my 1997 blazer gauges and speedodemeter going crazy it stiil starts and runs fine for about ten minutes then the oil pressure gauge goes from 40 to abot 10 the speedodmeter sticks on 55 and wont move and it makes a knocking in the engine but it only does this once it warms up any answers

 

need to check oil pressure with a manual gauge... more then likely it's your bearings being shot that's causing the low oil pressure.