Three speed swap to four...

[superdave]

  Pardon my ignorance but I wonder... we are working on a 318 car that will be a "Sunday driver". It had a three speed manual transmission and we plan to put a 4 speed in it. Does anyone know if we will need to change the rear end also? As I recall that first gear was really "tall", I have seen a few 383s with a three speed and I could see myself smoking the clutch or tires or both getting things moving with that setup.  

[RUNCHARGER]

It will depend on what your first gear ratio is in your 3 speed. I think they generally have a lower first gear than a regular 4 speed does so it might be a bit harder to get off the line than a 3 speed.  If your rear axle ratio is 3.23 that is generally what was standard with a 4 speed 340 or 383 car.

[Chryco Psycho]

the 3 speed is basically a wider ratio with only 3 speeds not 4 , no need to swap rear ends with the 4 speed

[superdave]

the 3 speed is basically a wider ratio with only 3 speeds not 4 , no need to swap rear ends with the 4 speed

Thank you. Now that I think about it that three speed seemed like they skipped first and you had to start in second or really close to it.

[Dakota]

Just curious - is the drive shaft length the same for a stock 3 speed and 4 speed?

[Chryco Psycho]

I believe so