np242 or np231?

how can i tell if my xj has the np231 or the np242 and which is better?
and how can i tell if i have a dana 35 or a chrysler 8.25"? any help would be greatly appreciated, thanks.

Ok, I know it's not cool to answer a question with a question, but sometimes it's necessary...

What year/engine/transmission?

The NP231 will have FOUR selections for drive (including Neutral) - 2WD, 4PT, N, 4LO. Insert 4FT for the NP242 - I believe it comes betweel the 4PT and the Neutral.

Of course, you can also look at the transfer case directly - since it has an ID tag (usually) on the rear of the case, opposite the front drive output. That will tell you directly - either NP242 or NP231. Typically, the NP242 was found on the Limited XJ's, and was (nearly, I'm not sure) always used behind an automatic.

The rear axle is just about as easy - look at the thing. If the cover is nearly oval, it's a Dana 35. If you have ABS, it's a Dana 35. If the cover is more hexagonal (and so is the flange it's bolted to,) it's a ChryCo 8.25"

Search up "old_man" here, and check out his website for an axle ID guide - I haven't created mine yet.

5-90

5-90 said:

If the cover is nearly oval, it's a Dana 35. If you have ABS, it's a Dana 35. If the cover is more hexagonal (and so is the flange it's bolted to,) it's a ChryCo 8.25"

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Actually, the cover is pretty much oval for both of them, although the Chryco cover is a little more flattened than the Dana. It's the differential housing itself where it's really easy to see the difference. The bottom of a Chryco housing is very definitely flattened where the Dana is rounded.

As for the transfer cases, which is better? Neither. They're just different. If you feel that you need full-time 4WD then the 242 is for you. If you don't then the 231 is a simpler design and has more aftermarket parts available for it.

dmillion said:

Actually, the cover is pretty much oval for both of them, although the Chryco cover is a little more flattened than the Dana. It's the differential housing itself where it's really easy to see the difference. The bottom of a Chryco housing is very definitely flattened where the Dana is rounded.

Click to expand...

Perhaps its best expressed;

Both have oval Covers, the Dana's Cast Iron Carrier/Differential follows the shape of the cover around the entire perimeter; the Chrysler 8.25 Cast Iron Carrier/Differential has a lip on the bottom that is a straight edge that extends well outside the edge of the cover.

The best thing to do is find a picture of the back of both axles and compare it to your axle. Do a Google search for Dana 35 and Chrysler 8.25 and click on Images.

And don't forget the earlier metric tonne Dana 44!