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This only occurs when I pull anything. There is a shudder, like a heavy vibration - can't tell if it's from the front or rear - starting at about 35 mph and most prominent at 55 mph. It comes and goes - that is, one day it wont do it and the next day it starts again. Putting it in nuetral does not make a difference...different tires did not help either. Maybe the rear end???? If I can't solve this problem, I am going to sell this thing! I have 140,000 trouble-free miles on it...I only tow a trailer occasionally, but when I need it, I need it to work well. Any suggestions??
 

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PCM issue, or tranny?

Check out this similar post on another site: AllExperts

excerpt:

Car now shudders when towing over 50 miles per hour. Car is a 1999 Chevy Tahoe we have all regular maintenance done, use premium gas, change oil every 3000 miles, no one has been able to help on this!

I had a 1999 tahoe with this exact problem. First, you will need to contact your dealer to ask if there is a PCM (Powertrain Control Module) update for this problem, which is what cured the problem with the first Tahoe like this that I ran into.
 

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One more question?

Any mods like a tbi spacer?
 

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I wonder if it is the trany?

With all the new electronics in these newer tranies I just think it could be the trany.
 

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vibration when towing

I have encountered this problem with my last burban. 1997 1500 4x4 5.7 vortec.

I am curious what your tongue weight is and what your ride height is at present? Rear leaf springs tend to sag almost an inch by 100,000 miles.

What caused my vibration was a combination of loose leaf spring u-bolts allowing a shift in driveshaft to differential geometry and a + 2 degree driveline angle when loaded more than 500 pound tongue weight causing phase pulse on driveshaft

It is also important that tires are well balanced and have no fatigue related belt separation

crank
 
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