speedometer problem

hey i just noticed my speedometer dont work. i have a 74' in6 any suggestions. and i need the bolt size of the bolt that goes from my alternator bracket to my block. please help....

 

I hope this is what you asking, three bolts are 9/16" one on the top front of the Alt is 1/2"

 

no that is the head size for a wrench end, the bolts them selfs are 3/8 and 5/16" nc

 

I would check the plastic drive gear located in the tail shaft of your transmission. It's a pretty simple fix.

 

thanks ive been lookin for the size of that bolt for a month now and all the dealer said was 5/8 those guys kill me over info.