I have a 68 Dart that needs a longer drive shaft..383 with a 4 speed... I inserted the yoke into the tail shaft but it doesn't bottom out, and I assumed it would and then I would pull it out and measure 3/4 of an inch to get the exact length needed..The yoke is 6 1/2" -just thought it would bottom out.. THANKS

You mean it is bottoming out solid into the trans but there is still some length left (like it should go in there further)? Different yokes have different lengths so I think you are good here. As you know have the rear suspension loaded before you take your measurement & if needed this'd be a good time to check angles.

The end where the U-joint is bottoms (hits the seal) and the front of the yoke doesn't make contact with anything..

There are other ways to order one also... some places want the length from the end of the output shaft. I just push it in all the way til it pushes the seal and then back out 3/4".

Are you sure that the yoke is the right one? Correct diameter and spline count?
The 727 and non trunnion 4 speed use the same spline count.

What year is your Dart and does it have the A body NP833 trans in it?
I have a 1969 Dart GTS original 383 4 speed car that I have two original drive shafts for, one is for the 7260 pinion yoke and the other is for the 7290 yoke.
I've had a lot of drive shafts shorten for some of my old street and strip cars, push the tranny yoke in all the way until it is bottomed out on the output shaft on the tranny,(that will probably push, crush the seal up some, no big deal on that ) then slide it back towards the rear end 3/4 of inch with suspension loaded like it would be on the road. Use the center of the U joint on the tranny yoke to the center of the pinion yoke for your drive shaft length

hi tm, your 68 + 69 dart 383 4 speeds use a 7290 joint, 51.53" , 3" dia part # 2852 212 shaft. how about a stock dodge b body 383-440 8.75 shaft. same 7290 u-joint ,52.07" long , and 3" diam . part # 2852 162. I know I have extra lengths kicking around just for this reason. do you have 51.5" between center to center on your joints? ronnie

The dart was a GT born with a /6 auto..Previous owner had a GTS donor for some parts.I replaced the 383 and am using a tubular K frame with a 66-67 383 which had a different style motor mount that may have moved the engine ahead a bit and that is why the shaft needs to increase the length.. Getting some good info from all that responded..Thanks so much..

The 3/4"-1.0" from bottom is an old rule of thumb, not gospel.

The factory shows the position as 3 3/4" from the end of the tail housing to the center of the u-joint with the car at curb height. This allows clearance for the seal dust boot if used.

I will defer to others for the final word on this but I think you are OK.

The picture says it all-Thanks again to all and MOPARTS

I would just use the PDF sheet from Doctordiff and measure it correctly and then go ahead and order it from him.
You will not get a better shaft for the money

Gus

I'm about to order my second one from the good Doctor.

you won't get "SHAFTED" [] from the good doc !