Questions about running 37s on a Dana 30 front axle

[Mean Green]

Hello everybody. Recently I traded in my Ram 1500 truck for what I have always considered my dream vehicle. 2016 Jeep Wrangler Unlimited Sport S. This isn't just another sport s, this thing has some modifications done to it as well as factory installed extras including heated leather sears, upgraded premium sound system. This Jeep had just over 15000 miles when I bought it and was previously owned by a doctor that I work with. Currently its sitting on a 4.5 inch bds lift, 37x12.5r17 mt/r's on beadlock rims, poison syder front and rear bumper, aev snorkel, aev procal, and winch. The down side (or so people say) is that it is on the factory dana 30 and dana 44 with the factory 3.21 gears. The gearing will be fixed soon as i have ordered 4.88 gears to make this thing run properly. Given that it is on this set up, I'm amazed at how well it does run. I know people say they cant tolerate even 4.56 gears with 37's so i can't wait to have the 4.88's. The interesting thing I have found on forums and throughout the internet is that you shouldn't run 37's with the dana 30. Everyone is always saying that as you wheel and bind up that front axle, it'll snap every time. But with the gears I'm going to add axle sleeves and gussets and eventually upgrade the axle shafts. My goal is not to have a rock crawler but an everyday driver with the ability to take me out and run back roads and two tracks all day long. I'll also be getting rid of these mt/r's for some all terrain tires which will drop the weight to 68 lbs per tire vs the 80 lbs the mud terrains are. Am i completely out of my mind thinking that I can't make this work for a long time? Just for reference, I have a 1978 jeep cj7 with the factory two piece axle shafts in the amc 20 in the back. I've been running 33x12.5r15's for many years off road and still haven't had a break. I'm guessing the dana 30 can be made to last just like I have made the amc 20 last.

 

[Chris]

Realistically speaking if you aren't going to wheel the piss out of it, you'd be fine just putting in some alloy axle shafts (I recommend Revolution) in both the front and rear axles, and you should be fine.

If you took it out wheeling with 37s on the stock Dana 30, I have no doubt you'd probably break some axle shafts in short order. However, with alloy shafts and responsible driving (meaning not using heavy throttle every time you get in a sticky situation) you should be just fine.

There is no doubt a Dana 30 can be made to be much beefier.

 

[Mean Green]

Definitely won't be Wheeling it that hard. Like I said, I want to explore back roads and two tracks, although I know sometimes they can get pretty sketchy. I like the thought of covering miles every hour and not feet every hour. Mostly I go hunting and fishing and that doesn't take a crawler set up for. I like the looks of the 37's and that is the main reason I want to beef up the 30 and ride it out. Thanks for the response, it makes me feel better about the 30 with new gears, sleeves, and axle shafts.

 

[Chris]

You'll be fine. One thing I've learned is that you can't believe everything you read on the internet. People instantly just want to dismiss something (the Dana 30 in this case) as being garbage.

I'm not saying I would want to wheel the snot out of it with 37s, but I'm pretty confident that with alloy shafts and responsible driving, you will be fine.

The guys who will break it will be the guy who gets stuck and instantly applies as much throttle as possible. As soon as the tires break free and get traction, then SNAP, there goes your axle shafts (or ring and pinion).

The moral of the story of course is that the answer is not always more throttle. With enough bad driving you can break even a Dana 60.

 

[Mean Green]

Maybe that's something I learned with the cj7 and the amc20 that gets such bad rap. I drive smart and refuse to tear up what I drive. I've never even had a winch on that one. Guess time will tell on the Dana 30.

 

[Chris]

It will be interesting to see how the Dana 30 holds up, you'll have to report back from time-to-time to let us know. Wouldn't hurt to try and dispel an internet myth.

 

[Mean Green]

Correct me if I'm wrong but the weight of each tire that I will be going to is equal in weight to most and less than some 35's. This would effectively help the axles since weight is less right?

 

[Chris]

It largely depends on the tire. This is why I always use Tire Rack when shopping for tires, as they list the weight of each tire. Given that the size is equal on both tires, a M/T will weigh more than an A/T tire most of the time. However, an E rated A/T tire will weigh more than a C rated M/T tire most of the time.

There's a lot of variables that come into play, so it really depends.

Also remember that a 37 inch tire is not really 37 inches.

Case in point: My BRAND NEW BFG KO2s are 315/70R17. According to the BFG specs, they are 34.4".

I measured them on the vehicle with 35 psi, and they measure at 33.25" almost exactly, and that is brand new with 100% tread on them.

This is true amongst almost every tire manufacturer. If you measure those 37" tires, I'll bet dollars to donuts they aren't bigger than 36", but probably closer to a high 35" tire.

 

[Mean Green]

Yeah. The tires I'm looking at are the Cooper discoverer at3 xlt. Cooper site says they measure right around 36.5. I honestly would expect about 36 when I get them mounted. But the weight is 68. Plus, since they are an at they may not grab as hard when they do bite and have less chance of breaking the axle. Course this is just speculation. Watch me snap an axle first day out.

 

[Chris]

Your expectations sound accurate to me in that case. I was shocked when I found my 315s were over an inch shorter than the claimed 34.4". I guess what it means to me is that my 315s are really "true" 33s

Good choice on going with an A/T tire though. I see a lot of guys run M/T tires on the streets for looks, but they suck in inclement weather, and unless you're rig is a dedicated off-road rig, I think it's pointless to run M/T tires.

If anything breaks it will be the axle shaft. However, the good news is is that an axle shaft is much easier to replace than a busted ring and pinion. It's actually a relatively easy trail fix as I'm sure you know.

 

[No.343]

I have the same setup you are discussing. I had my Dana 30 sleeved and gusseted and had alloy shafts installed, as well as, Yukon 4.88 gears and air lockers. I'm running 37" KO2 tires. They measured 36" when new. I've been running this setup for about three years now. I've taken mine wheeling and made it through a couple of the trails rated as a 6 in SMORR, which was the highest rating at the time. I don't have a heavy right foot, and when it starts bouncing I find a different way. Best of luck.

 

[PM1]

Realistically speaking if you aren't going to wheel the piss out of it, you'd be fine just putting in some alloy axle shafts (I recommend Revolution) in both the front and rear axles, and you should be fine.

If you took it out wheeling with 37s on the stock Dana 30, I have no doubt you'd probably break some axle shafts in short order. However, with alloy shafts and responsible driving (meaning not using heavy throttle every time you get in a sticky situation) you should be just fine.

There is no doubt a Dana 30 can be made to be much beefier.

I have an 06 Lj with a hp trussed 30 up front running 37x12.5 bfg's no issues. I also have a 83 cj7 for 25 years with the stock front end and a Currie 60 rearend on 35 bfg's. 2 Rubicon runs countless rock crawling runs with no issues. I rarely read someone saying that I broke my hp 30. It always seems to be a,referral about someone else breaking. Bottom line from my perspective is that it's all about how you wheel. If you're the "gas to the pedal guy going up the hill" you'll probably going to break something. For me it's about knowing your rig, the hill, the right line and some common sense.

 

[DirtDauber]

Just my 2 cents.. For the type of offroad you're describing, I'd have some C gussets welded on and with the lower gears you have planned it'll most likely not give you any trouble. I will be going up from 35s soon to 37s BUT I like to wheel a little harder trails than you describe. My 30 has been geared along with a Detroit trutrac, trussed, gussets, and I run chromoly shafts with the larger 1350 Ujoints. Bottom line, all depends on the type of wheeling/driving you do and it sounds like you'll be just fine.