Delirium
New member
- 7
- 5
- 3
- Location
- Raleigh, North Carolina
Hey y'all, I'm new to the L/FMTV community and wanted to share an interesting story about my experience with the transmissions used in these trucks. There are a lot of folks here with great experience and knowledge that have already helped through their prior posts, so I want to start by saying thank you to everyone that's contributed and posted to share their knowledge here. Between the TMs, manufacturer manuals, and community wisdom, I haven't really needed to do much more than just search and read people's stories. I'm posting this hoping that maybe it will help do the same for someone else, and maybe provide some entertainment for everyone else.
History and Context:
I picked up my M1078A1 a couple of months ago, and planned to drive it down from PA to NC. I had already flown up to take a look at it, and it was from what I could tell in great shape for the asking price so I bit. Had some troubles on the back roads on the way down, a blowout that I had to ride on for 1/4 mile so I could get towed, but the most concerning issue was that after driving for ~15 minutes or so the transmission would start to noticeably slip when starting from a stop light, and occasionally suddenly bang into gear or skip 1st (2nd really, knowing that 1st on these transmissions does not engage in D) and bang into 2nd (3rd) lock into that gear and drop a boatload of codes on me. If I stopped and shut off the truck for a while and cleared the WTEC codes, it would get somewhat better, then progressively get worse as fluids would move around more and the truck would warm up. Anyway, I got it towed home to get rid of the dry rotted tires (dated 2004...) and prepared for some transmission troubleshooting.
Troubleshooting:
Following TMs and advice on this forum, I started with fluid level which was slightly low but close at temp, and I corrected that. Moved on to wiring and modules. Seems the wiring specifically is troublesome. All the electrical components tested fine however, literally everything was in spec both when cold and warm. Things were getting interesting. I cleared the WTEC III codes and did some driveway testing. R, N, D, N, 1, N, R, N, D etc going back and forth in the driveway. A few things would consistently happen at this point:
What I Found:
They say a picture is worth a thousand words.
Hm.. I don't remember seeing that part in the manual
... oh and look it has friends.
Fantastic. I wonder what's in the filter?
Oh good. And underneath?
Great. Let's see if we can count the grains of sand on this beach.
So some drunkard was in here at some point and left this... thing?... inside the valve body and sandwiched it with the separator plate, where it proceeded to bounce around happily until it got stuck in some choice valves while they were in the open position... Other than the big piece on the bottom which was right in the pass-through on the separator plate, the other pieces and valves were all stuck fast, nothing was moving here and it was seriously a pain in the rear to fish these things out. Two valves were stuck halfway open, including the lockup valve. Between a 1 and 10 on the idiot scale, this is an absolute 11. I've never seen such a large and obvious object crammed into such an unbelievably small and critical space in a machine. And the filter being choked with thrust bearing chaff, not really the pot of gold I was hoping for. It's safe to say that fluid movement inside of this transmission has not been optimum.
This leaves me to tonight, posting this and having a laugh while considering what next step might not cost me $9,000. The needle bearings from what I read are likely from the faulty P6 thrust bearing and if that's the case I should be able to get at that without dropping the entire transmission which is acceptable. I'll spend some time investigating, probably pull off the scavenge pump line and see if the screen is loaded with it and that should let me know. Also, as I haven't yet reassembled anything I don't know for sure if the clogged filter and drunken soldier trash were for sure the source of my problem but based on the symptoms and troubleshooting done so far it seems likely. I may still have a roached clutch as well, we'll see. I don't plan on driving it around until I find where the dead bearing is located and decide on next steps. If anyone has any other ideas that would be worthwhile to do while the control valve assembly is still off let me know, else it's going back on in short order.
At the end of the day this is a hobby and like most of you I do this for fun. Sometimes you just have to do things the hard (exciting?) way and start taking things apart, you never know what you'll find. Just remember bad ideas always make for great stories. I hope some of you got a giggle out of this circus, I sure did. More to come here, I'm not through with this thing yet.
