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post #1 of (permalink) Old 09-21-2003, 10:36 AM
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Truck lunges between first and second gear

Hey everyone,

I have a 1996 GMC Sierra 4x4 that I recently purchased(about 5 days ago) I bought it from a used truck dealer. Yesterday I experienced the following problems and I'm looking for verbage, suggestions, or ideas on what this could be. The vehicle I'm referring to is an automatic
with 133000 miles on it.

When sitting at a stand still and then accelerating the truck takes off fine but when the transmission shifts into second gear the truck has a hard lunge feeling.(almost like being hit from behind) It only does it between first and second gear. Yesterday was the first time the truck has done this since I bought it 5 days ago. I also was able
to make it stop doing going over a speed bump at a fairly fast clip...I know that sounds stupid...but the bumping seemed to correct it...cause now its not doing it...could a plate or something in the transmission housing be sticking or something...

Thanks for any input you can provide

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post #2 of (permalink) Old 09-21-2003, 02:06 PM
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Re: Truck lunges between first and second gear

Did you get any kind of a warranty, or sold-as-is?

The very first thing I would check is the fluid.
#1 is it low?
#2 is it red, or brown with a burnt smell?

If its brown, a tranny service is in order. Change the fluid and filter. When you drop the pan, look for metal shavings. A small amount can be expected, but a lot could mean a major problem.

Hopefully, a fresh bit of fluid will solve your problem, otherwise you could be looking at a more expensive fix.
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post #3 of (permalink) Old 09-21-2003, 11:20 PM
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Thanks everyone for the emails and the <one>

I found out what was causing it...I had an alarm system with remote start put on...when I would remote start the when it would do it...apparently GMC trucks have a third ignition that wasn't hooked up correctly - so its being fixed tomorrow...because it wasn't hooked up correctly when I would remote start the truck and then insert the key...and disarm the alarm and drive off is when the shifting was lunging...apparentlty the computer module that controls the vacuum pressure doesn't function the transmission shifts either too early or too late...whew...and I thought I had a bigger problem...

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