Driveshaft/Rear Axles for Big Tire, Fully locked heavy rigs?
 

I have a question for some of you seasoned off-road guys with heavy rigs, big tires, lockers, etc:

-How many are running something other than OEM rear axles and front/rear driveshafts?
-Has anyone had any issues with the driveshafts or rear axles failing under NON abusive conditions just due to added weight, being locked and having large, heavy tires?


If anyone is familiar with my build, I have full steel Coastal front and rear bumpers (with dual swing out in the rear), RTT tent and recovery gear when fully loaded, full front and rear ARB lockers with 4.56 nitro gear, RCV front CV axles, gusseted spindles, and I am running 35" tires.

I know that I wont (at least not very easily) be breaking the RCV front axles, and hopefully with a bit of common sense and smart driving the lockers should allow me to not grenade the ring and pinion front or rear, but my next thought is that the weak link has to be the rear axles or the driveshafts?

It looks like Nitro also makes a slight upgrade of an axle for the rear at a halfway decent price point, but I'm not looking to upgrade (if it truly is an upgrade) until the next off-season as the minimum. For a driveshaft option, I found a company that does a double cardan custom length built front and rear, but its 1000 bucks total, and if I am going that route I would go ahead and swap the FJ T-case into the car and call it a day. With the build at the stage it is now I am looking to take on the more technical offroad route locally (At the Uwharrie offroad park) and want to get an idea of where I should stand with regards to the driveshaft and rear axles since they are completely stock.

I don't mind having a couple of spare parts with me on the trails, but the idea is to have a build I can rely on to hopefully NOT fail and have to do trail repair on (hence the RCV axles.. pricey, yes, but I don't feel like swapping CV axles out on the trail..).

And I know, I know, there will always be weak link in each system and with the upgrades I have I pushed the weak link from a potentially easy cheap repair (ie: the cv axles) to something more serious, like a cracked housing/destroyed 3rd/clamshell etc. My idea is to have this "fuse" sufficiently large enough where it doesn't have to pop from the condition I subject my rig to.


Any and all input is greatly appreciated! ps: let's see those fully decked out rigs!

The next thing to go is going to be that 8" rear ring and pinion, in my opinion.:jump:
So go get something decent under that pig.

There will always be a fuse. Something will have to break. It is better to candy cane a driveshaft over a ring and pinion. Double cardan driveshafts aren't any stronger than standard u-joints. Lot's of offroaders upgrade to a thicker drivershaft tube. I recommend against this as I prefer my driveshaft to go before my axle shafts.

100% agree on the driveshaft being a much better fuse than the ring and pinion, rear axles, etc. I guess the question for me become how close to overloading this fuse am I with my current set up? OEM CV axles I have a pretty good feeling for how much abuse you can expect them to take before popping, but now that I have those taken care off via RCV axles I curious to know if moderate offroad use/rock crawling without bouncing spinning tires off of rocks and what not will allow the factory rear axles and drive shaft to stay together for a bit, or if I am on a ticking time bomb at this point.

I have driven a friend's 2009 4Runner through Swamp Lake Trail in the Shaver Lake / Sierra Nevadas. It rock crawled well and didn't pop or break anything. The control arms in the rear took the most abuse and were bent.

Do you have upgraded rear arms and pan hard? That is where I would spend some money.

Weight: The closer you get to gross vehicle weight or past it the better chance you have of breaking. Try and keep weight down. I personally refuse to offroad with RTTs.

Still on stock links and panhard. That is definitely next on the list of things to do. I don't do much rock crawling really, and for the serious stuff I only try to have the recovery gear with me with no tent, but for the most part this is more of an overland build that I am hoping to make a bit more on the reliable side to keep the trail-repairs to a minimum.

You won't break a front driveshaft ever on our rigs, its short, covered, and completely stationary. The rear driveshaft will only break if its damaged by rocks first or you have a 400hp LS with sticky 40s.

Your rear axle is your weakest point, but it's been rebuild probably with a solid pinion spacer and you've got the lockers so you probably won't be bouncing around on the rocks compared to an open diff.
The stock from-the-factory rear diff I've seen first hand blow up many times with 35's and light rock crawling but since you've had yours rebuilt it *should* be stronger.

You haven't really mentioned tie-rods, steering rack, or alignment. Steering rack will wear quicker with 35's but it should hold up for a number of years especially if using a steering cooler. Tie rods could be bent when trying to turn in weird offroad situations. Alignment could move when the factory bushings deflect and allow the tabs to flatten, so you might want to beef that up.

Axles
 

In the FJ community the 8" rear is the weak spot. This is the same axle under the 4R minus the E locker, same axle shafts, same ring and pinion. Lots of pictures of ugly blown up R & P from those folks. Ironic though, that the towing capacity of the V8 4R doesn't produce those same ugly blown R & Ps. I recently towed my FJ with my 08 4R about 350 miles so I'm guessing I was pulling close to 6500 lbs. I installed an 8.2 axle in my 4R from a '13 FJ as soon as I got back to my shop. I haven't seen pictures of failed drive shafts (without damage), or u-joints.

Thanks for the input!

When you say the rear axle, are we talking the actual axle shafts shearing or the more of a 3rd member grenading? My rear diff is was done with a solid spacer so in combination of using lockers and , like you said, not bouncing around open much I am hoping to keep it together for a while.

Beefing up the cam tabs is definitely on the list of things to do, this will probably be a next off-season project.

The tie-rods are stock, and I have new replacements as one of the few things I carry with me for trails at this point. I know I can beef those up as well, but I would rather them be the fuse rather blowing out a steering rack on the trail.

As far as the steering rack goes, wear on this is also a very solid point I did not consider. No, I am not running a cooler of any sort but will definitely do some searching into this .As with everything that gets upgraded, I don't expect it to last the same as a stock, street driven car, but whatever can be done for increased longevity would be nice.

The 3rd member almost always. I haven't heard of too many axle shafts biting the dust on our 8-inchers.

Thanks again man. That does (and doesn't) make me feel better about the current setup. I know my 3rd is far from indestructible at this point, but between the solid spacer and lockers, theoretically if I don't get stupid with it and bounce it up a climb with significant wheel speed, it should be OK for crawling since it seems like the majority of the failures are from shock loading the Ring and Pinion vs overall torque generated while climbing.

I don't do any crazy/frequent crawls, the plan was to have a capable overland rig that could be taken off road for some more serious stuff here and there. But, we do have a 3 day trip to Uwharrie this weekend and I fully intend to go up (and down where possible) all of the harder, more technical stuff, so I guess we'll see how she holds up.

:thumb: