Three speed to four swap

[CichliDart]

Hello,

I have a 71 Slant six, three on the tree manual. I also have a 4 speed to swap into the car.
The 4 spd is in storage other wise I would take a tape measure to it.

What I really want to know is if I need a new driveshaft.

The 4 speed is from an a body.

Thanks!

Mike

 

[yellowdart72]

if you are keeping the same rear end in place then you can use the same driveshaft but you need to change the slip yoke from the u-joint. The three speed uses the 904 slip yoke and the 4 speed uses the larger 727 unit. but with the right u-joint combo they interchange and you keep the same driveshaft.

 

[Double M]

Check your 4 speed trans first before you change the yoke. 1966 and later A body 4 speeds came with small and large output shafts according to application.

Russ.

 

[chryslerfat]

Yup the 66 used a small yoke and so did the OD 4 speed the others used the same one as 727 as far as the trans. same length and if your bell is drilled for both it will bolt right up same clutch and all.

 

[CichliDart]

Thanks chryslerfat, Double M, and yellowdart72.

The car eventually will get a rear end upgrade to 8 3/4 or 8 /14. For right now I want to see what I can get away with as far as driveshaft. If I recall I will probably need a different driveshaft if I swap in the 8 3/4.

The trans is a later model over drive unit. I bought a bellhousing for a slant that can fit the four speed as well as 3 speed unit. It would be nice to have a larger clutch than a 9 1/4 :hmph: but I will work with what I have for right now. I understand there is another factory bellhousing that will accomodate a larger flywheel but it as well as the aftermarket one are out of my price range right now.

Normally I would not worry about a bigger flywheel clutch combo, but eventually I am putting a small turbo on this slant and want it to hold up.

So far I have a 4 speed shifter hump for the floor board for the swap and the trans came with an inland shifter. I have never used one before, my four speed challenger had a hurst shifter. I suppose I can adjust, shim, or lubricate the inland before I install it.

Any idea if this shifter will work with a bench seat?
The factory green bench seat is in really good condition, no rips or tears.

Thanks for your help guys :cheers:

Mike

Yup the 66 used a small yoke and so did the OD 4 speed the others used the same one as 727 as far as the trans. same length and if your bell is drilled for both it will bolt right up same clutch and all.

 

[Woods74]

Even with a turbo, Your rear end will be fine. The shifter location should be fine, seeing as it was designed for these cars.