1967 Driveshaft

[jmsdell82]

Hey guys,
I have a 67 mustang fastback
A 4 speed transmission conversion was done but now the driveshaft is too long. The place that has it is saying the driveshaft is a step down meaning the diameter/ujoint at the rear is smaller than the front.
I am looking for a new driveshaft but im not sure how to get one with this step down feature. Is it required that it has a stepdown or will a solid 3in shaft work?
If it will what joints do i need at the end?

Any help would be nice, every step of this process has been a headache.

 

[horse sence]

First of all is the front u joint the same as the rear u joint? It should be ,unless you have a 64 1/2 4 speed .The 65-70 Small block 4 speed is a 28 spline output shaft ,but the 64 1/2 has a 26 ,it think it is rear shaft spline size.
67 drive shafts were the first to use a press together drive shaft with a rubber coupler for vibration but even that had same size joints front to rear . A step down shaft is not correct for 67 but will work if the correct length and u joint are the same front to back. Next question is what rear end is in the car 8 inch or 9 inch they may have the wrong yoke and had to make a drive shaft . Do you have a measurement for your drive shaft ? I have a 67 shaft i will measure and get back to you .
There is another possibility ,it could be a Torino 4 speed ,they are longer than a mustang 4 speed . Can you get a length measurement from the front mounting flange to the end of the tail housing of your 4 speed ?

 

[horse sence]

Well the pics didn't turn out real great but ,this is a 67 early drive shaft .It is the one piece shaft and has the same size joints on both ends .it measures 50 3/4 inside of cap opening to inside of opposite cap opening , it does not have a step down .

The measurements on the 4 speed is 24 inches from the front of the mounting flange to the end of the tail housing ,not the shaft .

 

[jmsdell82]

Thank you for the response.

I figured it was the wrong one because i went on mustangtek and found the right information for my year. The guy who had the car before me must have put a different drive shaft on the car.

I am just getting one made with the correct u joints so i can get the length i need because the transmission/yoke make me about 2 inches too long.

Thanks again for the helpful response and pictures. Thought i was going crazy!

 

[7991LXnSHO]

Good call on just having the right one made. Cutting it down would have been another option.