I originally posted this info on another forum many moons ago. I got this info from an issue of "Off-Road Adventures" which is a publication by 4 Wheel Parts.

If you have a 4x4 Durango you can see that 31" tires are the normal max recommended for the front axle (although many have run 33" front tires offroad without problem).

The front axle for 2000 - 2003 D's is rated 2+ (which is between the weak and moderately strong rating system described below). The 9.25" rear axle in 4x2 Durangos (and some 4x4 D's) is rated as strong (35" tire size rated). Since Dodge used both the 8.25" and 9.25" rear axles in Durangos interchangeably, it is hard to tell which axle you have without checking. To determine whether your D has a 8.25" or 9.25" axle look at the rear diff cover. If it has 10 bolts it is a 8.25". If it has 12 bolts, it is a 9.25".

I would say that the front axle is not particularly well suited to a locker or LSD due to it's relatively weak rating. If you do want to use a locker in the front diff, you would need PT4WD. Since locking hubs or a selectable locker are not available for the front axle of a Durango, a front locker cannot be used safely in a FT4WD Durango. If you have FT4WD and installed a front locker, it would cause serious steering problems on the pavement.

Here is a synopsis of the information:

Axle overall strength ratings:

1= Very Weak
2= Weak
3= Moderately Strong
4= Strong

Chrysler 8.25" Rear Semi Float Axle
Overall Strength Rating: 3
Max Tire Diameter Recommended 33"
Ring Gear Size 8.25"
(10) #3 Ring Gear Bolts on a 8" diam bolt circle
1.21" dia axle shaft with 29 splines
Notes: This axle first appear in light 4x2 trucks in 1966 as was also used heavily in medium powered cars. It was the last solid rear axle used in Chrysler's rear drive cars built into 1989. It saw extensive use in Dodge half-ton trucks (4x2 as well as 4x4) with 6 cylinders. There is much conflicting information as to when this axles was last used in full sized rigs. When the Dakota debuted in 1987, it was used for the V6 models and is still used today. It was also used extensively in the rear of Jeep Cherokee XJ's after 1997. Early units used the reather spindly 27 spline axle shafts, which were upgraded to 29 splines for 1996. A reasonably wide selection of lockers and LSD's are available. Take care with this unit in a full sized truck. It's a c-clip unit.

Chrysler 9.25" Rear Semi Float Axle
Overall Strength Rating: 3+
Max Tire Diameter Recommended 35"
Ring Gear Size 9.25"
(12) #7 Ring Gear Bolts
1.3" dia axle shaft with 31 splines
Notes: This unit flrst appeared in 1969 era half ton trucks with V8's (small and big-block engines). If you think it looks like enlarged 7.25-inch unit-that would be a fair assessment. It is even used in '70s muscle car applications and in the last of Chrysler's luxury tuna-boats into the early 1980s. This axle is unusual but cool and convenient in that it uses carrier bearings that are adjusted with hex adjusters reached through the axle tubes via a long tool. This can generally be considered to be a keeper in most half-ton applications, though the available lockers makes a fairly short list.

Front Axle
'00-'03
Chrysler 7.625 IFS Front Axle
Overall Strength Rating: 2+
Max Tire Diameter Recommended 31"
Ring Gear Size 7.625"
( #3 Ring Gear Bolts on a 8" diam bolt circle
1.12" dia axle shaft with 27 splines
Notes: The aluminum cased unit is produced by Detroit Axle but is very similar to the Dana 35. Prior to the 2000 model year, either Dana or Chrysler produced units coud be seen, but since the turn of the millennium, Chrysler has been trying to produce as much as possible in it's own Detroit Axle facility. The Chrysler and Dana units are effectively in the same strength and durability area.

Front Axle
'97-'99
Dana 35 IFS Front Axle
The new era Dakota and Durango models often came with V-8's, and the Chrysler 7.25 IFS unit wasn't stout enough, so the Dana 35 IFS front is used. It has 27 spline axle shafts and CV assemblies. In the late '90's, it is found mixed with almost identical Chrysler built units. It's proven to be a decent performer in TTB or IFS form in the front of Fords and Dodges. In these units, it's merely a D35 ring, pinion and carrier in a new case and many of the solid axle's weak links are eliminated. The housing can easily be tweaked by spirited driving or simply difficult terrain in combo with big tires. This will cause other failures, including broken axle shafts, blown differentials (or lockers) and failed axle bearings. The D35 is reliable in stock form with axle ratios as low as 4.10 combined with a 31x10.50 tires. It may be reliable with a 33 inch tire and 4.10 gears with a six and an automatic if the driver is smooth. With 35 inch tires, or bigger, the axle is over- matched big-time and you need to think about a swap or serious mods. Dana 35 mods start in two areas, a truss and beefier shafts. The improved shafts can be either units made of a better alloy steel or larger diameter shaft with a higher spline count, as with the Genuine Gear "Super" 35 kits Next up is your choice of a locker or limited slip. With these mods, you could be reasonably safe to 35 inch tires and 4.56 axle ratios If you need more than that, you are best off doing a swap to a Dana 44.[/align]