okay here is the deal. I have a 97 PSD auto with 157K on it. i have been having transmission issues off and on for a couple of months. I have no clue what it is. Some times it will drive just like it should and others it will shift late and hard from 1-2 and then early from 2-3, 3-4, 4- lockup. I was getting a code for the VSS i replaced it. no change sometime it was fine other times see above. more recently the TC will not always lock up when it should and sometimes it will unlock driving down the road. I am thinking something electrical.
yesterday is change the fluid in the rear diff and inspect the tone ring, fluid is a little dirty tone ring seems fine, clean the vss and put it all back together. check all the brake lights find that the sockets for the 3rd brake light are burnt (though it still works.) swap with one from my other truck. I took it out today and it drove fine for 8 miles then it had the problems it has always had shifting hard and late then early with a flashing OD button. then it got worse hunting for gears not upshifting TC locking and unlocking randomly (sometimes manually shifting solved the shifting issues). got to where i was going turned it off. when i left it drove fine shifting when it should hav the TC locked up like it should. then once i hit about 60 the TC unlocked then relocked a couple times then settled in. as i came to a red light and took m foot off the gas the truck slowed down with the TC unlocked then the TC locked back up then unlocked.
What could the problem be? bad solenoid pack? bad TC? something else? i'm not against rebuilding the trans if i have to, but if there is another idea i'm all for it.