Th 400 tranny question

[Sierra sin fin]

My 85 GMC has been having some transmission problems. My TH 400 transmission has 140k miles on it, the engine 60k. This summer it started occaisionally taking a few tries to get into park- I would put it in park and the truck would move with a clicking sound. A try or two or three would soon result in a slight clunk as park engaged, then that three ton plus some truck would stay nicely in place. I took a look at the linkage, and as nothing seemed ready to fall off, I chalked it up to a worn linkage. Not the most thorough troubleshooting. It has been leaking fluid of late, and I see a drop of anti freeze on the bottom of the flywheel cover (anti freeze goes down slowly). Recently, on a hill, it just was out of gear when I went to accelerate. Not a trans mount or engine mount problem, I think, as there was nothing as I touched the gas. It had magically gone from drive to neutral, it seemed. Some fooling with the shift lever got me going after a few stressed moments. That has gotten my attention. The fluid was really low, which was funny as I had added a pint a few days before. A quart seems to have stopped that problem. My next planned step is to adjust the linkage and maybe replace the half moon bushing (not sure where it goes yet-just found out about it on the phone from the local Chevy/GMC parts dept ) and I am considering adding a bottle of the Lucas transmission renewal stuff they sell at NAPA.

My questions are these: Has anyone had this sort of problem? What was it? What might it be? And has anyone tried the Lucas additive? Did it help? Do I seem on the right track? What else might I do?

Thanks for reading,
Dave

[cableguy0]

the outer linkage probably isnt going to do you any good. it sounds to me like the parking paw isnt being engaged inside the trans if its skipping and then finally locking in. the clicking sound is the parking paw bouncing in and out of the holes in the shell. if you drop the pan the stuff im saying will make sense. it sounds to me like that linkage inside is loose. the antifreeze is either leaking from a freeze plug or the head gasket to be dripping off the flywheel cover. You also need to locate your transmission fluid leak. clean everything off really well and then take it for a ride to see where its leaking from when you get back

[54Caddy]

the antifrezze may be coming out of a rear frezze plug that has a slow leak, the frezze plug is behind the flexplate one on left side and one on right side, the clunking noise in your transmission is just the parking gear engaging once it has caught onto the parking pawl inside of your transmission, as far as it slipping out of gear and going into neutral i have no clue you mite want to check and see if your collum lever isnt saging

[Sierra sin fin]

Thanks for the quick replies, I will follow your suggestions and do more detective work.

Dave