Hey, I've got a 99 gmc sierra 5.3 L V8 with 360,000 KM on her and not a tick to it. However when I'm going about 70kmh or 40 mph, if I hold the peddle in just the right spot (right before it wants to change gears or rev higher) the truck studders or hesitates and shakes like it doesnt want to change gears, the rpms don't change and the idle isn't rough, if I push the peddle past that point it changes gears fine. I'm also getting a 171 and 174 code. I've cleaned the maf and throttle bottle and probably going to do the injectors next, Just frustrating because where it studders is somewhere I tend to like to hold the peddle and I know it's not an immediate problem as I've put more than 40,000 km on this truck. So just wondering if there's any input on what it might be before I do the injectors. Thanks!
when is the last time you replaced the transmission fluid + filter?
How much is on the dipstick and what does the fluid look like?
P0171 is usually caused by a vacuum leak.
This engine is known for the factory intake gaskets to fail.
Follow instructions here:
https://www.obd-codes.com/p0171
No clue when the tranny fluid would've been done, I checked it fairly recently and it's at a good level and isn't too discoloured. I heard its bad to mess with changing the tranny fluid on something that old and is unknown when it was last changed? Or do you think the vaccum leaks is the cause?
maybe. It's also been known to fix problems
https://carkiller.com/scottykilmer/qa/2005-chevy-colorado-shifting-issue/
if the filter gets plugged up with crap then it'll stop shifting completely
Fair enough I'm reluctant to do it on something so old but I'll give it a shot. Thanks!
if you're worried then keep the old fluid. If tranny gets worse, put the old fluid back in.
More just worried about 22 years of gunk and shavings being dislodged into the tranmission after I change it
if you just gravity drain nothing will get dislodged. That's how fluid gets into the pan during normal operation anyway. The magnet there catches metal.
Awesome thanks so much, made me feel about doing it
I wouldn't expect miracles .It does have 360k on it. But it could help. last ditch attempt before replacing tranny.
You could also try some lucas transmission fix.
I just double checked the fluid and it looks really good and is pretty bright so I might go for the change, would the lucas be hard on anything? Seals and other parts?
don't dump in the whole bottle. Maybe try 1/2 first and see if things improve. It's made for trannies so it can't be too bad, and it sounds like yours is near the end of its life anyway. Like I said these are desperation fixes to keep things going a little while longer. If you want to keep driving it the way it is then you can do that.