What's my gear ratio?

[Shandley]

Say, is there an easier way to find out what gear ratio my differential is rather than marking the drive shaft and tire and rotating the tire one full spin only to watch how many times the drive shaft spins?

[cracker]

There should be a tag on the diff cover of your axle with the gear ratio stamped into it.

[Eagle]

There should be a tag on the diff cover of your axle with the gear ratio stamped into it.

Or not.

 

The rear axles almost never had tags. Front axles did in the early years, I haven't paid attention to them after 1988. But if the axle was ever serviced, the tag may not have been put back.

 

Simple rule: If the engine is a 4.0L, the 5-speeds came with 3.07 gears and the automatics came with 3.55 gears.

 

4-cylinders aren't that simple.

[dasbulliwagen]

This is a generalization, but usually

4 cyl 4 spd = 3:55

4 cyl 5 spd = 4:10

4 cyl auto = 4:56?

 

But all of these would have to be confirmed visually either by doing the driveshaft thing or pulling the cover off the diff housing.

[XXLMJ]

If you pull the cover off is it stamped on the gears or something?

Or would that be too easy

[Geonovast]

The tooth count will be stamped on the gears... but most people don't want the hassle of dumping all the fluid, resealing the cover, and filling it back up just to find out ratio. Jacking up one wheel, turning it twice, and counting driveshaft turns is easy and accurate enough.

[Automan2164]

You can pull the cover, and it IS stamped on the gears, but in numerical form. IT has the count of teeth on each gear, right next to each other, set off from the part numbers. So, my recent setup I looked at was:

 

41 11

 

So take the ring gear count(41), divide that by the pinion (11), and you get the ratio...

 

41/11=3.7272727272727

 

Round that, to get 3.73's.

 

Rob L. :D

[89eliminator]

You can pull the cover, and it IS stamped on the gears, but in numerical form. IT has the count of teeth on each gear, right next to each other, set off from the part numbers. So, my recent setup I looked at was:

 

41 11

 

So take the ring gear count(41), divide that by the pinion (11), and you get the ratio...

 

41/11=3.7272727272727

 

Round that, to get 3.73's.

 

Rob L. :D

 

yeah, note to self...don't do division in my head :thumbsup:

[Pete M]

all you need to do is jack up one rear tire, put trans in neutral, and spin that tire around 2 full revolutions. Note how many times the driveshaft rotates and you will have your gear ratio. :thumbsup: There are only so many number possibilities so it's a pretty fool-proof way to find out.