Busted Rear Axle - Chromoly now?

[bobbynelson0730]

Despite some poor wet weather conditions, gave claw hammer a go in the FJ. Lots of slipping even with the Lefty and then traction.....then POP....rear passenger wheel doesn't move under power. Jacked it up at camp, I can freely spin the wheel in park, or with the rear locked. Had to limp home in 2wd locked to get power. Since there were no grinding noises, diff still locked and normal power to driver side I'm assuming just the axle shaft is busted.
Running the 4.7 marlin, stock 3.73's and 35" tires. Should I replace the stock shafts with the Nitro Chromoly ones? Only ones I can find for the FJ width. I always like improving on what broke, but it don't want to make the next weakest point my R&P. Any of you guys run these shafts before swapping in a bigger axle? Any pros/cons to going chromoly or sticking to stock. Thanks

 

[Mtbcoach]

You need to find out what is the failed component first...

 

[Delancy]

You need to find out what is the failed component first...

X2, but if you're going to consider chromo shafts, now would be the time to look at swapping the whole unit out, since it's a step out on the ledge of a very slippery slope.

 

[1911]

No experience with those particular chromo axles, but I would guess that this is part of your problem right here:

Running the 4.7 marlin, stock 3.73's and 35" tires.

The 4.7 Lefty is delivering almost twice the torque to the rear wheels as a stock case, and 35's are a huge lever on the stock diff gears. You really need to re-gear your diffs lower IMO. Would make your highway driving so much nicer too.

 

[bobbynelson0730]

You need to find out what is the failed component first...

Is there anything else it could be? I mean yes something additional could need replacing but based on the way the rear end acted on stands it's definetly an axle.

X2, but if you're going to consider chromo shafts, now would be the time to look at swapping the whole unit out, since it's a step out on the ledge of a very slippery slope.

Already living on that ledge after going with the Lefty... Would love to swap in a bigger axle, and was planning to. Hence holding off on regearing baiscally until I had to. No sense in upgrading a part headed to the FS section, done plenty of that as it is.

No experience with those particular chromo axles, but I would guess that this is part of your problem right here:



The 4.7 Lefty is delivering almost twice the torque to the rear wheels as a stock case, and 35's are a huge lever on the stock diff gears. You really need to re-gear your diffs lower IMO. Would make your highway driving so much nicer too.

Yes regear is definitely needed, more for the leverage reason first since highway driving isn't a concern. The rig isn't my daily. But that also makes these breaks tough since I work away from home, and won't be able to strip it down till this weekend (or Turkey day if I'm not napping..)

 

[BMThiker]

At $250 per axle, I'd bet that price is cheaper than dealership axles. Or you could look for a junkyard FJ/4R axle and get the whole shaft/hub/brake assembly for cheap and you wouldn't have to break down your existing axle assembly (right away). Just bolt the used assembly to your axle housing and carry on.

 

[Delancy]

Will the inherent plasticity of chromo axles not pose a similar issue with the rear e locker, like they do on the 80?

 

[BMThiker]

I thought the 80 issue was because its full time 4WD. Most that I know running chromo axles do the part time conversion.

 

[1911]

I thought the 80 issue was because its full time 4WD. Most that I know running chromo axles do the part time conversion.

Problem is, the rear axle on an FJC is full-time and semi-float to boot, just as 80-series front axles are.

 

[Delancy]

Most that I know running chromo axles do the part time conversion.

We're talking the rear axle, I thought.

Chromoly are known to stretch, being the benefit of, but can pose issue with an 80 e locker, if the splines twist.

Not sure if it'd be a similar issue on the elocked FJC....

 

[LouisianaFJ]

No experience with those axles, but did recently finish swapping out the stock rear end for a ford 9 on dockbox's rig. If you're thinking of swapping it all eventually can you just go and do it now? Obviously a much bigger price but also a good excuse to do it.

