Hesitation In Overdrive?

mattison · April 29, 2009

I have a 1999 GMC Sububan. It has 177k miles and I pull a trailer daily for work. Lately as soon as the truck drops into 5th gear it sputters like crazy if I'm excelerating. When I ease off the gas it smooths out. No check engine light comes on, maybe because I don't keep my foot hard on the gas. Not sure if it happens in other gears, it's just most pronounced as soon as it hits 5thMy thought is to change the fuel injector. Any other thoughts?

VR021302 · April 29, 2009

I thought they only had 4 speeds in '99, maybe thats the prob.

hockeypro1411 · April 30, 2009

I thought they only had 4 speeds in '99, maybe thats the prob.

Yea, I'd be more worried that my truck was finding a 5th gear...

ss502gmc · April 30, 2009

Is this Burban a manual Trans ? I thought they didnt put a manual in those.

superjim · April 30, 2009

He may mean when the TC locks up.

That may be what he is calling a FIFTH GEAR.

mattison · May 1, 2009

If you count the shifts as you accellerate there is definitely a fifth (overdrive) gear. It may be called an automatic 4 speed but you can watch the tach drop at each shift change(four times after you initially start off in 1st)

66nova · May 1, 2009

If you count the shifts as you accellerate there is definitely a fifth (overdrive) gear. It may be called an automatic 4 speed but you can watch the tach drop at each shift change(four times after you initially start off in 1st)

That's the torque converter locking up. You only have a 4 speed. It will lock up at highway speeds when you are at a constant speed. It should unlock any time you press on the brake or give it a little extra gas.

mattison · May 2, 2009

So I'm guessing nobody has any input as to my hesitation/bucking problem?

66nova · May 2, 2009

So I'm guessing nobody has any input as to my hesitation/bucking problem?

It's hard to diagnose from that description. One of my first thoughts would be it needs a catalytic converter, but there are a number of possible fixes.

Has it been tuned up recently?

When is the last time you replaced the fuel filter?

How long has it been doing this?

mattison · May 3, 2009

Sorry I was a bit vague. At roughly 170k miles as I noticed that as soon as the truck would hit 55 mph and the final down shift it would sputter occasionally. I just either let off the gas some or stepped harder on the gas to downshift. Some days it would do this, other days not. Staring at 168k miles, I've had the transfer case and transmission rebuilt, new dist cap, rotor, wires, plugs, and fuel pump/filter replaced. Recently the hesitation is getting worse, especially when in overdrive running between 55 and 70 mph. after 70 it does seem to smooth out until I have to step on the gas to go up hills. Driving around town, under 40 mph, it's as smooth as can be.

superjim · May 3, 2009

Sorry I was a bit vague. At roughly 170k miles as I noticed that as soon as the truck would hit 55 mph and the final down shift it would sputter occasionally. I just either let off the gas some or stepped harder on the gas to downshift. Some days it would do this, other days not. Staring at 168k miles, I've had the transfer case and transmission rebuilt, new dist cap, rotor, wires, plugs, and fuel pump/filter replaced. Recently the hesitation is getting worse, especially when in overdrive running between 55 and 70 mph. after 70 it does seem to smooth out until I have to step on the gas to go up hills. Driving around town, under 40 mph, it's as smooth as can be.

My guess..based on the new details, is the Torque Converter CLUTCH.

It may not be locking up properly and causing what you feel, as a sputter.

At around 50/55 is when the TCC will lockup, depending on throttle position of course.

I don't know if the 1999 TCC would set a code or not.

It may be worth checking with a code reader, to see what (if any) codes are set.