Transmission oddness (Safari AWD content)

[rodekyll]

 have a 1996 GMC SAfari van with AWD.  It's got about 160k on it now.  I has started to act oddly. 

It started after an hour of stop-and-creep driving in ~80f weather.  It did not seem to be accelerating properly, and there was an intermittent "shuddery" feeling behind me, but not at the differential.  The shudder happens at the point of shifting, occasionally.  Also occasionally on neutral throttle, and occasionally when the t/c "locks" and "unlocks".  It's not sharp and bumpy, like going over rocks.  It's more of a "slippery" shudder, like slipping on those rubber dot-pads they put in the sidewalk at crosswalks.  I've wiggled the drive shaft and checked the fluid so far.  No clues there.

It's not happening often enough for me to be able to get a good feel for the source, but it does have me riding the Convert only, on account of I'm nervous about a total failure while on the road.  The Convert is a problem because the odometer goes nuts.  It reads 4 miles to the store, but if the weather gets warm and sunny, it can show 30 miles for the trip home.  Also, the trip home takes a LOT longer.  What's up with THAT?

But I digress.  Anyone got a thought on the problem?  I'll give more detail if that helps, but I need to know what is significant.  Last time I had oddness was about 40k ago.  The fix then was to drain and fill the transfer case.

[Chesterfield]

Sounds to me ( no expert ) like sticking shift solenoids that I have experienced in GM automatics. Is it the 4T60E transmission?

[RinkRat II]

  Well now RK, 96 should be OBDII and if you can pull drivetrain trouble codes it should steer you in the right direction. Could also be simple like fluid and filter change.
       Paul B

[rodekyll]

The heck, you say.  And all these years I was keeping it running without the codes.  I'll see if I can limp it in to NAPA and get a reading.  It's 7 miles away.  The Autozone is 40.  I don't want to drive it that far without a little peace of mind.  It will be fun to see what the computer has collected over the years.

[Two Checks]

Typical symptoms of worn out fluid. Change, do not flush fluid and filter.

[Chesterfield]

Flush it if possible. Lot`s of misinformation on do not flush. Or pump out and replace at the same time, it becomes sort of a mini-flush then. If you`re lucky sometimes clearing codes works, but I doubt it from what you are describing.

[rodekyll]

Typical symptoms of worn out fluid. Change, do not flush fluid and filter.

Are you saying to not mess with the filter?

Flush it if possible. Lot`s of misinformation on do not flush. Or pump out and replace at the same time, it becomes sort of a mini-flush then. If you`re lucky sometimes clearing codes works, but I doubt it from what you are describing.

What is your flush routine?

[Two Checks]

I am saying do not flush. Drop the pan and change both fluid and filter.
Flushing runs any swarf in the pan where? Think about it. Plus when the pan is dropped you can see if there is anything in the pan which will say its time for a rebuild.
If you flush the filter is still dirty.

[RinkRat II]

I am saying do not flush. Drop the pan and change both fluid and filter.
Flushing runs any swarf in the pan where? Think about it. Plus when the pan is dropped you can see if there is anything in the pan which will say its time for a rebuild.
If you flush the filter is still dirty.

    100% :1: :1: :1:
      Paul B

[rodekyll]

I am saying do not flush. Drop the pan and change both fluid and filter.
Flushing runs any swarf in the pan where? Think about it. Plus when the pan is dropped you can see if there is anything in the pan which will say its time for a rebuild.
If you flush the filter is still dirty.

That's what I was trying to get clarified, thanks!

[Chesterfield]

That's what I was trying to get clarified, thanks!

Of course drop the pan, take a look, change the filter. Then flush. If any swarf goes in the pan from a flush, that`s what the filter is for. There`s a reason machines to flush transmissions were made and it`s not to ruin your transmission.