shudder during down & up shifts

[realtime]

We drove our '97 4x4 EB Expedition (4.6 auto) to Maine for vacation (i.e. loaded up w/ kids, dog, kayak, bikes, etc etc) and I noticed that when the truck was under load on the open hi-way (accelerating esp. up-hill, or passing) there was a breif shudder when it down and up shifted. It seemed to do it in both "2WD" and "AWD" modes. We dont notice the shudder (or it doesnt shudder?) just driving around town, etc. only when we are at 55-75mph and step on it or need the extra umph to get up a hill. Does anyone know what this could be caused by or the best place to start looking for problems - I dont smell the trans burning and the universals seemed ok.. Thanks in advance for any suggestions. DAM

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[Mark Kovalsky]

The transmission fluid could be worn out. How many miles since the last fluid change? You have the 4R70W transmission, and that transmission likes fresh fluid every 20-30K miles.

[realtime]

Thanks Mark,
That thought had crossed my mind when it was happening- thanks for the suggestion! We bought the truck in Feb. 2000 w/ about 25K on it and it now has about 45k and I've never changed the fluid so thats a good starting point (and probably necessary anyway).

Much appreciated!

DAM

[WLF]

If that doesn't fix, it do a search on this forum on Sonnax valves. They are pritty strait forward to install and they fixed my shudder problem.
BTW, if you are doing your own trans fluid change, drain the torque converter as well and install a drain valve (about $5) in the pan for future changes.