History and Context:
I picked up my M1078A1 a couple of months ago, and planned to drive it down from PA to NC. I had already flown up to take a look at it, and it was from what I could tell in great shape for the asking price so I bit. Had some troubles on the back roads on the way down, a blowout that I had to ride on for 1/4 mile so I could get towed, but the most concerning issue was that after driving for ~15 minutes or so the transmission would start to noticeably slip when starting from a stop light, and occasionally suddenly bang into gear or skip 1st (2nd really, knowing that 1st on these transmissions does not engage in D) and bang into 2nd (3rd) lock into that gear and drop a boatload of codes on me. If I stopped and shut off the truck for a while and cleared the WTEC codes, it would get somewhat better, then progressively get worse as fluids would move around more and the truck would warm up. Anyway, I got it towed home to get rid of the dry rotted tires (dated 2004...) and prepared for some transmission troubleshooting.
Troubleshooting:
Following TMs and advice on this forum, I started with fluid level which was slightly low but close at temp, and I corrected that. Moved on to wiring and modules. Seems the wiring specifically is troublesome. All the electrical components tested fine however, literally everything was in spec both when cold and warm. Things were getting interesting. I cleared the WTEC III codes and did some driveway testing. R, N, D, N, 1, N, R, N, D etc going back and forth in the driveway. A few things would consistently happen at this point:
- Going into D would result in either no engagement (rolling backwards down the driveway) or very weak engagement (barely holding itself or creeping at 0.5 MPH).
- Going into R would always work, but:
- When cold, worked fine but needed quite a bit of brake force to stop the truck from creeping.
- When warm, would engage but immediately prompt a 55-87 and lock itself back into N.
- Going into 1 would always engage properly no matter what, and was consistent but also required what felt like a bit too much brake to hold.
- Checking the transmission fluid before/during/after this testing process resulted in worrying results. The level would look good after a few minutes of operation, and at temp would start to drop until the level disappeared off the stick.
- Note: The first time this happened I freaked out and thought the transmission dumped fluid everywhere, but it didn't... so I added a few more quarts while it was running and no matter how much I added I couldn't see it on the stick. The next test session after letting the truck cool down, I lost about a gallon of fluid through the breather. Something was definitely wrong.
What I Found:
They say a picture is worth a thousand words.
Hm.. I don't remember seeing that part in the manual
... oh and look it has friends.Fantastic. I wonder what's in the filter?
Oh good. And underneath?
Great. Let's see if we can count the grains of sand on this beach.
So some drunkard was in here at some point and left this... thing?... inside the valve body and sandwiched it with the separator plate, where it proceeded to bounce around happily until it got stuck in some choice valves while they were in the open position... Other than the big piece on the bottom which was right in the pass-through on the separator plate, the other pieces and valves were all stuck fast, nothing was moving here and it was seriously a pain in the rear to fish these things out. Two valves were stuck halfway open, including the lockup valve. Between a 1 and 10 on the idiot scale, this is an absolute 11. I've never seen such a large and obvious object crammed into such an unbelievably small and critical space in a machine. And the filter being choked with thrust bearing chaff, not really the pot of gold I was hoping for. It's safe to say that fluid movement inside of this transmission has not been optimum.
This leaves me to tonight, posting this and having a laugh while considering what next step might not cost me $9,000. The needle bearings from what I read are likely from the faulty P6 thrust bearing and if that's the case I should be able to get at that without dropping the entire transmission which is acceptable. I'll spend some time investigating, probably pull off the scavenge pump line and see if the screen is loaded with it and that should let me know. Also, as I haven't yet reassembled anything I don't know for sure if the clogged filter and drunken soldier trash were for sure the source of my problem but based on the symptoms and troubleshooting done so far it seems likely. I may still have a roached clutch as well, we'll see. I don't plan on driving it around until I find where the dead bearing is located and decide on next steps. If anyone has any other ideas that would be worthwhile to do while the control valve assembly is still off let me know, else it's going back on in short order.
At the end of the day this is a hobby and like most of you I do this for fun. Sometimes you just have to do things the hard (exciting?) way and start taking things apart, you never know what you'll find. Just remember bad ideas always make for great stories. I hope some of you got a giggle out of this circus, I sure did. More to come here, I'm not through with this thing yet.
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