What is causing my Z71 to buck and jerk?

LANDISDB

MEMBER
1999 GMC SIERRA
140,000 MILES

My 1999 GMC sierra z71 bucks and jerks between 45 and 60mph and the battery light comes on and it looses power. When given gas it kicks in gear on drives fine once out of the range. The computer has been replaced and transmission rebuilt. It continued with the same symptoms and the transmission broke again, rebuilt for free by the mechanic. The mechanic is having a hard time locating what is causing the transmission to break. What is causing my problem?

3 Replies

HMAC300

MECHANIC
48,601 POSTS

It may be your torque converter kicking in and out of gear. But if your battery light comes on check the battery if it's over 4 yrs old it may be bad Also check to see if your belt tensioner is working and tight and check fuel pressure.

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Tuesday, March 27th, 2012 AT 1:01 PM

LANDISDB

MEMBER
2 POSTS

I have had the battery and alternator checked, both checked out good. The belt is tight and the truck is getting good fuel pressure. The mechanic initially said the computer was pulsing and causing the torque converter to kick on and off, that led to replacing the computer. But it is still having the same symptons. Can a faulty/shorted Vehicle speed sensor or throttle position sensor cause these symptoms?

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Tuesday, March 27th, 2012 AT 1:28 PM

HMAC300

MECHANIC
48,601 POSTS

Usually if htosea re fualty they will et a code but stranger thins have happened. I would check all my grounds eng to bat bat to body, engine to body maybe try cleaning throttle plate on both sides and if your tires pressure is one with 80 psi the put the back ones to 55 when empty.

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Tuesday, March 27th, 2012 AT 1:31 PM