Toyota Land Cruisers have long been recognized as stout off-road vehicles. They do, however, have their shortcomings just like any other vehicle. One of these Achilles' heels is the lack of a granny First gear for rockcrawling. Although FJ-40s do well with the inline-six in front of the factory three- or four-speed transmission, they could do better.
With the inception of the 3.55:1 First-geared four-speed transmission in 1974, a new transfer case with a sad 1.99:1 low-range emerged. The previous three-speed tranny had a weak 2.75:1 First but an admirable 2.31:1 low-range in the transfer case. Some 'Cruiser owners swap in the three-speed transfer case behind a four-speed transmission, netting a small reduction in gearing. Many Land Cruiser owners are quick to get rid of the original six and replace it with a V-8, but this hardly cures the low-range quandary. What the six really needs is the 7.02:1 First gear of an SM420. But how can a Chevy transmission bolt to a metric transfer case and engine? Advance Adapters, baby.
We decided to replace our four-speed transmission and transfer case with an SM420 mated to the earlier three-speed's transfer case. This combination would give us a 67:1 crawl ratio, while still maintaining factory 4.10 gears in the diffs and the original parts inside the transfer case. Much better than the anemic 29:1 crawl ratio of the original driveline. Of course the SM420 can be mated to the four-speed transfer case, resulting in a 57:1, which isn't all that bad.
Our 'Cruiser is a '74 and we happened to have a '72 parts vehicle rotting in the garage. The three-speed bellhousings and transfer cases can be found in '63-'73 FJs. Early model vacuum-shifted 'cases can be modified to work or converted to a regular shifter. Check out the details of this creepy bolt-in swap.