4WD 'thrumming'

I bought a new 2020 1794 which now has 1300 miles. I'm also new to pickups and 4wd, so please bear with me for a rookie question.

As soon as I engage 4wd high, there is what I can only best describe as a 'thrumming' in the drivetrain - not exactly a vibration, but a sensation that I can feel through the wheel and the seat too. This is on dry pavement, driving straight with no turns. The thrumming is not extreme, just different than when the truck is in 2wd. When I disengage it, it immediately goes away.

Is this normal?

 

Hard to say not feeling it and hearing it myself, but it sounds normal to me. As you use the system more it should loosen up and quiet down a bit. Be careful using it on dry roads though.

 

You’re not supposed to be using 4wd on dry pavement for regular driving. What you’re feeling is you’re driveline binding. It’s 4wd. Not AWD. That’s bad and you can and will damage your front drivetrain components.

 

Sure you can... As long as you don't make turns with it in 4wd. It wont bind going in a straight line

 

Right - I'm driving only in a straight line when on pavement, and just to engage the 4wd for the recommended 10 miles per month.

Aside from that though -- with all the 4WD experts here, I thought I'd get lots of feedback about whether this situation is normal. Anyone else have an opinion? If you engage 4WD hi, do you sense any difference at all from 2WD?

 

Yes, I feel it. It’s in 4wd. Of course there will be noticeable changes to how it feels. I think we’d have to hear the sound to tell you if it’s normal. But being new I’d say it is. Take it to the dealer and have them test drive it.

 

Incorrect.

Or BS to put it less politely.

I have a first gen so I can't tell the OP if its normal or not. The only time I could tell that I was in 4wd or 2WD on pavement from noise was when I had a bad U-joint.

 

Like I said. “Regular driving” as if it’s an AWD system. So no, it’s not bullshit.

 

Long and short, it’s a brand new truck. Take it back to the dealer and have them give it a once over. But if you’re at all sensitive to steering feedback and drivetrain noises, you can most certainly tell the truck is in 4WD. And I’ve owned 4WDs of all kinds for almost 40 years.... my guess is it’s totally normal.

 

Yeah, you're right. Regular driving wouldn't do in 4wd.

 

Mine does make a thrumming noise too, but not a grinding. It's just the front differential working

 

Yes it’s normal to have a different sound you have the front driveline and differential turning.

yeah, it will.

there is no way your tires and diffs match exactly. The farther you drive the more pressure you will build up in the system from the small differences in effective gear/tire ratio. An AWD system has a center differential that prevents this, the tundra doesn’t.

It’s not as bad making turns on dry pavement in 4wd, but it’s definitely not good to run around in 4wd on dry pavement any more than you have to even in a straight line.

If the general conditions are snow/ice and there are a few dry patches of road I wouldn’t worry about it, as the benefits of the 4wd outweigh the wear and tear. But no way would I run down a dry highway in 4wd if I didn’t need to.

if you want to run the front diff once in a while as a maintenance thing, best to do it on gravel or dirt roads imo.

 

Its normal because youre on pavement and there's power going to all 4 wheels which explains why when you go to 2wd it goes away. Its perfectly normal to drive in 4wd on pavement, I've done it many times with no problems just don't turn. To me its not a thrumming noise when I put 4wd on pavement but like I can feel the power going to all 4 wheels, like there's a giant hand on the top of my truck like a kids hand playing with it, feels like more weight if that makes sense.

 

Add me to the list that thinks its probably normal. Also add me to the list that thinks driving in a straight line in Hi 4WD on dry pavement won't damage anything. Toyota recommends 10 miles per Month which i think is a generous amount on their part. Do it every now and then to keep everything lubricated including the actuators, and i think everything should be fine. At least that's how i plan to do it on my truck. Just my 2 cents.

 

4WD is not magic. It's an old, well established and simple technology.

When you drive, even in a straight line, all four wheels turn at slightly different rates. When you turn, this difference increases.

A four wheel drive vehicle like ours with two open diffs and a locked center will always have one wheel in the front, and one wheel in the rear, mechanically locked together while in 4WD, This means their will be a certain amount of skidding. On a slippery surface this skidding happens easier so this 'binding' force is more easily released. On dry pavement with good traction, this skidding takes more force, which means more force on the driveline.

Luckily, the driveline is meant to take large amounts of torque so we can do things like accelerate, engine brake, tow, etc.

Yes driving in 4WD when you have traction puts more strain on the driveline, just like accelerating, towing etc does. Nothing comes for free.

No, it's not going to suddenly make your transfer case explode. The strain is proportional to the difference in wheel velocity. Tight turns will be harder because your having to drag a least two wheels. Nothing you do on a highway will ever have a tight enough turning radius to matter.

Yes, you may feel a difference in how the truck handles or sounds. It should be slight.

Never be afraid to use 4WD when you need it. Its your vehicles super power. No, don't use it when you don't need it, just like you shouldn't step on your brakes or your accelerator if you don't need it.

 

A dirt road is best for your 10 miles a month.

 

10 miles a month? Damn I better go drive about 200 miles in 4wd then I did not know about this. I am sure though their are people who never test their 4wd until they use it

 

The thrumming I hear cannot be driveline binding because it occurs the instant I engage 4hi, so there has not been enough time for a differential in wheel speeds to have occurred. Also, the dealership and the manual said that dry pavement is okay for straight line driving, but just to be clear I don't drive that way normally - I only do that to exercise the 4WD system for 10 miles and then it's back to 2WD.

It seems that the best thing is to have the service tech drive it and see if he thinks it's normal, but I fear I will hear the usual "they all do that" explanation, which would make me wonder if it's true.

 

Two simple solutions to your worries.
1) drive somebody else's 4wd truck and see what it feels like (most likely feels they same as your truck as this is normal) (has to be a 4wd and an AWD example)
2) test drive a brand new one and see if it does it. (I still feel this is normal, remember your asking more participants in the drive-train team to play along when in 4wd, So of course you're going to feel those extra players involved).

I like the try it on a dirt road idea as well. And see if you still feel it (or grass or wet roads).
Most likely you will feel it but not as pronounced.

Report back when you have the opportunity to test these theories.

Also, its important to keep this sense of feeling for future issues with your truck. This will help you diagnose and repair issues down the road noting what is normal and what isn't.

 

Triharder -- I agree. Nothing else covers it all. Merry Christmas!