Is the 91 a direct replacement? Ratio the same?

In general how 'big' are these axles? Dana 44-range or smaller?

The 8-inch V6 M/T '91 front diff will fit with the ARB RD110 locker, but as I understand it the diff-mounts will require some minor modification. Need to use V6 axles as well but my original hubs will work.

I believe the gear ratio is the same (stock 4.625) but I haven't considered it since I'll be putting in 5.29 gears front and rear. I've got the front-end and the front locker, just waiting on the gears to be delivered. The whole thing will be done once I have the gears in hand (early May?).

I think I'm going to add a rear locker to the 'to do' list.

Front? I'll see how I do with 'just' a rear locker.

Thanks, all.

what is your source for the 5.29s?

So are you going ARB in the front? If so, did you have to get the whole V6 axle? Or does using the 5.29s in your stock axle allow you to install the ARB without upgrading to the V6 axle?

I may not be making sense here - i'm not much of a gear head. I'm trying to figure out a good upgrade path for my 86. I'd like to go 5.29 eventually and leave the door open for ARB but use a LSD in the front in the meantime.

Source is Mister Bishi (see his post 5.29 Supply Breakthrough !!!!!!!!). I bought mine a little over a month ago and I probably won't get them until early May.

I will be using an ARB RD110 locker in the front. You don't have to use the ARB locker if you wish to use an LSD, however, there's no point in doing the diff swap unless you plan on using the ARB in the future. You can use an LSD in your current front diff. The diff swap is only necessary if you intent to install the ARB.

I would suggest, though, that you decide what your long-term goal is and set a path to it. If you don't do the diff swap now, and get 5.29 diff gears for your 8" rear and 7.25" front, and decide to swap the diff later for putting in an ARB, you'll find you won't be able to use the same front set of 5.29 gears until you get a front set of 5.29's for an 8" diff. You also won't be able to use 4WD until getting 5.29's for the front (they have to match the rear diff ratio).

Clear as mud? Let's see if I can simplify it:

-To install the ARB you must swap to the 8" diff (must be from a '91 M/T V6).

-To swap the diff you must use V6 axles (the axles are not dependent on the gears or the locker...which axles are needed are only dependent upon which diff is used).

-To use 5.29 gears you have to decide what you want down the road. If you get a front 5.29 set now for your current 7.25" diff you cannot use that same front gearset in an 8" front diff. Of course, you could decide to buy a 7.25" front set now and an 8" front set later, but I doubt anyone would want to waste that kind of money, and those gears may once again become unobtainable.

I am going to wind up with an 8" rear diff (already has an ARB RD05 locker), an 8" front diff, an ARB RD110 locker in the front, an MB241981 5.29 gearset in the front diff, and an MB241981 5.29 gearset in the rear diff (note the part numbers are the same because both of my diffs will be 8".

Does this help? Let me know if you have more questions.

now could you explain that in english <img src="/forums/images/graemlins/lol.gif" alt="" /> i'm mechanically inclined but all this dif. talk has got me so screwed up.So what I take you'll are saying is the front and rear diffs. in my 87 montero and raider are crap.And that i need to either change them or go with different gears.

Is anybody else not getting this?

i'm sure there is, they are just not admitting it <img src="/forums/images/graemlins/ignore.gif" alt="" />

Yes! I get it - I should have bought a later model V6 SWB thanks for explaining. No seriously, it makes sense. I think i'm going to want the V6 front end even though it takes some work to install and modify. A feeling of symmetrical zen will overcome me once I have matching 8" gears front and rear with LSDs to start out with and ARB lockers if I find the LSDs insufficient.

No need to change out your rear differential. It's fine. You only need to change the gearing inside of it if you change the gearing inside your front differential as well. If you don't, you'll have different ratios in your front and rear differentials and that would bind your drivelines when in 4WD. In stock U.S. configuration, both front and rear differentials are geared with 4.625 ratio ring & pinion gears.
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You only need to change your gearing in the differentials if you want to (you don't have to get new gears, but they are nice to have). Changing the gearing has no bearing on whether you have a locker or vice versa. You can get new gears. Or you can get a rear locker. Or you can get a front locker. Or you can do any combination of those. Or you can do none of it. It's up to you.
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These are the only requirements if you want to get an ARB locker for the front differential of your '87 Montero without doing a solid-axle-swap:

1) The only way to do it is by swapping out the front differential. The front differential you must use is one from a 1991 manual-transmission V6 Montero. I don't know if a 1992 or higher will work in a Gen I but perhaps someone else may know.

2) If you do the swap indicated above you will be required to use axles from a V6 Montero (I believe any Gen I V6 axles should do, but if you have a choice, get the axles from a 1991).

3) The ARB RD110 locker is the only front ARB locker available for Monteros. They list it as being only for the '91 and up.
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If you want a rear ARB locker for your '87, no problem. Just put in an ARB RD05 locker and a compressor to actuate it. Done.