Do I need an axle truss or differential armor?

Kyle_W

TJ Addict
Supporting Member
Joined
Nov 16, 2016
Messages
1,341
Location
Spicewood, TX, USA
I am curious about the possible worth of these two pieces of equipment - I am replacing my whole front axle soon, and while I have the knew one sitting on the shop floor, would it be worth throwing on a truss and / or an armored differential cover? I figured that this thread could serve others in case they ever have the same question in the future, hence why I posted this in the FAQ, and maybe Chris could make it a sticky too?

Basically, of all the Jeep pro's on this forum who have been Jeeping their whole life, I want to ask you what the real reasoning is behind an axle truss? If the Rubicon didn't come with one, then to me, why would you ever need one? Or, do people add it to their axles just to reduce the possible and gradual bending of the axle in the case that you are bouncing your Jeep pretty often on the rocks with added weight to the vehicle (heavier bumpers, winch, etc.)?

Also, I have been told that having an armored diff cover is really unnecessary, that is unless Moab is a part of your daily commute to work. That being said, I wanted to see if anyone have any other input on this matter? Has anyone accidentally caved in their front (or rear?) diff cover and effed up their ring/spider gears as a result?

I am not out to spend money, however i'd like to make the most out of any project that I have for my Jeep if it means obtaining a better end result.

NOTE: No I do not intend on climbing rocks and other undesirable earth features with my Jeep. However I do enjoy going to the local off-road parks and use my Jeep for it's real intended purpose.

Thank you!
 
I would say no to the truss and only get the cover if you just want the bling. Most run with stock covers and never have an issue.

Roger that! Thanks!

Why no to the truss? I just want to know exactly why.

And, whenever you take your Jeep off the pavement, you've just never worried about hitting your diff's?
 
For the type of wheeling that you described it would be a waste of money to add the truss. If you are planning on wheeling Moab or the Rubicon on 37's then add it.

I try to approach obstacles with good angles and at appropriate speeds. This normally keeps my front diff safe. Most everyone I wheel with has stock covers and have never had an issue. Now that being said, I would do a diff cover before I did the truss.
 
I agree with what @JP98 said, and I'm sure most others will as well.

Unless you're wheeling in some very, very rocky terrain, you won't benefit at all from a truss or even a protective diff cover.

Now in all fairness, I think a diff cover is cheap enough that it may be beneficial to put on any off-road rig. Sure, you're a lot less likely to smash your diff when you're in the mud, but you never know where rocks can be hiding.

A truss though, that's a waste of money unless you're running some huge tires and doing some very extreme rock crawling (IMHO).
 
I would bypass both of those items unless the diff cover in question is the Barnett or Currie design. Those huge beefy diff covers from other companies are all bling and only cause problems with steering interference and if you truly need that type of protection, you're asking for problems when you finally hit something fast enough to warrant that huge of a diff cover.

My thinking is, you're already downsizing from 33's down to some pretty streety 31's. If guys on 35's on tough trails aren't bending axles on 35's, what would make you need any of that on 31's?

Side note, what are you replacing the front axle for? Just for my curiosity.
 
Last edited:
  • Like
Reactions: Kyle_W and StG58
For the type of wheeling that you described it would be a waste of money to add the truss. If you are planning on wheeling Moab or the Rubicon on 37's then add it.

I try to approach obstacles with good angles and at appropriate speeds. This normally keeps my front diff safe. Most everyone I wheel with has stock covers and have never had an issue. Now that being said, I would do a diff cover before I did the truss.

Understood, thanks!

I agree with what @JP98 said, and I'm sure most others will as well.

Unless you're wheeling in some very, very rocky terrain, you won't benefit at all from a truss or even a protective diff cover.

Now in all fairness, I think a diff cover is cheap enough that it may be beneficial to put on any off-road rig. Sure, you're a lot less likely to smash your diff when you're in the mud, but you never know where rocks can be hiding.

A truss though, that's a waste of money unless you're running some huge tires and doing some very extreme rock crawling (IMHO).

Understood sir. I was just trying to rationalize why people even put trusses on their axles if an axle tube is hard as hell to bend anyway. But, got it thanks!


I would bypass both of those items unless the diff cover in question is the Barnett or Currie design. Those huge beefy diff covers from other companies are all bling and only cause problems with steering interference and if you truly need that type of protection, you're asking for problems when you finally hit something fast enough to warrant that huge of a diff cover.

