in my 87 E350, it seems to me that its shifting gears at a much higher RPM than would produce good fuel economy. i have the 6.9, C6, 3.55 gears, and 235/85r16 tires. during a gentle acceleration, it shifts to 2nd around 25mph, i can make it happen as soon as 15 if i fully get off the throttle, and from there if i give it more than a little pedal, it'll get back into 1st. shifting to 3rd is similar, usually around 45 or so, and absolutely not below 35. at 35-40, to give any little bit of pedal drops it back into 2nd.
the PO said something about having the modulator (IIRC) changed, and from that time on it acted like this, so he thinks its the wrong part. i read somewhere that its adjustable, but i haven't played with a c6 much, and suggestions to get it adjusted better?
during the course of playing with this, i've found that if the shifter is in 2nd, the truck will take off in 2nd, whereas with teh shifter in D, it starts in 1st and shifts from there. is this normal, it seems strange to me...
and advice/info would be appreciated

 

Try tipping the vrv on the ip towards the rear of the truck a little play around with it til your happy with it. And it could have the wrong modulator i think you need the green stripe i think im not positive though. check that first adjusting them just adjusts the line pressure though.

 

My 87 E350 motorhome had somewhat a similar problem when I bought it. The engine would rev all the way to the governor before shifting for each gear.

When I got it home, got under it with a good can of WD40, and sprayed the crap out of the kickdown linkage on the side of the tranny, and it's been working like new ever since!

It was so dirty, and stiff it couldn't move by it's self.

 

good to know, maybe i'll find time to take care of that.... and maybe that pesky fuel leak too, might really boost my economy, especially since i drove 265 miles yesterday, i really need to!
it seems my kickdown linkage is working, as moving the throttle does cause a downshift, especially in the speed ranges i mentioned... so i think the main issue is in the adjustment that 84-6.9 was talking about
thanks guys

 

Before you go adjusting things, check the vacuum line at the transmission for vacuum at idle. If there is a pin size rust hole in the steel vacuum line you'll have your result of hanging in gears and hard shifts. My bet is you developed a vacuum leak.