901 Transmission & 210+ HP

[jhora]

Factory 911R and 914-6 Race Engines rated at 220HP had 901 transmissions...as mentioned good clutch and no burn outs...they do just fine...

[kenikh]

Strengthen the 901 (side plate and int plate), good clutch, no burnouts (no Porsche tranny drivetrain that) and you should have no problems.

I have more HP than that and have never had a problem.

If it is a mag 901, yes. If this is your factory 901 for the 67S, it will be aluminum; no need for an aluminum side and intermediate plate since it is already all aluminum!

[RSwannabe]

John,

I've been running my stock 901 mag cased tranny with my 2.8 for over a year now with no problems. In its current state of tune my 2.8 makes about 220 HP. I use a centerforce 215mm competition clutch which holds the power with no problems and has light effort and really good feel. It is a perfectly stretable clutch that I highly recommend. Like everyone says, just go a little easy on 1st gear, and other than that you should be fine. I used to beat the #$%# out of this tranny, including 1st gear, when the car still had the 2.2S motor and it dealt with it just fine. That was a STRONG 2.2, making 172hp at the wheels. So while I do not stomp on it in 1st with the 2.8, I don't baby it either.

I'm about to bump the power of the 2.8, so I'm looking for a strengthened/reinforced 901 with alunminum intermediate plate and side cover and an LSD (by the way, if you're running an LSD, that will stress the transmission more as well). I don't think it is absolutely necessary, but it will be good for peace of mind for those 3,000 mile road trips down to Treffen when it gets flogged pretty well.

Brooke

[JohnT]

John,

I believe there are big issues getting SWB driveshafts to mate with 69 or later (LWB) transmissions. I understand this is a major project involving changes all the way back to the differential side gears. (though I have been mistaken before )

Unless you change ratios, 4th in a 4 speed is the same as 5th in a 5 speed so one would not see any difference in top speed.

johnt

[Bruce M]

With all transmissions max HP is not the question.

The problem is too much torque. I believe the stock 901 box is good for around 200 ftLbs max. Any more than this and a 915 is a safer option.

Don't forget that a highly strung race motor may have over 200HP but it is likely that the peak torque is less. However an upgrade to a later larger engine could cause problems even if the HP was in that ballpark.

As everyone has said, don't try a drag start with a 901 with any engine or you'll break it.

[preS]

With all transmissions max HP is not the question. The problem is too much torque.

Exact. That is what my experiences are.

Richard