I've read that front/rear ratio differences can be up to 1% on-road--possibly higher if used exclusively offroad--which covers 4.10 vs. 4.11. If given the choice, 4.10 is meant to be slightly stronger, because the tooth count is 41/10 (vs. 37/9 for 4.11). The extra tooth on the pinion means a bigger, stronger gear.
On finding gears, I started looking for D35 TTB 4.10s this past February. Placed a number of different orders, at steadily increasing prices, and watched every retailer refund me and flip their listing to "out-of-stock". Even people you would expect to have parts in-hand, like Ebay sellers, were just drop-shipping from Yukon. I would not be surprised if 9/10 listings at this point are misinventoried, rather than actually available.
Yukon told me they do plan to make more, but it could be "up to a year". Since then, the topic has come up and I've seen people say October and December, but at this point obviously both of those dates were wrong.
More recently, I saw don4331 point out
that factory 4.10s were only available in '90-'92 Rangers/BIIs, which substantially limits the pool of used gears.
I would give up on finding 4.10s before Yukon resumes production, and either do the front axle swap or bump up to 4.56. Over the past year, Yukon's higher ratios have also slowly started showing out of stock, but allegedly Nitro still has 4.56 available*,
and without insanity pricing to boot.
I was apprehensive about highway RPMs with 4.56, but it's actually been pretty manageable (although it was better before my rubber body mounts failed, and I had to switch to poly). I also appreciate the acceleration and especially the power driving on sand. That said, I do have the 2.3L. YMMV.
Maybe the biggest pain in the ass is that they literally don't make the right gear to correct the mechanical speedos for that much gearing.
*EDIT: Nitro moved the page,
and now shows 4.56/4.88, but no longer 5.13
. Yukon shows out of stock for all D35 Reverse (TTB) gears.
That's not to say no resellers have gearsets on the shelf (ECGS says they have exactly one 5.13
), but like I said before, drop-shippers who haven't updated their listings are a lot more common.