Ive got an 89 F250, fecently threw in a rebuilt 302 and true dual exhaust. Im hoping to step up from my one tire fire. What can i do? can my existing rear end be changed to posi or do i have to swap in a whole new rear end? And what is the difference between limited slip and posi?

 

No, You don't have to replace the whole rear end housing. (depending on how much you want to spend?) All you would have to do is to replace the center yoke differential. Most of the time you can keep your existing axles. I've done this to my truck because I had a "one wheel Peel" that burnt up. I bought a Auburn limited slip locker for around $400. If the rear is stock, it should be a 8.8 10 bolt 31 spline. Always double check this.

The difference between a limited slip differential and a posi rear end is, a positrac differential (rear end) distributes equal power to both rear wheels at the same time while a limited slip differential only supplies power to one rear wheel while the other only moves when the car is in motion. When you turn a corner, the limited slip will allow the inside tire to rotate less than the outside tire. A posi-trac has torque to both wheels all the time. If you've ever drove in a car that has posi, you'll notice the tires churp a bit on tight corners.

A limited slip becomes a posi-trac when you get in a place where both wheels are going to spin. When you get in mud or ice your right rear wheel will start to spin while the left rear does nothing. With posi-trac they both will spin. With a limited slip, after your right rear starts to spin, the left rear will do the same. The limited slip came in after everyone saw how dangerous the posi-trac is on wet pavement or ice. With posi-trac, both wheels are pulling constantly. This will cause a tailspin when you gun it on wet pavement.

I hope you didn't fall asleep during my long winded answer.
Cheers!

 

Posi-trac was just Chevrolet's term for there traction differental. In early years it was a typical clutch type limmited slip. Later they used what is called the Gov-lock, this was a full locker that had a speed govener that switched it to open at speeds over about 20mph. This is probably what gravydude refers to they could be rather unpredictable to drive.

For some good info check out Limited slip differential - Wikipedia, the free encyclopedia

I recommend for a daily driver a Torsen Gleasman type differental they drive great and are easy on tires. Detriot locker sells these for your truck they call it the Softlock.

If this truck is used alot offroad then you are limited only by budget there are alot of good options.

I don't think your truck has an 8.8 rearend as gravydude stated and if it does getting rid of that boat anchor is your first step. They are not strong enough for a full size truck.

Tell us more about the truck and what you do with it.

Hope this helps

 

Powertrax No Slip automatic locker. Replaces your spider gears. You don't have to reset your ring and pinion. Easy instructions if you know your way around a truck. Realiable. Works well. About $500.

 

Thanks, lots of help now i have an idea of what to shop for
my truck is 2wd and i use as a daily driver, but im looking for any way to give more power and have a little more fun. And considering most of my friends are chevy folk any ways to show off a little more always helps.

 

For a daily driver I would stay away from all positive lockers like the powertrax and lockrite. Agian check out the detriot softlock if budget allows if not grab a stock type clutch posi.

 

If a used trac lok unit was purchased, how hard is it to install, or should it be left to a mechanic?

 

How hard is relative. It's pretty easy to swap the parts, it's doing it right that takes skill. If you have the proper tools, instuctions, patience and mechanical aptitide I'm sure you can manage.

 

You don't know what you're talking about.

 

why stay away from the positive locker???
Will any lockers interfere with turning raidus or drivability at all?

 

That's very helpfull Bill, care to back that up with some great insite of your own?

And yes positive lockers on a daily driven pickup can and will interfere with your turning radius and drivability. Probably not much but enough to notice, and enough to make it not worth it on all but the more extreme trucks. For a daily there's no real benefit and only drawbacks. The constant locking and unlocking will drive you nuts, and with the light rear end of a pickup it can make driving in the rain real interesting. And there's no real benefit for a street rig, a locker over a posi only becomes helpfull if one tire is up in the air. A good posi is plenty to never allow a "one wheel peel" on the street.

That said I drove a truck with a spool(always locked) on the road everyday for a while. But it was a big 4WD, I spooled it(lincoln locked) because the spiders were toast and it was a free option. And I like driving around fishtailing everywhere.

 

My dad's 350 HP and 350 Ft Lbs El Camino has a Powertrax No Slip locker. Been running it for a while now, no problems. Very reliable. He leaves two identical black tire marks anywhere he wants to burnout. So do I.

My F150 has the same locker. No problems. Incredibly smooth. I don't even know it's back there until I need it. When I need it, dirt and mud are being thrown from both back tires.

No noise. No vibrations. My turning radias has not been hurt.

Better off road capability. Better towing capability.

Powertrax No Slip lockers are good. You don't know what you're talking about.

 

I never said there weak, in fact the oposite is true, I'm just saying there generaly not the best choice for a daily driven 2WD pickup. If you and your father like yours, that's great and your choicce.

But, the fact that you bring up the hp on the el camino, and slinging mud and off-road capability with the f-150 tell me you two are more happy spinning tires and slinging mud. (and wearing out tires)

Does he drive that el camino in the rain, I would think not, is your truck 4wd, sure sounds that way?(Is it the 94 in your sig with the mudders)

That el camino with a GOOD posi would lay just as much rubber, be more drivable in all weather, and launch straiter at the track. Your truck is probably better with a locker over a posi it sounds like you do occasionaly hang a tire in the air off road.

Bottom line it's a personal choice that has everything to do with what the vehicle is and how it's going to be used.

My truck is a 4wd F-350 with 37" Interco Truxus Mud Terrains. I spend plenty of time off road but I run a tight posi, cause I work it everyday, and don't like paying for tires. If I felt like spending the money I'd get a selectable unit that is selectable from posi to spool. But I don't.

 

I'll agree with you on this point.

 

I cant find a no slip locker for an f250 axle (10.25) so it may be out of the question.