Rear wheel spin in 4x4?

[TRSCobra]

While backing my trailer up in my yard, I typically use 4 low to make it easier and prevent wheelspin from tearing up the grass. WellI did it for the first time with my new XLT and even once engaged, the rear tires will spin for about a half turn before the fronts engage.

This happened almost every time I hit the gas, so not just a one time thing. Same thing happened when I put my 2018 in 4 auto, as it needs to see wheelspin to engage the 4x4, so I learned to just put it in 4 low to begin with.

Do these transfer cases need to see some slip before engaging the fronts or something?

PS: I engaged the rear diff lock as well and it still spun the rears first.

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[Geo]

Have you tried doing this maneuver with the traction control off or on. Don't know if it disengages with 4x4 on, or differential lock on. I haven't read up on that yet.

 

[TRSCobra]

Have you tried doing this maneuver with the traction control off or on. Don't know if it disengages with 4x4 on, or differential lock on. I haven't read up on that yet.

No, but this has never been an issue in trucks before.

 

[Vulnox]

While backing my trailer up in my yard, I typically use 4 low to make it easier and prevent wheelspin from tearing up the grass. WellI did it for the first time with my new XLT and even once engaged, the rear tires will spin for about a half turn before the fronts engage.

This happened almost every time I hit the gas, so not just a one time thing. Same thing happened when I put my 2018 in 4 auto, as it needs to see wheelspin to engage the 4x4, so I learned to just put it in 4 low to begin with.

Do these transfer cases need to see some slip before engaging the fronts or something?

PS: I engaged the rear diff lock as well and it still spun the rears first.

The truck doesn't respond to slip to engage 4x4 when in 4 Auto, it's constantly in 4WD, you can see it clearly by going to the power distribution module. Was the same last gen too. It's a common misconception on the 4 Auto system in the F-150. The reason you can turn without binding even with that happening is that it uses a clutch between the front and rear that allows for slip when there is enough tension.

This slip can happen even in 4 Low or 4 High because the mechanical linkage is that clutch. The Raptor and the high trim of the Tremor also have a 4 Auto transfer case, but they have a "HighLock" or "HiLock", I forget the term now, that can mechanically lock the transfer case and it engages this function automatically in certain drive modes (Rock Crawl, Mud and Ruts), but uses the standard clutch transfer for Rain/Snow/Normal 4A around town driving.

This "slip" is something that can cause issues if you try to take a Lariat or Platinum or whatever into serious rock crawling, as there is a maximum load where the clutch will slip. 99.99999% of those trucks won't see that condition though, as it is generally more extreme than you would take those trim level trucks. But what you describe could just be momentary slip in the clutch engagement, or it could be due to slop in the driveline which is possibly in any 4WD vehicle since the distance of power travel to the rear wheels is different than the front.

But in any case, there isn't a ton you can do about it.

Edit: I wrote the above thinking you still had a Lariat, but you have an XLT now, just got caught on you saying 4 Auto from your 2018. In the case of the XLT I expect it's just the difference in power travel from the front to the rear. There can be extra torque load on the driveshaft and it can release and cause rear wheel spin when the fronts do not. That would be my guess anyway. In an XLT the front and rear should be largely mechanically locked.

 

[TRSCobra]

The truck doesn't respond to slip to engage 4x4 when in 4 Auto, it's constantly in 4WD, you can see it clearly by going to the power distribution module. Was the same last gen too. It's a common misconception on the 4 Auto system in the F-150. The reason you can turn without binding even with that happening is that it uses a clutch between the front and rear that allows for slip when there is enough tension.

This slip can happen even in 4 Low or 4 High because the mechanical linkage is that clutch. The Raptor and the high trim of the Tremor also have a 4 Auto transfer case, but they have a "HighLock" or "HiLock", I forget the term now, that can mechanically lock the transfer case and it engages this function automatically in certain drive modes (Rock Crawl, Mud and Ruts), but uses the standard clutch transfer for Rain/Snow/Normal 4A around town driving.

This "slip" is something that can cause issues if you try to take a Lariat or Platinum or whatever into serious rock crawling, as there is a maximum load where the clutch will slip. 99.99999% of those trucks won't see that condition though, as it is generally more extreme than you would take those trim level trucks. But what you describe could just be momentary slip in the clutch engagement, or it could be due to slop in the driveline which is possibly in any 4WD vehicle since the distance of power travel to the rear wheels is different than the front.

But in any case, there isn't a ton you can do about it.

