4x4 effects on driving

Hi TW,

2012 TRD Sport Crew Cab, Long box, automatic transmission.

I have a few questions regarding 4x4 engagement.

1) Last winter, I did a two hour, round trip, twice. Once was 4x2 and the other was in 4x4. I noticed nearly identical gas mileage, with 4x4 potentially being a little better. That's doesn't make sense to me, but I'm wondering if there should be a difference between the two and I would think 4x2 SHOULD have the better mileage, should it not?

2) What are the effects of 4x4 on the driveshaft? The reason I ask is, accelerating in 4x2, I sometimes get a "bump" in shifting at some of the shift points. It's sporadic though. In 4x4 this doesn't happen, or at least not nearly to the extent and I'm wondering if it's drive shaft related? Perhaps needs some grease?

Looking for thoughts on these two points as I've pondered both of them.

 

1. How different? The actual mileage difference between the two driving conditions is probably less than the margin of error of your calculation

 

It probably won't make much of a difference in mileage. Even when you're in 2wd all the front axles are still spinning.

On the older pre Tacoma trucks with locking hubs I would get a decent mpg increase with my hubs unlocked.

 

1. likely no change in gas mileage as its affected by so many other things.

2. in 4x4 you get far less axle wrap as the front wheels pull you forward, this is why the bump is reduced.

 

You should not be using 4X4 for 2 hour road trips. Unlike AWD vehicles 4X4 was designed to be used OFF ROAD. It is OK to use it for brief periods in ice/snow on pavement, but only long enough to get moving from slick spots or up inclines. While driving at speeds of up to 60mph or so won't damage anything, driving on pavement will at any speed. If it is safe to drive at speeds over 25-30 mph operating in 4X4 is if anything a disadvantage. People who do this is why I'd not buy a used 4X4 vehicle. While you may not have broken anything yet, that 2 hours on the road has caused premature wear and damage to your transfer case. It will fail much sooner than it should.

All things being equal you WILL see a reduction in fuel mileage operating in 4X4. But I'm betting road conditions were much different on the trip you made in 4X4 and your driving style was much more cautious. Speed kills fuel mileage.

 

No, just no. Maybe you just worded it weird but this is bad advice to the OP.

4x4 Tacomas get worse gas mileage than 2x4 no matter what because of additional weight and that's all. It's total BS that you shouldn't drive in 4x4 except for brief periods of time and only buying NEW 4x4s??!? Alright dude. Guess someone has to pay the sticker... carry on

 

OP, the reason people are saying not to use 4x4 all the time is that Tacomas do not have a center differential. That means if you are in 4wd torque is split evenly (50-50) between front and rear axles and during turns your front wheels travel much further than the rears. On slippery surfaces such as snow, ice or dirt this is fine because the wheels can just skip thru but on very grippy surfaces such as dry pavement it can cause the driveline to bind up which does cause premature wear and tear.

 

Anytime you have more components moving you create more resistance.

All things being equal a 4X4 operated in 4X2 gets virtually the same fuel mileage. But all things are rarely equal. Most 4X4's get worse fuel mileage because they are 200-300 lbs heavier because of the extra running gear, they have larger tires with poor rolling resistance and the higher stance catches more wind. The more mods and accessories added makes it worse. Keep them stock, use the same tires and you won't see 1/2 mpg difference.

Here is a good link explaining why not to operate in 4X4 on pavement. Toyota does not do a good job of explaining this in their owners manual. Most of the other manufacturers offer stern warnings. They all use the same systems, the transfer cases are built by the same vendor on almost all of them.

http://4x4abc.com/4WD101/def_turnpart.html

 

I put at least 10k miles on my truck running in 4wd the last 2 years, it also snows 8 months out of the year. Never heard of ruining a 4x4 system by using it. I always get a slight loss while in 4wd and the winter gas doesn't help either.

 

I appreciate the feedback from everyone and I believe I got my answer and some additional useful information. Thanks everyone!

 

4x4 always uses more fuel
don't drive in 4x4 on dry pavement
4x4 on wet pavement is ok but sharp turns will cause drivetrain to bind
4x4 after 50 MPH isn't that safe on pavement

 

Bad advice, not sure why other people are liking it.

If you are traveling straight on pavement or even slight turns, why would this damage your truck?

 

in a perfect world, no problems

but there are always slight imperfections in the diameter of front vs rear tires

if in 4x4 and turning even slightly, or having even 1mm difference in tire diameters, it wears on
the transfer case harder...wears on everything harder.

so yes, on paper with perfect mathematical circles for wheels and straight lines, zero issues
in real life, much more likely to be in a 'greater stress' condition the drier the pavement is,
and the faster you go, in 4x4

if you had AWD all these problems go away, but tacoma ain't got AWD, so it is
always --always-- best to pick 4x4 only when really needed, and leave it in 2wd when 2wd is enough

 

We don't have enough information to say this. If those 2 hours were driven in snow or on dirt then there's no problem.

 

4x4 will always consume more fuel; however I haven't noticed it much running in 4x4 this last winter (all winter). I stop worrying about fuel consumption after about 3 months of owning the truck because I was getting shitty gas mileage either way.

Running in 2hi I'm now averaging about 17-19mpg, I get the 19mpg when I'm constantly aware and go easy on the acceleration. In 4hi, I was consistently getting 17.3-.5mpg.

If you have a pre-runner you should see better mpg's due to not having the front drive train as a parasitic drag because we don't have manual locking hubs, however I think the difference is too small to be worth much.

 

If you really needed 4wd on this trip it is likely that you had more wheel spin and struggled more in 2wd and that is what resulted in your lower 2wd mileage.

 

I did once get better mpg in awd on my 4runner on a out-back trip from Boston to NYC

I did it twice in two days ...and once in awd once in 2wd.

got 40 more miles on a tank in AWD...so I was like wtf???

but after examining the situation that was because traffic was balls-thick but f-a-s-t the whole time in CT and I was basically riding
in the slipstream from everyone else for half the trip, so I got better mpg as I was pushing less air out of the way

next time I did any awd vs 2wd comparo's they were so close to the same it was meaningless

summary: all external factors removed....more parts to move more friction = less mpg