freight train

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)

SOOT4BRAINS

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

freight train

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

SlingShot

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

SlingShot

43divided by 14 =3.0714285

cLAYH

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

freight train

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

Philip

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.

BC847

"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.

pulltilbroke

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.