Hey guys, I'm troubleshooting an issue on my 2002 F250 with a V10 and the 4R100 transmission. I thought I had this locked down and was going to fix it this weekend. Weather is preventing that, so I was doing some more road testing and now I think I am off on my original diagnosis. If anyone has some opinion on what I am seeing, I'd appreciate it.

Truck:
2002 F250, V10, 4R100, 2WD
280k miles
Original transmission and converter
Maintained religiously
I got stuck in the sand a few weeks before all this started and it was an ordeal to get out. I think I might have finally pushed something past it's limit.

Symptoms:
After warmed up to operating temp
-Torque Converter shudder/rumble strips around 35-45mph that clears up once converter locks all the way up
-Occasional high revs when taking from a stop light before moving
-When the high rev condition happens, it does not slam into gear. It's firm, but it's not the head jerking dumping the clutch or high-stall converter shift
-Operates perfectly on the highway
-Driving on the highway and then a quick stop in town is fine. It's when I drive all around town with lots of stop and go that seems to make this worse,
-I can't pull codes because my ODB port is not working. (Probably a ground issue. Fixed A LOT of those on this truck. Should be next on my list.)
-Although I cannot pull codes. The OD light IS NOT blinking like I think it would if a code was thrown.
-NOTE: Those symptoms do not happen every time I take the truck out. They happen a lot, but not every single time regardless of trip length.

Initial Diagnosis:
I though this was a classic torque converter starting to go out. Same symptoms from other vehicles I have worked on. My plan was to replace the TC and move on.

New Info:
Since I couldn't work on this today, I decided to just use it to run errands and see it I could reliably reproduce the symptoms. For some reason, I decided to put a tube of LubeGuard Shudder Fixx in there to see it that helped the shudder. I never use any of that stuff. So I don't really know what came over me, but I was reading a bunch of old threads last night and some members whose opinions I trust suggested that particular product. I figured why not. Well, that made it worse.

New symptoms:
-All the same shudder as before, but it lasts longer and starts earlier.
-High rev at stop lights almost every time now, but the shift is still smooth once it goes. If it does grab and take off like normal, then a few feet later it slips a bit then reengages,
-Manually shifting into 2nd makes the shake immediate and worse
-Manually shifting to first acts the same as if I put it in neutral.
-I was able to get to a place where I could test reverse while this was happening. Reverse is fine. No slipping. Immediate take off, etc.
-So it's a bit obvious to me that I screwed up using that shudder fixx as it seems that the friction modifier in there has made things too slick and whatever traction was left on the components is having a harder time engaging. If I try to be positive, I can say that maybe it has pointed to a more serious problem than the TC and might save me some time there.

New diagnosis:
-Slipping in forward, but not in reverse can't be a TC. It would do that in both
-Now I am thinking the forward clutch is shot. However, when this started a few months ago after that stuck in sand episode, I changed the fluid and there was not any metal. Fluid was a bit dark, but still red. Didn't smell burnt. In fact, I didn't think it was any different from other trans fluid changes on this one.

Thoughts? I'm thinking a rebuild or a new transmission.

 

I can't come up with any way the first gear problem could be the torque converter. If the converter were bad, it would be bad all the time. It wouldn't be a problem in first, then work fine in second. The shudder when it locks IS the converter, though.

I think you have a bad forward clutch.