I just bought a 79 F100 4x4 with Dana 44 front and 9" rear , 466 engine and C6 trans. I'm going to go play in the national forest trails, powerline trails, places like Lexington Muddy Playground and Uwharrie National Forest. I intend to drive the truck an hour or several hours on the hiway to get to the play areas. I also will drive truck to work on occasion. Truck has 35" Mud Terrain Radials. I am going through the u joints and brakes and I want to make both differentials posi. I know I could weld spider gears but I'm told something will break driveing on the street. Like maybe an axle or maybe truck won't turn right and steering wheel will jerk around on tight turns. Powertrax lockers are least expensive option I have seen. I have been advised that is good for rear end but again some have advised agianst using one on front differential because it will fight on tight turns. The clutch type lockers or detriot lockers are even more money. I'm trying to do this on a reasonable amout of money. Anybode have experience on the subject?

 

a powertrax lock right just turns your existing open diff into a detroit basically. their only real weakness is that they use the stock open carrier as opposed to a detroit where it is all a big forging designed for more severe use.

a clutch type is not a "locker", neither is a Positraction. a "posi" is a limited slip, a locker is different. trust me, there is a HUGE difference in street manners between the 2. a detroit/lock-right essentially uses torque (go pedal) to mechanically lock the 2 shafts together, then when the torque disappears (i.e. coasting through a turn) the shafts go back to being open. if your tires spend a lot of time in the air 3 wheeling through obstacles, lockers work great.

a clutch type/posi/limited slip uses clutches just like a manual transmission. they allow the tires to turn at different speeds through turns because the clutches slip, but if a tire goes in the air 3 wheeling through the woods, they slip pretty good and act a lot like an open diff.

limited slips tend to allow the front wheels to turn tighter, lockers will cause the front end to "snow plow" on tight turns and push in the mud. i ran detroits front and rear for almost 10 years in my bronco, and you get used to them but they do not work as well on the street as a posi. you really notice it in the ice/slick rain etc. having a lot of power doesn't help. i ran 40s, and even with a stock 351 the backend could break out pretty easily. 4x4 was basically useless on icy roads in that truck, granted running swampers didn't help, but if it had an open diff or posi in the front it would have worked a lot better.

for what you're doing, (especially if you have full time 4x4), i would say lock right in the back and find a spicer power lock for the front (ideal) or at the very least one of the old ford "trac lock" D44 diffs. you'll probably be a lot happier in the woods cause a "posi" in front will let you turn a lot tighter in the mud. but being fully locked in the back i think you'll be surprised how far you can get even with an open diff in front. do the rear diff first and see how you like it.

spools/welded diffs should be considered for dirt only, and even then, they are terrible. kiss your turning radius good bye and be prepared to change your u-joints at least every 3-6 months if not every trip. they just don't last when everything is bound up all the time. i can't tell you how many guys i've known who welded a diff to save some coin, then spent hours on the trail and a fortune in junkyard parts constantly swapping broken shafts and u-joints. don't be "that guy"...

 

You might also want to look into Tru-Tracs. Not for the hardcore rock crawler and buggy types but they are excellent on the road & trail.

 

That's a big help thanks a lot for taking the time to explain the performance issues with each option. I used to have a different 79 F250 and got stuck before with diagonal tires off the ground. That truck otherwise did pretty good off road but it was mainly my work truck. This is a toy. With open gear up front if one wheel comes off ground the other does not pull right? That is what I want to fix. I looked for the Spicer product you mentioned on my prefered parts source and they did not list it. Auburn makes a limited slip for the Dana for less than $300 buck like the Powertrax for the rear. The limited slip will apply power to the other wheel when one is off ground right? And not cause steering problems on turns right? Oh I just noticed the Auburn gear option is for rear and not for front. The units for up front are twice the money. How does the unit know if its up front or not?

 

Put a powertrax in the front and leave the rear open for the best compromise.

The powertrax in the rear is fine in a straight line, but you will notice some noise and surging going around corners. They say it is better with an auto trans to smooth things out - I had one on my ZF5 truck and I did not like it. My truck bucks anyway and the powertrax made this characteristic much worse.

