98 Grand Cherokee
30" Tires

I have a bent Axle Housing with 3.55 gears. So I went to Pick A Part and got a newer Axle Housing with 3.73 gears could not find one with 3.55. So the question is are D30 housings the same? Because what I have discovered is the housing with 3.73 is longer than 3.55 so the pinion shaft is about 1" longer. And if I stay with 3.73 and match the rear with the front do I have to change anything else.

 

There are high pinion D30's and Low pinion D30's. There are also versions with vacuum disconnect for the 4 wheel drive.

 

Also the wj grand Cherokee dana 30s are wider and I believe jk dana 30s are wider.

 

If its from another wj like yours then its the same,If its from any other jeep then its not the same and won't work.Same thing goes for the rear axle it has to come from a wj and both front and rear have to have the same gear ratio in them.Yours being a 3.55 thats from a 6 cylinder wj the v8s had the 3.73 and optional 4.10 i think.

 

Standard gearing for jeeps is 3.55 and the tow package jeeps are 3.73, BUT could be either if the original buyer ordered it otherwise. The 4.10 could be an option, IDK. The LSD was optional only on 2wd models. The axle width flange-to-flange is about 6" wider on the WJ than the ZJ and the wheel bolt pattern is 5x5 rather than 5x4.5. When looking at them in the junkyard, that's an easy way to tell which they are from. Measure the wheel bolt pattern.

The standard gear ratios hold true regardless of axle type, D30, D35, or D44a. The 3.73 gearing was intended to lessen the load on the engine when towing. IMHO, that little bit doesn't help much to lessen the load. Locking out O/D does a lot more. After all, 3rd gear is 1:1 anyway.

I think the high pinion D30 was only used on the XJ for more ground clearance.