'94 4L60E won't move until restart

[riccnick]

I have a 94 K1500 that has been pretty reliable and is used mainly as my Plow Truck. I don't beat it and I go as gently as I can, although I do have a long driveway, and we do get some good snow. We bought the truck with 133,*** miles on it, used it one year, and then my younger brother cooked the transmission when the serpentine belt came off and he overheated the truck. Transmission was replaced with a re-manufactured unit to the tune of almost $2,500, by a local shop here in Westfield. That was at 134,*** miles. Then the torque converter shaft snapped and they replaced the torque converter with a "Heavy Duty" one under warranty, still at 134,*** miles. It has since worked perfectly, until now. The truck is at 142,8xx miles and is doing something I cannot fathom, nor can I find a similar case out there online. When cold, I can start the truck and drive completely normally in D or R (switching back and forth if I need to) for about five minutes. Then suddenly, when switching gears (doesn't matter what gear you are in or going to) the truck acts like its in Neutral, but with a slight transmission noise that is hard to hear if you're not listening. I can play with the shifter all day long and it will act like its in Neutral until I restart the truck. Then once the ignition is cycled, I can select whatever gear I want, start to move, and drive fine until I want to switch again. Then I have to restart the truck in order to switch to another gear. I pulled the pan, and the fluid looked fine, and there is a little bit of gray material in the pan, I'm assuming from this "slipping" or Neutralizing that keeps going on, but nothing that looks catastrophic. I have tested both the A and B shift solenoids, and removed the Pressure Switch Manifold and checked that for damage or debris. I have not re-installed the pan or refilled the transmission yet because I don't believe my problem will be fixed with just a simple fluid and filter change. I have read every single article I can get my eyes on, and I have seen and read the "30 Most Common Failures" lists what seems like a million times. My truck is NOT and OBDII truck, so I cannot just plug in a reader and see what's going on. I did "pull codes" and got the normal Code 12 which indicates its in diag mode, but no other codes flash. This transmission only has roughly 8,000 miles on it, and started doing this without any warning. I am pretty familiar with working on vehicles, so I know what a slipping tranny feels like, and this transmission exhibited no signs of shift flare, or slipping, or any sort of malfunction before this. I was about three hours into plowing my driveway when this happened all of a sudden when switching into Reverse. Sorry for the book, just trying to give all the correct info. Any advice / help is greatly appreciated!

 

[riccnick]

Nobody? Im going to put the trans back together tonight and see if it will start working again with a fresh filter and some fresh fluid
-Nick

 

[RyanMerrick]

Welcome, I wish I could help, but I have a manual...

Nice Bronco by the way

 

[98_k1500]

I also have a manual, but the reason i have one is i broke ALOT of these automatics. I would suggest maybe testing continuity between the trans case and - battery cable (make sure the trans case is properly grounded, this was an issue with some of these trucks, did not cause what you are describing but may be worth a shot) and be sure the trans fuse is staying hot. Outside of that, the only thing the truck is changing when you turn it off is dropping the line pressure down to 0. (unless that is whats causing it to have no forward/reverse gears) If that is the problem, if you turn the key off and back on quickly (not letting the truck go dead, just for a split second, it should not have any effect on the trans situation (it should still act like its in neutral). First thing i would suggest testing is the line pressure with a gauge. That should point you in the right direction. Never head of one doing exactly that tho, strange issue. Keep us updated with what you find and feel free to ask anything else you may need to know.

 

[riccnick]

Thanks for the responses guys. So I have the truck working again (I think). I pulled the pan, cleaned out the pan and magnet, pulled the Pressure Manifold Switch and cleaned that, re-installed with a fresh filter and gasket, and topper her off with fresh fluid. Drove around for a half hours Saturday night with no issues what so ever. Tomorrow I'll put the plow back on and clean up the driveway and see how she does. Not sure if it was a fluke, or if this fix is only temporary, but we'll see.