Beginners Guide To Rear Ends!

[Naterenfo1]

Now, I didn't know much about rear ends, axles, differentials, or any of the such before I actually took a class on them in college. So here I am, getting ready to give YOU some non-specific to Comanche rear end info!

 

To start it off, I am going to give you some basic information about rear ends, and their internals. Now, there is a lot of complicated parts, and measurements inside of our rear ends. I am going to try and keep this as simple as possible- basically a starters guide to every thing axle, and hopefully I can inspire you to do some learning on your own!! this info is for an open differential.

So! Here we go! here is a list of some basic parts

 

1. Ring Gear and Pinion Gear

The RING GEAR, is the gear on the right. The PINION GEAR is on the left

These two gears determine your gear ratio. How? based on the amount of teeth one has, versus the other. For example: a 4.10 gear ratio would imply that the pinion gear, spins 4.1 complete revolutions, before the the Ring gear spins a complete revolution. Why does this matter? gear ratios will change EVERYTHING in your drivetrain. from shift points in your transmission, to wheel speeds, to engine RPM at speed, acceleration and more. In a 4wd vehicle, you always want to make sure you have matching gear ratios in your front axle, and rear axle, or windup/wheel hop, and potentially irreversible damage to your drivetrain will occur. This of course, would not matter to you if you only engaged 4wd when you absolutely know that your tires will be slipping, and can rotate at different speeds such as in very soft dirt, mud, ice, deep snow, etc. (correct me if I am wrong). What do gear ratio numbers mean? basically, the higher the ratio (bigger numbers) means better acceleration/more power at low speeds. the lower the number, the more power/acceleration at higher speeds. EX: 4.56 gears would make an excellent rock crawler, or a drag car, because you need all the power at the low end. 3.55 gears would be great for a highway car/truck that wants their engine to do less work in higher gears, and wants better passing power at speed.

 

2. Differential Case

This is a differential case. Not much to say here, except that this whole thing rotates with the ring gear, and contains other gears, such as spider gears and side gears, which we will go over in a bit!

 

3. Axle

http://www.diffandgear.com.au/images/gallery/BigImg/M35axle.jpg

Sorry about the size of this image! I needed one large enough to show the splines at the end of the axle shaft!

This is an Axle. Most people refer to the rear end of the vehicle, but this is actually what it is. The axle transfers motion from the differential to the drive wheel. The left of the axle in this picture, is the hub where your wheel studs go, and the right end, is a splined shaft which fits into a side gear (which we will break into next!). The mid section, is the axle shaft. Which needs to be able to handle shock loads from both ends, and be tough enough to transmit the power from one end to another ie: acceleration, and stopping.

 

4. Side Gears

This my friends, is a SIDE GEAR. The side gear, you will notice, has inner splines, and outer teeth. Your inner splines are for the splined shaft of the axle (from above) and the outer teeth are driven by the Spider gears. They drive the axle, and are driven by spider gears.

 

5. Spider Gears

I couldn't find an image of a simple spider gear assembly, so here is a modified image. the circled assembly, is spider gears, and a pinion shaft. The spider gears are mounted onto the pinion shaft, and the pinion shaft passes through the differential case. the spider gears rotate on the pinion shaft, and rotate with the pinion shaft and differential, so they go through 2 phases of motion. linear rotation with the differential case, and horizontal rotation with the side gears. Spider gears may also be referred to as Pinion GEARS The spider gears transfer motion from the differential case, to the side gears which host the axles, and rotate your wheels!

 

That sums up a basic rear end, now lets see the assembled unit!

Explanation of Power Flow!

The power ultimately starts with the engine, through the transmission, through the drive shaft, through to the yoke on the pinion gear, to the Pinion Gear, which rotates the Ring gear, which is bolted onto the differential case, which rotates the spider gear pinion, which allows the spider gears to rotate, and transfer the power to the side gear of least resistance, which rotates the axle. The axle holds the hub, which connects to the wheel! that's it!

 

There we go!! that is essentially how a differential works! I know this isn't going to make sense, So I found a helpful video on youtube! I apologize for the fact that its old, but I think it adds a touch of class!

 

 

I'd like to ask to REFRAIN from comments for the time being, I am still writing another section to this post currently, and will ask for comments when it is all ready! thank you for reading, and for your patience!!

-Nate

[Naterenfo1]

Locking Differentials!

Locking differentials, what a cool invention! this locks the power of both axles together, and causes them to rotate at the same speed. What good does this do for you? Quite a bit!

A normal open differential will translate all its power to the wheel with the least resistance. What does that mean? if you have one tire on ice, and one tire on dry, clean, just paved perfect condition pavement, the wheel on ice is gonna spin like a b**** and your not going to move anywhere. A locking differential, will lock the axles together and presto! you get traction!

 

How do they work? what types are there? there are several different types I can think of straight off hand

Limited slip, Ratchet, and Torsen styles. There are air lockers, Electronic lockers, and automatic lockers

 

Now, I am not an expert on lockers, so this is where the pro's come in THATS YOU! I am just trying to explain a couple, and just know enough to be dangerous. Please feel free to comment, or message me on some new info you would like to add.

