Hey everyone, I got a problem on my dad's 85 300sd. My oldest brother drove the car and ran it low on fluid with a leaking front seal over 2 years ago since his pickup truck was broken and it took out 4th gear, he complained about it sounding like a jet engine under the car, what a moron. So the car sat for awhile and it got driven around my community since it was a 3 speed now, it would just slip horribly and not go anywhere in 4th gear. Me and my two buddies did a transmission swap and the donor transmission was given to us by a reputable form member and we were told it worked great on the car it came off of. Now this is where everyone is going to roll their eyes probably but, the transmission got water in it somehow, so there was an atf/water mix in the transmission and we drained all gunk out since it sat for "a while" and cleaned the inside of the trans with brake clean. We also used some wd40 to try and sop up any leftover moisture, but after we cleaned the pan and the exterior of the valve body we went after the front main seal and oil pump seal since the water probably ruined those. Water is heavier than transmission fluid and thus it all piled into the bottom of the pan and lower valve body, when we drained the torque converter it was perfectly clean with bright red fluid and with the front oil pump out it was almost spotless clean, so I am assuming the water never reached the clutch packs just the pan, filter, and valvebody. Anyways after our cleaning fiasco, the reinstallation of the transmission was pretty easy however the problem came along when we went on a road test today. After making sure the fluid level was perfect, we drove it around and found the transmission has no fourth gear, it will lurch forward trying to find fourth gear and will decelerate. I can drive around in 2nd and 3rd perfectly fine but it just wont shift into 4th gear. I spun the bowden cable all the way in to give the cable maximum slack just in case it was binding up, but to no avail. I drained out some of the fluid just to see what it looks like only to find it looks like pepto bismol, I added more fluid to make the fluid level at the maximum again in case I need to move the vehicle in my driveway but I am at a loss and am reading Kent Bergsma's manual on automatic transmissions. After a little research, I found that the pink color of the fluid is from moisture (water) in the trans that we didn't remove and it diluted the fluid. I also want to point out that the transmission is strong when its in gear and when its shifting into gear. It doesn't take more than 1 second to shift into reverse or drive and with my foot on the brake you can tell the car wants to move. My question is where do I start diagnosing? I would assume the vacuum to the transmission and the hydraulic pressure within the trans would be wise, I don't think the transmission fluid will affect the shift into 4th since I have 2nd and 3rd, I may be wrong but I do know it needs a fluid change until the fluid is bright red like its supposed to be. As a last resort, we have a spare valve body from a transmission out of a junkyard that had bright red and clean fluid, so if the valve body is clogged or something is rusted shut I can swap the valve body and use a new gasket from the complete gasket kit we have. I know this transmission will be a headache from the water that is in it, but I don't have a choice the car needs to run and drive correctly since it will be getting sold by the end of the month to a family friend who is in need of reliable transportation. Any thoughts appreciated