A while back I asked the standard length of a drift shaft for a 1970 Plymouth Satellite with a 318 and a 904 torqueflight tranny. I was given 55.47" The weather has been rotten (till now) and a lot has happened this past fall (Mom passed away) so I'm just getting back to trying to replace my drive shaft. Since the weather has improved, I rolled my car out of the garage last evening to measure the shaft. It always looked about an inch and a half too short. It drives fine like this, but I know it isn't right and I don't get on it because of this. I'd like it to be right. I measured the length and it was 55.5, which surprised me. See the attachment. You can see that about 2.5 inches of the slip yoke is showing and that's too much. I'm assuming it should only be about an inch. Given that the shaft measures 55.5 inches from the centerline of the front u joint cup to the centerline of the rear U joint cup...and given that the called for length is 55.47", I was thinking, "Well, maybe I have the correct drive shaft..but that can't be given that too much of the slip yoke is showing and not enough is in the tranny. So, my uneducated question is, "Can I assume, based on my measurements and the picture, that I can tell Cincinnati Drive Line (I'm close to them) to make a drive shaft that is 57" (an inch and a half longer than current)?" Or, am I missing something? I probably am. I'm not good at this part of the repair...still learning. Thoughts? Thanks.

stands under the rear axle/not the rear subframes so the springs/axle is loaded (& you have room to work). Front jacked up roughtly the same amount. unbolt rear ujoint. shove the yoke in all the way in the trans. measure C to C. subtract 3/4". give that dimention to the shop. That yoke ain't in far enough. Mine was not that far out & I had a part time vibration problem

I'm looking at the picture of his drive shaft, and see there are several "clean" places on the yoke. That would indicate to me that drive haft often runs much farther inside the trans then the current picture shows. My concern is if you have a new shaft made, (they can't add to your existing shaft) it will bottom out at some point, and that would be as bad (or worst) then not being in far enough.

When your picture was taken, how are you lifting the car? If you are unloading the rear suspension, you are not getting a true picture of where your drive shaft is normally riding. If you are jacking up the body and the rear axle is hanging, that may be as far as the shaft comes out of the trans, and that would be OK (unless your offroading and lifting the rear tires off the ground a lot.)

Disconnect the drive shaft at the rear axle, and push the driveshaft into the trans until you can't see the "clean" part anymore, and measure how far that is from bottoming. Then get back to us. Gene

that shaft (or at least the yoke) has recently been somewhere else (shiney/no rust). When I had my part time vibration problem the driveshaft shop said they could not lengthen it (but can cut one down) so I luckily I sourced another one ~1" longer in my stash & swapped ujoints/yoke & all good

Thanks all. I had the rear wheels on the ground under full weight. I jacked up the front just enough for me to get my chest under the rockers so I could reach in and measure/take a picture. I get what you are saying about removing the rear of the shaft and pushing it in to the tranny to see what type of play there is. I will do that shortly. Thanks again. Chris.

That would look a lot different if the rear seal had the boot on it. It probably had one in the past. Which could account for the clean areas on the yoke, too.

Personally, if there is no vibration issue, I would just drive it. A 318 and (assuming) street tires will not put a large load on the drive train.

With the seal change this makes it look incorrect. The spline sticks out about 7/8"-1" from the end of the case. I think I'd leave it alone too.

Thanks yall. It has been driving fine, but when I rebuilt the engine, I had the tranny rebuilt and the guy (old time Mopar tranny guy) suggested it was too short, fine as long as I didn't run it down the drag strip hard. I have been driving it like that with no issues at all up to 75 mph on the hwy. Since I had it repainted this past fall, I was hoping to go on some longer trips and thought I'd cover every base and get one just the right size, but I wonder. What do you mean by the "seal change"? Thanks! Chris.

The seal at the back of the trans is not the same design as the seal the car would have originally come with. The original seal had a rubber dust cover on the back of it. Without that extra piece of rubber on the back, the driveshaft looks short. If that rubber piece was on the seal, the shaft would look the correct length.

burdar...got it. I was thinking that the dust cover was back by the rear housing and since mine never had one since I purchased the car seven years ago at the rear of the tranny, I didn't realize what he was saying. I do now. Thanks for clarifying. And, it makes perfect sense. Anybody have a picture of what the dust cover looks like? Thanks again everyone.

The factory slip yoke dimension is 3 5/8" from the rear of the tailhousing to the center of the u-joint.

Thanks John!