Limited Slip
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From: Lansing
Limited Slip
Hi all, I've been a lurker in this forum for a while, I've had numerous Ford trucks over the years. I just purchased a 1991 F-150, Lariat, reg. cab, long bed, 302, 4wd, 5 speed manual. I've been looking for a truck like this to use for occasional hauling, trips to Home Depot, nasty winter roads here in Michigan, etc. Except for having the oil sending unit let go 3 days after I bought it, I'm really happy with this truck.
Here's my question, and i've had different answers over the years. I know the truck has a Limited Slip rear end, the two tracks on the gravel road show that. But did these trucks also have a limited slip front axle? I've always thought no, but several people have insisted they do. It's not an urgent question, but it will bug me until I know the answer.
Thanks,
Rich
Here's my question, and i've had different answers over the years. I know the truck has a Limited Slip rear end, the two tracks on the gravel road show that. But did these trucks also have a limited slip front axle? I've always thought no, but several people have insisted they do. It's not an urgent question, but it will bug me until I know the answer.
Thanks,
Rich
More Turbo
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i believe if you have LS in the back it must have LSin front, It need the same gear ratio to work... dont hold me to that mayb some one can give you a more definite answer...
It makes sense to me though.. if you put an 8.8 in where a 3.55 was, you would need 8.8 in front or else the front wheels would be turning 3.55:1 when the back is 8.8:1 which is bad..
While im in here, what LSD should i try and find for my truck (1994 F150 Flareside 4x4 302cid)
It makes sense to me though.. if you put an 8.8 in where a 3.55 was, you would need 8.8 in front or else the front wheels would be turning 3.55:1 when the back is 8.8:1 which is bad..
While im in here, what LSD should i try and find for my truck (1994 F150 Flareside 4x4 302cid)
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From: Lansing
I agree with the ratios, but I Limited Slip wouldn't be necessary. It could still be an open 3:55 front end. I'm almost ready to just find really soft gravel, put it in 4wd and see if I can break all four wheels loose and see what tracks they leave. But until I get rid of the auto hubs in favor of manuals I don't want to beat up on the 4wd.
Originally Posted by NeXtras
i believe if you have LS in the back it must have LSin front, It need the same gear ratio to work... dont hold me to that mayb some one can give you a more definite answer...
It makes sense to me though.. if you put an 8.8 in where a 3.55 was, you would need 8.8 in front or else the front wheels would be turning 3.55:1 when the back is 8.8:1 which is bad..
While im in here, what LSD should i try and find for my truck (1994 F150 Flareside 4x4 302cid)
It makes sense to me though.. if you put an 8.8 in where a 3.55 was, you would need 8.8 in front or else the front wheels would be turning 3.55:1 when the back is 8.8:1 which is bad..
While im in here, what LSD should i try and find for my truck (1994 F150 Flareside 4x4 302cid)
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From: Ottawa, Ontario
No.. Front LS diff was a special option not included with other packages. All f150's of this vintage have 8.8 rear ends, that's the ring gear diameter in inches. The gear ratio is completely seperate and can range from somewhere around 2.5:1 up to 4:56:1. In a 4x4 the front and rear ratios are the same. To know for sure what you have check the axle codes on the door jamb, and look at the metal tag attached to the diff cover bolts. On the tag you'll find a sequence like 3L55 starting the second row of numbers, the 3 and 55 are the gear ratio, L is for limited slip, a space between the 3 and 55 means open diff.
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From: Davis & Newcastle, CA
Paul's right. 8.8 is the number that we use to designate which axle we have in our trucks, it is the measurement of the ring gear diameter in the differential, as Paul stated.
As for LS matching front and rear, again, not necessary for normal operation. And in my experience, the factory Ford LS was only put into the rear, as with my truck. I have factory limited-slip (although it is completely shot... junky LS) in the rear and not in the front. But my 3.55 gearing does match front to back, it has to or else I would have big problems when throwing it in 4wd because the front wheels would be turning at a different rate than the rear wheels.
