hi, its a 2000 ls and since i got it it does this...... if you try to pass someone, when it downshifts.. it ticks wicked loud and you dont go nowhere, well, the truck tries to go but it doesnt-then it does-then it doesnt. it sucks on the highway. its like you gotta keep the rpms under 2500 in the same gear or it starts doin it. so...i brought it back to the dealer, cuz ive never done transmission work, and they replaced it. but guess what...it still did it. so i didnt bring it back cuz obviously they dont know what it is or dont wanna fix it and now the warranty is up. has anyone had or heard of this kinda problem? any info is much appreciated!!! thanks!!!

 

Does the engine rev up when you go to pass and is this problem worse after the engine is fully warmed up.
If the rpm's don't pick up I'm thinking that you either have low fuel pressure, a partly plugged fuel filter or a plugged exhaust.

 

the engine acts normal. its like if you try to accelerate too fast it does it. its done it since i bought the truck and when i brought it back they said the front pump of the transmission was bad, so they replaced the transmission. i got an exhaust put on it so i dont think it will be a plugged one. the noise seems to be coming from under the truck, more towards the rear. ok...it almost sounds like the sound you get when you put the truck in park from drive. i did the u joints to take care of another noise, but i was thinking maybe the part on the end? the slip yoke? to be honest... im a 12volt installer and i havent done much work with mechanical stuff like transmissions and driveshafts. but i cant wait to get this problem fixed!!!!

 

oh i forgot.... it doesnt matter if the truck is cold or warm and it does it in all gears. meaning drive and 2 and 1 . or 3 and 2, i forget them but you know what i mean. it doesnt do it in neutral or park and i havent tried it in reverse

 

How many miles are on it. Sounds like it might be so clogged up with carbon that it's pulling timing like a ****. You don't have any CELs?

 

The quick down function (very high rpms and not a clear advance in speed) is controlled by the butterfly (or whatever the name is) sensor at the throttle body. I believe the signal is saying full throttle when isn't. So the auto box shift down due to the wrong PCM input. If I'm wrong is an easy/cheap part to swap. Maybe you just can clean the contacts there with electronic contact cleaner in spray. Remember that when at full throttle the gearbox will stay in 3rd for ever.
I don't have signature.

 

You need to get your fuel pressure tested while driving.
How many miles are on it?
Ever get a tune up?

 

it ended up bein the crankshaft position sensor. fixed it a while ago but forgot to post the it

 

Wow! Thanks for the follow up!

Did you have a case re-learn done? This is done whenever replacing the crank position sensor so that the PCM can learn the precise variance between the true position of the crank and the indicated position via the CKP sensor. It is a calibration of sorts.

 

yea i did. 480 bucks lol. ok, i drove it 20 mph to the closest dealer cuz my scanner dont so that stuff. mind you i told them what i had done and that it needed to be relearned blah blah....but still....... they needed to "check" it out. told me i needed spark plugs rotors all kinds of stupid stuff. said they couldnt relearn it cuz the truck is lowered? basicallt got to the point where i said nevermind gimmie my truck back. 2 and a half hours later my truck comes around all better and i have a 480 bill lol. i dont care tho.