What are my options, if any, for turning my front differential into a limited slip or positive traction type of differential? And what would the pros and cons of such a modification be?

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98 F-150 XLT 4X4 ORP Super Cab Short Bed, 4.6, Auto. Superchip, Gibson sing. cat-back, Airaid, 80/100w German head lamps. Warn HS9500i winch with semi hidden mount. Wrangler dual battery kit with red & yellow top Optima batteries. Torsion bars cranked up 2 turns. Needs one more door and a lot more power. I think I need to talk to Mr. Whipple.

 

I think there was a discussion of this either here or in the digest. I remember that the LSD in front will change the steering feel while off-road, but many professional off-roaders use them. Depending on the type, like a Detroit Locker, some can be pretty noisy, but that's not going to matter.

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'99 Lariat Supercab 4x4 SS
5.4L, 3.73 Diff (9.75" LSD Rear, 8.8" Front)
ORP
Skid Plates
LT265/70R17 GY Wrang. AT/S
Group III towing
HD Electrical/Cooling
GVWR 6500# (Extra leaf spring)
Step Bars
K&N filter
Stock Items That Differ Across F150s:
Steel Driveshaft
Oil filter bolted to engine w/ drip guard
4R70W transmission

 

A front locker/limited slip is an iffy proposition. If you run off-road only then it's probably a very good thing and the effects on handling may not matter nearly as much as the greatly improved traction.

When you operate on road, a locker always drives at the speed of the slower moving wheel, which in a turn is the inside one. This causes a HUGE amount of push.

A clutch type limited slip may chatter like crazy in the front and jerk the wheel around as it alternately locks and slips the drive wheels and will cause the front to push when it locks then act normally when it slips.

What the front-wheel drive road-racers use is a Quaife or Torsen differential, which distributes torque to the wheels proportional to the load they see. This does not tend to cause strange handling. I'm pretty sure the 4wd World Rallye cars use some variation on the Quaife/Torsen all around, but the builders don't talk much in public about their drivelines. There are Torsens available fot the Ford 8.8, not sure about the Dana. Might be worth investigating. Their web site is: http://www.torsen.com/

 

Thanks, guys! I went to the Torsen site and found that Saleen is the distributor for the 8.8 differential. Not as bad as I thought, $500 for that setup. Their online catalog only lists an application for the Mustang though. I'm going to give them a call during business hours to get more detailed information. I would only be interested in this type of modification if it had no adverse effects.
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98 F-150 XLT 4X4 ORP Super Cab Short Bed, 4.6, Auto. Superchip, Gibson sing. cat-back, Airaid, 80/100w German head lamps. Warn HS9500i winch with semi hidden mount. Wrangler dual battery kit with red & yellow top Optima batteries. Torsion bars cranked up 2 turns. Needs one more door and a lot more power. I think I need to talk to Mr. Whipple.



[This message has been edited by 98fword (edited 02-12-2000).]

 

There is another option it is called a arb air locker it use's air to lock the axles together, it activates in less than 1 sec and release's as fast Huge amount's of off roaders use them it gives you the best open for driving on hard pack where handling would be an issue and lockes for a true 4 wheel drive. They are advertised in off road magazine i put one into a mustang it was easy.

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2000 blk xlt f150 sc 4x4 orp pkg 5.4 3.55 ls tow pkg herculiner ,sony 10 disc cd-player A.R.E. cap remote start

 

Is your front diff a Ford 8.8 or is it a Dana? If it's a Dana they may not have a Torsen application. Saleen can probably point you in the right direction, but be sure what you're really looking for.

 

I may be mistaken but I'm pretty sure it's an 8.8. At least that's what's cast into the housing. And I'm not sure if that's what I really want. I'm going to have to do more research. Like I said, I don't want the truck to handle any differently, push, grind, clunk, or any other of those nasty words.

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98 F-150 XLT 4X4 ORP Super Cab Short Bed, 4.6, Auto. Superchip, Gibson sing. cat-back, Airaid, 80/100w German head lamps. Warn HS9500i winch with semi hidden mount. Wrangler dual battery kit with red & yellow top Optima batteries. Torsion bars cranked up 2 turns. Needs one more door and a lot more power. I think I need to talk to Mr. Whipple.

 

StrangeRanger,

Sorry to bring up a long dead topic, but conversation lately has got me curious.

Although the Torsen will fit the 8.8 front axle, will it cause the pull to the left that lockers and limited slip systems will cause because of the center disconnect 4x4 system? I am really not that familliar with the theory behind Zexel-Torsen's operation (or the Detroit sister, TrueTrac I think it's called). Yes, I have read the website pdf, but am not an engineer. I can't tell if there would be resistance in 4x2 that would cause the pull.

 

just my opinion, but I wouldn't think that there would be any more resistance with a locker than there would be with an open diff... not too sure, though. unless, that is, on the open diff, the input from one side spins the output on the other side at speed... not sure what happens there... If I was going to make a reccomendation (unsolicited, of course) I'd say get the ARB. It gives you all the normal function of an open diff for street use with the ultimate locking capability of the full locker off-road. I can't think of a time on or off-road where a limited slip would be preferable to a manually selectable locker... then again, I'm a bit of a control freak too...

-Joe-

 

Joe,

I think that is what happens. I have seen numerous articles, web based and magazine based, making recommendations not to put a locker or limited slip in the front. They site the reason you just mentioned. In 4x2 the left side gear is connected to the left axle shaft, but the right is disconnected (and connects upon activation of the SOTF). While you are driving in 4x2, the left shaft spins the left side gear, which spins the pinion shaft gears, which spins the right side gear in reverse (at least that's my understanding of how the center disonnect works). I presume this extra load on the left is so minute you don't even notice (in fact, just the other day I was screwing around with a open diff carrier, and you can spin all those gears with one finger).

Now put a locker (or lsd) in, or for that matter just spot weld the pinion shaft gears. Now the left side gear spins the left side gear, which now is forcs the entire differential carrier to drag along with it. A spinning diff carrier at high speeds will cause alot of pull to the left side.

You're right, ARB would solve the problem. But I am more curious about the Torsen. I don't understand the gear operation enough to tell if it would have the same problem with center disonnect 4x4 systems. What I like about the Torsen is that it is proactive is sensing torque needs (thus the TORque SENsening name). Even with he ARB, you won't turn it on until the think you need it, which may be a moment too late. Besides that cost and modification with the vacuum pump, switch inside the interior, etc.