Ok I seem to be willing to expose my lack of knowledge quite readily and this forum seems to be tolerant of my dumb questions! On a 2003-2004 Discovery 2, are the differentials the same? Meaning, If I carried a good 3rd member (from a parts rig) as a spare, would it work in either the front or the rear axle housing? I am looking at putting an locker in my rig and the Lucky8 website says "Air Locker locking differentials allow you to tackle the toughest terrain. The world's premier traction aid, ARB Air Lockers keep you moving in all conditions.These units fit the front or rear of RRC D1 D2 110 and D90." Does that mean the ARB locking unit is the same or is the 3rd member the same?

Thanks for tolerating my dumb questions!

 

I’m pretty sure they’re identical.

 

They are the same except, in stock form, the front has a 4 bolt flange and the rear has a 3 bolt flange for the rotoflex. The rears are generally in better shape (I'll explain this), so if you are going to carry one for a spare it is best to carry a rear with a 4 bolt flange having already converted your truck to a universal joint in place of the rotoflex. The reason the rears are generally in better shape is because in stock form the gears are cut the same direction, meaning the front diffs are applying pressure on the coast side of the gear while driving [forward].

Now, if you are moving to lockers then there are some things to consider. First, the assembled 3rd members from L8 all come with a 4 bolt flange, so the rotoflex delete is necessary. All that is required is to find a rear driveshaft out of a D1; bolt in operation. Second, are you regearing? If so, the aftermarket gear sets do have reverse cut gears for the front differential so that pressure is applied to the correct side of the gear teeth. So yes, you can carry an extra, but if you blow up the wrong differential your replacement will be weaker than what you just blew up. Third, if you are going to lockers, what is your concern that makes you want to carry a spare diff? The weak point in the LR 3rd members is the spider gears, so installing a locker resolves that issue by replacing the entire center section. Ring and pinion failures are very rare, especially when you use reverse cut gears in the front differential. You would be far more likely to experience an axle shaft failure than a center section failure.

No dumb questions here as far as I'm concerned - none of us are born with this knowledge, we've all got to learn it somewhere.

 

I have a front spare in storage for years and hope my suspicion of being the same works if I ever need to replace my rear one which shows some 'play'. The 'play' is supposed to be correctable with some shim rings, but anyway I keep the whole animal.

 

Does your D2 have working traction control and CDL? Just curious because I have found that it can take me quite far and I haven't felt the urge to spend big $$$ on lockers. If you are wheeling hard out in BFE you might want to carry a spare axle....the axle is like a fuse and its going to break before your differential.

 

On these diffs, shims aren't even necessary. They are adjustable VIA a threaded "end cap" on either side of the center section that will allow you to adjust it left/right as well as bearing preload.

 

Great question and advice! Thank you. I will admit that some of my rabbit trails are based on "what would be cool.." In this case, the question was posed by brother in law, who is a jeep guy. I didn't know the answer and started researching by looking at Lucky 8's website. Which led me to dream about better gears, and then, ARB lockers..
I really appreciate this forum as it has helped me with a ton of learning on my 2004 so far. I am old enough to remember the "old days" of if it wasn't in a haynes or chilton manual you just had to figure it out!

 

If you get lockers get the ashcroft. the arb's are not near as good and cost more.

 

I can guarantee you that if you are on stock axles, you need to carry spare rear axles before taking a spare diff. Right side rear axle will break before anything else.

I’ve broken at least 4 of those on the trails before I went hd axles.

Also, I have Detroit tru tracs front and rear and love them.

 

The tru tracs may be some reason for the breaking of axles. the requirement for them to slip before "locking" shock loads the system unnecessarily vs an actual locker (detroit, e or air). Knock on wood haven't had any issues with stock axles and a rear ashcroft rear locker on my white truck and that truck gets abused pretty good.