I think you can find sources to support a difference of 1-2% is workable. I think where I’ve seen different gear ratios on rigs in magazines they generally had the lower gear ratio in the front so that the front end was pulling rather than the back end pushing. I’d guess that you’d be ok in the dirt where there’s some give, but don’t know how it might change things on the rocks.

I would bite the bullet and put 4:56 in both(as opposed to 4.10) if you have bigger than stock tires or find a pair of used takeout thirds. I guess it depends on how your 4-speed feels now with the 4.37s but I would imagine 4.56 would give a bit of improvement all around.

Thanks for the replies! Ideally I would definitely re-gear both differentials, but that’s not in the budget right now. Based on your responses, and some other research, I think I’m going to go with the 4.30s. The new 4.30 diff will be in the rear, and 80% of the time it will be in 2 wheel drive, so it should be ok. The truck is on 31 inch tires, right now, and the biggest tire I would put on it would be a 33. The 4 speed does alright right now, it’s an old Toyota, so it’s slow, but I can get it up to 70 on the freeway if I push it.