2016 TRDOR question about front hub engagement system-

My son has an F-150 (2015) which uses vacuum to keep the front hubs NOT engaged (maintain 2WD) and when you switch to 4WD vents off the vacuum (using solenoid valve) to engage the front hubs. With this arrangement if you get an air in-leak (hole in tube, heck valve that won’t seal, solenoid that sticks mid-position) the axles will bring attempting to engage front hubs while driving. It can ruin the front hub gears. The check valve is a maintenance item to replace about 4 years. This seems like a dumb design. I would prefer to need vacuum to engage the 4WD (vs maintain 2WD) to avoid this failure. How does the Tacoma engage the front axles? Does it use vacuum to Engage or to maintain 2WD? I hope that loss of vacuum just disengages 4WD since you are in 2WD most of the time. I suppose it could be independent of vacuum using solenoids only but I don’t know. Thanks

 

It is all electrical. I think of hub locks as similar to my old truck whee you manually lock the hubs at the wheel. For Toyota technically it is an always locked hub. The lock occurs in the differential

 

My understanding is that it’s electrical. The transfer case has solenoids to engage/disengage the front differential

 

Thanks. I can see the solenoid housing on the front diff. Sounds like a good system. I mean you are rotating the axles since locked at hub which introduces additional friction but it seems more reliable than vacuum actuated system. I had manual hubs on my 1999 Tacoma so you could disengage the hubs.

 

Ford designed the hubs to default to 4x4 in case of vacuum loss as a fail safe for those of us who live in snowy country. I’d much rather the front end be locked in, costing me a minimal amount of extra fuel, than be stuck in 2wd when i need 4x4

And my Taco’s diff actuator went out around 30k. I don’t think it’s sealed well.

 

This system of locking the front axle shafts (ADD) also keeps the spider gears whirring in the diff since the front driveshaft doesn't turn in 2wd. So, swapping the fluid in the front diff is just as important as the rear diff.

There is a person here that has a free hub kit for sale:
https://www.tacomaworld.com/threads/free-wheel-hub-conversion-3rd-gen.513930/

That's a big time wishlist item for me.

 

AKGSD, thanks for explaining the rationale for Ford’s design. I guess you have to pick one way or the other. It seems to me that when driving on non-slippery surfaces, failing to engage 4WD can damage axle splines or hubs. My son’s truck was making an awful metal grinding noise. Ford did fix under the power train warranty however.