School Me on my Front Diff
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Mountain Pass
Joined: Jun 2005
Posts: 121
Likes: 1
From: Baltimore
School Me on my Front Diff
2014 F150 FX4, 3.55 Gears with Electronically Locking Rear.
What is my front Diff? Open, Limited Slip, Locking? Does traction control somehow lock both wheels when it detects slippage? Why can't I turn on dry pavement, my thinking would be front wheels are locked together.
Thanks!
What is my front Diff? Open, Limited Slip, Locking? Does traction control somehow lock both wheels when it detects slippage? Why can't I turn on dry pavement, my thinking would be front wheels are locked together.
Thanks!
Hotshot
Joined: Jul 2005
Posts: 11,931
Likes: 180
the differential is open... there are IWE ( vacuum pistons) at each wheel end that LOCK the tire to the axle half shafts.... This does make it possible to turn a corner, since the pumpkin is not LOCKED.... but you will get some resistance....
The "drive" for the front is an electric motor in the transfer case that engages the front driveshaft when you select 4 x 4.
The rear end can be OPEN or ELECT LOCKED depending if you pull the 4 x 4 **** OUT when rotated to 4 x 4.
The "drive" for the front is an electric motor in the transfer case that engages the front driveshaft when you select 4 x 4.
The rear end can be OPEN or ELECT LOCKED depending if you pull the 4 x 4 **** OUT when rotated to 4 x 4.
Laughing Gas
Joined: Dec 2010
Posts: 1,200
Likes: 45
From: Timbuk3, MI
wojowojo16 - so......when in 4wd, is it possible for both front wheels to pull at the same time? And if so, how does that work?
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Hotshot
Joined: Jul 2005
Posts: 11,931
Likes: 180
it is POSSIBLE for both wheels to pull at the same time, but it just a matter of ground conditions and other factors....For arguments sake, lets say one is pulling 80% and the other is 20%.... If your asking if BOTH tires can pull 100% TOGETHER like they are locked together, NO, that does not happen. If the front end was LOCKED or more of a LIMIT SLIP, you would have a lot of problems turning corners. I don't know of any trucks that have a LS unit in the front... and surely NONE are LOCKED.
Cargo Master
Joined: Sep 2005
Posts: 2,963
Likes: 897
From: Montana
it is POSSIBLE for both wheels to pull at the same time, but it just a matter of ground conditions and other factors....For arguments sake, lets say one is pulling 80% and the other is 20%.... If your asking if BOTH tires can pull 100% TOGETHER like they are locked together, NO, that does not happen. If the front end was LOCKED or more of a LIMIT SLIP, you would have a lot of problems turning corners. I don't know of any trucks that have a LS unit in the front... and surely NONE are LOCKED.
Tuned
Joined: Dec 2012
Posts: 432
Likes: 112
the differential is open... there are IWE ( vacuum pistons) at each wheel end that LOCK the tire to the axle half shafts.... This does make it possible to turn a corner, since the pumpkin is not LOCKED.... but you will get some resistance....
The "drive" for the front is an electric motor in the transfer case that engages the front driveshaft when you select 4 x 4.
The rear end can be OPEN or ELECT LOCKED depending if you pull the 4 x 4 **** OUT when rotated to 4 x 4.
The "drive" for the front is an electric motor in the transfer case that engages the front driveshaft when you select 4 x 4.
The rear end can be OPEN or ELECT LOCKED depending if you pull the 4 x 4 **** OUT when rotated to 4 x 4.
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Hotshot
Joined: Jul 2005
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The older F150 trucks ( 1997-2004) had each half shaft splined solid to the hubs. When you were running down the road in 2 x 4 both half shafts were turning and rotating the gears in the pumpkin even tho you had no connection from the transfer case.... I would guess the change was made to IWE to get all those rotating parts to stop and have less rolling resistance and therefore possibly raise the fuel mileage............. similar to the old time "manual locking hubs" where you had to get out of the truck and manually lock the half shafts IN or OUT of the hub.
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Tuned
Joined: Dec 2012
Posts: 432
Likes: 112
The older F150 trucks ( 1997-2004) had each half shaft splined solid to the hubs. When you were running down the road in 2 x 4 both half shafts were turning and rotating the gears in the pumpkin even tho you had no connection from the transfer case.... I would guess the change was made to IWE to get all those rotating parts to stop and have less rolling resistance and therefore possibly raise the fuel mileage............. similar to the old time "manual locking hubs" where you had to get out of the truck and manually lock the half shafts IN or OUT of the hub.
Hotshot
Joined: Jul 2005
Posts: 11,931
Likes: 180
My 2001 and 2002 had the axle half shaft splined solid to the hubs and rotated ALL THE TIME.. There was a vacuum piston on the pumpkin that engaged one half shaft to the differential as you said when in 4 x 4... Im not sure the other half shaft was LOCKED as you mentioned, but it did steer like herding elephants when it was in 4 x 4........ It had 2 x 4, 4 x 4 lo and 4 x 4 high... The switch would engage the transfer case motor to lock the drive shaft in, then the vacuum piston on the differential would lock ONE wheel on the front.......
The NEW design trucks start out the same way... the transfer case motor pulls in the front drive shaft to drive the pumpkin.. Then the two wheel end vacuum pistons engage the half shafts to the hubs and the wheels drive.... What percentage of power goes to each front wheel and how much internal slip you get , I don't know... but the front end is OPEN on most of the trucks.
The nice thing about the newer trucks is the rear Limit Slip can be changed out with an ELECTRIC LOCK UP drive ( factory option) that does actually PIN the two shafts together and LOCKS the rear end.. no slip.
The NEW design trucks start out the same way... the transfer case motor pulls in the front drive shaft to drive the pumpkin.. Then the two wheel end vacuum pistons engage the half shafts to the hubs and the wheels drive.... What percentage of power goes to each front wheel and how much internal slip you get , I don't know... but the front end is OPEN on most of the trucks.
The nice thing about the newer trucks is the rear Limit Slip can be changed out with an ELECTRIC LOCK UP drive ( factory option) that does actually PIN the two shafts together and LOCKS the rear end.. no slip.
Hotshot
Joined: Jul 2005
Posts: 11,931
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Our 2002 Explorer has the "auto" 4 x 4... I believe the front axles are locked to the hubs and rotate all the time... the computer engages the transfer case when it sees the need and drives the drive shaft to the pumpkin... There is no lockup inside the front pumpkin.... I think this is why the MPG on the EXP is not so good.... axles turning all the time.
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
4wd should never be engaged on dry pavement unless the intention is to travel a short distance straight forward or backwords. When a vehicle turns a corner the front wheels travel in a wider arc than the rear which means the front tires cover a larger distance, and in order for this to happen the front and rear drivelines must operate at different speeds. With a transfer case locked in 4wd that isn't possible and if you force it the driveline binds up until a tire slips or something breaks.This is where 4wd differs from AWD, the latter includes a limited slip diff in the t-case that allows some slip between front and rear drivelines which produces smooth operation on clear pavement.
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