Ok so I have had my monte for about 4 years now and i think it was about two years ago when i started realizing my car would Shift really hard every now and then. Now my first thought is that I have a bad electronic cylinoid but i wonder if it may be something else. It doesnt happen all the time, it happens at random times. sometimes it is when i am baby'ing the the hell out of it and each shift is a hard tug. I am more familiar with older non-electronic transmissions and motors. I do not know much about this electrical **** so as far as i know it could be a simple fix or it could be a big one. It has 140,000 miles and is stored away for the winter. I have ran transmission sea-foam in it. but that was just a simple "why not try it." Please feel free to comment and share your opinions with each other cause i have no clue about these transmissions. -not good with this newer technology! Thanks

 

Samething would happen when I had my 2002 impala ls, something I noticed was it only started shifting hard after the car was up to operating temperature, literally one day it didn't do it until it was about half way on the temp gauge. Car had less than 85K on it, got it to our mechanic and he said there is a pressure control solenoid that goes in the transmission, when it does go that causes it to start slamming into gear and every time it shifts. A replacement solenoid corrected the issue with that car, it shifted great for probably a year and started shifting odd again we never got it looked at and it ended getting wrecked. When I got my monte last feburary that solenoid in the transmission was one of the parts that needed replaced. Its possible that is the the issue your having. The transmissions in these cars suck.

 

Could be a catalytic converter starting to clog.

Or just simple shift solenoids.

 

I would lean toward a shift solenoid.

 

My transmission also started doing that very same thing around 130,000 dispite my haveing the fluid and filter changed once a year...

So, I had the trans shop scan the transmission...solenoids checked ok...
Ended up haveing a soft rebuild done on it...and its been fine ever since...That was 40,000 miles ago...

I recommend takeing it to a qualified shop and it scanned...for a solenoid issue...

Also as mike (chibi) reommended also have the cat checked to see if its clogged...which has also cause this condition.

 

Thanks guys! The solenoids was the first thing that popped in my head to so i figured thats what it was. I will probably have it checked by a family friend that works for a transmission company in mason city. i will probably either look for a high flow cat as well because im sure it is clogged. Thanks for the help guys!

 

A high-flow is going to throw a P0420 code on your car and you'll fail emissions. Once you get a high-flow, you need a tune or an anti-fouler o2 sensor.

 

How much money is that gonna run me?

 

Anywhere from $10-$150. Depends on what parts you already have, if you can make the anti-fouler yourself, or if you decide to try to find a local tuner, or get a mail-order tune from a vendor.

 

one other thing you can try is max life fluid. I hear is smooths out hard shifting from selenoids going bad. Reason it works is because as dex III gets older it thins as well as when it heats up. DEX/MERC max life is pretty much a thicker synthetic dex III it has cleaning agents in it to free sticking valves, sealing agents for seals and hold up against heat better to remain thicker for higher pressure thus smoother shifts. i recommend if you do a change do not flush the system, change the fluid and filter then just drive it.