72 911t with 4spd?

[rogman]

guys i have a 911t 2.4.mfi that is an orignal motor car but it does have a 4sp tranny could this be an orignal tranny??

i ask only because i did get the orignal paper work from porsch and it shows it being a 5 speed but when at that shop i was told they believe it to be the trany that came with the car???? thoughts??

[equality72521]

1972 had a 915/12 4 speed tranny or a 915/02 5 speed tranny. Possibly came with it, Porsche documentation is notoriously inaccurate.

[rogman]

Thanks equality.......i also heard that its possible the 4sp was more likely to be in euro cars vs the u.s. But good to know i guess next step is to pull the numbers off the tranny and see what i can find out from them...

[Christien]

My ROW 72 (originally sold in Germany) has a 4-speed tranny, which is original to the car. Call 1-800-porsche and give them your vin - they'll look up original engine #, tranny #, paint code and options codes. Takes a couple days for them to call you back, but it's free. Then just compare the serial # they give you to the one on your tranny.

It's entirely possible it's been swapped out at some point. When I rebuilt mine, I strongly considered putting a 5-speed in. A used 5-speed is worth a good bit more money than a 4-speed, so someone might have just gone the less expensive route with yours, rather than rebuild the original 5-speed.

[rogman]

will call monday appreciate that!!

[ennisk1]

Fairly uncommon on US cars as the dealers typically ordered with 5 speeds. Kind of like a sunroof in SC's and Carrera's, optional, but most came with it.
However, not out of the question as it may have been "special ordered" without the 5 speed option. I'm also curious to see if it was original to the car.

[rogman]

will find out and post results....

[haycait911]

in 72 the 4 speed was 'standard'. very few found their way into the US as dealers tended to order 5 speeds. four boxes are much more common ROW and Canada. funny, I had a hell of a time finding a 4 speed 915 for my drag car. not easy to come by.

[rogman]

pelicans are great!!!

[coldstart]

My 1972 911T has a 4-speed stock but it was/is a Canadian delivered car.

The final drive ratio is supposedly the same or close to the same. I want to get a five-speed with a higher ratio 5th for comfortable highway driving.

Best of luck!

[french911]

Hi

There is no difference in MPH/100revs between 4 and 5 speed boxes. The pinion to ring ratio is the same at 7:31 and 4 or 5 gear is 29:22 ZA. The big advantage of the 5 speed box is the closer ratio of the gears giving better drieability and climbing ability. Both boxes have approximatly 22.2 mph/100 revs. If they could pull 7000 revs that would give a top speed of 155mph. 5 speed car don't have a higher top speed than 4 speed cars they both top out at around 128mph pulling about 5600 revs. Psychologically 5 speed feels better in 5th.

Barry

[rogman]

great info guys ......

[haycait911]

Originally Posted by french911

Hi

There is no difference in MPH/100revs between 4 and 5 speed boxes. The pinion to ring ratio is the same at 7:31 and 4 or 5 gear is 29:22 ZA. The big advantage of the 5 speed box is the closer ratio of the gears giving better drieability and climbing ability. Both boxes have approximatly 22.2 mph/100 revs. If they could pull 7000 revs that would give a top speed of 155mph. 5 speed car don't have a higher top speed than 4 speed cars they both top out at around 128mph pulling about 5600 revs. Psychologically 5 speed feels better in 5th.

Barry

that's why I wanted one. first in both is the same and top gear is the same in both. my motor has gobs of torque and lightweight so I don't ned the middle gears as much. and I'm lazy, shifting is work. and when drag racing I can eliminate one shift I also heard that first is stronger in the four because it's on the main shaft?

[Christien]

I've heard the top gear is the same in both, but are we sure? When I'm in 4th gear at 100 km/h on the highway (62 mph) I'm at about 3900 rpm. At normal highway speed of 120 km/h (75 mph) I'm at 4200 rpm. Does that sound right for 5th in a 5-speed box?

[rogman]

not sure im following the math if your getting 75mph at 4200 revs anorther 1400 revs takes u to 5600 and in doing that math at 22.2 mph per 100 revs you be going 300 miles an hour....lol let barry help us with this caculation...

[TimothWinter]

i also heard that its possible the 4sp was more likely to be in euro cars vs the u.s.

[rogman]

the 5sp was for sure a u.s. demand as it was pushed by salesman to be better lets face it thats how they sell cars....quite honestly the 4 spd makes more sense to me unless that 5th gear offers higher top speed or lower rpms for fuel burn but after reading some of these very insightfull posts that dosent seem to be the case.....i am just anxious to get back home from this tripp to pull a number off that tranny!!!

[gptom]

When I ordered my 72T, the 4 sp was standard & the 5 sp an option. The top gears in both were the same ratio, just more steps in between to keep revs happy

Tom

[Matt Monson]

Depends on the year. A '72 4spd is geared differently than a '73 4spd:
Type 915 Transmission

[tharbert]

I have a US 72T w/ 4 speed. I'd go to 5 speed for an even swap but wouldn't consider spending money to change.