Enlighten Me

[TOXIC]

I’m no stranger to 4 wheel drive on vehicles.  I have owned multiple trucks, 2 jeeps and I understand manual and vacuum hubs.  My first jeep had manual hubs where I had to lock them in on each wheel.  My 1993 Wrangler had auto hubs just like the rest of my trucks.  My daughter has a 2001 Ford F-350 with the 7.3 diesel.  It has the manual hubs but the shop she takes it to that is a diesel speciality repair shop told her that she has auto in addition to the locking hubs so she doesn’t have to manually lock them in.  Something just doesn’t sound right about that.  They told her 2001 was the first year ford offered the auto locking hubs.  So my question is, does she still have to manually lock the hubs? Any advantage to doing so? I’ve never seen both manual and automatic on a truck.  

[Woody B]

Those particular hubs don't work......all that good.   If she knows she's going to need 4wd it would be best to get out and manually lock them in.   

[throttleplate]

never knew of auto locking hubs by themselves, how would thay even work? I do and have had vacuum operated and electric solenoid differential locks to engage the front axle shafts to the differential.

[TOXIC]

I am calling everything other than having the locks on the front hubs “automatic” which is what most all 4wd vehicles are today.  In my early jeep with manual hubs, if you didn’t lock them in at the wheels and tried to shift into 4wd inside the cab, you would not get 4wd.  My reason for asking is that she was having problems in the snow getting her gooseneck trailer out of a field and when I asked her if she got out and locked her hubs in, she told me that the shop told her she had the first year that ford put the vacuum controlled “automatic” hubs in their trucks and that she did not have to lock them in at the wheels.  She verified she is getting 4wd without locking them at the wheels but I wondered if there was any advantage to locking them at the wheels or if it was redundant.  

[slonezp]

My 2017 F250 has auto/manual locking hubs. I keep them set in auto year round. 

[TOXIC]

11 hours ago, slonezp said:

My 2017 F250 has auto/manual locking hubs. I keep them set in auto year round. 

Now I’m really confused.😂. My 2016 Silverado has the option of 4 Auto but no outside locking hubs and the general consensus is not to leave it in Auto mode all the time.  

[MN Fisher]

1 hour ago, TOXIC said:

Now I’m really confused.😂. My 2016 Silverado has the option of 4 Auto but no outside locking hubs and the general consensus is not to leave it in Auto mode all the time.  

My 2001 Silverado also has the auto-lock option - but the only time I have it set there is when I'm driving 'mixed' conditions...cleared highway to snow covered side-roads to cleared main roads...I'd be punching the 2-Hi/4-Hi buttons so much I wouldn't be paying enough attention to the road.

[DaubsNU1]

@TOXIC & @MN Fisher, GM's four wheel drive system is different than Ford.

 

Most 1/2-ton, 1500 GMC and Chevy trucks have these options:

- 2 wheel high (only rear tires have power)

- Auto (runs in 2 wheel drive...when system senses slippage, the transfer case automatically engages 4x4 mode. This is a great feature...loved it! Sadly, my 2019 2500HD does not have an Auto mode).

- 4 wheel high (sends power to 4 wheels)

- 4 wheel low (lower gear ratio, sends power to 4 wheels...used for rock crawling, off road situations...max speed is limited)

 

GM trucks do not have locking front hubs. The front wheels are connected to the axle via splines, the transfer case disengages the front driveshaft and the axles disengage via actuator within the front axle housing.

 

[TOXIC]

Some of the new GM 4wd don’t have 4 low either.  

Let’s not mistake the settings within 4wd to engaging the 4wd.  When I say “auto” I mean no outside hubs to lock not the auto setting once in 4wd. 

[Woody B]

Regarding vacuum hubs,  the first generation(like the OP's daughter has) was problematic.  I was working at a Chevy dealer at the time, but our local EMS had several Fords with those hubs.  They didn't take long to decide it would be best to manually lock them if they knew they were going to need 4wd.  

 

 

Regarding the "Auto" setting on GM transfer cases.  This setting has destroyed a BUNCH of transfer cases.  The owners manual states to not use "Auto" on dry pavement.   On GM trucks "Auto" engages the front axle and puts some load on the transfer case clutches.  This increases fuel consumption and caused premature wear to the transfer case clutches.   People who drive around for thousands of miles on dry pavement in "Auto" will have worn transfer case clutches.  When they need 4wd the clutches won't hold.  There's many different types of "Auto" 4wd.  I'm speaking specifically about GM trucks and utilities.   

 

The front axle on these GM vehicles and many others (including my Titan) have a shift collar that connects or disconnects one of the front axles.  When the front axle is not engaged one axle (inside the front differential) is 2 pieces spinning separately from each other.  This allows most of the front 4wd "stuff" to not spin.   When front axle is engaged a splined collar connects the 2 piece axle.  This design works great, and is pretty much trouble free.  I suspect that's why similar designs are used my many different car makers.  However this design does have more stuff "spinning" when going down the road in 2wd that locking hubs.   

[slonezp]

My SuperDuty doesn't have an auto setting on the electronic transfer case. The hubs themselves has auto and manual settings. The last Ford truck I had prior to this was a 84 Bronco. Had to manually shift the transfer case, manually set the hubs, put it into reverse to engage 4wd and then go about your day. 

[MN Fisher]

21 minutes ago, slonezp said:

he last Ford truck I had prior to this was a 84 Bronco.

My '84 Cherokee was easier - shift the transfer case and go...

[slonezp]

8 minutes ago, MN Fisher said:

My '84 Cherokee was easier - shift the transfer case and go...

Today's Jeep isn't that of yesteryear. 

I never owned a Jeep but, I worked at a body shop in the 80's that had a Jeep CJ rigged up with a snow plow to plow the lot. Fun little truck, for what it was.