Porsche 5 speed conversion
 

what are the limits of the porsche 5 speed? I was told a 914 could be used by flipping the differential or the 901 as is. I was thinking of upgrading the early straight axle to a 5 speed to help keep up with traffic on the freeway. I am running a 310 hp turbo type 1 engine and keep killing trans cases. I thought to upgrade to the 6 rib bus trans but after all the conversion and upgrade pieces it will be over 5K. To go with a berg 5 speed type 1 box its about the same but not that strong. Will a stock porsche hold up to the power?

BTW I keep hearing about the "horseshoe" in regards to the porsche trans, could someone ellaborate?

thanks

is there anyone here that actually works on the porsche transmission that could shed some light on the questions? I think it would be the same question if someone was putting a 5 speed into an early 356:eek:, I would never do it but to a vw it would be an upgrade.
Thanks

cannot help too much though the stock 901 box is able to cope with around 200hp look on www.shoptalkforums.com as they have heaps of info and very active forum users.

cheers Michel

what is the 5 speed going into? We had to do a bunch of mods to our 5 speed trans to deal with 325 hp race motor. The stock teeth don't hold up very well, and you have to deal with the heat, ie a trans cooler.

My old '57 v.w. bug had a 901 5 speed and 2110 / 125 h.p. motor. My '68 crewcab has a 3.2, 250 hp, '84 5 speed trans w/7:31 r&p. The 5 speed makes a great up grade to the bug and bus. The newer 915 trans are much beefier than the early ones. Swapping out the stock 8:31 to a early 7:31 gave it a much better bottom end. Less money than custom gearing. However with the h.p. your talking about you will probably need to go with a stronger aftermarket gear set.

With that amount of power on tap, you'll need to beef up a 901, or fit a 915 gearbox which would likely require cutting the torsion tube. I've heard of 914-V8 outlaws using 901's behind Chevy, and Porsche M28 engines, so it is possible to make it handle the power, but it may be more cost effective to use a 915. The trade-off with the 915 would be modifying the critical rear torsion tube by cutting the center section away for the gearbox to fit through, and bracing it from underneath the chassis, plus having to modify the body for the taller front section of the gearbox.

In my '73 Super I put a 914/901 gearbox along with a Type 4 engine that makes around 160 hp. The benefits of a 5 speed are worth the trouble. The conversion was easy for me because it was all stock parts made for a 914. I had to remove the gear stacks, and flip the diff. Checking and adjusting the backlash for the ring, and pinion took 3 tries, and 4 gaskets, but was not hard to do.

There's also a wealth of info on www.germanlook.com, as well. Search the forums for the username "Wally" regarding the 915 install in a '75 Super, and the technical article for a 901 install on the main page.

With all that power and torque, you'd be better off beefin' up a 901 4 speed. Besides not needing close ratio gears, you won't have to be sacred of ripping the teeth of that dogleg 1st gear