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what exactly causes an axle to break?
- Thread starter acannell
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TheWhiteHO
NAXJA Forum User
- Location
- Indianapolis, IN
The hatred towards the Dana 35 is clearly overwhelming. I still have the D35 on my '92 with 33's and freshly built motor and have been wheeling with no issues over rocks/trails/whatever. This has been my rig for the last 8 years but the 31's to 33's upgrade and new motor came 2 yrs ago. It has been said that wheeling styles/habits have a huge effect on thisand that is very true. Personally I don't rev my engine and "force" my way over problem areas, it works just as well to get a better line and do it with a technical approach. Before I get attacked, let it be known that I am not doing any upgrades to my D35 and my intent is an 8.8 with 4:10 or 4:56 gears when funds allow.
Regardless, the question is "what breaks an axle". I'm not even going to try to use math but if you think it through, it's pretty simple.
Use the ratchet and bolt example.
A D35 axle is not a grade 5 bolt but more like one made of hard polymer(naturally weaker).
Stock engine would be a standard length ratchet and then any additional torque would be like adding a cheater pipe in increasing lengths therefore creating more torque from that side of the bolt.
Stock tires would be a standard length ratchet and by adding larger tires you would be like adding a cheater pipe in increasing lengths therfore creating more "resistance" or torque from the opposite side of the bolt.
As you spin the tires at "engine speed" and then apply resistance from the ground, when enough is added, it will apply so much torque in opposing directions that the weak axle will break. Compounded with larger tires (more resistance) and upgraded engines (more torque) it only gets easier to break.
This is why the beefier D44, 8.25 and 8.8 are much better. They are more like a grade 5 bolt that can withstand the extra torque/resistance.
Regardless, the question is "what breaks an axle". I'm not even going to try to use math but if you think it through, it's pretty simple.
Use the ratchet and bolt example.
A D35 axle is not a grade 5 bolt but more like one made of hard polymer(naturally weaker).
Stock engine would be a standard length ratchet and then any additional torque would be like adding a cheater pipe in increasing lengths therefore creating more torque from that side of the bolt.
Stock tires would be a standard length ratchet and by adding larger tires you would be like adding a cheater pipe in increasing lengths therfore creating more "resistance" or torque from the opposite side of the bolt.
As you spin the tires at "engine speed" and then apply resistance from the ground, when enough is added, it will apply so much torque in opposing directions that the weak axle will break. Compounded with larger tires (more resistance) and upgraded engines (more torque) it only gets easier to break.
This is why the beefier D44, 8.25 and 8.8 are much better. They are more like a grade 5 bolt that can withstand the extra torque/resistance.
MoparManiac
NAXJA Forum User
- Location
- Amherst, NH
You forgot to divide by 2 after multiplying the transfer case low range ratio.
(transmission ratio) x (transfer case low range)/ 2 since you're splitting the torque, optimistically 50/50, between two outputs then x (axle ratio)
(transmission ratio) x (transfer case low range)/ 2 since you're splitting the torque, optimistically 50/50, between two outputs then x (axle ratio)
- Location
- San Diego
^this.
the increase in distance from the axle to the street creates a long lever and more force that the shaft is required to handle. this also applies if you were to do the opposite, a 4500 RPM dump of the clutch. not only does the increased diameter, leverage, make it easier to stop motion of the wheel, but it also makes moving the wheel much more difficult.
xcm
NAXJA Forum User
- Location
- Southern Oregon
offroading, what we all enjoy doing, is basically unsafe, by your logic.
i'll fallow offroaders math, you have fun with your calculator.
rweaver138
NAXJA Forum User
- Location
- Brooklyn, CT
Can I ask what the point of this "calculator" would be? Is it supposed to warn someone, "oh shit, on this hill with this 45 degree climb i can't go over 2.5k rpm because if my tire comes off the ground 4 inches while going 35 mph then comes back down to 1 mph when it lands it will shock load and break my shaft, shit guess i cant wheel now"
or before anyone tries an obstacle there like "hold on guys let me get my calculator out and figure out this math so i can be reassured i wont brake any shafts"
or before anyone tries an obstacle there like "hold on guys let me get my calculator out and figure out this math so i can be reassured i wont brake any shafts"
- Location
- Rainy side of Washington
- Location
- Rainy side of Washington
... I'm an electrical engineer with two degrees :wave:
so no, I'm not some ig'nant redneck. I just realize that the d35 sucks out loud and should be dumped before it screws you over, instead of after.
so no, I'm not some ig'nant redneck. I just realize that the d35 sucks out loud and should be dumped before it screws you over, instead of after.
