My last Ex I bought the 4x4 didn't work so they replaced the front hubs, U joint, actuator and repaired the vacuum line. That 4x4 worked well until I sold it. When I bought this truck one of the hubs was slightly hanging out so I knew I would need hubs and the shop that did my engine work replaced both hubs and repaired the vacuum line and said 4x4 worked. I picked up in the fall and didn't get a chance to test it but recently when I tried the HVAC went from vent to defroster and I didn't notice any changes in the steering effort so I knew it wasn't working. The shop told me to just put the auto hubs in manual and I did that and found out that I still had to put the dash switch on 4x4 to engage. I tried it in a snow filled lot and could tell the difference.
What does the dash switch do?
What happens in the hubs to engage 4x4?
What else is engaged/turning in the front driveline when in 4wd compared to 2wd?
Is I harmful to drive with the hubs locked and the dash switch on 2wd?
What wears or what damage happens if it is driven in 4x4 on dry surfaces? Does driveline binding only occur in sharp turns?

Thanks

 

Row, go to the Excursion Tech Folder and scroll down to the Suspension, Steering, Axles, Hubs, Driveline, etc section near the bottom of the post. Right around halfway down that section will be a link "ESOF and How It Works"

Click on that link.

Stewart

 

It engages the transfer case, connecting the front drive line to the gears in the front differential (not correct terminology) but that's the idea. Now the transmission is powering both the front and rear drivelines.

Locking Hubs doesn't engage 4WD they just lock the wheels to the front and cause the Ujoints in the axle knuckle to actually turn with the rotation in the differential. If the hubs are locked when the 4x4 is engaged then the front wheels will be locked to the front axle AND will be powered by the transmission. If you engage 4x4 with the hubs not locked then you will still be powering your front driveline and your axle shafts will rotate with that power BUT the wheels will not be powered, they will just be spinning with the momentum of the truck because they are not locked into the axle stubs but just rotating around them.

With ESOF if you are set to Auto then engage the 4x4, the ESOF should also lock the hubs in, if your vacuum system is working properly. With your hubs set to Lock they are locked in and turning all the time and as soon as you change the switch to 4x4 then the transfer case engages and you are in 4WD.

No. I drive mine like that a couple months a year, then can quickly flip to 4WD if needed. I have Warn manual locking hubs. You can lock the hubs and leave it in 2wd, this just connects the wheels to the front axle and they will spin with the truck but will not be powered by the transmission.


in 4WD with hubs locked the wheels will be spinning at different speeds when you turn. Binding will occur on tight turns because something has to slip and if you have it all locked together on "dry" surfaces you have taken away the last thing that can slip. Don't drive locked and in 4wd on dry surfaces.

 

Thanks, will do

 

Thanks for the explanations. Another question about binding, since we have an open differential in front doesn't that absorb the different wheel speeds when turning? Or is the binding in the front U joints when turning?

 

No but good question; You can lock your front wheels and turn with no problem but the binding starts when you lock the T-case which locks the front wheels to the rear ones and since the front wheels will now turn at a different speed it binds. The wobbling effect is caused by the fact that the distance changes in the U-joint parts (trunnion or cross piece) as they go through their motion, so they speed up and slow down as they cycle.

The binding problem lies in the speed of the front and rear pinion gears. If they don't turn at the same speed the wheels will attempt to make them turn the same speed by scraping the tires on the pavement..........in simple terms.

To answer the binding U-joint question; No the joints are not binding by themselves but do relay the overall binding and shaking to the rest of the truck due to the design of the joints.

 

Very good Christina.