Tachometer bounces up and down in my 2002 Chevy S10 during fast acceleration. Truck has been in the shop for a week. Rear outer seals and bearings replaced, left rear axle replaced, serpinten belt replaced, water pump replaced, front driver side hub assembly replace and intake manifold replaced because of a coolant leak. Now under fast acceleration the tach bounces everywhere and causes the transmission to shift funny. Any ideas?

Mr. Clay, thanks for your response. I will check the fluid level today and see where it is at. Something that I thought of after my post is that I hear a rattling noise perhaps coming from the transmission during the quick acceleration in conjunction with the bouncing tach and odd transmission shifting. I saw a post on the Internet referring a sun gear. Do you suppose that could be an issue if the fluid level is ok? Also someone mentioned a part that is supposed to be clamped back in the intake manifold after the gasket is changed and if not done so could cause a tach problem as well. I know it's hard to tell from a message but any info or suggestions would be greatly appreciated. Thanks for your time! Mr. Clay, thanks for your response. I will check the fluid level today and see where it is at. Something that I thought of after my post is that I hear a rattling noise perhaps coming from the transmission during the quick acceleration in conjunction with the bouncing tach and odd transmission shifting. I saw a post on the Internet referring a sun gear. Do you suppose that could be an issue if the fluid level is ok? Also someone mentioned a part that is supposed to be clamped back in the intake manifold after the gasket is changed and if not done so could cause a tach problem as well. I know it's hard to tell from a message but any info or suggestions would be greatly appreciated. Thanks for your time!