I am slowly working towards my coversion ....I have a 3.0(stock) and hope to mate it to a 901 that bone stock....This car will be a street car and i am sure the 901 will handle the torque..but...what about the gear ratios...will first be to low? how about 2nd,3rd and so on... what is a 904 main? should I be looking for one??? how about recomendations on a LSD? do i need one
thanks
steve

5th is too short. The engine will be turning some serious RPM's with 50 series tires. I suggest a taller 4th+5th. I wouldnt worry about the tranny with a stock 3.0 unless you do burnouts with it. It wont last 100k miles... but it will last for awhile.

The 904 mainshaft has a removable 2nd gear (unlike the stock 914 mainshaft) I wouldnt be too concerned about it. They are typically pricey.

Be very careful with what you spend on the 901. By the time you are done you could have had a 915 with stock gears configured for mid-engine. I get a lot of people with 5k in their 901's... it would have been cheaper to do a 915 (which is what the 3.0 was mated to in the 911)


B

speaking of 915s I have one in the 911 sc donor car I have in the shop...

QUOTE (Brad Roberts @ Feb 22 2005, 10:25 PM)

5th is too short. The engine will be turning some serious RPM's with 50 series tires.

Steve - what size tires are you gonna be running? I have a completely stock 901 tranny and a mostly stock 3 liter. I am running 225 - 50 - 16 tires. The low gears work well and 5th is fine for anything close to legal speeds. I wouldn't want to run at 100+ for very long, but it cruises at 80 like a dream.

QUOTE (Brad Roberts @ Feb 22 2005, 11:25 PM)

I wouldnt worry about the tranny with a stock 3.0 unless you do burnouts with it. It wont last 100k miles... but it will last for awhile.

It can be broken if you like to light 'em up.

My rear tires are 225x 50 x16s...

QUOTE

Steve - what size tires are you gonna be running?

This is important. I had 205/50/15 tires and the first was way too short. Now with 205/55/16 tires it is better.

QUOTE

Be very careful with what you spend on the 901. By the time you are done you could have had a 915 with stock gears configured for mid-engine.

Forget the 901 and chance to 915. That is what I am going to do some day.

QUOTE

speaking of 915s I have one in the 911 sc donor car I have in the shop...

Here is what I would do:

1. Buy the KEP adapter for the 3.0 stock flywheel (this allows you to bolt a stock style 901 pressure plate and custom ring gear to the 3.0 flywheel)

2. Run the stock 901 and save your money for the 915 conversion.

Using the KEP setup on the 3.0 flywheel means you can keep the old 915 clutch components and use them later when you switch the car to the 915. Sell off the adapter ring gear and pressure plate/throwout bearing when you are ready for the 915.

B

We lit up my 225 A3SO4 Hoosiers 20-30 times a month for 7 months last season. Been doin' it for 2-3 years. The 901 is hangin' on, but it's gonna have to deal with more grip this year. I'll baby it...

Brad makes sense. His hiatus done him gud.

Tires spin easy on GRAVEL JP...


B

901s are cheap....break one, find another and slam it in....done it for years....

3.0s and burning it in first gear....weeeeeeeeeeeeeeeeeeeeeeeeeee

I've been running my race car with a 901 for five years. First three years were with a 3.0 and last two with a 3.4. I've rebuilt the gearbox twice in five years - once due to a R&P failure and once due to 4th gear failure. I know I'm probably exceeding the limits of the 901 but they a cheap and plentiful. My gear sets have been A,F,M,S,X and A,F,M,S,Y. Rear tires are 275/45/16 Hoosiers which are about 25.5 inches in diameter.

Steve

QUOTE (Brad Roberts @ Feb 23 2005, 01:30 AM)

Tires spin easy on GRAVEL JP... B

That's true. Those surfaces I run on suck.

I did have the opportunity to run it hard on a good surface.
It just hooked.....which is even more fun
The instructor riding along goes "daaamn".....hay, he's a Boxster guy....whatda' they know

I've heard that torque limit of a 901 with a 6 is lower than with an 8. Makes sense, since each revolution has 3 torque spikes instead of 4. To get the same average torque the spikes would have to be higher. Just something to keep in mind when doing comparisons.

I am fond of A, E, J, Q, X in a 901. Sure it's low, but at 7500 RPM with a 7:13 transaxle in X you are still going 150 MPH.

901 gear ratios....