PeachParts Mercedes-Benz Forum - View Single Post - 722.4 transmission now shifts from first to fourth

mach4 · #42 01-19-2013, 11:02 PM

I thought I'd close out this thread with a description of the solution that I went with. I decided that the transmission was bad and needed rebuilding or replacing. I opted to replace.

I had a spare '83 617 with a 722.315 of unknown condition sitting in the garage. I also had the original engine from the 380SL with a known good 722.312 transmission. I thought long and hard about trying the gasser transmission as a test, but in the end chose the safer option of the diesel transmission even though it was a junk yard unit and untested.

I pulled the engine and transmission, swapped transmissions and put the combination back in the car. I was also able to eliminate my NSS pigtail and, by using the tailcone from the 380SL transmission, I was able to eliminate my variable reluctor bracket from the external speedometer pickup and use the stock mount in the tailcone.

Wow, what a difference. It was like a different car. I also swapped in the new filled motor mounts with the softer urethane and eliminated the filled transmission mount at the same time so the elimination of the vibration problems helped a lot.

Initially, the new trans did have the annoying 2-3 and 3-4 flare, but only under very light load. I put a pressure gauge on the modulator test port and found it was reading about 2 pounds light. After turning up the modulator to the 42 pounds spec, it now runs absolutely perfect. I am running the blue vacuum transducer from the 722.5 transmission and it appears to be running just fine. I may try eliminating this as a test in the future, but for now, it's just fine.

At first the transmission leaked fluid like crazy. One problem was a bad cooler flex hose that just decided to start leaking and the other was a leak around the cooler lines banjo fittings. Swapping out the hose and reseating the banjo fittings took care of the leaks.

Thanks to all for all the diagnostic help with the 722.4xx problem.