Ford 8.8 gear ratio ID- no tags on diff cover

Recently I picked up an 8.8 already set up for an xj. The guy I bought the axle from wasn't the guy who installed it in the jeep it came out of and he didn't know the gear ratio. The tags that usually show your gear ratio on the diff covers are completely gone, and I bought the axle already pulled from the jeep so I couldn't use the driveshaft spin trick. Today I pulled the cover and inspected the gears. There's some assorted markings on the ring gear but none of them appear to be a gear ratio or a code for one. Am I just looking in the wrong place or not seeing something I should be? If it's really not marked on the ring gear where else could it be/ how could I figure it out? It has a limited slip if the helps. Thanks!

Should be on the outer edge of the ring gear. If all else fails, mark a tooth and count ring gear teeth while turning it. Shine a light in and count the pinion...the divide.

41/10= 4.10
41/11= 3.73
Etc.

JohnX said:

Should be on the outer edge of the ring gear. If all else fails, mark a tooth and count ring gear teeth while turning it. Shine a light in and count the pinion...the divide.

41/10= 4.10
41/11= 3.73
Etc.

Click to expand...

Couldn't find any ratio marks on the ring gear so I counted the teeth. 39 on ring gear, 11 on pinion. 39/11= 3.545. I'm going to assume that rounds up to 3.55?

Yup, 3.55's it is.

What gear ratio do you need? I am about to put 4.56's in my 8.8 and will be getting rid of my 3.73's

clydefrog said:

What gear ratio do you need? I am about to put 4.56's in my 8.8 and will be getting rid of my 3.73's

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My d30 now has 3.55s, so this will work great for now. I have a set of 4.10s out of a 4cyl xj Dana 30, so eventually I think I'll just pull 4.10s out of an exploder in the junkyard and swap those in.