My only issue with putting in stronger axles would be as others have stated, moving the weak point to gears. No limping home when those are messed up.

 

[Delancy]

No experience with those axles, but did recently finish swapping out the stock rear end for a ford 9 on dockbox's rig.

Did y'all transplant the Currie 9"?

Any issues with pinion angle?

 

[LouisianaFJ]

Yep

We were talking about that Saturday. Doesn't seem to be but we were talking about measuring it cause of the bypass shocks on back we wanted to clock it a little.

 

[Delancy]

Yep

We were talking about that Saturday. Doesn't seem to be but we were talking about measuring it cause of the bypass shocks on back we wanted to clock it a little.

The original Currie 9" on air2air's was built just like their D60, which is HP, and it threw the pinion angle off beyond what adjustable links were capable of correcting, creating an incongruent pinion flange angle (not parallel) without the ability to return to parallel.

Their solution, at that time, was to rotate the other way, pointing the output flange at the center diff (0 degree angle to driveline angle) and run a double cardan driveshaft.

Most others I've seen ran three/four linked at the same time, so not sure that it has even been changed. If not, and y'all have to go to a DC joint, it might worth checking the OE length of an extended can tacos shaft. May be a direct swap...

 

[LouisianaFJ]

We didn't do anything special. All lined up great from the get go.

Granted I didn't do any of the research. Axle was ordered from Currie, showed up, then I showed up and helped dockbox install it. He did all the homework I just did the wrenching. So not sure if there were additional options to select.

 

[bobbynelson0730]

At $250 per axle, I'd bet that price is cheaper than dealership axles. Or you could look for a junkyard FJ/4R axle and get the whole shaft/hub/brake assembly for cheap and you wouldn't have to break down your existing axle assembly (right away). Just bolt the used assembly to your axle housing and carry on.

Called all my tech buddies and best pricing for a new OEM is 383.77. Not to appealing. Leaning towards the chromoly for the cost, but if I stumble upon a used set I won't hesitate.

No experience with those axles, but did recently finish swapping out the stock rear end for a ford 9 on dockbox's rig. If you're thinking of swapping it all eventually can you just go and do it now? Obviously a much bigger price but also a good excuse to do it.

My only issue with putting in stronger axles would be as others have stated, moving the weak point to gears. No limping home when those are messed up.

That's my gut feeling too. Hoping to get home Wednesday night for turkey day and get busy pulling it apart while the bird cooks.
Got another response saying it could be the side gear? He said it was passenger side every time, and was still able to get home same as I was able to. His was the 8", mine is the newer 8.2" so not sure how much is different between the two. Pretty new at diving into the axles so bear with me. Doing the work myself so I can learn what really makes this turd move...

And would love to swap it all out. But just not thinking its in the cards to do it all now since as it goes- axle + gears + locker, then the front would need a regear so add that cost....then you get into the "while it's apart" statements..add another locker. Also would had preferred to re work the rear links at the same time... We'll see. No problem letting it sit for a while. Maybe the other toys will get some love now that it's desert season..thanks for all the input everyone.

 

[LouisianaFJ]

Pulling the axles are easy. Separate calipers from the backing plate, then disconnect last portion of break line take out of bracket and connect again(as quickly as possible so you don't loose much fluid) Disassemble ebrake to remove cable, then four nuts and it will slide out.

 

[LouisianaFJ]

Yeah that swap is a slippery slope, all the stuff you listed is exactly what we did to his truck, go big I guess

 

[bobbynelson0730]

Yeah that swap is a slippery slope, all the stuff you listed is exactly what we did to his truck, go big I guess

Yes, yes it is. Thought I went big doing the Lefty, Tummy tuck and the additional little re workings.....then I started doing the math on this one

 

[LouisianaFJ]

We are in the middle of the tummy tuck at the moment, still have a hole in the floor right now.

Yeah I haven't asked him a final number cause I don't want to know lol

What did you have to do to tuck the lefty? Modify floor, body lift?