sergiDA

Hi to all:

Thinking about new pinions to reduce the gears on 3rd 4th and 5th in order to have smaller jump between them and reduce the top speed as on track i don't think I will ever achieve more than 230/240 km/h.

Have heard some very expensive prices around 3000 Euros, and I can't belive that could be so expensive, if so it might be better wait a bit more and get a 993 g50/21 box instead

I would like to know your opinion on such transformation and if posible would like to have some adresses of places where the equipment could be purchased.


Thanks to all and enjoy summer.

Sergi

ChaseN

[RANT]

I'm very interested in this as well. The stock 964 1-2 drop is MISERABLE for autocross - you've got two options. Either leave it in 1st for the entire run, bouncing off the rev limiter on some straights (I've found this the fastest option for the vast majority of the courses I've run), or risk shifting into second and completely dropping the motor out of its powerband for a few *critical* seconds (really only viable for the fastest /longest of AutoX courses, like those set up on race tracks). Then of course, if you shift into second, trying to go back into first while still on the move feels like one of the most painful things you could do to any transmission. I'd kill for a nice meaty 2nd gear I could run in for the whole of the faster courses out there. Sure the claim is that they did it for gas mileage concerns, but come on, the 964 doesn't get THAT bad gas mileage that they were forced to do it. NONE of my similar vintage BMW's have/had such poorly spaced gear ratios. In fact, I'd go so far as saying the transmission is the GLARING weakness in the 964 IMO.

I've thought about taking out 5th, putting 4th where 5th was, 3rd where 4th was, and 2nd where 3rd was (not sure if those gears would 'fit' in their new respective locations, but it sure would be nice not to have to pay for new ones). Then, a nice custom 2nd gear put in. Maybe even a shorter 1st as well. Would be stellar IMO. Of course, while I'm in there, an LSD sure would help put the power down, especially on the crappy lots the club I run with uses... (WTF is/was Porsche thinking not putting a LSD in a 911 as standard? Heck, my old '84 318i had a LSD from the factory. So does my '90 325iX and '89 M3.)

[/RANT]


A 993 G50/21 would be awesome as well, but a good amount of extra unnecessary weight I would think, and manufactured out of unobtanium here in the US it seems. For a car that sees a lot of highway driving but is still at home on the track, I suppose it could afford reasonable cruising RPM's.

Anyone know the exact figure for the differences in weight between the G50 5- and 6-speeds?

BTW - the old autocrosser's rule of thumb I've always heard is that if you bounce off the rev limiter three times or more, it may be beneficial to up-shift in that spot next time. I've found I need to spend a solid 6-8 cycles on the rev limiter before I'll even THINK about up-shifting in that spot on the next run. Of course then you're still screwed for the rest of the run unless you want to tear away at the guts of your tranny trying to downshift into 1st on the move.

Did I mention I really really really really dislike the 964's 1-2 RPM drop?!!!!

flash_malmö

So you don't like the drop? Is that what you are saying?

I feel the same way, on the slalom we drive we have a 180 degree that needs to be handled in 1st gear, and getting in to it is just a pain.... Would have been much nicer with a lower 2nd gear.

sergiDA

We don't do autocross here, so i don't mind the gap between 1st and second, the problem for me starts between 2nd and 3rd.

May be in the USA we could find some better priced pinions to adapt the gears...i think prices on O.E parts are extremely high.

Bye.
Sergi.

Earlydays

I don't experience the 1-2 problem here because of the prevailing local autocross course designs. The only time it's an issue is if I have to deal with 180 degree turns, but that's only when the 914 drivers design the course.
We've got some courses here where I'm hitting the rev limiter in second.....

Cosmos99

What about changing the final drive ratio? I did it not too long ago on my M coupe and I loved the quicker acceleration through all my gears. Anyone know the options on final drive ratios available for the G50?

ChaseN

Oh so you caught that? I wasn't sure I was clear enough

The local BMW club I run with picks the smallest lots, then let's the Miata drivers design. I'm pretty sure they're in like 3rd where I'm hitting the limiter in 1st anyways

That would increase the overall acceleration, but wouldn't really fix the RPM drops (a problem your M coupe certainly didn't have). I would absolutely love to change it still - though its nowhere near as cheap as on a BMW :/ I would love to know our options though.

sergiDA

I have contacted guard transmisions on your side of the Atlantic, they will send me some graphs of a more apropiate ratios (3/4 and 5th gear) for track use mainly. 240 km/h @ 6800 rpm.
.
I find this a bit pricey, 1000 usd per pinion, 3000 all.

I will post the graphs once I have them.

Geoffrey

I've regeared 5spds and usually take 4th gear ratio and use it for 5th (new gear required) and buy a new 2-4 ratio set. Works excellent.

Cosmos99

It was very cheap for the M coupe because you can buy a used diff from a salvage yard for $350.00....I am looking into changing the final drive in the 964 as it is now I am at 3000 rpms at 80mph. I wouldnt mind something that would achieve 3500 rpms at 80 mph. I know nothing on the 964 ratios at the moment so I need to do some research.

Agreed that it wont stop the 1-2 rpm drops though. It is quite annoying.

ChaseN

Geoffrey -

What kind of price would one be looking at to do something like that? You can PM me if you like.

Yeah, its crazy how cheap the stuff is. I scored a freshly rebuilt 3.46 LSD onebay for $175 when I swapped the S50b32 into my M3. Not as many deals on prepped G50s out there

Jimjacqmx5

I'm keen too, especially on the final drive option.
I'd be happy to lower all gears, drop top speed by 20 km/h but i reckon I'd gain up to 2 sec a lap on most tracks.
And yes, it HURTS when you jam it back into first on an autocross event!

Geoffrey

Changing a ring and pinion DOES NOTHING to reduce the RPM drop between gears. The only thing a ring and pinion does is increase the available torque in each gear. The RPM drop is the problem.

sergiDA

Geoffrey, do you/ can you supply regearing kits for the 964?

By the way i have read about your Motec transformation on Excellence magazine of a 964 white with blue decalls, a couple of months back. This story together with some conversations with Colin at 9M have convinced me that a stage 1 Motec conversion will be the next upgrade after regearing the car. THANKS FOR THE INSPIRATION!!.
.

ChaseN

Group buy on re-gearing from Geoffrey