Go with the 5.13s as you don't want to diminish the pinion size any more. This is based on a buddy of mine also with a 318, lifted, and ran 38s with 5.13s in D60s. Do all truck. MPGs for your setup is just out of the question. I'm gathering you'd be experiencing 8-9 towing the XJ.

Let us know what your path is going towards.

 

WN,
5.13 & 5.38 gears both have 8 teeth so you're not loosing anything strength wise.
5.13=41-8
5.38=43-8
I wasn't positive so had to go check and make sure my thoughts were correct. I got into this discussion with a buddy when we were regearing his D44 that we were swapping into his Suzuki Samurai. You run into this with a few different gear ratios. Some will have the same tooth count so then you just need to figure out which one you want to go with.

 

You don't get something from nothing. Assuming you're correct about the teeth numbers, the ring diameter must be equivalent on the 41 and 43 toothed gear to fit in the case, which is a given. That means the diametral pitch of the gear teeth must be larger on the 43 tooth gear in order to fit more teeth on the same diameter, meaning your working depth is shorter and your tooth thickness is less than that of the 41 toothed gear. To compensate for the shorter teeth, your ring gear would need to be thicker to push the teeth further into the pinion, as both would have shorter, skinnier teeth. Not sure of the impact on strength and the differences but you could calculate it if you really wanted to

 

I don't think pinion/ring gear strength are really all that much of a concern on our trucks though. The ONLY busted ring/pinion gears I have seen, disintegrated because something else failed first, (or, improper installation) and took the R&P with it when it failed. (sometimes, quite spectacularly..... always fun to pop open the diff cover, and have several pounds of scrap metal come out, in chunks no larger than 1 inch.....)

 

Yes sir, I stand corrected in that this is not a case of reduced pinion teeth. The compensation is more ring gear teeth, which results in thinner teeth. Thinking back and not wanting to drive in micro details, the strength issue is present and really dependent on driving style. The strength comes from teeth overlap and it is different for those sets.

In any case, another good thing people consider for gear sets is what kind of tranny, auto or manual. Auto can tolerate a taller set.

Would be good to know what the OP deduces though.

 

Ok so I know this has been answered but I want to add a little more. I have a 03 ram 1500 5.7 hemi 4x4 with pacesetter longtube headers magnaflow exhaust 33x12.50x18 tires and wanting to know what size gears would be recommend I was wanting to go with the 4.10 gear but not sure what would be best. I do some mudding and highway driving.

 

4.10's would be good.

 

Hey Frank. You're in a whole different arena with a 345hp 5.7 and 5spd automatic (or manual, you didn't specify) than the old Magnum 318/360's in 2nd gens. You may already have 3.92 gearing, in which case there's no reason to change it at all. Even with 3.55's you probably don't have the power struggles of the older engines. The 360's made only 245hp. I don't see it worth your money to change your gearing for what you say you do with it.

 

I have a 01 ram 1500 4x4 5.9 liter 360 engine. I put 4.88 Nitro gears for 37 x12.50x 20 Gladitator Xcomps 4.88 ratio is great for 37s. But I also put a Monster Transmission and transfer case it's a Beast.

 

How long have you been running that trans? I hear an awful lot of horror stories about Monster Transmission........