In the last 3 weeks I've put near 2500 miles on my Blazer, most interstate. When accelerating to speed the truck does this shudder thing, (like driving over rumble strips) at about 45 to 50 mph's, thinking it has something to do with tranny/over drive/torque converter? This truck has done this before but now does it on a regular basis, and will do it at 70mph on cruise when going up an incline on the freeway. Any ideas as to what it could be? it is an automatic, not sure how many gears or if there is an overdrive, what was standard on these? 97, 4x4, 4.3L vortex, 2 dr.
Thanks for any help or ideas you might have. Mike.

 

I'm placing a bet on u-joints. Mine did the same thing, and u-joints were gone. Easy fix... With a u-joint press, shouldn't take more than 20 mins in a driveway.

 

midnightmekanik, will check out the u joints, would you think if i got under the truck and gave the drive shaft a good twist back and forth that it would give me a good indcation with play in it, it would be the u joints.

 

Might or might not... My u-joint only had one bad bearing cap, so trying to twist it to check did nothing. In all honesty, it took a matter of 5 minutes to take out the driveshaft to inspect it properly. Just four bolts at the rear end that hold it into the yoke, then slide it out of the transfer case/trans. Cake walk really... and then you can properly check the u-joints.