venture transmission

At about 85,000 miles, my 2000 Venture's transmission has started shifting hard, making a whining noise. Took it to a shop Summer 2005 and they were unable to get the transmission to act up for them. They changed the trans fluid and filter. It still acts up sometimes, but not consistently enough that I would be sure it would still be doing it if I took it to the shop.

Any suggestions?

Mine would downshif in the middle of driving at constant speads on level hwys. It turned out to be the TPS (Trottle Possition Sensor).

Was is the whining from the tranmission?

Natureboy. I am having the same problem with my transmission as you did. Did you ever get the transmission jolting resolved?

Mine does the same thing.  Occasionally, during hot weather only, it shifts very hard.  It does not rev any higher than normal to get into the next gear, nor does it down shift hard, only when going up through the gears.  In cooler weather it never does it.  This indicates to me that it is not mechanical, as any worn out part internally would not cause such an intermittent problem.  I haven't gotten into it yet, (because it is so intermittent,) but I'd bet it is electrical.  I intent to first clean any and all electrical connectors going to the trans., to ensure good contact.  As heat builds, there is more resistance.  If not fixed then, I'd bet it is some kind of electrically controlled devise on or in the trans itself....If anyone pegs it in the meantime, PM me with your results...
Thanks!
Chris

Has anyone figured out what is going on with the thunking while upshifting.  Mine whines every once in a while, then bangs between every gear.  If I let it cool off for a while, it is fine.  Did the fluid change, no help.  Van has 100K.  Anything else short of rebuilding the transmission?   Thanks

The problem is the pressure control solenoid, when it gets hot it shorts out and commands full line pressure. This is the whining that you are hearing from the trans, its the pump. No cel will set but it will store a code of p1811 max adapt shift. I have done alot of these for this problem. You can diagnosis this yourself when its happening and the vehicle is shifting hard stop shut it off wait a minute restart and see if the whining is gone and it shifts normal again. If so thats the problem.

What is the fix for a code p1811 and the symptoms ktm521 is describing?

 The fix for the problem is to replace the pressure control solenoid in the transmission. The symptoms are after driving awhile the soleniod shorts out and when this happens commands full line pressure to the trans. When this happens the driver will feel a really hard shift to every gear from take offs. If this is happening shut the vehicle off wait a couple of minutes then restart and see if it shifts normall if it does then thats the problem.