my truck bucks when it reaches 45 mph

i have a 1999 z71 with the 5.3. when i am driving and reach 45 mph my truck starts to buck and it seems like it is in the motor. when i give it more gas it stops or when i give steady pressure on the gas it does not do it. the only time that it does do it is when i am always going 45 or when i go past 45 slowely. has any one else had this problem and how did you fix it

Reply to
coderreoif3
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starts to buck and it seems like it is in the motor. when i give it more gas it stops or when i give steady pressure on the gas it does not do it. the only time that it does do it is when i am always going 45 or when i go past 45 slowely. has any one else had this problem and how did you fix it

have you ever tuned it? well, plugs and fuel filer....? if not its time for sure.

Reply to
ShoeSaleman

i put in brand new platnum 4 plugs and new wires. i do not think that it is the fuel filter because it always bucks at the same speed. i would think that if it was the fuel filter that would do it at different speeds and not just at 45 mph. wha do you think. and arnt the 5.3 timed automaticly by the computer?

Reply to
coderreoif3

the fuel filter because it always bucks at the same speed. i would think that if it was the fuel filter that would do it at different speeds and not just at 45 mph. wha do you think. and arnt the 5.3 timed automaticly by the computer?

yes the comp controls the timing. Is the "buck" small, not real bad? If so it could be the torque converter. You can test this by putting your foot on the brake just enough to turn on the brake lights. this disables the TC. See if it still "bucks" like that. If that is it, a trans filter and fluid should help, also look for a additive called shudder fix or something similar. Oh, and fuel filters are cheap. Does the check engine light ever come on?

Reply to
ShoeSaleman

it was on but it was on for the knock sensor. do you reccomend lucas trans addiatative or no. i was going to change all the fluid anyway in the trans so i am going to try that.the check engin light does not come on for anything else though.

Reply to
coderreoif3

addiatative or no. i was going to change all the fluid anyway in the trans so i am going to try that.the check engin light does not come on for anything else though.

You have a drivability problem, you have a trouble code, get a book and diagnose it. While your under the truck change that fuel filter. It might fix, it it might not, but either way its a $5 part that gets overlooked way too often. it will also help save your fuel pump(expensive). I don't know anything about lucas, the product I know that works on a shuddering TC is "trans doctor" (I think its called, could have been "DR. Trans". It comes in a red tube. You are looking for a product that is for shudder.

Reply to
ShoeSaleman

thanks i am going to try that if i can fingd it. and yes i will change that fuel filter. thanks for your time i will let you know how it goes

Reply to
coderreoif3

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