This is for you transmission experts out there that know things about transmissions. (I'm not one of them.) I have noticed that on my aurora which has the 4t65E with the 3.27 gear ratio that between 5 and 14 MPH if you've been coasting and you press the gas down to accelerate you get a hard thud that makes the entire car shake. It'* a similar feeling to if you were to slightly rev in neutral (say, 1,300 RPM) then drop the car into gear. It feels like THAT. It will also sometimes do it in a 2-1 downshift while making turns. Any ideas? The dealership says there'* no common problems with the 65E and that it sounds normal to them. We own two other cars with the 65E and neither of them do this. I know it'* not normal for it to thud like that upon transmission engagement. It also has harsh shifts occasionally under light throttle. It never shifts rough under hard acceleration.

I don't know if it'* related either, but while decelerating from 60 MPH without braking at 50 MPH the RPM'* go from 1,500 down to 600 or so for a second in which time the car makes a distinct feel as the RPM'* drop, and the car feels like it'* "free wheeling" then the RPM'* will shoot back up to 1,500 and slowly drop as the car slows. You can feel the transmission 'downshifting' into lower gears as you slow. I've never felt anything like it. ideas?

I know of 2 cars with that same tranny that do the same thing. I was told these tranny'* are slow in getting into gear and that'* what you're feeling. My GTP never did this. My Bonnie does it and so does my brothers Buick Regal GS. His broke earlier this week. I would always tell him I didn't think it was right for his tranny to be doing that. He said it'* always done that. I think the ones that exhibit this behavior will fail prematurely. The torque converter ends up giving out. I found if I give it a second to get into gear when coming to a stop, then accelerate, it doesn't do it as much. Just my .02.

I had a problem with my car hard shifting in all gears shortly after my first transmission flush. Everyone pointed to the pressure control solenoid inside the tranny valve body. I tried everything I could think of before that. Adding Seafoam transmission additive, adjusting the fluid level, but nothing worked.

I finally had my local dealer change the solenoid and clean the valve body. It doesn't do the extreme hard shift anymore. I advise against tranny flushes on this car, just do a drop n fill.

Your problem only sounds 1-2 shift related. I'd at least have the valve body cleaned. BTW, this isn't cheap. Cost me a little over $400 as they have to remove the left front wheel assembly, etc. to get to the valve body.

I have a 5 year/ 60,000 mile GM warranty. Would something like this be covered?

If the dealership thinks it'* acting normal, I doubt they will cover any repair you think will alleviate the problem.

Seriously, if you don't have a warranty, take it to a tranny shop. It'll cost you about $2000, but atleast you won't here the BS you get from a dealer. The GM dealers also told me it was "normal" for the window regulators to give out. Give me an F'n break!!!

sort of sounds like my old problem... and it was the torque convertor... replaced the whole tranny...

FYI, I have a company car that is a 2004 Chevy Venture van.. I am doing a couple miles an hour like you and it really hits hard when you touch the accelerator. I have to feather it before I push down on it. Really painful when you are in a bunch of traffic coasting.

It has 16K miles on it and has done it since new.

I call it a torquey motor on a tall first gear. Patrick

My bonneville started doing that at low speed, now its at any speed, now the tranny is on deaths bed, but if you have warranty, i wouldnt be to concearned!