 

A good way to determine if you have a locker of some sort in your truck, is to pop off the dif. cover, and look at the differential. the if it is split down the middle, chances are there is a locker of some sort, because the case needed to come apart to put gears and such in for assembly.

 

Lets start with limited slip.

There are 2 common types of limited slip differentials. There is a cone style, and a clutch pack style.

The clutch pack style limited slip uses several friction discs that look like small manual clutch discs. The cone differential uses a cone shaped clutch that engages a matching cone shaped receptacle. Limited slip differentials have various brand names, including positive traction, sure grip, anti-spin, traction lok, and TXT. lots of people refer to limited slip differentials as Posi-Traction differentials even though General Motors owns the brand name.

 

Clutch Pack Style

The most obvious difference between an open differential and a clutch pack style limited slip is the clutch disks between the side gears and differential case. The discs and plates are applied by the pre load springs and by the mechanical pressure of the spider gears on the side gears. Since the side gears and spider gears are bevel gears, the teeth try to come out of engagement when the differential is trying to transmit engine torque. this creates a pushing action on the side gears, forcing them outward against the differential case. the outward pressure of the side gears presses the friction discs and steel plates together between the side gears and case. Whenever the plates and discs are locked together, the splined and dogged connections ensure the side gear and differential case are locked together. There are pre-load springs centered in the differential, that push out on the side gears, and provide the initial force to the clutch packs, but not so much that it doesn't allow enough slippage for normal differential operation.

 

Cone Style Limited Slip

In place of clutch packs, friction lined cones are used. The operation of the cone style, is similiar to the clutch operated LS. Pre-load spring and side gear pressures force the cone into a dished depression in the differential case. Friction tries to lock the cone and, therefore the side gear to the case, sending power to the wheel with the most traction. Limited slip style differentials require special gear oil.

 

Ratchet Style Differential

Nicknamed the "DETROIT LOCKER"

This style, uses a series of cams and ramps to direct power to the wheel with the most traction. Its operation depends on relative wheel speed, rather than on wheel traction. The ratchet differential transfers power through a set of teeth that can be engaged, and disengaged.This kind of engaging teeth system is sometimes called a dog clutch. The series of cams and ramps disengage the teeth of the dog clutch on the side of the wheel with the least traction. For straight forward driving, both sets of teeth are engaged and the differential case and wheels turn at the same speed. During turns, or when one wheel loses traction, the speed difference between the wheels causes the internal cam and ramp to disengage the teeth on the side of the faster moving wheel, and all power is then sent to the other wheel. SInce the faster moving wheel is always the one that is slipping, power always goes to the wheel with traction. On turns, the loss of power to the outer wheel is not noticeable. this design is durable and does not require special gear oil. It is often rough, and noisy when in operation. It is usually used in off road and racing vehicles.

 

Torsen Differential

This differential uses complex worm gearsets. The gearsets include worms (drive gears) and and worm wheels (driven gears). The Torsen Differential has been available since the 60's. This is a High Performance replacement for standard differentials. The basic mechanical principle of this differential is that while the worm can drive the worm wheel, the worm wheel cannot drive the worm. The Torsen differential has two central worms. For purposes of clarity, these will be referred to as axle gears. One axle gear is attached to each axle shaft. Worm wheels ride on and are driven by the axle gears. The worm wheels are held in place by the differential case. Spur gears machined on the ends of the worm wheels mesh and form the only connection between the two axle shafts. Engine power drives the differential case, and the worm wheels, held by the case, turn with it. The worm wheels cannot turn the axle gears, so they lock themselves to the gears. Int this way, power is transmitted; the axle gears and axles are locked by the case, and rotate with it. During forward operation, the differential assemble operates like a standard differential; all internal gears turn as a unit. When the vehicle is making a turn, or when one drive wheel is slipping, the relative speed of drive drives wheels, and therefore, of the axles changes. This speed change is transmitted from the faster axle to the slower one by the action of the meshing spur gears. The axle gear on the faster axle can drive the respective worm wheels. This driving force is transferred from the spur gears on the faster turning worm wheels to the spur gears on the slower turning worm wheels. Engine power is transferred from from the faster to the slower worm wheels by the interaction of the gears. The wor wheel on the slower side still cannot drive the slower axle gear, but it can transfer the increased power from the faster wheel as pressure. This pressure increases the amount of power sent to the slower axle gear and axle. It does not turn the axle gear, but it does allow it to turn with more force.

 

 

Hydraulic Locking Differentials

This system may be called Hydra-Lock, Vari-Lock, or Gerotor system. This system consists of a pump with internal and external gears, a ring shaped pressure diaphragm, and a clutch pack that resembles the clutch pack used in the LS system. Special oil is not needed. The gear oil that operates the system comes from the rear axle assembly sump. The same oil is used for rear axle lubrication, and the the hydraulic system does not have to be sealed from the other rear axle components. The pump resembles a rotor type engine oil pump. with a six point external gear that turnes inside of an internal gear with seven cavities. The spaces between the pump and internal and external gears are filled with gear oil at all times. When the gears move in relation to each other, spaces on the intake side of the pump open and draw in gear oil. The fluid is carried around to the output side of the pump, where the spaces begin to close.

