2.66 low gear vs close ratio

Careful now
your current ratios are 3.34-1.66-1.00 (granny not included).
The 833 O/D ratios are 3.09-1.67-1.00 (od not included)
You might be trading one big pos for a little pos.

Huh, interesting. Did not realize they were so similar!

But... even though the ratios are almost the same, the NP435 and 833 OD are totally different in terms of character. The 833 has a usable 1st gear and the OD allows a steeper rear gear (mitigated for highway driving with the OD) which would obviously help with torque multiplication in gears 1-3. I do a lot of highway driving with my truck but I need the steeper gear too because it's a heavy vehicle that tows sometimes. Only real option for anything like that with a 435 is to put a Gear Vendors behind it but you are still saddled with that giant, unwieldy shifter.

I could see how I'd potentially wind up in the same situation with the 833OD where I'm at the practical rpm limit for a given gear and have to shift into a higher gear where it falls flat. Again though, a steeper rear gear would help keep it closer to where the rpm needs to be so the drop may not be as noticeable.