I have an '89 D250 with a Cummins and 727 3 speed with a bolt on yoke. If the truck sits for a couple of days, I have a pretty bad leak from the splines (not from the output seal). I have been told to use sealant on the splines and torque the shaft. I have a couple of questions though. First I do not think that the nut is designed to torque against the yoke. I think it torques against the raised portion of the output shaft. I believe the yoke is meant to have some movement on the shaft (similar to a slide on yoke). Am I correct in that the fluid level should not reach high enough to leak from the splines? A search of this site shows a post that indicates that there is no check valve in the circuit to prevent the torque converter from draining back to the pan. Is that correct? Where is the fluid coming from that is allowing it to escape from the splines? I have rebuilt several automatic transmissions and never had this problem, however I don't think I have ever worked on one that had a bolt on yoke. Has anyone ever had this problem and corrected it with sealant? Any and all help on this problem is appreciated. Also, there is no leakage at all when the truck is driven daily.

Dodges do have a drain back issue. I would seal up that area. Does it have a nut and washer or bolt and washer?

It has a lock nut with a raised shoulder. It has been close to a year since it initially leaked. I had retired from my job so the truck was no longer used daily, and I went out one morning (after a few days of non-use) and found a puddle. I figured output seal so I pulled it apart. When I got the drive shaft out I could see the leak at the splines. I went ahead and replaced the seal since I was there. One thing I noticed was that after torquing the nut there is still slight movement of the yoke. I do not think there is a washer there behind the locknut. There lies the problem as I see it. All output yokes I have ever seen had to have some movement in and out to offset the flex from engine torque and frame flex from terrain.I could probably add shims to tighten the yoke as long as there is a raised part of the output shaft for it to torque against, but if it came from the factory with the yoke able to flex I would think that I might damage the shaft if I lock the yoke in place. Why is the fluid rising to a level now that it apparently never did before and causing a leak?

it has to have some play in it . also when you let it sit up the the seal probably got hard and when you used it and let it sit and so forth the seal just got dryrotted. does it leak after you put a new rear seal in?

also when you let it sit up the the seal probably got hard and when you used it and let it sit and so forth the seal just got dryrotted. does it leak after you put a new rear seal in?

Yea it still leaks. The problem was never the seal. When I got the driveshaft out I could clealy see the leak coming from the area between the splines and the yoke (the nut that holds the yoke sits in a recess and fluid from the seal could never get there). Since the 727 had a drainback issue from the factory, What keeps it from leaking on a new one?