Salvatorparads

Hey guys, i recently bought a 1989 E350 Box Truck with a 7.3L diesel IDI and C6 transmission. I had it in for a basic transmission service, new filters, new fluid, bands adjusted. After I got it back I found that it leaks fluid at what appears to be where the output shaft from the transmission meets the drive shaft at or around the universal joint. It's odd, it doesn't leak at all when totally cold. Doesn't leak at all when truck is running and hot. After I drive for awhile, shut off and truck cools down for about 2 hours, a drip, drip, drip drip starts at this spot. About 1 qt will come out before it stops. What the heck could this be? An O-ring there gone bad? Could this have been caused when they serviced it, or just coincidence? Here are a few photos:

jwko

Hi and welcome for the forums. Its more than likely the rear seal (Extension Housing Seal) that's leaking. Its a common issue and a pretty easy fix. Unbolt the drive shaft from the differential (if its a two piece drive shaft also unbolt the carrier bearing from the frame), slide the drive shaft yoke from the tail shaft of the transmission. Pry out the seal and in with a new one. I believe there are two different seals so you might as well take the old one it to match up to the new one. Also, if you'll jack up the rear of the vehicle you will minimize fluid loss when you remove the yoke from the transmission.