2004 GMC Sierra has been fine until today when I approached a hill at 45 mph it would not shift and accelerate. After making it up the hill I could not get it over 40 - 45 mph. Each time I slowed down for traffic or curves, etc it got worse and eventually would not go over 20 mph and message on dashboard said "transmission hot". Haven't had any problems before this, could it be a sensor or a fuse?

SOURCE: the car will not accelerate;

this sounds like 1 of 2 possible problems.
a bad headgasket or a clogged catalytic convertor. i would lean more towards the convertor

SOURCE: Lack of acceleration

Hi, I had the same problem with my 2003 Impala and it was a clogged catalytic converter and fuel filter. I had both of those replaced and my car runs like new again. I'm 99% sure this is your issue. My car had the exact problems you're experiencing. It was horrible trying to get on the highway from an on ramp that went up a hill :o)

I also work with someone who has a 2002 impala and the same thing happened to hers as well.

I got mine fixed at a local repair shop for around 300.00. If you take it to a dealer, it would be a lot more.

Good luck :o)

SOURCE: Transmission slipping or stalling around 45 mph and down shifts

if fluid isn't burned, shifts aren't slipping or flairing and you did not find a large amount of debris in the pan, chances are that the electronic shift control is malfunctioning. Have someone check it out.

Michael Koerner

• 14 Answers
• Posted on Oct 11, 2009

SOURCE: 2004 GMC sierra 5.3 eng 1500 transmission shutter 40-55 mph

I too have that problem. I own a 2005 GMC Yukon. Shutters between 40 + 55 mph. I thought for sure the stumble I felt was a plug or coil pack because it only does it under a load. With A/C on the whole truck shakes! But it wasnt the plugs or coil packs. Answers anyone?

SOURCE: 1997 Buick LeSabre, 54,000 miles

remove plugs and check for carbon tracing . if found plugs and wires will fix problem