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Torsen front diff, 4HI on dry now okay?

Donnelly713

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Considering a 400a tremor with the Torsen front diff. Will this allow me to drive on dry or mixed surfaces in 4HI without windup on turns? The jump to 402a just for 4A is a lot.

Thank you

 

Bryan Simon

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I’m thinking “Nope”
the front and rear axles will still be locked together and it will bind up.
You need to have the equivalent of a differential inside the transfer case that the standard TC does not have.
All the Torsen is doing is providing limited slip to the front differential, so that you actually have 4x4 pulling
 

hotrodmex

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I’m thinking “Nope”
the front and rear axles will still be locked together and it will bind up.
You need to have the equivalent of a differential inside the transfer case that the standard TC does not have.
All the Torsen is doing is providing limited slip to the front differential, so that you actually have 4x4 pulling
Agree.

If anything it would make it worse for driving 4H on pavement.

The jump to 402a just for 4A is a lot.
Unless you really want the appearance stuff, and plan on keeping it stock with the Tremor suspension, I think you might find a 500a a better value vs a 400a.

400a is $3500 more than 500a. For that what you're getting that the 500a can't is the appearance stuff (pretty extensive, but not what I would call "functional"), the mildly better suspension, the Trail Turn Assist, Upfitter switches, 3.73s, and the ability to add the Torsen for $500.

500a you're getting the 12" cluster instead of the 4" in 400a, the 12" Sync4 instead of the 8", and the 4a transfer case.
 

Pedaldude

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You need the 4A torque on demand transfer case for dry or mixed conditions. The torsen is in the front differential on the Tremor, only coming into play when there’s a load and doesn’t have anything to do with the connection between the front and rear axles. The torsen does not prevent wind up using part time 4X4 (4HI) and as mentioned above, might actually make it worse.

My 2001 Lincoln Navigator has the early 4A TC and 2HI is locked out from the factory so they could market it as a full time 4WD vehicle.

The 4A TC uses a clutch pack system to approximate a center differential while being lighter and cheaper to mass produce. There’s some discussion on other threads about the two different 4A TCs, the newer Raptor TC case bypasses the clutch pack for true part time 4X4, instead of just locking the clutch like the older ones, which would sometimes overheat.

Either way, the 4A is worth the extra few bucks; these new trucks are definitely traction limited in the dry and when going for the best acceleration, you will want that power going to all four wheels.

Good luck!
 

Oxford_Powerboost

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No, you’d need 4A.
The torsion won’t affect front to back, only side to side. Front to back is the issue. Plus, torsion only makes the diff tighter. It’s an open front diff without torsion
 


amschind

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My old exploder had front and rear torsens and was 4A/4H/4L. It chirped less (and then only in tight parking garage corners) with that setup than the stock front open/rear LSD setup. The front torsen is not a limiting factor, but how the 4A behaves will make a difference because the front and rear wheels also have different RPMs in a turn on pavement.
 

HammaMan

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Torsens are great diffs, but diffs nonetheless. There's no center diff available in the F150, just simply a locking center(XL / XLT), a slipping center (4a), and a slipping center that can lock (raptor / tremor) -- and the latter is only needed for some heavy 4WD action (I personally don't see the reasoning of using the F150 as a HD 4WD machine as there's better options available for such purpose). The 4a should be standard while the 4H only TC should be left in the parts bin.

Torsens just make for a better front diff so a vehicle is closer to 4WD than 3WD when a front tire is loose. They don't affect the TC at all. Typically 3WD is plenty (when the rear diff is locked).

I've not explored if ford has a competent electronic traction system or not that would help by braking the 'loose' front wheel. It's not a replacement for a good diff, but it's a whole hell of a lot better than an open diff peg-leg.

Regardless your diffs, running in 4H is a bad idea. 4A is fine as it's really just 2H until slipping occurs.
 

Tall Tail

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How do I know if my truck has a torsen diff in the front?
If it doesn't have a torsen, what type of front diff does my truck have?
 

DBL R

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4a is worth every penny.
 

Oxford_Powerboost

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Regardless your diffs, running in 4H is a bad idea. 4A is fine as it's really just 2H until slipping occurs.
4A does not require slipping to send some (the amount varies) power to the front axle. Drive mode, steering angle, throttle position, vigor of throttle application, windshield wiper position, etc. all factor in to if and how much power is applied to the front in 4A.
 


HammaMan

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4A does not require slipping to send some (the amount varies) power to the front axle. Drive mode, steering angle, throttle position, vigor of throttle application, windshield wiper position, etc. all factor in to if and how much power is applied to the front in 4A.
It's just a simple variable pressure electric clutch. Nothing fancy about it. ECU sends it a PWM signal and it just applies the pressure. The marketing is mostly fluff.
 

hotrodmex

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How do I know if my truck has a torsen diff in the front?
If it doesn't have a torsen, what type of front diff does my truck have?
Torsen front diff can only be optioned on the Tremor. You just have a regular open diff.

Drive mode, steering angle, throttle position, vigor of throttle application, windshield wiper position, etc. all factor in to if and how much power is applied to the front in 4A.
It's just a simple variable pressure electric clutch. Nothing fancy about it. ECU sends it a PWM signal and it just applies the pressure.
Both can be true.
 

Icecoldak

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4A is like sliced bread!! No way I would not have it!!
 

Tomatoboy

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It's just a simple variable pressure electric clutch. Nothing fancy about it. ECU sends it a PWM signal and it just applies the pressure. The marketing is mostly fluff.
While it is true that it’s just a normal old electromagnetic clutch pack, it’s also true that the clutch is not -only- active during wheel slip. The clutch is active and power is sent to the front wheels during acceleration below certain speeds and during certain other maneuvers where wheel slip is possible. It’s perfectly normal for example for it to engage the clutch pack and send power to the front wheels during acceleration from a stop without any sort of wheel slip. As the other user noted, a number of sensor variables are used by the ECU to determine when to send said signal. This isn’t to be pedantic or dispute that it’s a fairly simple device, only to emphasize it is important people understand the system isn’t -only- active when slip occurs, so they aren’t surprised when it is functioning on dry pavement.

(The benefit being that with the system already engaged in many of the situations wheel slip is most common, you aren’t waiting for the system to engage like you used to with older systems that did require slip to engage.)

 
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