Have a '90 E350 long chassis with a 20' U Haul box on it.
Has a 7.3idi and C6.
Rebuilt the C6, and put around 200 miles on it, with prefect performance.
Then started out yesterday and it didn't want to shift from 1st to 2nd, then 3rd.
Letting off throttle it would eventually upshift to 2nd, never took it out of the neighborhood to see if it would hit 3rd.
Got it home and adjusted the band, but I think that's where I'm doing something wrong.
Loosened the hex nut and torqued the band to 10ft. lbs., then backed off 1 1/2 turns.
By the time I got to 1 1/4 turns it was finger loose.
Is that normal?
From a stop it shifts to neutral, or goes into reverse or drive smoothly, coming to a stop it downshifts to 1st.
I disconnected the kickdown at the IP to eliminate that whole process, but it worked yesterday, after the shift issue became manifest.
This is the only transmission I've ever cracked open.
The parts were easy enough to replace, and I did new plates, bearings, seals, etc., and used a ton of goo on everything that went in.
The air checks were dead center of spec, and added a spacer to get exactly.030 end play, which is dead center of the .020-.040 spec.
Installed a stage 1 shift kit for diesel/towing, but didn't drill out the valve body, as it was optional, and to be honest I was just scared to start modifying it.
From my very limited experience I'm pretty sure it's the intermediate band, as up shifting is it's exact function.
Hoping for advice from someone that has been there before.
Thanks

 

Your shifting problem is caused by a vacuum leak between your vacuum pump and at your vacuum control solenoid on the rear of the transmission's oil pan. The vacuum hose on the vacuum control solenoid travels on top of the transmission to a 'vacuum regulator valve' on your injection pump. Since diesel engines don't create their own manifold vacuum, the vacuum regulator valve gets it's vacuum from the engine driven vacuum pump.
Somewhere in that system, vacuum isn't getting to your transmission to tell it to shift correctly. I'm a big fan of instrumenting thing that I suspect are malfunctioning, so if I were you, I would install a vacuum gauge in the cab and run a vacuum line down to the vacuum control solenoid and use a t-fitting to monitor the vacuum signal. It should be about 20 in-hg at idle and 6 in-hg (iirc) at wide open throttle.
From what I remember of the intermediate clutch band, adjusting the nut affects the timing of the 2nd gear engagement. Too tight will cause the the clutch to drag and create heat and suck up horse power. Too loose causes a sloppy shift between first and 2nd. Someone may correctly on this.