hi i just put in a autometer performance tach in my blazer. i put the sender wire on the negative(i think) pole of the coil. it looks to be running fine just ever thirty or so seconds it jumps, like a false reading or something then it goes back to normal. i have only tested in idle. could it be sensing that my coil is bad? how do you tell wich is the negative side of the coil? I think i have 3.75 gear ratios and a 12 bolt rear and d44 front. can i run 36s if i stick to mud and hills or will i beak stuff. will the 36's be harsh on my th350 tranny? thanks a lot.