Axle Swap Advice

[ffh24054]

I’m sure this topic has been killed in numerous posts, but I couldn’t find anything on my specific situation. I’m planning on doing the clayton 8” 3/4 link with the rear coil conversion. They claim you can only run around 35s due to the flex. I’ve seen people go back and forth about stock axles and 35s, but I also plan on doing a 350 swap. I’d rather have it overbuild than worry about breaking anything. Should i go 1 ton, or will a built 30/8.25 hold up? Would a 30/8.8 be good enough?

 

[XJ_ranger]

I think a 30/8.8 is good for 35's. Any more than that, and you need bigger.

Use case helps too. Rocks, lockers, wedges, ledges? 35's max. Mud, dirt roads, 37's might work for ya.

I think @CRASH made a thread titled "axles for rocks" 20 years ago with a lot of relevant advice and some good discussion followed.

Edit to add link:

https://naxja.org/threads/axles-for-rocks.51252/

 

[ffh24054]

I think a 30/8.8 is good for 35's. Any more than that, and you need bigger.

Use case helps too. Rocks, lockers, wedges, ledges? 35's max. Mud, dirt roads, 37's might work for ya.

I think @CRASH made a thread titled "axles for rocks" 20 years ago with a lot of relevant advice and some good discussion followed.

Edit to add link:

https://naxja.org/threads/axles-for-rocks.51252/

The link doesn’t seem to work for me, it says i don’t have permission to view it. As for use, it would be mostly mud just because that’s what’s local to me, but i do plan on taking it crawling. I will also probably end up using it for a little bit of off-road towing because i tend to be the recovery guy and my family seems to like to break things you can’t fix on the trail. I’m not set on a tire size, i’m just basing it on what the lift suggests (35s).

 

[XJlimitedx99]

I also plan on doing a 350 swap. I’d rather have it overbuild than worry about breaking anything.

This statement makes this decision less straight forward.

What really matters here is your use case. How do you intend to drive the rig?

V8 + locked diff + 35's + party pedal = ka-boom!

For the most part, the rear axle will take it. 8.8's are good, even the 97+ factory 29 spline 8.25's are pretty stout and will handle a beating. The Dana 30 front is a different story.

First weak spot is the u-joints and axle shafts. The factory shafts just do not have enough meat around the u-joint yoke ears. Broken shafts or u-joints are pretty common. So then you upgrade to chromoly shafts and everything is pretty good. Problem then becomes your ring and pinion is not much stronger than those chromoly shafts. Put enough power in one end and resistance on the other and the gears will flex away from each other causing the stress to concentrate on the tip of the tooth, and then all the sudden you've stripped out your ring gear. This can be combatted by making the whole system more rigid with a full case locker, heavy diff cover, axle truss, hell you could even use a load bolt and girdle cover. Cryo treat the gearset. Go crazy. Put all the money into polishing the turd, and you'll have an axle that will hold up to a thrashing on 35's, probably. Even then, I wouldn't call it "overbuilt".

That's not to say people don't run that setup for years without issue. Many people do exactly that (more or less) and have great success for a long time. It all comes down to how you drive it. If your answer to a tough situation is skinny pedal, you might want to consider other options. If you're more about finesse and line choice, that will be good.

On the other hand, one tons are massive and IMO don't make sense for anything less than a 37 inch tire. There are also so many supporting mods that must be made to have one tons last. A full cage is probably necessary, not for safety but for chassis rigidity. The extra unsprung weight will tear the body apart over time. At that point you're probably also looking at hydo assist, a beefier transfer case, etc, etc.

The middle ground of building for 35's/37's is tricky. For a long time there wasn't a great option because Ford Dana 44's use the same u-joint as Dana 30's, so without an expensive shaft upgrade (like RCV's) they really were not much better. Now we have the option of JK 44's, which have some pro's and con's, but have been becoming a popular mid-grade swap. I'm currently in the process of putting JK axles under my XJ. The JK 44 ring and pinions are much beefier than the older 44's, and the front JK 44's use a slightly larger u-joint (1350 series Spicer 5-7166X). Downside is the housings are still pretty wimpy, and they use Dana 30 outers (ball joints/unit bearings). And also they're pricey.

I've been thinking about this for a long time if you couldn't tell lol. I could write a lot more about this topic.

 

[ffh24054]

V8 + locked diff + 35's + party pedal = ka-boom!

For the most part, the rear axle will take it. 8.8's are good, even the 97+ factory 29 spline 8.25's are pretty stout and will handle a beating. The Dana 30 front is a different story.

In the mud there is definitely a little party pedal lol, but realistically there’s not bad enough mud here for me to worry about a front locker, that would be more for the once in a while trips rock crawling.

Hmm A lot to think about.

I leaning towards an 8.8 swap and forgetting about the 350. I have a yj that should be simple enough to throw tons under for that. I’m also not one to really beat on things, so i think i’ll be soft enough most of the time to keep the polished turd from grenading.

 

[Ol Blue]

Tons are way overkill for your needs and built up stock axles probably won't be worth it. And with overbuilt stock axles you will always have to be careful and limit your throttle. I was in a similar position to you, minus the 350, and ended up with 44/9". Its built correct once and will be more than I'll ever need, while still having the flexibility to go to 37s. Also this combo is pretty unbreakable on 35s. You could do 44/8.8" as well, but at that point why not go with a 9"? The reason I don't like 8.8s is the C-Clips. You can buy the C-Clip eliminator kit but that's over $500, so just start with a 9" and you don't have to worry about that. Plus with the 9" you get a stronger axle, dropout third member, and the largest aftermarket support for any axle out there.

