Thoughts on MTS for on-road Snow driving

I initially thought 4HI with MTS in setting 1 (Mud and Sand + snow per the manual) would be ideal for on-road snow driving because we get the very active traction control tailored to each wheel. Some Toyota models allow MTS setting 1 in 4HI, but Tacomas don't. This limitation prompted a deeper dive into the suite of traction systems available on my 3rd Gen OR and I now think the ideal setting is actually just plain 4HI. It comes down to Speed, Traction, and Stability when moving vs when stuck.

Speed. Snow requires slower driving but in my area it's 15-20 mph slower, not 4LO slower. The torque boost and improved throttle control while in 4LO aren't very helpful and the limitations to speed are terrible. It's icy here so the loss of momentum is a great hinderance. +1 for 4HI.

Traction. In those same icy conditions I came from a 2wd 96' Ranger with traction problems in light rain. It felt like a helium bed despite none horsepower available. If you're able to manage momentum you can get a LOT done with even a little boost from traction systems. +1 for traction control but no additional points given for more aggressive traction control.

Stability. For on-road snow driving you aren't likely to just suddenly get stuck while moving. You generally get stuck when you slide off into the ditch which is a much different terrain than the road, despite being only feet apart. Stability in this context is lateral traction beyond acceleration and braking as well as maintaining control over the attitude of the vehicle. Stability aids help keep you out of the ditch and in control. Stated another way, not stuck and not crashed.

4HI defaults to TRAC on (traction in the braking and accelerating sense) and VSC on (Vehicle Stability Control in the yaw and don't lose control sense). In 4HI with defaults you can drive at normal speeds appropriate to the traction the road surface will afford, light traction control to reduce brake sliding while braking and while accelerating from a stop, and prevent or mitigate yaw and loss of vehicle control before we humans begin to detect it.

MTS is an off-road mode and behaves accordingly. To take a step back to the comment about being "not stuck and not crashed", you can't undo a crash but you can undo a stuck and this is where the roles reverse from 4HI defaults to MTS in setting 1. The speed and stability are no longer relevant. Tie between 4HI defaults and MTS1. Additional torque may be helpful, +1 for MTS 1. Additional throttle control is helpful, +1 for MTS1. More aggressive control of slippage at each wheel is likely necessary, +1 for MTS1 (or more aggressive MTS settings depending on your particular stuck).

Lockers. Lockers are less effective than MTS in snow for on-road AND off-road driving unless a specific situation requires it. Lockers provide torque to each wheel on a given axle simply by forcing them mechanically and the system is either on or off. Lockers also do nothing to limit wheel spin. MTS provides torque to each wheel by selectively braking the wheel that would otherwise be freely spinning on an open diff and does so in a highly controlled way to prevent unnecessary wheel spin. In the context of snow a locker says "yes, wheels will spin" but MTS says "yes, each wheel will spin exactly as needed".

Some spin is fine and maybe even helpful in snow but too much spin can ruin what little traction the surface afforded you. For example I grew up on a short road that began with a very steep hill. My road teed off another road in the middle of a moderate hill. In other words you had to take this steep hill while turning with low momentum or else risk sliding into the very deep ditches. Every time it snowed/iced - without fail - one of the neighbors with a giant van would attempt to take the hill at full throttle and would slide over the whole surface as he fishtailed back down. Repeat. Repeat. Repeat. Park at the bottom and walk. This left the hill polished to perfection and ruined anyone else's chance to drive home so we also got to walk. If he had used a little throttle control he would have made it many of those times and would have given others better surface to attempt. All that to say, take as much advantage as you can of what traction you have available. MTS was designed to sense slip and control braking to each individual wheel in ways a human never can, even if we had 4 brake pedals. What it can't do is determine the acceptable level of slippage for the surface, path of travel, and each person's driving style which is why we get control over that part. Computers do certain things better and that's good. I could never monitor the mass airflow sensor and adjust the fuel mix as well as a computer but that system still lets me do the driving. MTS is no different and I consider this approach to be the ideal level of vehicle automation.

Crawl Control. CC is basically MTS with throttle control added. We understandably see this used in sand for self-recovery because it's hard for a human to hold their foot on the exact right level of throttle for a few minutes while it builds up sand and so on. Even though we can maintain that level of control I wouldn't want to when an automatic option exists. It's nice for ascending and descending long roads with light obstacles not because it's necessarily better at it but because it's easy. I would never use it for driving in snow but would keep it as an option for getting unstuck if nothing else was working. It disengages when the driver's door opens but I would see a (stupid and ill-advised) scenario where it might be nice to slip out the passenger side while CC is going so I could guide traction boards into place or try to pry it into a better line.

To conclude this whole thing: on-road driving should be done in 4HI with defaults unless there's a specific reason otherwise. Sometimes we think "aid good. more aid, more good." but we don't learn about the problems these different aids are designed to solve and methods they use to solve them. Use the right tool, not the most tools.

 

Totally agree.

None of the knobs/levers really matter, in my experience. 4HI/4LO/CRAWL/MTS are all bandaids that might inch a little extra traction and performance in certain conditions but the optimal combination of them varies based on how much snow is on the ground, how much is ice, if its crusty or wet or powdery. You could be tweaking traction control knobs 24/7 while driving to inch out that performance but I've decided that the distraction is more dangerous than leaving it in 4HI. Use the tools when you're stuck not when you're driving.

They won't do anything nearly as much as a dedicated set of downsized snow tires. Slap snow tires on, slap on 4HI and don't forget to put some weight in the bed.

YMMV. We regularly get 5-8ft storms and I drive the Taco most days.

 

"4HI/4LO/CRAWL/MTS are all bandaids..." I don't think you read the post.

Snow tires and weight in the back are great but that's not what this thread is about. It's about why 4HI is probably your best bet and when it might not be. When you use 4HI you are using TRAC and VSC by default.

 

Sure. I’m just pointing out that even if the other tools in the toolbox do have benefits in a technical sense that much of that benefit is lost by distracting the driver. Even a very aware and focused driver might not correctly assess the terrain because snow driving is so much more dynamic than traditional low traction scenarios.

I think the human element is worth mentioning as much as the technical one. And “just stay in 4HI and focus on the road” is a good driving tip even if it didn’t give you VSC/TRAC by default.

But I appreciate you pulling this together regardless even if you disagree!