700r4--what happened?

[jaredts]

I put a 700r4 in my truck about three years ago and haven't had any issues until a few days ago.  Drove about 30 miles down the interstate on a really hot day and pulled into a gas station.  When I came back out the trans would barely hook up in drive or reverse--just a bunch of slipping.  I checked my fluid and it was not even on the stick!  This thing has never leaked a drop and drove perfectly.  I added four quarts of fluid before the level was right!  There was oil splatter all over my tailgate but after adding fluid and starting it there were no apparent leaks.  It hooks up fine with no slipping but won't shift into second.  I get it towed home.

Hook up a gage today to troubleshoot (although I'm really just about to yank the transmission).  Start the truck and the thing is at 125psi and pulling the tv cable doesn't change the pressure at all.  I yank on it several times and finally it drops to 85psi (where it always has been at idle).  Using the gage to be sure, I reset the tv cable and drive it down the road.  To my surprise it shifts perfectly, but it won't go into overdrive no matter how fast I go or what I do with the throttle.  So, what happened and is there any hope of getting overdrive back without pulling the trans?  Will it hurt it to just drive it like this and forget overdrive? Obviously I have nothing to lose.  With my 2.73 gears having no overdrive really isn't all that bad.

[VileZambonie]

Sounds like your t-case input seal is shot and is drinking your trans fluid. Pull the check plug, if it comes spewing out you know that's the culprit. You will need to replace the t-case input seal.

Correct the fluid level in the transmission and re-adjust the TV cable. If it behaves correctly you'll be fine.

[jaredts]

this is 2wd--sorry I didn't mention that.  tv cable is correctly adjusted and fluid level is good but I have lost overdrive.

[1967KaiserM715]

How's your coolant look? It's rare but if the radiator intank cooler is busted, it is possible for the oil to push it's way into the radiator, but not allow fluid back to tranny.

It may also be worth it to get some UV dye, just to make sure you haven't lost any seals.

Sent from my SM-S920L using Tapatalk

[jaredts]

I checked the coolant--I've seen that problem.  It looks bright green with no oil.

[VileZambonie]

So it doesn't go into OD or it slips when it shifts into OD?

[jaredts]

Never shifts into od. As if I had it in 3 instead of D.  Not sure about the other gears, but when it gets into 3rd gear and I let off the accelerator the rpms drop down to idle.

[VileZambonie]

Readjust the TV cable and check the governor. Pull the governor out and inspect, make sure the valve moves, the gear looks good. Clean it with brake clean before reinstalling it.

[square81]

My 700r4 had no 4th gear. Found the 2-4 servo piston seal had dried out and split. Replaced both seals and retested the pressures. All was good.