I looked under the hood and found the tag that has the info but the only thing visible was that the tranny was a A518, my truck is a 91.5 with the intercooled cummins engine so any ideas what gear those come with?

 

do you have a tach? if you can make an educated guess at what rpm you are running on the highway in 3rd gear you will know your gear-ratio there is a calculator that is very good for this, http://www.wallaceracing.com/calcrgr.php when you click enter the page will refresh and the answer will be below, its either 3.07 or 3.55

 

Either 3.53's or 4.10's, if I was a betting i'd say 3.53's

 

Look in the glove compartment. There should be a sticker on the inside that tells you what ratio that you have.

You can take your vin to a dealer to get a breakdown of your trucks specific options.

 

Mark never owned a 1st gen.

 

Huh? It ain't there? Guess I shold stick to stuff I've worked on...

 

Tag hanging off the differential cover under one of the left side bolts. Should say 3.54 or 3.54 LS if its limited slip

3.54 or 4.10's were available on the factory O/D trucks. 3.54 was standard, 4.10 optional.

 

Cool, I will look tomorrow.....Thanks for the help guys!

 

If the tag is gone, Jack up 1 wheel. With the truck in neuteral, turn wheel 2 full turns while counting the the drive line rotations. 4.1 turns = 4.10, 3.5 turns = 3.54

If you have limited slip that works, jack up both wheels, turn tires 1 full turn while counting drive line rotations. Both tires have to turn together. Drive line rotations will be the same as above.

 

Yup what he said....