jerking at 20 mph & 35 mph (intermittent)

I need some advice...every couple of days, while I am driving my 2000 Montana, it jerks at 20 mph and again at 35-40 mph. It doesn't make any engine noises while it does this. The van has 108,000 miles...just had the oil changed...my dad checked my trans. fluid and it was orange/brown...he said GM vehicles tran fluid should be pink (??)...any input would be greatly appreciated...
BTW just bought it amonth ago...no warranty...please tell me how I can stop the "jerking"

how heavy are you on the gas when accelerating? I have noticed a lot with automatics that when you put full throttle to the ground that shifting in lower gears 1-2 and 2-3 there is a slow lag in gearshifts. I don't drive an auto myself, but in other peoples cars I have noticed it a lot. just accelerate slowly in autos is all I can say, and changing the tranny fluid might not be a bad idea.

since it has over 100,000 miles on it and it is only 3-4 yrs. old, I baby the gas pedal...I never lay on it too hard, just ease into the speed.
looking around for the best price on a tranny flush...HOPE that is all it needs...If not, I will be back!!! :lol2:

Those speeds are your shift points!! Heavy accleration changes the shift points. Make sure you don't have a misfire it can easily be confused with a trans problem.

I would be worried about doing a trans flush at that many miles. I would never reccomend a trans flush if one hasn't been done before it could cause more harm than good!! I would reccomend doing a small fluid change and filter replacement. Your best bet would be take it to a trans shop or a dealer to check out. You have an electronic trans in the van and it could be something minor.

yes i agree it might be a missfire your feeling,When was the last tune up done? It might be due!!!

This may sound like a stupid question, but what is a small fluid change? I mean, what does it consist of? And what filter should I get replaced...air??? fuel??? I know nothing really about cars and all that...so any help would be great!
And the "jerking" doesn't happen all the time, like I said before, since it has so many miles on it and we just got it a month ago, I baby the heck out of it...no hard accelerating.
Thanks so much for all your advice so far, I just don't know what I should do...and I don't want to take it somewhere and pay a ton of money for something that didn't need to be done to it...

You have a filter for your transmission inside your trans pan!! A full flush would change roughly 12 quarts of fluid. Dropping the pan and changing the filter changes 6 quarts.

I 'm having the same problem . . . already replaced injector 6 (misfiring per p0306 code ) that didn't fix the jerking . . .now another injector is doing the same thing . . .so I'm thinking . . .fuel pump

Anyone fixed this jerking problem ?

FIXED . . . it ended up being the fuel filter . . $12 :-)

also check the air filter.

believe it or not, i was having problems with our 2000 van cutting out intermittently at all speeds. changed the fuel filter, then had codes deleted. then had the problem again. checked the codes and they indicated low fuel pressure, so paid $500 for new install of new fuel pump. problem persisted, so i checked the air filter (no small job on the 3.4 l engine), and a dang mouse had shredded it such that filter paper was ocassionally getting sucked into the intake manifold! i changed the air filter ($8) and fixed the problem.

good luck,
berto