5.7L RPM

Bo185 · September 15, 2005

My 1999 C-1500 2wd with a vortec 350 rpm's rev up and down some 2 to 3 hundred rpm's at a speed between 30 to 55. And I can notice it rev up and then back when driven with my foot on the pedal . I can be driven at say 35 and the rpm goes up 300 than goes right back down to the correct rpm I know the engine is rev up than down because I can hear the exhaust going up and down as well!

Anybody help me out! I have tried everything I could think of and it kills my gas mileage!

Could it be the torque converter locking than unlocking?

Only mods. are reprogram computer, thottle body spacer, KN filter, and single flowmaster 70 with single 3'' tailpipe.

Engine has 60,000 on it trans has 148,000 like everything else!

marko · September 29, 2005

Sounds to me like you might have one of two problems:

either a vacuum leak somewhere, or a problem with the transmission as you say. If the tranny has 148k on it, that could be the culprit.

But as they say, fix the easy stuff first. See if there is a vaccuum problem, or there are any loose screws in your throttle linkage anywhere (assuming there is such a thing on a 99 and it's not drive by wire).

Have you changed the tire size or anything? This can make the transmission 'hunt' as well.

Dans Denali · October 3, 2005

Every time you let off the gas, touch the brake or depress the gas a long way the torque convertor unlocks, drive steady and smooth, it will stay locked up.

Dan

Bo185 · November 5, 2005

Sounds to me like you might have one of two problems:

either a vacuum leak somewhere, or a problem with the transmission as you say. If the tranny has 148k on it, that could be the culprit.

But as they say, fix the easy stuff first. See if there is a vaccuum problem, or there are any loose screws in your throttle linkage anywhere (assuming there is such a thing on a 99 and it's not drive by wire).

Have you changed the tire size or anything? This can make the transmission 'hunt' as well.

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Don't think it's a vacum leak it only does it at 30 to 40 miles an hour. I think its the torque converter lock-up servo burned out! Trans works fine shift great!

Bo185 · November 5, 2005

Every time you let off the gas, touch the brake or depress the gas a long way the torque convertor unlocks, drive steady and smooth, it will stay locked up.

Dan

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I know how to drive!!! It only does it when I am curisin 30 to 50 I am not hittin the brakes or lettin of the gas dumb ass!

Goob · November 9, 2005

Bo185,

I am having what sounds like the same problem. Have you changed torque converter yet and was that the problem? I have yet to find a vaccum leak or a leak in my intake. I don't have any trouble codes for any misfires either. I have my post on the GM-Tech forum. I'll let you know anything I find out.

Bo185 · November 27, 2005

Bo185,

I am having what sounds like the same problem. Have you changed torque converter yet and was that the problem? I have yet to find a vaccum leak or a leak in my intake. I don't have any trouble codes for any misfires either. I have my post on the GM-Tech forum. I'll let you know anything I find out.

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I think its the trans causing the converter to lock un lock under thottle, I got like 150000 on it so it's not to bad yet to pull and rebuild yet for me!