Im an electrical engineer as well. The good engineers I've worked with, and for, are always up to discuss things and figure things out, if not just for the fun of it. They see the value and enjoyment in thinking and discussion as and end in itself, whether or not a valid conclusion has already been reached.
The engineers that don't like talking about things tend to be very timid when it comes to actual problem solving, and their designs tend to be very messy with lots of loose ends. But they LOVE telling people what they SHOULDNT do.
math is used for lots of things, including designing all kinds of off road parts. i swear!
- Location
- Rainy side of Washington
I have enough statistical evidence to come to a conclusion here.
I mostly focus my energy on reverse engineering XJ electronics (ECUs, TCUs, ACMs, etc) and deciding what mods to do, rather than wasting my time being anal about axle strength analysis when the basic rules have already been figured out, especially when there are an extremely large number of variables some of which cannot be measured as they change when you run the trail.
Have fun with your d35. I will laugh when I see you post up a thread detailing your 8.25 install while keeping quiet about what prompted the swap.
ive seen first hand a STOCK welded d35 on 33's make a few runs thro indy (trail system here) and still be working just fine even after being installed in another vehicle
but anyway, back on topic
Hey I said I'd post the details if and when it breaks, dont worry
BTW I have a chrysler DRB II with the jeep adapter. Let me know if you ever feel like decoding the renix data stream and/or making a knock off of the drb II
- Location
- Rainy side of Washington
Hmm...
sounds like an interesting project. The RENIX can be debugged with a DMM, most of the signals are (as far as I know, I seem to recall an SCI/serial pin somewhere in the schematic I looked at a while ago though) analog plus the tach/ICM signal, so it should be easy to build that part.
OBD-I and OBD-II interest me more, but I haven't felt like ponying up the cash for a copy of the OBD-II protocol spec.
sounds like an interesting project. The RENIX can be debugged with a DMM, most of the signals are (as far as I know, I seem to recall an SCI/serial pin somewhere in the schematic I looked at a while ago though) analog plus the tach/ICM signal, so it should be easy to build that part.
OBD-I and OBD-II interest me more, but I haven't felt like ponying up the cash for a copy of the OBD-II protocol spec.
While I may not agree that making a calculator would be practical because of the large amount of variables.
I do see the logic in doing this calculation for the average of those variables and the maximum when planning your build.
If I did this maybe I wouldn't of dumped a ton of cash into my d30 and d44 before springing for rockwells.
If you know how rough you want to wheel I say go for it nothing wrong with being exact in finding your required axle strength, and maybe you'll crawl past those haters while their doing trail repairs.
I do see the logic in doing this calculation for the average of those variables and the maximum when planning your build.
If I did this maybe I wouldn't of dumped a ton of cash into my d30 and d44 before springing for rockwells.
If you know how rough you want to wheel I say go for it nothing wrong with being exact in finding your required axle strength, and maybe you'll crawl past those haters while their doing trail repairs.
- Location
- West Sacramento, CA
Lol Rockwells.
Lol I know you are way more tardcore than me.
If I was you I would totally scoff at my build too.
:worship::worship::worship:
lowicz96
NAXJA Forum User
- Location
- Flint/Asheville
Torque has a big part in axle breaks.
But so does deflection in the housings and axle tubes from the weight of the vehicle, larger tires and uneven terrain. Deflection in the housing will cause the the ring and pinion not to be perfectly lined up causing more stress in the teeth of the gears, which could break off. defection in the tubes puts more stress on the axle shafts.
When steel is put under stress, tiny cracks form at the atomic level. These are called dislocations and while these can be good like in things that require work hardening, you dont want it to happen in your axle.
Think of it this way, when you bend the metal back and forth, it gets weaker and weaker, then it breaks. Same thing can happen where the axle shaft meets the side gears from the force of the torque and from defection of the housing/tube
But so does deflection in the housings and axle tubes from the weight of the vehicle, larger tires and uneven terrain. Deflection in the housing will cause the the ring and pinion not to be perfectly lined up causing more stress in the teeth of the gears, which could break off. defection in the tubes puts more stress on the axle shafts.
When steel is put under stress, tiny cracks form at the atomic level. These are called dislocations and while these can be good like in things that require work hardening, you dont want it to happen in your axle.
Think of it this way, when you bend the metal back and forth, it gets weaker and weaker, then it breaks. Same thing can happen where the axle shaft meets the side gears from the force of the torque and from defection of the housing/tube
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