My thinking is, you're already downsizing from 33's down to some pretty streety 31's. If guys on 35's on tough trails aren't bending axles on 35's, what would make you need any of that on 31's?

Side note, what are you replacing the front axle for? Just for my curiosity.

I looked for a Barnett cover just for the heck of it, and I couldn't find one. But yes I have heard the same things about Barnett and Currie covers!

And, a while back, I know it makes me sound like an idiot though, but I ran over a fire hydrant with my jeep. We straightened it back out the best we could, but I still am getting negative caster on my front right wheel. I'd rather replace the actual problem than put an offset ball joint in there. So I have a used Dana 30 sitting at my Grandpa's place ready for me to throw under my Jeep.

As well - i'm trying to decide if I want to sand blast the good axle to expose the bare metal and make sure it isn't rusted away in any places? I bought it off of eBay and you couldn't tell in the pictures that the damn thing was driven through the surf and clearly wasn't cleaned off before the salt made damage.

I'm tempted to replace all of my ball joints and control arms too in the process, but i'm trying to wear my current ones out first to save $$$.
 
I looked for a Barnett cover just for the heck of it, and I couldn't find one. But yes I have heard the same things about Barnett and Currie covers!

And, a while back, I know it makes me sound like an idiot though, but I ran over a fire hydrant with my jeep. We straightened it back out the best we could, but I still am getting negative caster on my front right wheel. I'd rather replace the actual problem than put an offset ball joint in there. So I have a used Dana 30 sitting at my Grandpa's place that I am not sure how to tackle, but, I am thinking i'm just going to put all of my current internals (except my carrier) from the bent Dana 30 into the non-bend Dana 30. Then just bolt it all back up!

I'm tempted to replace all of my ball joints and control arms in the process, but i'm trying to wear my current ones out first to save $$$.

I see. Well, I'd just do the axle swap and leave the rest alone. It shouldn't be too hard of a swap. Drop your old axle out and get it out of the way. Bolt up the empty axle and then install all your stuff into it. As long as you aren't touching the gears then you'll be okay.

Ball joints might be a good idea. Go with Spicer if you do. If you're wearing out the current arms, I'd leave them alone and just reinstall them.
 
I also was wanting to make sure that my "good" axle was not already bent before I slap in in there. I heard about buying an angle finder and just using that to be double sure - however, would that even work? You need the full length of the axle to put the angle finder against and the pumpkin is right in the way of doing that.

Yes, if I did i'd only buy spicer!

The only tough part about the axle swap is that I have never disconnected an axle shaft before. YouTube will suffice for my ill knowledge. But is there anything else that I should be wary of? Don't fucking touch the carrier? :D
 
Ugh.. Negative castor.. I think the thing (Whatever part of the axle the ball joints are mounted on) is bent on mine as well. Very slight but noticeable lean to the tire.

Is there something bad about offset ball joints you know that you'd (or anyone for that matter) like to share? Because I sure as hell can't afford to buy a Dana 44 to replace mine.
 
It shouldn't be too bad really. Jack up the Jeep. Set the frame on stands. Remove the tires. Let the axle fully droop. Set the jack under the axle to hold it up as you remove the items holding the axle in place.

Unbolt the shocks, brake calipers from knuckle, control arms from axle, track bar from axle, sway bar from axle, diff breather. That should be everything unless I'm forgetting something. Remove the axle.

Put the new axle in place, connect the control arms first to hold it in place and then make all the other connections.

The only thing you might consider doing is removing the guts from the old axle before removing it because you'll need the axle to be secure for doing things like pounding on the knuckles, swapping ball joints, etc. And, pulling the guts out is not hard at all.

Remove the tires, pull off the brake caliper, remove the little push nuts on the lug studs, if there are any. pull the rotors, unbolt the 3 unit bearing bolts with a 13 mm 12 point socket, and then do the bolt trick to push the unit bearing out of the knuckle. I'll upload a pic to demonstrate. It's pretty self explanatory once you see it. The only thing after that is to pull the shafts out with the unit bearings, and then undo the ball joint nuts (leaving them partially threaded on to keep you from killing your feet with the knuckle, and then pound at that knuckle with a 3 lb shop hammer until it comes off. It takes some good solid hits to get it to come down.

