Can't seem to find the correct length for a 56 3100 short bed driveshaft.. Currently has a long tail 3 speed out of who knows what. It looks like the original 3 speed trans had a short tail ie about 16.5 inches long total length. is the SM420 4speed also a short transmission? Trying to figure out what I need to put a 4 speed truck transmission behind the 283 already in it. The long tail 3 speed looks like it came out of a passenger car and they cobbled up a floor shifter for it. want to get away from that and back to a manageable setup . The current transmission is about 21 inches long vs the 16.5 short truck 3peed and that looks to take a driveshaft about 58 inches long c/l of joint to c/l of joint.. Is this correct. Hoping to find an original drive shaft and not have to have one fabricated the current 3 speed shifter is way to short and in an awkward place . Actually below seat level. Thank You Charles
If you're planning on using the SM-420 make sure you get the yoke that bolts to the trans output shaft and the slip joint that's attached to the front driveshaft yoke. That said, finding a 3100 4-speed drive shaft may be hard to do as most 3100's came with 3-speeds that had a splined output shaft.
Your assumptions are wrong about the length of the stock transmission. The "short" transmission was used in 58 in cars and late 62 (up) in trucks. If your transmission has the long tail shaft and has a rear mount it is likely from a Nova or Chevelle from 64/65. It simply replaced the original transmission and you will probably find it will be close to the year of the engine. There is nothing wrong with that transmission with regard to operation, gear ratio, or performance. The original transmission and/or overdrive transmission is 22 1/2 " from the mounting to the end of the tail shaft. If the floor shifter is junk, find the shift linkage components and convert it back. It looks like you are chasing a problem that doesn't exist. Fred
1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes 1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes 2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans 1947 Willys CJ2A w/F-Head engine
So the original 3 speed was a long one then. Problem with converting back to original linkage is that the steering column has been changed to an Oldsmobile column without shift linkage. Has had some brackets welded to the frame for it and power steering was installed. That part was going to leave. . Was looking at the SM420 as was a top shift and took care of the shift linkage problem. Not finding any floor shift kit made for the 56 truck 3 speed transmission. Biggest problem with current setup is difficult to use as have to reach down to shift and awkward when driving and it is to close to the legs. The column looks good as installed and everything works.
