so im somewhat new to my truck, its an 06 level II and i was wondering what kind of front and rear diff's it has? and what the disadvantages/advantages of it are! so if anyone can inform me thad be great! thanks guys

 

Do you mean the size or the limited slip in the rear?

 

your front differential is a hybrid D30/D35 center chunk. Your rear end is a Ford 8.8" center chunk with the stronger 31 spline axles. Installed in the rear axle is a Torsen torque-sensing limited slip differential. You have 4.10:1 axle ratios front and rear.

Your weakest points in the driveline will be the front CV shafts, particularly if you decide you would like to install an Aussie locker in the front axle.

 

Dana 35 front, open differential. 4.10s.

Ford 8.8" Rear, Torsion limited slip differential. 4.10s. 31spline.

Front axle...junk...it's IFS.

Rear axle....Beefy...often called better than a 12 bolt chevy rear end. Espicially with 31splines in the axle shafts. Limited slip allows the tires to spin and different speeds, but when it "senses" no spin on one side, and alot of spin on the other, it'll "lock" the axle shafts together to put down power to BOTH wheels. Back in the day was called "POSI". Basically there power going to both wheels at the same time, rather than only 1. Open differentials have no "locking" mechanism to provide power to both sides. "Freespin" i suppose would be a correct term.

Does this kind of answer your question?? I hope i explained it correctly.

 

ya thanks alot guys! i was mostly just wondering if they were lsd open or locking or what! but thanks for the info about my truck! im lookin forward to learning alot more abotu it! and thanks gearhead for the heads up on the cv's ill remember to take a look at those if i think somethings goin on up there! so drivetrain wise, should i leave my rear end alone and beef up the front or what do you guys suggest? its mostly street driven but i do foul around with it a bit

 

Your stock 4x4 system is fine as-is for casual offroading.

With the exception of the differential, the 31-spline LII rear axle assembly is taken directly from the 1-ton commercial Ranger sold in South America. It is very strong. The differential used in the LII is a geared, limited slip Torsen - like other limited slip diffs, it is designed to send some torque to the wheel with most traction but it never locks.

The half shafts are the limiting factor up front and will not survive being seriously hammered offroad. If you don't drive that way, the front end needs nothing done to it.

 

anybody got a extra 31spliner just lying around?? Cuz I want one.

 

Maybe I've been the first to find out, but I destroyed the CV inner bearings before I broke the actual shaft while off roading.

Atleast as far back as 05 Ford changed CV shaft styles. They went with a smaller "plunge style inner bearing". That is the one that goes into the diff for those who don't know. The cup is physically smaller in diameter than the 98-0? style CV's. This also means the inner bearings are slightly smaller.

Not sure why Ford did this though. Maybe to make the bearings the weakest link that way if you break a CV off road you can atleast get back to civilization and not have a shaft clanking around ????

Either way, I found this out the hard way, and found out that you cant slip the older style half shaft/bearings into the newer plunge cup for a quick cheap fix


If you're going through the trouble of swapping rears, go to a JY and pull an Expo rear, same 31 spline shafts, found with LS easily, and usually a 4.10 or 3.73 ratio. Plus disk brakes.

 

great well looks like i wont be changing to much drive train wise.. what if i was to go to 33" tires though? whould i ahve to re-grear it? im probably gunna stick to 31" for a bit, but maybe next year i was thinking of going a bit bigger. what would get harmed by having the slightly larger tires?

 

I have 33's with the stock 3.73's. It's ok, will squeel the tires just a hair if I wanted. The truck is a dog to say the least, and to me it seems like the truck has trouble making up its mind when it wants to shift. It doesn't hesitate or slip, just doesn't shift when *I* think it should.

Eventually I'm either going to swap to 4.10's to get back to stock like performance,... or I'll just completely go back to stock suspension and everything.

 

was more worried about it screwing up the diff's and my rear has 4.10s i blieve, so i should be ok? what about clearance? if i styed stock, how much would i rub if i stayed stock, and went to 33"'s? would it bebest to get a small body lift?