cwmoser wrote:
I read a lot that one should tow with Over Drive OFF - and 3-rd gear ratio in my LX470 is 1.000
I have little doubt you'd be towing in 3rd with OD off and your 4.7L V8 coupled to a 4.30 axle
will be spinning pretty high at 60 mph ... no worries, that's what it's designed to do. :) In contrast, my 5.3L GM V8 runs ~ 2200 rpm in 3rd, my
only choice when towing because in 4th it's only running ~ 1500 rpm which is
way too slow when I'm dragging a barn door down the highway. Given a choice I'd rather be running a 3.73 axle so my engine would be running just a bit higher at the same speed but it is what it is and does well enough under most circumstances ... significant upgrades though do force me to manually downshift to 2nd so the engine can spin closer to 3000 rpm and thereby manage to maintain sufficient road speed.
As you have surmised tire diameter does play a role as well but rare would be the case when an owner would swap out the tires / wheels for a new set with a smaller diameter if they weren't otherwise required. In my case I could have my ubiquitous 3.42 GM axle replaced with a 3.73 but for me it's just not worth the cost. If I were replacing my current truck I'd certainly be looking to another GM 1/2 ton but with the narrow ratio 6 spd transmission coupled to at least a 3.42 axle or if possible a 3.73.
I wouldn't overthink this too much ... now that we know your Lexus is equipped with a 4.30 axle I'd have every confidence you'd be satisfied with how the vehicle tows a 192RBS or some other trailer similar in size. If in doubt find a dealer that will agree to a test tow and put your mind at rest ... but in the meantime go weigh your Lexus as described earlier so you then have accurate information to plug into that towing weight calculator. :)
