stock gears for my 98 XJ

[Eagle]

Dont be too sure. Sequoia and Capt. Ron blew up a t-case simply because of that gear ratio being off just that much...

No, they didn't.

The difference comes from using different axles on each end. The ring and pinion gears are different diameters for a D30, a D35 and a D44. Depending on the exact tooth count, the ratio may calculate out to 3.54 or 3.55, or 3.07 or 3.08, or 4.10 or 4.11. They are functionally the same. You would have a larger difference if had the same ratio on both ends and you replaced the tires on one end with new tires.

 

[johnnyc]

No, they didn't.

You're right, they didn't. This happened on the way to the Moab Fall Fling last year. There was a plastic piece inside the t-case that melted, rendering it useless.

The difference between 3.54 and 3.55 gears is .01 of a driveshaft revolution for every revolution of the tires. Which is negligible (if I'm not mistaken), especially when driving off-road.

 

[carnuck]

Axles

Front Axles
Dana 30 high pinion - reverse cut - 27 spline, 1.16" diameter shafts, 7.13" ring gear - used 84-99 (some axles through 91 are vacuum disconnect, 92+ are non-disconnect, 89-95 with ABS have 5-297x u-joints, all 95+ have 5-297x u-joints, all others have 5-260x u-joints)

Addenda: 84 to '87 could also be CV joint.

Dana 30 low pinion - standard cut - 27 spline, 1.16" diameter shafts, 7.13" ring gear, 5-297x u-joints - used 00-01

Rear Axles
(Note on Dana 35 axles sometimes referred to as Dana 35C - The "C" does not stand for c-clip. It stands for "custom" meaning it came from Dana unfinished.)
(Note on 8.25 axles - none of these axles were used on XJs with ABS brakes. If you have ABS, you have the Dana 35. Without ABS you could have either axle. 8.25 axles are c-clip)

Dana 35 non c-clip - 27 spline, 1.18" diameter shafts, 7.58" ring gear, 2.62" axle tube - used 84-89
Dana 35 c-clip - 27 spline, 1.18" diameter shafts, 7.58" ring gear, 2.62" axle tube - used 90-01
Chrysler 8.25 - 27 spline, 1.17" diameter shafts, 8.25" ring gear, 3" axle tube - used 91-96
Chrysler 8.25 - 29 spline, 1.21" diameter shafts, 8.25" ring gear, 3" axle tube - used 97-01
Dana 44 non c-clip - 30 spline, 1.31" diameter shafts, 8.5" ring gear, 2.75" axle tube - used 87-89 on some(not all) XJs equipped with towing package.

Addenda: To tell C clip from non-C clip axles, look at the axle tube behind the backing plate. C clip tubes are 1 size the whole length and non-C clip are larger at the backing plate because the bearing is bigger.

Also: Model 20 was available instead of D44 in MJs and some XJs '84 to late '86 as a tow package option.

Gearing

3.07 - used with 4.0L engine / manual transmission
3.31 - only available on older (pre87?) 2 door XJs with "Fuel Economy" package
3.55 - used with 4.0L engine / automatic transmission
3.73 - found in some XJs with the towing package
4.10 - used with 2.5L engine usually, and older XJs with the "Off-Highway Vehicle" package.
4.56 - rare but can be found on some older (~ 89 ~) models with 2.5L engine and auto transmission

Addenda: The D44 came with 3.07 (86/87 only) and 3.55 stock. A few 07/86 to 09/86 2WD 4.0L with 4 speed came with 2.72 gears. (I saw 2 so far in Canada and one in the US)

 

[5-90]

I would say probably just a cereal #,I dont think any thing that special,open it up and see if anything looks different

Nothing personal, but I think you mean "serial number."

"Cereal" is the stuff you have for breakfast.
"Serial" is a sequential number assigned to parts/assemblies at time of assembly to track ownership and/or production.

Again, nothing personal meant, but good spelling helps the "search" function work... This includes using the correct homophone, in cases like this (or break/brake - another very common error...)

5-90

 

[falcon556]

You're right, they didn't. This happened on the way to the Moab Fall Fling last year. There was a plastic piece inside the t-case that melted, rendering it useless.

The difference between 3.54 and 3.55 gears is .01 of a driveshaft revolution for every revolution of the tires. Which is negligible (if I'm not mistaken), especially when driving off-road.

You'll prolly say who cares, but here it comes. According to my calculations, the tires will turn .0019 of a turn more with the 3.55 than the 3.54.
46/13=3.538, 39/11=3.545
3.545-3.538=.007
.007/3.538=.0019
Nobody will notice that. If my calculations are correct.

 

[5-90]

Gear ratios are selected to slightly favour the front, which gives the front axle a "pulling" effect, and allows for recovery of steering in a slip, or allows for the steering wheels to "pull" the vehicle around a corner.

That's why. Just for your edification - a slight difference in gear ratios front/rear (usually .01:1 or .02:1) ia actually good engineering...

5-90

 

[Eagle]

Nobody will notice that. If my calculations are correct.

More than likely nobody will notice even if your calculations are NOT correct. :jester:

 

[rocklandxjer]

i was just about to say that whole pulling thing,
pulling forces are much more efficient than pushing, so a 3.55 up front and a 3.54 rear will actuall help with pulling forces. though the reverse would have no ill effect