Specifically 2001. I got what I consider a score this past weekend from a pick & pull. A 9 1/4" limited slip diff from under an '01 Dakota. Was a four door with a presumably aftermarket steel shaker hood on it. Scoop was gone, had a 5.2 or 5.9 under the hood.

Question 1. Was a 5.9 available in those trucks and the reason for the 9 1/4?

Question 2. If not, was the 9 1/4 an option otherwise?

I had heard only the Dakota R/T's with the 5.9 had the 9 1/4" diff.

TIA

I seen both with V8 u could probably order it I also think what was laying around

Question 1) A 5.9 Magnum was available and probably resulted in a 9 1/4 being installed.

Question 2) I believe a 9 1/4 was an option for any Dakota after 97. A limited slip was definitely an option.

The Dakota RT probably was the reason that Dodge installed the 9 1/4 in a Dakota, the 8 1/4 was known to be on the weak side for pretty much any abuse, and Dodge had to cover the rear end under warrantee, add the 360 (5.9), hop up the computer a bit, and throw in the 9 1/4 to save on the warrantee expenses, add it to the price. Once they stuck them in the trucks, offer them as an option.

Before you install it, you want to be sure the pinion nut is still tight, that era 9 1/4 had a habit of the pinion nut loosening up and letting the pinion gear fall back into the ring gear and locking up the rear ends..

Just spit balling here, but maybe the truck had a 9.25 rear because it was a quad cab, which is heavier. I have an 04 Dakota quad cab with a 'Won't pull a greasy string out of a cats ass' 4.7, and it has a 9.25 one legger in it. Just a guess.

2wd or 4wd?
My 98 4wd 5.2 5-spd has a 9.25

I have a 2001 SLT (non rt) with the 5.9. It has the 9.25 with 3.92 sure grip.

Well nuts, now I have to reserach the rear axle in my 2001 Dakota. It has drum brakes, single ABS sensor, 3:55 ratio/limited slip, powered by the 4.7V8. The codes inside on the glove box lid say DSA and DRB which indicate the anti-spin diff and the 9-1/2 diff size.

I had planned to rebuild the limited slip clutch in the axle when it goes under my 56 Dodge pickup project, powered by a remanufactured 4.7HO V8 with a few mods making about 325 hp at the crank (goal). But if I am better off to just find a different 9-1/2 rear axle with disc brakes and 3:55 gearing I'll start hunting the local self pull yards and CL. Which then brings up, what would be the best rear axle to use versus just searching for rear axles for a Dakota? I also plan to use the rear frame half from the 56 Dodge which likely means I'll have to relocate the spring perches anyway. Oh, and so far I had planned to go ahead and use the Dodge 6x114.5 wheels/hubs as I already have the stock Dakota 16" wheels and a set of 18" aftermarket wheels to fit also.

In my opinion, the rear axle under your Dakota is going to be too narrow to clear the frame rails on that 56 rear frame. If the tires do clear the 56 frame, they are going to be really close. Close enough that at least your going to need a much smaller backspacing then the OEM Dakota wheels will give you. When I put my 49 together the bed sides sat on top of the Dakota tires, but that was with the Dakota rear frame, so I just cut a tire sized arch out of the lower bed sides (with the Dakota raised floor, the arch cut was below the floor line).

You can always narrow the 56 rear frame, near the wheels, and trim the bed sides with an arch, and use the Dakota rear end. (or use the Dakota rear frame and re-drill the mounting points on the 56 bed crossmembers). You may have to do a small wheel tub on the bed side to clear the tires if the arch is above the floor line).

I suspect your 01 Dakota probably has an 8 1/4 (Chrysler now calls them 8 3/8" but little changed other then Chrysler's terms). Unless you plan on doing serious burnouts with sticky tires and really good traction, that 8 1/4 rear will hold up well to normal driving and some occasional mild abuse. Were I in your shoes, I would keep the current Dakota rear, and modify the frame and bed sides for the clearance you need (I would want at least 3/4" (1" would be better) tire sidewall clearance to anything the tires could contact. Drag out the tape measure, measure the widest point on the tire to tire on the rear axle and check the 56 frame and bed sides.

The challenge with changing the rear end will be the wheel lug bolt pattern. Only the Dakota and the Viper share that 6 bolt pattern (unless things have changed recently).

this is what is printed on the sticker inside the glove box door:

DRB----------Axle Rear 3850# Corpo
DSA----------Anti Spin Diff

So my 2001 Dak has the Anti Spin rear Diff, but at 203,000 miles I'd bet the clutch in the diff needs to be rebuilt. The DRB code indicates the Corporation 9-1/4 diff, which agrees with the VIN build list from the favtory, So my Dak chassis has the 9-1/4 rear axle, anti-spin diff, heavy duty service group, power steering cooler, heavy duty cooling group. So some of the better specs for a Dak.
When I get to the point of figuring out the rear frame I'll consider what I can do to maintain the inside width of the box. But your points about the track width and tire offset are well taken. The aftermarket 18" wheels I have are less offset than the stock 16" OEM wheels, so they may be the answer for my warm season tires. If the stock OEM 16" wheels don't work out I have seen steel wheels (the standard steel spare for a Dakota or Nissan frontier) that have less offset for the winter tires I'd use. I have a set of dropped A-arms for the front of my Dak chassis, and I may have to notch the rear frame (Dak or the 56 frame rails) to get the right stance. I don't want a big drop, just a lowered stance, fo I'll be modifying the frame one way or the other.

Thank you for all the replies. Seems these are not near as rare as I thought. And that is a good thing!