After all that, bolt in your empty axle and reinstall all your junk.

Are there 3.73 gears set up inside the new axle? You can remove the carrier as long as you install it like you removed it, but you absolutely can not mess with the gears themselves or the pinion or remove or reinstall any of those parts. You need to be installing this into a new axle with 3.73 gears already installed into it.
 
  • Like
Reactions: Kyle_W
Understood sir. I was just trying to rationalize why people even put trusses on their axles if an axle tube is hard as hell to bend anyway. But, got it thanks!

They aren't hard to bend if you're doing some serious crawling (i.e. Johnson Valley). I mean if you had a Dana 44 axle with 37" tires, and you were really going at it in Johnson Valley, I suspect you could easily bend an axle tube. We'd have to ask Blaine or @Jerry Bransford, since they have seen this stuff first hand, but that would be my guess.

So yeah, in that sort of situation, a truss serves a purpose and then some.

But for guys like myself who are mostly doing overloading and mud type stuff, a truss really has no benefit.

Rock crawling is a lot harder on our rigs than mudding.

I believe anyone can benefit from a differential cover though. If you're going into unknown territory, it never hurts to have your diff protected from what could be hidden obstacles.
 
  • Like
Reactions: Kyle_W
For 35's and under on trails 35's and our TJs can handle, I see no need or benefit for a truss. I haven't done the toughest trails in areas like Johnson Valley but I have done trails in JV and others (most would consider them extreme) that are the equal in some spots and have never bent an axle. Done those trails with a Dana 30 and Dana 44, and f/r Dana 44 axles in my current TJ... never a bent or tweaked axle tube or housing. I've broken a Dana 30 axle shaft and tweaked/twisted a rear Dana 44 axle shaft but that's it.

If I were you, I'd forget about trusses.

But a skidplate under the pumpkin that also protects the u-joint area in front of the pinion shaft wouldn't be a bad idea at all. I don't have any protection there and the rocks are always dinging up the u-joint ears and that part of the driveshaft. One of these days I'll make or buy something like this to install...

sidethumb.jpg
 
Last edited:
It shouldn't be too bad really. Jack up the Jeep. Set the frame on stands. Remove the tires. Let the axle fully droop. Set the jack under the axle to hold it up as you remove the items holding the axle in place.

Unbolt the shocks, brake calipers from knuckle, control arms from axle, track bar from axle, sway bar from axle, diff breather. That should be everything unless I'm forgetting something. Remove the axle.

Put the new axle in place, connect the control arms first to hold it in place and then make all the other connections.

The only thing you might consider doing is removing the guts from the old axle before removing it because you'll need the axle to be secure for doing things like pounding on the knuckles, swapping ball joints, etc. And, pulling the guts out is not hard at all.

Remove the tires, pull off the brake caliper, remove the little push nuts on the lug studs, if there are any. pull the rotors, unbolt the 3 unit bearing bolts with a 13 mm 12 point socket, and then do the bolt trick to push the unit bearing out of the knuckle. I'll upload a pic to demonstrate. It's pretty self explanatory once you see it. The only thing after that is to pull the shafts out with the unit bearings, and then undo the ball joint nuts (leaving them partially threaded on to keep you from killing your feet with the knuckle, and then pound at that knuckle with a 3 lb shop hammer until it comes off. It takes some good solid hits to get it to come down.

After all that, bolt in your empty axle and reinstall all your junk.

Are there 3.73 gears set up inside the new axle? You can remove the carrier as long as you install it like you removed it, but you absolutely can not mess with the gears themselves or the pinion or remove or reinstall any of those parts. You need to be installing this into a new axle with 3.73 gears already installed into it.

Thanks for the explanation! Yes it already has 3.73 gears - and surprisingly they are in perfect shape. The salt really only got to the axle shafts. So I can just leave those in there.

They aren't hard to bend if you're doing some serious crawling (i.e. Johnson Valley). I mean if you had a Dana 44 axle with 37" tires, and you were really going at it in Johnson Valley, I suspect you could easily bend an axle tube. We'd have to ask Blaine or @Jerry Bransford, since they have seen this stuff first hand, but that would be my guess.

So yeah, in that sort of situation, a truss serves a purpose and then some.

But for guys like myself who are mostly doing overloading and mud type stuff, a truss really has no benefit.

