allison transmission issue??

[red]

2001 chevy 2500HD 8.1L 4X4 70,000 mi.
the external filter and trans oil was changed about 18months ago. well, a week and a half ago while accelerating from a stop, the allison would fall out of gear, the RPMs would jump up, then slam into gear and keep going. it did this through the first 3-4 shifts during the 25mi trip home from work. i drained the oil, dropped the pan and replaced the internal filter. slapped it back together and it still acted like this.
i got out on some back roads and started going through the shifter using each gear to speed up and to slow the truck back down. after going through the cycle about 4 times the trans acted perfect. we even took the truck to abilene last weekend and the truck was fine all last week.
this morning the trans started doing it again. as i was working my way to the highway, i went through all the gears again as i accelerated and slowed to stops. after going through the cycle 3-4 times the trans started acting fine and it performed as normal the rest of the way in to work. fluid levels were and still are normal. anyone else experienced this? anything else i need to look at?

[Palmetto]

What did the oil look like when you drained it?

[texas bound]

Sounds like a shift solenoid to me but I have never heard of that problem with an Allison.

[red]

What did the oil look like when you drained it?

Transparent cherry red. Just like the new qt. or 2 I added back in after dropping the pan.

[bboswell]

01 with 70K? Your not driving enough to keep it limbered up!

Following

[M16]

Shift solenoid

[red]

01 with 70K? Your not driving enough to keep it limbered up!

Following

my father and i bought trucks back in '01 about 6mo apart. he has been retired for over half that time. he wanted a new truck about 3months ago. mine had 200,000mi and an oil leak. his had 65,000 and in perfect condition. they wouldnt offer much of a difference on the trade in value so we swapped trucks prior to his trade in.

[krisw]

I'd say shift solenoid too. I had the tranny on my 97 z71 rebuilt a couple of years ago. A month or two after I got it back, the solenoid went out. (It was the original, why it wasn't change ill never know.) it was doing pretty much what you are talking about though.

[esp]

Sounds like the valve body to me. That is a common problem on the earlier models. The valves are sticking and causing a hard shift.