Put it in low range, and you will be fine. Unless you are doing some serious rock crawling.
I don't have a super low low range,and often find myself kicking my auto up into second because low is simply too slow. That's with 3.54's and 35" tires.
Wait on the upgrade IMHO. You are in the same pickle as I am. Looking for axles, and not wanting to put anything into the old ones.
78 CJ7.. 258.. TH400/Dana18.. SOA/stock YJ springs.. 35" General Grabbers.. Waggy 44s.. 4.88 gears...Spartan/Lockright...Fiberglass front to rear
I'll probably Do 33x12.5, and run spacers. and see how it does.
I just really am disgusted with the T150/D20, and thats on 31x10.5s!
My experience with the old/current combo has me gun-shy about jumping to 33s.
I run 33's with 3.54 axle gears. Great combo for the highway speeds. I have a sm420/Dana 300 with 4:1 low-range. Works outstanding. Low range is so low I often have to use 3rd gear to keep up with the pack.
Now I'm switching axles. Gears are going to 3.73 and using 36" tires.
I rarely use 1st gear on the trail. It's too low with the 4:1 in the t-case. 2nd gear works great for most of the difficult stuff. 3/4 of the time I'm using 3rd gear so I don't get left behind.
My opinion is to keep the 3.54 gears in the axle so you don't loose top end speed, but if it's just a trail rig, then who cares I guess.
4:1 low range will work great for the combo you are planning to run with 3.54 axle gears and 33's.
I know what you mean about the t150/d20 combo. I yanked those out within one month of owning my jeep. They were not going to cut it on the trails around here, in stock form. However in hind sight I think with a 3:15 gear-set in the d20 it would have been fine and I could have saved a boat load of time and money.