As for LS matching front and rear, again, not necessary for normal operation. And in my experience, the factory Ford LS was only put into the rear, as with my truck. I have factory limited-slip (although it is completely shot... junky LS) in the rear and not in the front. But my 3.55 gearing does match front to back, it has to or else I would have big problems when throwing it in 4wd because the front wheels would be turning at a different rate than the rear wheels.
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From: Sweetwater Texas
Not meaning to steal this thread, the tag on my door says I that my rearend is open, but anytime I have done a burnout, both tires are spinning (and this is with 35's) Can a open diff lock up through years of abuse.
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From: Davis & Newcastle, CA
Doesn't really make sense for an open diff to just BECOME closed. The only real reason that I could think would make BOTH tires spin would be if you had the EXACT same amount of friction at both tires, which is highly implausible. An open diff will spin whichever tire has LESS friction when you break traction. Are you sure one of the prior owners didn't install an aftermarket limited slip?
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From: Sweetwater Texas
Well, the only prior owner is my grandfather, and I know he didn't do anything to the rearend, and he said it has always done this with him. But sure enough anytime I spin the back tires, I leave two tracks.
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From: Davis & Newcastle, CA
Take a closer look at the tag hanging off of one of your rear diff bolts. If it says 4L10 then you have a limited slip rear end. But even if you did, I would think that an 87 would have fried the stock limited slip components by now anyway. My truck is a 95 with 100k miles and my LS is already totally useless.
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From: Greater Austin, Texas
LS F/R were seperate options on my '90 F150 4x4. You have to select rear to get front, but you could select rear only.
Jack up the rear-end and spin one tire by hand. If the other tire turns the same direction, you have LS. If it turns the opposite direction, you have an open diff.
Jack up the rear-end and spin one tire by hand. If the other tire turns the same direction, you have LS. If it turns the opposite direction, you have an open diff.
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From: Davis & Newcastle, CA
I've been told that if you have a properly functioning LS gear then it requires an incredible amount of torque to turn one of the tires (somethin like 200 ft/lbs). Is this true?
I know that my rear tires are incredibly easy to turn and also turn in opposite directions, so my LS is totally shot.
I know that my rear tires are incredibly easy to turn and also turn in opposite directions, so my LS is totally shot.
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Originally Posted by Skandocious
I've been told that if you have a properly functioning LS gear then it requires an incredible amount of torque to turn one of the tires (somethin like 200 ft/lbs). Is this true?
I know that my rear tires are incredibly easy to turn and also turn in opposite directions, so my LS is totally shot.
I know that my rear tires are incredibly easy to turn and also turn in opposite directions, so my LS is totally shot.
is it easy to install a LSD? i would like to get one for my truck but dont know what to look for.. any suggestions?
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From: Davis & Newcastle, CA
Originally Posted by NeXtras
if they turn opposite ways when u turn them by hand, you dont have a LSD...
Anything's possible 
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From: Ottawa, Ontario
Originally Posted by Skandocious
I've been told that if you have a properly functioning LS gear then it requires an incredible amount of torque to turn one of the tires (somethin like 200 ft/lbs). Is this true?
The real test of LS diff is with 1 tire in the dirt and another on pavement.. like at the side of the road. If it's in good shape the truck will spin both tires when you get into it.
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From: Hawkeye Country
Originally Posted by Conanski
The real test of LS diff is with 1 tire in the dirt and another on pavement.. like at the side of the road. If it's in good shape the truck will spin both tires when you get into it.
If your gonna tear your differential apart for a rebuild I would subjest skipping the limited slip and go for a locker. When I bought my 86 the stock LS was fried, peices clanking around inside the housing. It has a 9 inch rear so I bought a new center section with 3.73 gears and a locker. It made a world of differnce going from busted LS 3.55 to locked 3.73s.
Limited slip is ment to have some give to it, and if I'm not mistaken doesnt it disengage when the vehicle turns? The bad side of the locker is if you gas it around a turn in the snow, dosent take much to put ya in a spin. They do make for some wicked doughnuts though.