 

My f150 had a limited slip rear and I was cruising around the local mudhole wth bald 35x15.5 thorn birds where most trucks of equal lift and tires were stuggling with open fronts and rears. If you can keep both your back tires spinning then I thoroughly recommend doing so

 

in general, limited slips will not apply power to a wheel off the ground. (true trac's can to a point). keep in mind, if you get a posi it will need to be setup professionally and you'll probably need to replace the bearings as well, since with dana spicer axles, the bearings usually hold the shims on. no offense, but from the question's you're asking, you're not ready to setup a diff. if you simply pull the old carrier out, swap over the ring gear and stick the new one in, you're likely just going to waste the ring and pinion very shortly. doesn't matter if its a trail truck or DD, if the backlash and mesh pattern are off by a couple thousandths in any direction, it'll toast itself VERY quickly.

anything that comes in as complete case like this (detroit, auburn, power lock, yukon grizzly etc):

will need professional shop install

anything that simply replaces spider gears and looks like this (powertrax lock rite, aussie locker, yukon spartan locker AKA lunchbox lockers):

can be installed with basic hand tools in your driveway in a couple hours. this style is ONLY A LOCKER. you can't just swap the spider gears on an open diff for clutches and make it a limited slip/posi <--different words, same thing
posi and locker are two different animals entirely

http://www.ebay.com/itm/DANA-44-POWER-LOCK-POSI-TRAC-30-SPLINE-3-73-DOWN-REBUILT-JEEP-/151181216886?pt=Motors_Car_Truck_Parts_Accessories&hash=item23331a4c76&vxp=mtr

 

Using the "Brake Locker" method will get you out of quite a few spots too.

 

Sounds like strictly from a performance perspective limited slip front and rear would be best. No offense taken at all on the fact I'm not a qualified ring and pinion set up man based on experience. I have some limited knowledge but I know this is one chore most people decide to leave to the pro's. I'm going in phases of rear first since I had a bad u joint there that's where I started. In the interest of saving money I am considering learning the right way to install and set one up. I've been building engines for years and have tools to do stuff like checking crank end play and measuring crank journals and piston bores and file fit my rings. If I was going to install a limited slip ( the link to Ebay poses good option maybe of buying used units. ) I need to find a good book and or video link on the subject and follow the procedure step by step. I watched a video I might still have from Richmond Gear I got with a purchase before where it shows how to use the grease and check the pattern. I understand the 9 inch uses different details for adjusting the location of the ring carrier and pinion position than a DANA. I find the more stuff like this I do the more enjoyable the hobby can be and the more likely I can diagnose problems and fix them right. I have had times that I went with the option of professional service and still not necessarily done right. In this case I'm very confident in my local shop that I could have do this but when I add up the cost of all the work I'm considering it just makes sense to consider doing it myself. Right now on the rear I'm looking at limited slip unit, ( bearings or install kit or what ever is needed special tools? I have magnetic dial measure do dad and torque wrenches ) rear brake shoes, drums , hardware and wheel cylinders for brakes, u joint repairs ( including double cadan joint I need to take apart I have never dealt with ), and I want to ad drain plug in 9" housing so I can put in clean oil without pulling center section. Then fab up drive shaft safety loop and put it back together.

 

yup, you don't sound as dumb as i first thought

if you have a minimum 20 ton shop press with clam shell puller, dial indicator, INCH/LB beam style torque wrench, impact gun and a LOT of patience, you can do a gear install. the 9" rear is definitely the easier of the 2 diffs, personally, i'd just look for a used complete 3rd member that already has a Limited Slip Diff in it and just throw that in, keep your open one for a spare if the other one grenades.

personally, i think locked rear and limited slip front is the magic combo for a rig that will mostly be doing muddy trails in the woods. i think with a locker in back, you'd be damn surprised how much you can get through in 2wd and just keep the 4wd for rutted climbs, bogs etc. i used to do this all the time in my rock crawler, just 2wd as far as i could then kick it into 4 lo for anything technical, then back into 2wd when done with the obstacle. helps the u joints last a LOT longer.

 

I ran a Lock rite in a Jeep Cherokee I had. A tire got bound up while wheelin, and I grenaded the locker, and had to replace the whole rear axle because of the damage. For regular driving it was fine. They are not all that strong, but save the day when exploring trails.