I've read allot of threads in this forum where axles are talked about, in fact currently following a thread right now, and everybody suggests replacing their 2 piece with a 1 piece axle. curious to know or understand the reasoning behind this, and why it's recommended.
I have an 86 CJ7, 4.2, 258, 5 spd manual and my 2 piece has separated in the past so thinking is this is one big reason; the lack of integrity w/a 2 piece, which likely has a natural tendency to do this; separate.
would appreciate understanding all the drawbacks of the 2 piece, and the benefits of the 1 piece axle, my experience probably being a big one.
The two piece is a separate axle and hub mated together and relying on serrations on the axle shaft forming in the corresponding mating surface in the hub. When you look at a hub and shaft that have been separated, it makes you wonder that the setup even holds up as well as it does. A one piece shaft with the flange forged integral is a far stronger and more reliable setup. Most aftermarket one piece axle sets are manufactured from 1541H steel which in itself is stronger than the material used in stock Jeep axle shafts.
I've attached a pic of a separated stock 2 piece axle and hub. As you can see, the serrations don't really form very deep in the hub.
The two piece axle design was never intended to have larger diameter tires outside of the OEM tire size. All that extra weight and torque required to turn them, along with individuals who fail to re-gear to compensate for the added diameter and weight of over sized tires, leads to their early demise. The fact that they must be periodically checked for tightness. Meaning, one must check and adjust the nut on the end of the axle every once in awhile or the tapered splines will start to separate. Nobody checks them as far a routine maintenance.
Actually a tapered engagement is quite strong on the two piece design but the taper must be drawn extremely tight in order to work. Any tolerance between the the two tapers, or space, will render them useless. I still have the OEM two piece axles but every year I check the nut on the end to make sure it is tight and torqued to 250 ft/lbs. That's another reason, nobody really has a 250 ft/lb capable Torque Wrench either. Also, mind you, I have 32" tires and the axle gearing that is required to turn them. 4.10's with a T5 transmission that makes it easy to turn the larger diameter tires with ease.
The two piece axle design was never intended to have larger diameter tires outside of the OEM tire size. All that extra weight and torque required to turn them, along with individuals who fail to re-gear to compensate for the added diameter and weight of over sized tires, leads to their early demise. The fact that they must be periodically checked for tightness. Meaning, one must check and adjust the nut on the end of the axle every once in awhile or the tapered splines will start to separate. Nobody checks them as far a routine maintenance.
Actually a tapered engagement is quite strong on the two piece design but the taper must be drawn extremely tight in order to work. Any tolerance between the the two tapers, or space, will render them useless. I still have the OEM two piece axles but every year I check the nut on the end to make sure it is tight and torqued to 250 ft/lbs. That's another reason, nobody really has a 250 ft/lb capable Torque Wrench either. Also, mind you, I have 32" tires and the axle gearing that is required to turn them. 4.10's with a T5 transmission that makes it easy to turn the larger diameter tires with ease.
I don't think not regearing is the reason the joint fails.
I would think that the force the axle delivers to the hub to turn the wheel and tires would be the same no matter what gear ratio. It just makes it easier for the engine to turn the wheel and tires.
Although you are right about the larger size tires puts more force on the axles/hub.
The stock 2 peice design wasn't strong enough for stock let alone a rig with larger tire's and lower gears. Gears being a power multiplier certainly play into breaking parts.
Get the 1 piece. Well worth it. I've only broken 1 1-piece and that was due to a broken carrier caused by a failed lunch box locker.
Why did AMC use the 2pc to begin with? The larger AMC trucks got a 1pc axle on the AMC20.
The story I heard was that the smaller AMC trucks, jeep and cars that used the AMC20 all had different axle lengths, but otherwise similar setups, so the 2pc setup allowed them to use the same hub/brakes, and same diff... just different tubes and axles.
Many years ago, my jeep ignorance led me to an expensive transmission rebuild when I had the sound of gears grinding and power slippage. After re-installing the rebuilt trans I quickly realized the issue was not my trans after all, it was actually my passenger side 2-piece axle spinning... Have had 1-piece axles for over 15 years now, live and learn.
I had the 2 piece amc 20 with 31in tires and it lasted 200k plus miles in my jeep. It wasn't use for rocking but was abused in the mountains of Colorado for all the years of my ownership. I also had the SR4 transmission and it went 200k with 1 rebuild before I pulled both still running and replaced and that was with 3.54 gears. That being said I guess I got lucky with the transmission and the rear end was ok mostly stock setup and moderate abuse. The 1 piece is much stronger and is a worth while upgrade I went dana 44 and the transmission I went rebuilt t5 with 4.56 gears and 33in tires seems plenty strong for moderate trails.
would this be telling of a problem? if you look close you can see the tire/wheel on the right/passenger side sticks out slightly/noticeably further ( just past the flare), than the tire/wheel on the driver's side.
would this be telling of a problem? if you look close you can see the tire/wheel on the right/passenger side sticks out slightly/noticeably further ( just past the flare), than the tire/wheel on the driver's side.
was reading a response from a related thread called "It's been a while. Looking at coming back and CJ7- axle question." from deminimis, and 80cj replied:
"But yes, I would replace the 2 piece with one piece if you're going to go to larger tires and do anything more than street driving. If you elect to stick with the 2 piece, check the axle nut torque from time to time."
I don't off-road much if at all, mostly road, but do have 30.5" tires on it, so if I was to keep the 2 piece, I'm assuming the above check is a minimum maintenance check from time to time, as suggested by 80cj?
If really not recommended, i.e. staying w/the 2 piece axle, what are the downsides of sticking w/the 2 piece axle? what am I looking at happening? what should I expect to happen?
not sure if the passenger side wheel as shown in the pic attached is warning of something currently?
Jack the entire rearend of the Jeep off the ground and try shoving in on the tires. If you get more than just a few thousandths movement, then your bearings may be shot or your axle end play needs to be readjusted. Also, spin the wheels and see if you can detect roughness in the bearings. From the factory, there are adjustment shims under the driver's side brake backing plate. You only adjust one side since endplay is transferred to the opposite axle through the differential thrust block.
Bad wheel bearings would cause that but having the axle off center as much as shown in your pic would more than likely be caused by the body being off center as waynaferd mentioned.
Happens when the body mounts get worn allowing the body to shift. The bolt holes are a little oversized. Many possibilities. Was the Jeep in an accident?
A little time under the CJ with a tape measure should reveal what's causing the body shift.
As for 1 or 2 piece axles, I agree with Keith. The stock 2-piece axles are adequate with stock-sized tires and proper maintenance. I'd venture to guess over 90% of those who have had problems with 2-piece axles were running larger tires than the axles were designed for.
true enough, a good visual & measurements should tell the tale. also, given the Jeep's suspension and the pounding it takes, especially after 30 years, makes sense body mounts could be responsible.
shot body mount(s) may even be the cause of a lot of road noise in my jeep; i.e. as questioned in a related thread; "Driveline vibration sound"
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