Marlin Crawler 3.12 T-case gear for 100 series (1 Viewer)

[Escape Artist]

Installing a 3.12 low range gear into the T case on my 06 LC. It is the first modification this truck is getting, along with 4.88 gears and e-lockers front and rear. A couple of questions. This year Land Cruiser has the OLD style HF2A transfer case from the early 80 series. Toyota switched to the Viscous Coupling HF2AV in 93 to 97 when they introduced locking differentials to the US market. So the 91-92 models had a locking center diff with open axle diffs, then when Toyota offered the lockers front/rear they moved to a limited-slip center diff to dampen driveline shock ... with the 100 series, they went back to the old style T case with locking center diff but only offered a rear locker. Later model 100's have the four pinion front diffs. Are we thoroughly confused yet? Good.

My question is this, having a triple-locked 100 series, that is with the old style T case that is not a limited-slip but a full locking center diff ... will this cause too much driveline stress with lower gearing? Subjective I know ... how much is too much. I mean beyond design specifications since Land Cruisers never came to the US with true triple-locked setups ... they had the HF2AV T case if they were triple locked which allowed some limited driveline slip in the center diff.

a rather paltry build ... keeping the AHC, 4.88 (Not convinced yet but leaning that way) with e-lockers front and rear with a factory switch, left of the steering column. The tires will not be larger than 34.5". Pinch Weld and washer bottle trim ... possibly a ½" body lift when I do the front and rear bumpers (and adjust T bars and rear springs to mitigate AHC pressures etc). Nothing crazy, just modest in looks but capabilities unforseen.

Has anyone installed this Marlin Crawler 3:12 gear? 'They' say the T Case can stay in the truck to do the install. Right now the overall 35:1 crawl ratio is a bit high for what I am used to. I have 33's now and will go up an inch and a half in diameter so not sure about regearing yet. Going from 4.10's to 4.88's is a decent step but worth $1200 plus the cost of an install? I would have a 54 to 1 ratio ... but the torque would be multiplied excessively on the axles. This is not a daily driver, however will be taken down to South America on occasion.

 

[nukegoat]

It will add stress on the drivetrain, potentially, assuming you get into situations where the traction and loading on the tires can react.

Anecdotally I think it won't make a practical difference since usually people would just add throttle until slipping anyway, it's not like most of you all are hitting the stall on the transmission

 

[cybrstar]

First off what type of driveline stress? You trying to rock crawl and/or have solid axles in 40’s?

Yes the front pinion is weak but you already addressed that issue with the front locker.
I’ve had the gears installed in my 80 and I think the higher gearing actually reduces the stress on the driveline.

 

[ClassyJalopy]

Quite a few 100 series here with 4.88 and triple locked, some are even running 34.5" or 35" tires. . I have never heard anyone breaking the axles or destroying the locked diffs. Modify away!

 

[I Lean]

The viscous coupler-equipped trucks still have the locking center diff. When the center diff is locked ("real" 4WD mode) it's exactly the same as yours with the center diff locked.
when unlocked, yes there will be a difference...but not enough to really care about.
I regularly run in low range with all 3 diffs unlocked, if I need the gearing but not the traction of 4WD. Then it's just a button push to engage when needed.