What would cause a 4R100, when drained thoroughly, but not rebuilt, to need to run through the gears to get the direct drive clutch fluid path to operate? Meaning, the tranny sat several weeks with the valve bodies off, just sitting in the garage. After finally getting it back together, it seemed like it didn't want to pickup fluid for the direct clutch, as I did not have high gear, nor did I have reverse until the engine was revved up to maybe 2200-2500 rpm (in D with the rears up on jackstands). Do I have an early indicator of something else failing? The trans has 375k on it and has always done really well until a couple of months ago, when it slipped on easy acceleration in the forward gears. I brought it home, parked it and after researching the problem, I found the likely issue to be loose feed bolts. They were loose, and in the process of tightening them, I got the flu and Christmas happened, so the truck sat for a long time waiting for me to get back to it. After it seemed to pick up the fluid and the trans started working as it was before the feed bolt issue, it now seems normal and seems to go into reverse immediately, like it's always done.

Thanks for the help and advice/info.

 

So after getting the fluid to pick up (see above post), I've been driving the truck without any further issue. It works just like it has for the last 375k miles. I've got maybe 500 miles on it so far and it runs as well as a 375k mile vehicle should run. They trans immediately drops into forward or reverse as soon as it's selected.

 

What did you do to prompt the fluid to be picked up?

 

Nothing other than put her up on jack stands, put it into drive and rev it up a little. It went into drive fine, but took a little time to get past 2nd gear. I maybe got to 2300 rpm in 2nd, sat there a little bit (maybe 15-20 seconds), then it went into 3rd and on up the rest of the way. After that, it would run through the gears just like normal. Mine, on easy acceleration, will rev up to about 2000 rpm and change gears. So as I slowly increased the throttle, it would go into a gear, run up to 2000 rpm, and change into the next gear, all the way up to 4th and lockup. I didn't have to get extreme with the throttle, just it seemed like it had an air lock or some type of disappearing blockage that prevented the fluid from easily filling all the passageways. So easing it up in rpm's allowed her to eventually pick up the fluid and work like normal.

As an add-on, I did not do anything to anything else in the transmission. The cooler is stock, the lines are all stock, I put in a Sonnax and tricumulator when it was newish (maybe 25k miles on her) and she's run that way for the rest of her 375k miles. I should probably do the 6.0 cooler, but I may postpone that until the tranny fully dies and do it then.