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I am rebuilding my 1976 F150. I’ve got a rebuilt 390 and rebuilt the C6 transmission. The truck has a 9 inch rear end and the guy that built my motor says I should consider a positraction diff. He thinks the new engine will spin one tire. Anyway, a friend of mine happens to have a posi diff that was going to go into a 1968 Mustang, but they ended up doing something else with that car. How much should I pay for this?
I am rebuilding my 1976 F150. I’ve got a rebuilt 390 and rebuilt the C6 transmission. The truck has a 9 inch rear end and the guy that built my motor says I should consider a positraction diff. He thinks the new engine will spin one tire. Anyway, a friend of mine happens to have a posi diff that was going to go into a 1968 Mustang, but they ended up doing something else with that car. How much should I pay for this?
I wouldn't pay anything for that! That is not a limited slip, thats a straight spool!!! You would be dumb to run that full time on the street.
Looks more like a spool to me. Do they say what gear ratio it is?
Is yours a 4wd or 2wd truck? Long wheelbase or short? What tire size? If you're not going to use the new diff as-is because the gear ratio is wrong for your truck, then it's not worth much money since you'll have to re-do it to change the gear ratios to suit your truck.
If they were going racing, then it's possible for a Mustang it was 3.50, 3.73 or even 4.11. But if it's a 3.0 or even something in the 2's, that might not be great for you.
What ratio are you looking for?
And X10 what beartracks said. There's no such thing as a Ford Positraction. That was a GM product for GM differentials only.
The name has been used generically for generations, but with the widespread communications of the internet, it seems that now EVERYBODY calls any limited-slip, or locking diff a "Posi" so kudos to GM and fans of GM for coming up with such good names. Posi, HEI, small block, big block, and probably two or three others that have become ubiquitous over the years.
FYI the category of differential we're talking about here is "Limited-Slip" for this type. There are also Lockers (3 types?) and Spools (2 types).
And do you need one? Do you plan to spend a lot of time in sketchy traction situations? What about burnout competitions? Do you need max acceleration, or just a nice driving truck?
I'm just asking those questions because everyone seems to think they need a locker or limited-slip diff, when in fact most trucks probably had neither and did just fine. Granted, a limited-slip can be an advantage, but you need to really look to see whether or not you really need one.
My advice would be that if you're not sure, or you don't find just the right setup right away, then put the truck back together with all the new engine and trans stuff, then drive it around to see how you like it.
If you will drive it in muddy conditions, you might like a limited-slip. If you want the best acceleration out of a corner, you might like a limited-slip. If you live in an icy area and will drive the truck in those sketchy times, then you may NOT want a limited-slip.
But those are questions best answered by those that live in those conditions with their trucks. Out where I am we put traction aiding diffs in our off-road vehicles, but usually leave the street trucks with open differentials. Very mild climate, city conditions mostly, and race around in our cars instead of the trucks.
Should we be lucky enough to have both that is.
As has been said that's a spool and useless to you. and unless you're planning on racing you really don't need limited slip anyway that's why it was optional.
As has been said that's a spool and useless to you. and unless you're planning on racing you really don't need limited slip anyway that's why it was optional.
440, you've probably seen axle shaft splines that were pulled out of street car rearends that had spools. They look like barber poles!
Looks more like a spool to me. Do they say what gear ratio it is?
Is yours a 4wd or 2wd truck? Long wheelbase or short? What tire size? If you're not going to use the new diff as-is because the gear ratio is wrong for your truck, then it's not worth much money since you'll have to re-do it to change the gear ratios to suit your truck.
If they were going racing, then it's possible for a Mustang it was 3.50, 3.73 or even 4.11. But if it's a 3.0 or even something in the 2's, that might not be great for you.
What ratio are you looking for?
And X10 what beartracks said. There's no such thing as a Ford Positraction. That was a GM product for GM differentials only.
The name has been used generically for generations, but with the widespread communications of the internet, it seems that now EVERYBODY calls any limited-slip, or locking diff a "Posi" so kudos to GM and fans of GM for coming up with such good names. Posi, HEI, small block, big block, and probably two or three others that have become ubiquitous over the years.
FYI the category of differential we're talking about here is "Limited-Slip" for this type. There are also Lockers (3 types?) and Spools (2 types).
And do you need one? Do you plan to spend a lot of time in sketchy traction situations? What about burnout competitions? Do you need max acceleration, or just a nice driving truck?
I'm just asking those questions because everyone seems to think they need a locker or limited-slip diff, when in fact most trucks probably had neither and did just fine. Granted, a limited-slip can be an advantage, but you need to really look to see whether or not you really need one.
My advice would be that if you're not sure, or you don't find just the right setup right away, then put the truck back together with all the new engine and trans stuff, then drive it around to see how you like it.
If you will drive it in muddy conditions, you might like a limited-slip. If you want the best acceleration out of a corner, you might like a limited-slip. If you live in an icy area and will drive the truck in those sketchy times, then you may NOT want a limited-slip.
But those are questions best answered by those that live in those conditions with their trucks. Out where I am we put traction aiding diffs in our off-road vehicles, but usually leave the street trucks with open differentials. Very mild climate, city conditions mostly, and race around in our cars instead of the trucks.
Should we be lucky enough to have both that is.
My truck is 2wd with stock tires. I live in the south, no not much snow. The guy told me that diff is a 411.
My truck is 2wd with stock tires. I live in the south, no not much snow. The guy told me that diff is a 411.
Yes, but that spool will not allow one wheel to rotate faster than the other while you turn the vehicle. You'll hear chirps, feel a bunch of jerking, your pinion will develop a lot of slack, and you'll probably make stock axle shafts look like twizzlers.
Yes, but that spool will not allow one wheel to rotate faster than the other while you turn the vehicle. You'll hear chirps, feel a bunch of jerking, your pinion will develop a lot of slack, and you'll probably break stock axle shafts.
Thats after you destroy a set of tires, have so much spring hop you snap a u joint..... lol
Wrong speed in a curve could be very dangerous with a spool especially in wet conditions , could send you spinning out of control , get a limited slip ,,mopar calls them sure grips , but a spool on a daily driver not good,,
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