A 3RZ, 33s w/5.29s you must be pulling on everybody up the passes.
I run 5.29s and when I had my worn 35s (that measured 33.5"), I could pull the "Four Lanes" 6% ave grade up CA HWY168 east of Prather, CA in 5th gear @ 65 MPH the whole way with all my wheel'n/camp'n gear with *barely* power to spare. Never needed to downshift to 4th. One time a guy in a Cummings diesel swapped 2nd gen 4Runner asked me if I had a "big block or something" and I said "yes, a big block 4cyl".
Then I moved up to 37s (that probably measured 36.5" new) and holy smokes what a difference. Now I can only pull the grade in 4th and there are two sections that if I don't get my speed up just enough then I'll have to drop into 3rd gear to maintain > 55 MPH.
For reference most 22R(-E) powered rigs with 37" tires run 3rd gear the entire length of the climb. They just hold it at 4k RPM. I know of people who will shift their Marlin Crawler Crawl Box into Low and run 5th gear @ 4K RPM which is about 45-50 MPH.
People don't seem to realize the increased torque requirement when moving from a 35" tire to a 37". Because I like to jam in the hills I would not want to run 4.88s + 37" + 3RZ-FE.
Another thing that comes to mind is the 3RZ-FE's open loop. I have a narrow band AFR gauge in my truck (monitoring the upstream factory O2) and for my 5.29:1 + 37" combination the ECU switches from closed to open loop at approximately 76 MPH. This when there is no or minimal headwind. What this means for me is that at approximately 74-75 MPH I am making 19-20 MPG and then at approximately 76-77 MPH I am making 10-11 MPG (verified via OBD-II scanner). I've never ran 4.88s, but I'd imagine this load-point that triggers open loop would occur at a lower speed, perhaps at only 70 MPH in 5th. Now you're efficient highway cruising speed has a lower speed rating, and your poor catalytic converter would be cooking for hours and hours for all your high speed long distance road trips. Add an exo cage or similar high drag modification, headwind, wide heavy tires, and the ECU loop switch point MPH will drop even more.
Regards,
BigMike
