So here is my problem, I dont have enough money to get locking diffs for front and rear so which should I get? I would think rear would be the most beneficial in 2wd obviously but wouldn't the front be better in 4 wheel. I have a 9.75 in the rear and an 8.8 in the front. Fyi, I am what you might call uneducated in differentials so how do I now what 8.8 I have in the front, I know its open but how many splines, 28 or 31? And what size shafts does my 1998 f150 4x4 5.4l have?

 

You do not want it in the front, unless you are into SERIOUS off-roading. And then it should be both, front and rear.

 

Rear first. Without a question. The front is heavier and thus both front tires stay on the ground better. Plus, with a front locker you are much more likely to start braking CV joints, and steering sucks with a front locker in 4x4. The rear axle is much stronger and will handle a locker better than the front.
Having front and rear lockers is great, if you are really getting out there. But with a rear locker you will be surprised how much more capable the truck is.

 

I'm no expert on diffs either, but know that when I lock the diff on a big tractor's rear end, the rear tires don't want to turn. It will pull a house over with rear diff locked- but it's straight ahead or nothing. So putting locking diff on front wouid be a problem if you want to turn as when driving on roads. Now if you are crawling over boulders at .25 mph, who cares?

 

Ok, thanks. so does anyone know of a locker for the 9.75, maybe something that allows of the gears to overrun and allow for easier turning. I was looking at this one, http://www.rocky-road.com/lockright.html
but they dont have one for the 9.75

 

I think your only choices are a Detroit Locker or an Auburn ECTED for lockers. Detroit TrueTrac is a limited slip and is not meant for tires larger than 33".

Splines; From Randy's Ring & Pinion:

 

youve got a 9.75

Id look at the trutrac locker. what you will want is a selectable locker, or limited slip style.

Lockers will check tires up quick on the road. this is because the tires are resisting spinning different speeds while cornering so they drag or slide around the turn. This will be the same way with a locker in the front. You can drive with a selectable locker up front but be very careful cornering and go very slow if the selectable locker or limited slip decides to engage your bed will pass you. Ive had it happen.

 

A detroit will allow slippage for turning, under light acceleration or coasting. You can get around parking lots just fine. If you stomp on the gas and come out of a turn from a side street, you will chirp the tires and you'll feel a little bit of understeer, but nothing bad, nothing unsafe. It's not really noticeable on the highway. But you will go through tires a little quicker.
For a daily driver the etced would be a better choice for most people though. Much more transparent operation on the road, less tire wear.