First off, I bought a set of Dana's from a 1989 W250, auto with supposedly 3.07 ratio's for my project. I want the highway ratio for my DD. Now please read below

Hi, well I tore down my Dana 70/71 rear today to get it ready for the rebuild. I didnt remove the diff just the axles and hubs so I could pre order the needed bearings, races, and hub seals. I counted the ring gears teeth and there is only 44 teeth on it. I have a spare set of 3.54 ring and pinions laying in storage and decided to see if there was a big difference. The 3.54 ring gear has 46 teeth. The weird thing the rears I bought are supposed to be 3.07 ratio. In my mind I thought the 3.54 ring gear would have less teeth then the 3.07 ring gear. Am I wrong in my logic or did I buy a set of axles that arent what I wanted? Someone out there please ease my mind and tell me that a 3.07 ring gear does have 44 teeth

Thank you out there to everyone who has ever answered any of my questions. This site is so nice and friendly. I am buying and planning a RC swap in the near future and plan to use this site as a learning tool. Its so nice to have a referrence point to people who have done the same things and to be able to learn not only from your success but also your failures. Thank you

Robert A Miller (RAM)

 

A 3.54 and 3.07 are not only different ring gear teeth but also different pinion teeth as well.
3.54 is a 46 tooth ring gear and 13 tooth pinion
3.07 is a 43 tooth ring gear and 14 tooth pinion

 

^Soot
What about 4.10?
And how does 43 teeth r/g and 14 on pinion equal out to 3.07?

 

Count the teeth on the pinion, divide that number into the number of ring gear teeth, thats your ratio.

 

43divided by 14 =3.0714285

 

FYI ring gears and pinions are matched sets. You can not change one without changing the other and doing a setup procedure.

 

I understand now thanks sling shot.
cLAYH I knew that. I didnt plan on swaping ring or pinions. I just didnt get how they get the ratios. Thanks

 

If you look on the outer edge of a ring gear. The ratio is stamped into it.

It will look like this. XX-XX devide the small number into the larger number to get ratio.

 

"How many teeth should be on my ring gear?"

-> All of them.

No seriously. I tried running mine with a few missing some years ago and it didn't sound right. Kinda banged a little when pulling away from a stop.

 

The old mans did the same thing, it was missing 3 pinion teeth and the carrier had an eighth inch of side to side play.