Rock crawling is a lot harder on our rigs than mudding.

I believe anyone can benefit from a differential cover though. If you're going into unknown territory, it never hurts to have your diff protected from what could be hidden obstacles.

Understood - thank you!

For 35's and under on trails 35's and our TJs can handle, I see no need or benefit for a truss. I haven't done the toughest trails in areas like Johnson Valley but I have done trails in JV and others (most would consider them extreme) that are the equal in some spots and have never bent an axle. Done those trails with a Dana 30 and Dana 44, and f/r Dana 44 axles in my current TJ... never a bent or tweaked axle tube or housing. I've broken a Dana 30 axle shaft and tweaked/twisted a rear Dana 44 axle shaft but that's it.

If I were you, I'd forget about trusses.

But a skidplate under the pumpkin that also protects the u-joint area in front of the pinion shaft wouldn't be a bad idea at all. I don't have any protection there and the rocks are always dinging up the u-joint ears and that part of the driveshaft. One of these days I'll make or buy something like this to install...

View attachment 18723

Roger that. Thanks sir! I didn't even know that such a design existed. That actually makes a ton of sense.

Basically, I want my Jeep to be suited for the roads, because of how far I have to drive each and every day to work: 30" Goodyear Trail Runner's soon. Going back to stock bumpers. Keeping the winch. And trying to put aluminum where I can. But also have enough protection underneath to not have fear whenever I do take it on the trails.


Sent from my iPhone using Tapatalk
 
I think that to answer this thread conclusively, there are only two reasons you'd need a truss:

1) You've got 37" tires or larger on the stock axles, and you're doing some serious rock crawling.
2) You have a history of bending axle tubes (but if that's the case, I'd also suggest potentially modifying your driving style).

As for the diff protection, I think that anyone can benefit from that, even if you only do easier trails. If you go off-road at all (the beach doesn't count), I think that having that protection there is great piece of mind. I know that often times (even on the forest trails I do) there can be obstacles in the middle of the path, that can contact your differential, drivetrain, etc., if you aren't paying attention.
 
  • Like
Reactions: Kyle_W
I think that to answer this thread conclusively, there are only two reasons you'd need a truss:

1) You've got 37" tires or larger on the stock axles, and you're doing some serious rock crawling.
2) You have a history of bending axle tubes (but if that's the case, I'd also suggest potentially modifying your driving style).

As for the diff protection, I think that anyone can benefit from that, even if you only do easier trails. If you go off-road at all (the beach doesn't count), I think that having that protection there is great piece of mind. I know that often times (even on the forest trails I do) there can be obstacles in the middle of the path, that can contact your differential, drivetrain, etc., if you aren't paying attention.
The issue with trusses is they don't address the weak point of the front axle which is the ball joint upper hole in the inner C. You'll ruin that long before you need a truss to stop the tube from bending. If you are running 37's on any front TJ axle, the truss won't help it live longer and you'll grow weary of swapping ball joints long before you need the truss.

If you put on a diff cover strong enough to protect the ring gear, you'll ruin the housing long before the cover does anything useful with the exceptions being a Warn style to protect the lower half from dents and the Barnett/Currie that does the same things. Other thicker heavier versions typically interfere with the track bar and either limit up-travel or ruin the trackbar by smacking into it.
 
i bent my dana 30 but i was doing idiotic things. would I truss it? nah.

I also scraped the bottom of the cover quite a bit to cause a leaky seal. Diff cover? Yeah but only the half guards.
 
  • Like
Reactions: StG58 and Chris
The issue with trusses is they don't address the weak point of the front axle which is the ball joint upper hole in the inner C. You'll ruin that long before you need a truss to stop the tube from bending. If you are running 37's on any front TJ axle, the truss won't help it live longer and you'll grow weary of swapping ball joints long before you need the truss.

If you put on a diff cover strong enough to protect the ring gear, you'll ruin the housing long before the cover does anything useful with the exceptions being a Warn style to protect the lower half from dents and the Barnett/Currie that does the same things. Other thicker heavier versions typically interfere with the track bar and either limit up-travel or ruin the trackbar by smacking into it.

Would bracing the inner C's help this weak area?
 
So what's the solution on aftermarket axle housings (i.e. Currie RockJock, etc.)? Do they include a much beefier inner C with strengthened upper ball joint holes?