3 gear. As such it will have asymetrical dog teeth on it. Make sure your mechanic knows that he must use a GT3 3/4 slider assembly for that gear. A stock 993 slider will not be the right one. You cannot reuse the stock one.

hockenheimr

The gears were not purchased from that retailer.

Thanks for the heads up I bought all the sliders with the gears so I will just pass the info on to him.

GTgears

hockenheimr

I've got an issue, the 997 GT3 Main gear does not narrow to allow for a LSD.....where the origional 993 does. The whole transmission needs to be taken apart again at this point and I'm going to bring the main gear to a machine shop to see if they can make the alterations. Any idea if this can be done considering how hard the steel is? also, the speedo is not on the 993 lsd....so is it only on specific years?

Thanks guys