4x4 - Why Hublocks and Open Front Diff explained
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4x4 - Why Hublocks and Open Front Diff explained
I have seen quite a few posts on why our trucks have hublocks and open front differentials so I thought it might make sense to take a crack at explaining their purpose:
Why Hublocks: Hublocks disconnect the front axle at each wheel to allow the wheel to turn freely (less drag) when in two wheel drive. This increases fuel economy and reduces wear and tear on your front drive system. The 4x4 disconnects at both wheelends and the transfer case allowing the front axle and drive shaft to lay still during two wheel drive operation. Believe it or not, this is worth almost a mile per gallon improvement at freeway speeds and reduces noise significantly.
Why the dial on the hublocks: This allows us to lock our hublocks in case the vacuum actuation system has failed to work (sometimes in cold weather or if the line falls off or the seals are leaking) or if we want to keep the hublocks locked to make it easy on the transfer case in cold weather. The transfer case has a synchronizer that spins the whole front drive up before the hublocks are engaged with vacuum. This can be a big job in very cold weather. I usually turn my 4x4 on before pulling out in cold weather and leave the 4x4 on for 5 minutes to loosen/warm all the components up if I think I will need it during the drive at anytime. Not so good to switch it on during cold weather for the first time after sitting outside all night.
Why an open front differential: An open differential is inherently designed to balance torque across the axle while allowing differential speeds (which makes going around a corner infinitely easier for your truck). This is why if you have one tire on ice and the other on dry pavement the tire on ice will spin quickly and the tire on pavement will not turn. Believe it or not, they both have the same amount of torque, it is just very low because one tire in on a slippery surface. Handling is very poor and some might argue dangerous on the front axle if there is a locking differential (locked) on the front and you are driving on relatively dry ground. The inner tire will need to slip/skid to allow the other tire to go faster on the outside around the corner. This leads to unstable handling. On the rear this slippage is a bit less of a safety concern and why Ford is willing to put a locker in the rear.
I hope this helps.
Why Hublocks: Hublocks disconnect the front axle at each wheel to allow the wheel to turn freely (less drag) when in two wheel drive. This increases fuel economy and reduces wear and tear on your front drive system. The 4x4 disconnects at both wheelends and the transfer case allowing the front axle and drive shaft to lay still during two wheel drive operation. Believe it or not, this is worth almost a mile per gallon improvement at freeway speeds and reduces noise significantly.
Why the dial on the hublocks: This allows us to lock our hublocks in case the vacuum actuation system has failed to work (sometimes in cold weather or if the line falls off or the seals are leaking) or if we want to keep the hublocks locked to make it easy on the transfer case in cold weather. The transfer case has a synchronizer that spins the whole front drive up before the hublocks are engaged with vacuum. This can be a big job in very cold weather. I usually turn my 4x4 on before pulling out in cold weather and leave the 4x4 on for 5 minutes to loosen/warm all the components up if I think I will need it during the drive at anytime. Not so good to switch it on during cold weather for the first time after sitting outside all night.
Why an open front differential: An open differential is inherently designed to balance torque across the axle while allowing differential speeds (which makes going around a corner infinitely easier for your truck). This is why if you have one tire on ice and the other on dry pavement the tire on ice will spin quickly and the tire on pavement will not turn. Believe it or not, they both have the same amount of torque, it is just very low because one tire in on a slippery surface. Handling is very poor and some might argue dangerous on the front axle if there is a locking differential (locked) on the front and you are driving on relatively dry ground. The inner tire will need to slip/skid to allow the other tire to go faster on the outside around the corner. This leads to unstable handling. On the rear this slippage is a bit less of a safety concern and why Ford is willing to put a locker in the rear.
I hope this helps.
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