Edit: I wrote the above thinking you still had a Lariat, but you have an XLT now, just got caught on you saying 4 Auto from your 2018. In the case of the XLT I expect it's just the difference in power travel from the front to the rear. There can be extra torque load on the driveshaft and it can release and cause rear wheel spin when the fronts do not. That would be my guess anyway. In an XLT the front and rear should be largely mechanically locked.

How come my 2018 F150 didn't do this in 4 low?

 

[Vulnox]

How come my 2018 F150 didn't do this in 4 low?

That's a nearly impossible question to answer. Even different tires can lead to a situation where traction is better in one than the other. Differences in moisture on your grass can allow the rears to slip. Differences in weight. I mean, the options are limitless. You may have tried reversing before 4 Low completely engaged is also possible. A lot in the driveline needs to align for 4x4 Low to truly engage, you may have just been luckier with the 2018 than your attempt with this one.

But your XLT would be mechanically locked front to rear. A slip detection engagement would be extremely damaging in 4 Low, so the most likely answer is something more generic, like general traction/weight/etc.

 

[TRSCobra]

That's a nearly impossible question to answer. Even different tires can lead to a situation where traction is better in one than the other. Differences in moisture on your grass can allow the rears to slip. Differences in weight. I mean, the options are limitless. You may have tried reversing before 4 Low completely engaged is also possible. A lot in the driveline needs to align for 4x4 Low to truly engage, you may have just been luckier with the 2018 than your attempt with this one.

But your XLT would be mechanically locked front to rear. A slip detection engagement would be extremely damaging in 4 Low, so the most likely answer is something more generic, like general traction/weight/etc.

That's what I mean. It's really strange when it happens. Like a clunk where you can tell and the rear tires have broken grass in the tread for 1/4 of the tire from that slip and the fronts have none. Never had a truck do that before this one.

 

[Vulnox]

That's what I mean. It's really strange when it happens. Like a clunk where you can tell and the rear tires have broken grass in the tread for 1/4 of the tire from that slip and the fronts have none. Never had a truck do that before this one.

Yeah that does seem odd, especially re-reading where you said it happens every time you hit the gas. I could maybe understand when you first shift into 4 Low, but if already in and already reversed once, surprised it keeps happening. I still would suspect binding/torque on the driveshaft and then a release that causes them to spin, but none of the ideas I would have for it could explain why your '18 didn't do it aside from the tires on your '18 maybe performing better in that situation. Tires make all the difference in most situations, if you had even a little better traction with your '18s tires, then I could see the truck starting to move before the slip happened.

There is a loooot of weight right on that front axle thanks to the engine and a bit more still from you in the cab. Not sure what your tongue weight is from the trailer, but even then it isn't right over the axle. May just be a combination of different tires and just enough weight on the front that the front doesn't spin. Otherwise I am kinda stumped.

Especially if you tell me you moved the tires off your '18 to the '21.

 

[TRSCobra]

Yeah that does seem odd, especially re-reading where you said it happens every time you hit the gas. I could maybe understand when you first shift into 4 Low, but if already in and already reversed once, surprised it keeps happening. I still would suspect binding/torque on the driveshaft and then a release that causes them to spin, but none of the ideas I would have for it could explain why your '18 didn't do it aside from the tires on your '18 maybe performing better in that situation. Tires make all the difference in most situations, if you had even a little better traction with your '18s tires, then I could see the truck starting to move before the slip happened.

There is a loooot of weight right on that front axle thanks to the engine and a bit more still from you in the cab. Not sure what your tongue weight is from the trailer, but even then it isn't right over the axle. May just be a combination of different tires and just enough weight on the front that the front doesn't spin. Otherwise I am kinda stumped.

Especially if you tell me you moved the tires off your '18 to the '21.

We're talking 200 lb max tongue weight since its an unloaded open car trailer. Tires were the 20" hankook dynapro atm before and a 18" Goodyear wrangler territory AT now, which looks more aggressive and holds more driveway gravel than the hankooks did.

 

[KartRacer25]

Clueless about 4x4. But curious. I may be in the mud tomorrow.
But I tried 4L with elocker once to test on small dirt incline and seemed rears broke loose just a bit a couple times while climbing and turning, didnt expect it at all, figured it was normal. My Ranger had 2wd and LSD, or so they called it.
I wonder if one of other modes works better, tow/haul or slippery/snow mud.
I dont have rock crawl mode either, XLT Sport 4x4 non FX4.

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