Hello,
I am fairly new to Xj´S, so i have a couple of questions regarding axles
So i own a 99 (i think 2000 model), Jeep XJ 4.0 automatic transmission.
The rear axle is a Dana 35, which i understand is a very weak axle.
The Jeep will not see much offloading, and not be modified with big wheels etc.
All-though, i will be towing a small excavator (around 1.7 tons), So my first question is, if this axle is even capable of towing once in a while?
If not, i can buy a 8.25 axle out of an 97´ Jeep XJ 2.5L Manual transmission.
This lead me to ask, if this is fairly straight forward? im thinking about what to do with the driveshaft and so on??

Thanks in advance,
Oscar

 

year doesn't matter for rear axles, as they are all interchangable throughout the xj platform.
you may have a 99, or a 00. easy way to tell is if you have a high pinion or low pinion front dana 30.
another way to tell is if you have spark plugs/distributor, or coil packs. but regardless, doesn't matter for your question.
a d35 isn't that bad of an axle. i know guys who have wheeled hard with them on 35 inch tires. mostly tj's since it was basically their only axle choice, until later options with the d44 (rubicon/sahara).
so if you're not going to be doing any offroading, and not run 35's, you're likely going to be ok.
but since you are going to be towing more weight than your xj is designed for, you will be better off with an 8.25, but you're gonna want better gearing. you will also need to get a load distributing hitch. and still not really recommended. but i'm not here for that.
that 8.25 you can buy out of a 97, with the 2.5 manual, will likely have 4.10 gears, which would be much better suited in your application, so you will have to regear the front axle to match, or buy both axles, if you can.
now, since i assume yours in an auto, with d35, and the other is from a manual, neither driveshaft is perfectly matched, since a manual trans is shorter, and the 8.25 has a longer pinion, you may have to get a custom driveshaft at the proper length.
you can play around with some stock driveshafts to see which one fits, once it's all in.

 

I towed nearly 2.5 tons with my D35 and it held up just fine. The D35 gets a bad rap because most people don't really know how to drive. The thing it doesn't like is big tires with lockers and shock loads off road

 

I have seen Dana 35s with stock sized tires and no locker break an axleshaft.

 

Oh my last jeep, and 89 when I swapped from a D35 to an 8.25, the parking brake lines didn't fit right. Had to order ones for a newer XJ with a 8.25. They were like... an inch too short, and had the wrong end on them. (this was 5+ years ago so going off memory).

 

People seem to overlook the fact that for many vehicles, towing capacity and gross weight ratings are determined by braking capability, not mechanical strength of the drivetrain components.

An XJ in low gear with a D35 and a proper towing setup will be able to get much more than it's rated capacity rolling. But it probably is too light to be able to properly control that weight at speed, and very likely doesn't have the ability to stop as much weight as it can start. It's all about how much energy the brakes can dissipate in a finite amount of time.

If you are planning on towing beyond your vehicle's rated capability, your rear axle type should be the least of your concerns. Make sure you have good tires properly inflated with good tread, good brakes in good condition, an appropriate hitch and know how to properly load your trailer. And then drive with caution, knowing you are handling an overloaded vehicle. Folks scoff at towing ratings, not realizing they have succumbed to survivorship bias through a mixture of luck, engineering margin, and maybe skill.

I think it's dave1123 who has a good little quote about being able to stop your vehicle.

 

Looking to do the same with my 96 XJ. Have a 99 ive been using as a donor. Following ✌

 

the legal limit here is 1.5 times the unloaded vehicle weight, (or whatever is stamped on the tow hitch, in my case it is 4950lbs)

my mate who is a professional recovery/tow truck driver with over +50yrs experience advises that for amateurs towing, it is prudent for the towed load not to exceed the weight of the vehicle

 

3/4 ton and larger trucks are rated to tow twice their unloaded vehicle weight or even more in some cases.

 

just yesterday, i towed my broken down 2wd ram on a car dolly with my 2 door wrangler. i only did it this way, because i was only going about 10kms straight down the road.
with a towing capacity of just 1500lbs, i gotta say, it pulled it with ease, just as if it were a trailer. now, being on a dolly, there was absolutely no tongue weight to lift the front end of the jeep, so braking was good. i just took it real easy, understanding the overloaded weight i was pulling.
but i do have many years experience towing with weight. so that helped. would i suggest a novice with this type of tow, no.

the biggest concern for towing over limit, is braking, especially in a corner, or even up/down a grade. things can go very wrong going uphill, or more importantly, down hill, with a stop light/sign. add a turn, and no bueno.

i always thought it would be better to load the tow vehicle up with all the weight, making it heavier to handle the tow load behind you. provided you have the horsepower to pull everything.

 

Since the OP has not responded yet, I'll point out the OP has a '99/2000 4.0l Auto. This implies he has ABS. The 8.25 do not have tone rings so his ABS won't work. May not matter though. The donor is a 2.5L Manual so the gearing will be different.