Originally Posted by Uncle Ben
Jeff, Keep in mind there is more to final gearing than just math! Physics is a huge chunk of the pie! If you are running a 2F or some anemic 4 popper in a rig then low gears are your only choice. When you double or even triple your hp and torque you have to take into factor the strength. You don't need as low a gear with more power so you can get by with a higher pinion tooth count (stronger) and still pull hills that would kill a tractor engine! Tough choices I know! 4:88's are great gears but your pushing a lot of power through just a few pinion teeth! I have run 4:56's in Wild Rice(my 40) for years driving 36" grooved swampers by a perky F! Except on the highway up long grades I have no power issues! On those long grades it will still pull 40-45! The place you want to address is your tranny/t-case gearing! you already have a 700R4 which has a great 1st gear (3.06:1!) plus the almighty trail handling torque converter. Focus some thought on more than a 2-1 t-case and you will create the best of both worlds.....great highway gears that are strong and great crawling ability that lets you save the body by the use of finesse instead of speed!
....that is just about
Well I had been strongly considering a Marlin Toy Box between the 700r4 and the Toyota LC and was thinking of doing that as a winter project. To adapt the 700R4 to the Toyota TC you need an adapter (mine is from AA) which is the same length as the Toy Box. I was thinking I could remove the AA adapter, install the Toy Box with the 4.7 to 1 reduction and have some serious gears. Years ago I had a Ford F-250 with a six cylinder 4 speed w/granny low (6:1 I think) and 4.56s. The thing was awsome. I really enjoy the ability to use near idle rpm with tons of control.
To add the Toy Box, or put the 40 back together correctly I think I will need to extend the wheel base by moving the rear leafs back. The rear drive shaft has no play in the slip yoke and I think this may have caused some problems on the pinion shim preload (it was crushed according to Squishy). Alas, yet another project
However, UB, you bring up some very good points. The last time I had the thing dyno'd it had 310 ft lbs of torque at 3300 rpm, and 215 HP at 4400 RPM at the rear wheels. [Parenthetically, I was surprised that this 355 HP, 405 ft lb engine lost so much at the rear wheels but was told that was not surprising by the tuner]. I really don't want to eat R&Ps so maybe the 4.56s and Toybox are not such a bad idea. Can I re-gear my 75 LC TC to lower than 2:1? I looked at Mark's gears but they appear to be only for later model year TCs.