shifting from 2wd to 4wd
- Thread starter James5354
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boyfester
New member
Sounds like we're about to find out.
I've switched mine at lower speeds but have always had to have it in neutral to do so. Did he switch it to neutral first?
Engineer
New member
Trucks fine, general sense would state that if the conditions on the highway are bad enough that you think you need 4x4 at 60mph then you should not be going 60mph. I realize this was likely a "hey lets put it in 4x4" and as high speed limit roads have sweeping turns not 90 degree turns the truck is fine. If you use your 4x4 system on dry city roads and turn sharply the driveline will bind because of the lack of center differential and the fact that the tires are not rotating at the same speed in a turn. Binding once does not mean damage happened, but do it enough and something is bound to break
manofsteele2003
New member
Why would you put it neutral first? You do know you can go from 2H to 4H without putting it in neutral, it's called shift on the fly. You only have to put it in neutral first before you put it in 4L.
Owners manual
Yes I read it. It shouldn't shift if the vehicle is at an unsafe speed for transferring. And the dry roads comment is true when making hard turns but it also says to drive in 4x4 once a month for about 20 min or so to lubricate the front end and keep it smooth
Yes I read it. It shouldn't shift if the vehicle is at an unsafe speed for transferring. And the dry roads comment is true when making hard turns but it also says to drive in 4x4 once a month for about 20 min or so to lubricate the front end and keep it smooth
LXRunner
New member
It's not a good driving practice, but in your case you won't get any damage.
wfo9
New member
It's fine, nothing to worry about. I would not do it on a regular basis... But I think the 4wd control module protects itself anyway... If you have the push botton... it is in full control.
And there is no issue going over 50.. in 4h. Just shifting from 2h to 4h (you should not be spinning the drive-shaft very fast), It's hard on the Tcase to take the front drive-shaft from 0 to a high rpm.
Your truck is fine.
If you're talking about shifting from 4H to 4L then yes the transmission should be in neutral and you should be stopped. You will also pass through the neutral position on the transfer case shift lever (if you have one). If you're talking about 2H to 4H then it doesn't matter what gear the transmission is in or whether you're moving or stopped.
I think you're right about the electronics in the system protecting itself from undue strain. I seem to remember trying to shift into 4H while going faster than 50mph and only seeing the little green 4WD light blink until I dropped back under 50mph at which point it went solid. I think the ADD might protect itself and not lock above 50mph (possibly the same thing with the dial controlled transfer?) but the lever actuated transfer case has no way to do since it's a direct connection.
Jetboy
New member
I engage at any speed in my lever actuated trail edition. Did or do any of you own older 4x4s? Not much different. If you've done this in an older one with the hubs unlocked - trust me - you wont be engaging the front output shaft at significantly varying speed from the rear shaft. - by that I mean if the front drive shaft isn't rotating, it's like trying to shift a manual without the clutch at the wrong rpm. It simply won't go.
On my lever actuated transfer case (trail edition) - it will engage the front output at any speed. I did this on tuesday morning on my way to work at about 65mph. At some speed it will beep and not engage the front diff disconnect, but the transfer case output (front drive shaft) will engage seamlessly at about any speed. And it shouldn't hurt anything so long as you don't feel a grinding of gears and it slides easily into engagement. That means your gears are already spinning at a synchronized rate.
What this also tells us is that the front shaft - at least in mine - is always spinning at or near synchronized speed. So the disconnect idea isn't really disconnecting much in the front differential.
Anyway I shift the transfer case between 2h and 4h at will whenever I want to engage the front axle. If you're going faster than Mr. T wants, it'll tell you to slow down a bit. Otherwise its not meaningfully different from shifting between 4th and 5th gear at speed. It's just shifting synchronized gears together. No big deal.
On my lever actuated transfer case (trail edition) - it will engage the front output at any speed. I did this on tuesday morning on my way to work at about 65mph. At some speed it will beep and not engage the front diff disconnect, but the transfer case output (front drive shaft) will engage seamlessly at about any speed. And it shouldn't hurt anything so long as you don't feel a grinding of gears and it slides easily into engagement. That means your gears are already spinning at a synchronized rate.
What this also tells us is that the front shaft - at least in mine - is always spinning at or near synchronized speed. So the disconnect idea isn't really disconnecting much in the front differential.
Anyway I shift the transfer case between 2h and 4h at will whenever I want to engage the front axle. If you're going faster than Mr. T wants, it'll tell you to slow down a bit. Otherwise its not meaningfully different from shifting between 4th and 5th gear at speed. It's just shifting synchronized gears together. No big deal.
BLACK-FL4RUNNER
Member
wfo9
New member
I don't follow. In 2wd the chain in the TCase is not driving the front output shaft.
The ADD simply disconnects the passenger side axle shaft. So the driver side tire spinning results in either the passenger output shaft spinning in the opposite direction or the drive shaft spinning. I'm not sure where there is bias, but nothing would synchronize speeds.
I'm pretty sure there is a clutch synchronizer sleeve in the Tcase, that takes care of eliminating grinding (the output shaft is free spinning).
My point is going from 80MPH on the tcase input, to the front shaft spinning at that speed from potentially 0 rpm, might not be the best thing for it.
Sort of like doing doughnuts in a dry parking lot in 4wd is probably not the best idea either. It probably won't break anything, but it is not a best practice for long term reliablity.
BTW, the ADD will not engage without a signal from the Tcase that 4wd is active. I'm guessing the ECU won't engage it until the speed sensor is below some value.
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Jeremy556
New member
What the heck is a front diff disconnect?
Please explain that one to me....
On the passenger side of the front diff, there is a sliding collar which disengages the passenger side axle shaft. With the passenger side axle shaft disconnected, only the side gears in the front diff turn, the R&P and drive shaft do not turn. Reduces rolling resistance and improves mpg, a replacement for manual hubs.
4hi will engage at any speed, but the ADD won't connect under load. Easier for Toyota to say "do not engage above 55mph" than explaining the ADD engagement and that you can select it at higher speeds, but you'll have to go down a hill or let off the throttle for it to connect.