 

[ffh24054]

Tons are way overkill for your needs and built up stock axles probably won't be worth it. And with overbuilt stock axles you will always have to be careful and limit your throttle. I was in a similar position to you, minus the 350, and ended up with 44/9". Its built correct once and will be more than I'll ever need, while still having the flexibility to go to 37s. Also this combo is pretty unbreakable on 35s. You could do 44/8.8" as well, but at that point why not go with a 9"? The reason I don't like 8.8s is the C-Clips. You can buy the C-Clip eliminator kit but that's over $500, so just start with a 9" and you don't have to worry about that. Plus with the 9" you get a stronger axle, dropout third member, and the largest aftermarket support for any axle out there.

What 44 did you end up going with?

 

[Ol Blue]

I went with the ECGS "Dana 489". Its basically a beefed up TJ 44 housing (1/2" thick tubes vs 1/4" stock) with a JK 44 8.89" ring gear. Opted for RCVs so its warrantied up to 40s, not that I'd ever want to do that. Maintaining stock width and bolt pattern were important to me. Also in the long run I plan to eventually buy an LJ and when I do this axle will move over there. Yes its expensive but I'll keep this axle longer than the XJ.

Dana 489 High Pinion TJ, XJ, ZJ Front Bolt in Axle Assembly

Base Axle Includes: * High Pinion Front Axle Housing C to C * Forged HD Inner C's * TJ, XJ, ZJ Brackets * New 1310 U-Bolt Yoke * Your Choice of Ratio * 1/2 x 3.0" Wall Axle Tubes * Chromoly Inn

eastcoastgearsupply.com

 

[Evan03]

Raise your hand if youve broke a dana30 ring and pinion. Yup no hands raised.

First front locker before rear it just works better amazingly actually so much so you may decide to leave the rear open.

Chromo shafts can hold up well to locked 35s. Stock shafts break as you think about pushing the throttle. Ive broke 6 or 8 stock before going to chromo.

Yes i still drive the chromo 30 like its gona break but hasnt yet.

29spline 8.25 is holding up well.

Im running 4.88 gears and dont beleive ill ever break a pinion off. Going on 5 years maybe 4 with 4.88s. Rig is mainly only street driven to get to and from trails.

I do like knareley waterfall ledge climbs and follow rigs on 40s lines most the time.

Id like a narrowed 44 or similar someday for now thr 30 is working

 

[XJEEPER]

Evan, I'll raise my hand. Since building my 2000 rig back in 2008, I've broken two D30 ring and pinions. The first was my fault, as I was playing in the dunes in 2010 and accidentally hit reverse while moving forward at 20mph. The second time I have no clue what caused it, I just noticed a clicking sound in the front end in Dec 2022 and upon pulling the cover, found a missing tooth on the ring gear. There was about 100K miles and dozens of off-road shenanigans between these two incidents.
I run ARBs front and rear, 30 spline chromoly shafts in the HP D30 and D44 rear with 33 spline chromoly shafts in the rear. Both of my axle housings are trussed. 16+years with 4:88 gears and 295/75/16 tires. I'm not a throttle jockey (unless in the snow or sand where its required at times) and despise mud, with the majority of my wheeling being on slickrock, mtn shale or desert conditions.

 

[Ol Blue]

I have never blown up a D30 R&P but I know a guy who did. He was in a TJ so it was a LP D30. And he was running 37s for years so he was pretty much asking for it to blow up

 

[Anak]

I also plan on doing a 350 swap.

What do you mean by "350 swap"?

It is one thing if you are pulling a 350 out of an old worn out pickup in the junkyard and just dropping it in.

It is another matter entirely if you are buying a 400hp crate 350.

 

[Bent]

My XJ is a little old-school I suppose. But it durable.

Currie HP 9" (8.8 Ring gear) 31 spline alloy shafts, ARB up front.

Currie HD 9" housing w/True Hi-9, 35 spline alloy shafts, ARB, Explorer disc brakes out back.

4:88 gears turning 35/13.5" Toyo MTs on forged 10" Centerlines.

Have broken a 760 u joint.

 

[Evan03]

Evan, I'll raise my hand. Since building my 2000 rig back in 2008, I've broken two D30 ring and pinions. The first was my fault, as I was playing in the dunes in 2010 and accidentally hit reverse while moving forward at 20mph. The second time I have no clue what caused it, I just noticed a clicking sound in the front end in Dec 2022 and upon pulling the cover, found a missing tooth on the ring gear. There was about 100K miles and dozens of off-road shenanigans between these two incidents.
I run ARBs front and rear, 30 spline chromoly shafts in the HP D30 and D44 rear with 33 spline chromoly shafts in the rear. Both of my axle housings are trussed. 16+years with 4:88 gears and 295/75/16 tires. I'm not a throttle jockey (unless in the snow or sand where its required at times) and despise mud, with the majority of my wheeling being on slickrock, mtn shale or desert conditions.

Your the first ive seen thats actually broke one. Seems everyone else reads that it can happen in the bible or something.

Im on grizzly front with welded rear just 35s . Honestly probly been 6 months since my jeeps moved

 

[XJ_ranger]

Honestly probly been 6 months since my jeeps moved

That helps with longevity of parts Certainly in my Jeep too.