1971 Chevy Pickup rpm problems

[chazdo2]

I have a 71 Chevy 4x4. It has the old dash. It seems like it revs too high for the speed I am going. Not sure what the gear ratio is. The dash tac has no numbers on it but appears to work. It has inside and outside hash marks on the tac. When I am going around 55 MPH it is at about 4 oclock. You guys who know these trucks inside and out have a guess at what RPM I am running at that angle? If it is too high can I change the gear ratio in the rear end?

[trac209]

Need to know rpms from a tach with numbers before anyone can be of any help

[firedemon]

4 oclock position would be about 8000 rpm might be a bad tac or a 6 cyl tac in an 8 cyl engine or if the engine is screaming for mercy your gears could be crazy

[kwmech]

Sure you're not in lo-range

[chazdo2]

Its not in low the floor shifter is a bit stiff but works. Its an auto tranny and does shift. I was looking at pics of the dash board on the internet. It looks like the tac goes from 0 to 5k on all of them. So I guess I would be running around 4k. I think its a three speed auto. Maybe its not shifting into 3rd? Any suggestions here much appreciated. Kind of a newby back yard mechanic! Should add it has a 350 with a small lift and 30 inch tires.