Ganja Porsche

If I do replace the transmission on my car I want it to be a bolt on ooperation of course, but while I'm on the topic I thought I'd ask to see if anyone knew the answers to any of these questions...

Are any of the 924-968 series transmissions geared so that you hit 100kMPH(62.5mph or so) or above in second gear???
I would also like to try to get a LSD.
I know the 944 Turbo easily hits over 100kMPH in second, but are there any others?

Danno

Check out the gearing-chart on my website at: 951 RacerX websiteLooks like the '77 924, 944S/S2, 951/968 can all do it:

• '77 924: 2nd=10.068mph/1000rpm, (10.068mph/1000rpm)*(6.5*1000rpm)=65mph
• 944S: 2nd @ redline = 9.239*7.0 = 65mph
• 944S2: 2nd @ redline = 9.273*7.0 = 65mph
• 951: 2nd @ redline = 10.646*6.5 = 69mph
• 968: 2nd @ redline = 9.786*7.0=68.5mph

Ganja Porsche

So a '87 924S won't?

Ganja Porsche

Well, what do you guys suggest?
I want:
1) LSD
2) 60+MPH in second gear
3) Best possible for overall speed & performance...

Andrew

your 2.5 N/A car with the matching tranny. porsche aims for the best all around ratios for these cars. save your money.

-Andrew

Danno

Yeah, your car will actually be SLOWER in each and every gear with any tranny that's taller than stock. Sure, you can claim a quicker 0-60 time because you saved a shift, but when you're actually running down the road, like racing someone, they're going to be pulling away.

Ganja Porsche

I was looking for a faster overall, hardly even worried about some 0-60, more like 1/4 mile

jim968

By "faster," do you mean:

A) better acceleration? or

B) higher top end?

Changing gearing will get you one or the other, not both... unless you go with lower (numerically higher) gears in 1,2, 3, & maybe 4, and accept a big ratio gap to 4 or 5. Then you get better acceleration in the first three gears, with each redlining at a lower speed.

But doing that will have you shifting to second sooner, not later.

Changing the ring and pinion will get you either A) better acceleration with a lower top speed in each gear, or B) higher top speed in each gear, with slower acceleration. Changing tire diameter can do the same thing, tho' not as much so.

Jim, wondering if gearing changes would be better & cheaper than superchargers...

Renntag

Sorry Ganj, Andrew is totally right.

The best thing you can do with what you have is to lower your final drive slightly and install a 'slip'.

If you install any of the other trans units you will see a significant decrease in acceleration unless you then change the final drive. Additionally, your car doesnt have the power to push a bigger gear and achieve more top either. I have seen many times at the track where lowering gearing has actually increased top speed.

IMHO, Search for a used slip. Do your cylinder head, cam, chip and exhaust to make more power. That should make all the difference in the world.

Have you driven the early 911T and then driven the 911S, granted the 'S' has more power, but also has the closer ratio trans. Same thing with a Golf and a GTI, same motors, lower gearing in GTI makes it rip!

Give it some more thought.

Stick with what you have. Add the slip.

Ganja Porsche

I might go with a 924S Trans. with LSD and ...taller?... or ...shorter?... 5th gear? I forgot, I think you get higher top end w/ the 924S, not sure though...

ThE sPaCeCoWbOy

I went with the 944s2 tranny....

my reason, its stronger then stock, you have can reach higher speeds in 5th (that is if you have a supercharger or turbo), you dont lose acceleration like you would if you put a turbo tranny in, and plus i blew my n/a tranny and got this one for what i think is a good price...

thanks,
space

Andrew

The 924S is the same engine and tranny as the plain jane 944 with a VERY SLIGHT change in the 5th gear (.73:1 on the 944 and .83:1 on the 924S) the final drive is the same too. this means for every revolution at the wheel there is 2.84 revs at the engin on the 944 and 3.23 on the 924S. if you feel that you really need .39 revolutions out of your engine to make it "Better" then go for it ... Both cars have the same top speed though. So i don't see why you have such a need to swap. Now if you had a turbo and put the N/A tranny in then that is different. I did this and well... the G-tech now claims 0-60 as 4.89, 4.92, 5.00. this is on a stock car with just chips! that is worth it to me! since i never go to the track and i can't strech her lags anyway.

-Andrew

Steve Lavigne

Craig, if I were you I'd go with a 924S box. This has a shorter final gear which will let you accelerate a little faster in top gear. If you ever find yourself on a racetrack (not a pleasant thought) you will greatly appreciate it. Not sure about the 944 na, but you may want to see what ratios the European box has.

If I ever blow up my gearbox, I will try to source a European 951 R&P or gearbox. These R&P's have a ratio of 3.888, compared to the US 3.375. This should provide increased acceleration, though will cause a loss of overall top speed. It is also possible that less time in each gear may create a little too much time spent lagged.

I made an excel spreadsheet several months ago which allows you to plug in tire size, max rpm, ring & pinion, and gear ratios. From this, you get max speed, rpm at upshift, rpm range from upshift to next shift, and speed gain in each gear. It has a page with 951 gears and another page with 968 gears.

Thank Danno for all the gear ratios except the Euro R&P. Let me know if there are any errors.

951gearing.xls

'86 951
-Steve

Ganja Porsche

I'm not trying to replace my trans. just to make the car better, if I'm going to get another one because of a problem, I want to get a different kind, I duno why grrrrrrr... But I most definately want LSD

ThE sPaCeCoWbOy

did they make lsd differential wit 944's/924's

im pretty sure the 968's ahve lsd diff. not sure on the 944/924

thanks,
space