Closing the spaces produces pressure that can be used to operate the other components of the differential assembly. Check valves insure that pressure is always produced, no matter what direction of the pump rotation. The internal gear is attached to one of the side axles. The external gear is attached to the other side axle. When both wheels have equal traction, both axles turn at the same speed. Therefore, the internal and external pimp gears do not move in relation to each other, and no presure is developed. When the vehicle loses traction to one wheel, one side of the side axles begins turning at a faster rate than the other. The difference in axle speeds causes the internal and external pump gears to move in relation to each other, producing hydraulic pressure. THis pressure is delivered to the ring diaphragm, which expands against the clutch pack. With the clutch pack applied, the side axles lock together and turn as a unit. When the wheels begin turning at the same speeds, the internal and external pump gears do not move in relation to each other and no pressure is produced. with no pump pressure, the ring diaphragm de=pressurizes, and releases the clutches. When turning, they don't create enough pump pressure to lock the wheels together.

 

Last but not least, the always classy

LINCOLN LOCKER!

this my friends, is the poor mans locker. This turns your normal differential into an ALL TIME locked axle. This is NOT recommended for street vehicles. How is it done you ask? pop open your dif cover, and weld the living $#!& out of all the spider/side gears to the differential case. This will un-doubtably cause irreparable damage to your differential. Using this on road, will cause wheel hop, all sorts of wheel chopping, and tire damage beyond belief. Off road use, these things are fuh-reakin sweet.

imagine having all 4 wheels locked together in perfect time! that my friends, is real traction. This is for sure the poor mans way of locking an axle, but dang does it work good.

 

Well, thats the lockers I know about. For what I understand, air lockers work very similiar to the hydraulic clutch, except the pump is a compressor under the hood!

 

Any additions? please feel free to comment. I will post another long post like this, talking about full floating, semi floating, integral carrier, removable carrier, and! solid axles!

 

Thanks alot! hope you enjoy!!

-Nate

[veritas4156]

Wow. Awesome. I think I might print this out and bring it with me to work for the next time somebody wants to order in rear end parts. Maybe they'll actually be able to tell me what they need... Probably not though.

[terrawombat]

This made for excellent bathroom reading material last night - thanks!

[86MJ2WD]

Very well done post , called the beginners guide however i'm wondering how many will sit and read anyways as i just did . Nice job ! :clapping: :wrench: :clapping:

[86ComancheXNate]

Thanks a lot for this post. I have been confused about how locker work for a while now. Everyone in my jeep club has told me I should put one in my rearend and I just haven't been able to grasp what they do.

 

This has helped tremendously.

 

The other Nate

[Pete M]

nice post. :thumbsup: we'll move that over to the DIY section later.

 

why is the cross pin labeled as the "pinion shaft" in the 4th photo?

[bajajunkie]

wow good write up! pretty much sums up the basics of axles. what degree are you going for? Mechanical Engineering?

[Naterenfo1]

Thanks everyone! :cheers:

The textbook I was researching out of, called it the pinion shaft (technical name I guess!) so I just kept the name.

 

I am studying Diesel Mechanics, but am also a wannabe off road junkie ;)

 

-Nate

[kro10000]

Thanks everyone! :cheers:

The textbook I was researching out of, called it the pinion shaft (technical name I guess!) so I just kept the name.

 

I am studying Diesel Mechanics, but am also a wannabe off road junkie ;)

 

-Nate

 

Where do you go to school at?

[Pete M]

wouldn't the pinion shaft be the shaft connected to the pinion gear? :dunno:

 

---->

[btm24]

Thank you very much for this wright up very help full. After reading all of this I learned more in the past 30 min then I have in the past few months trying to understand this. :clapping:

 

Brandon

[Naterenfo1]

wouldn't the pinion shaft be the shaft connected to the pinion gear?

 

---->

 

That's what I thought too, and it confused me, but I read it over and over and thats what it said about that piece :nuts:

I think it would be safer to call it a cross pin! that is how I have always heard of it

 

The pinion shaft is also the name for the piece you described, the shaft of the pinion gear.

 

Thanks everyone! :cheers:

The textbook I was researching out of, called it the pinion shaft (technical name I guess!) so I just kept the name.

 

I am studying Diesel Mechanics, but am also a wannabe off road junkie ;)

 

-Nate

 

Where do you go to school at?

 

Alexandria Technical College! it's incredible. I can honestly say I am EXCITED to go to school every day! :smart:

Glad I can help guys! If there is enough interest, I can write an advanced edition involving how to take measurements and such that are critical to setting up a winning rear end. (backlash, endplay, etc.)

[SW86]

hell yeah! thanks for this. i just figured out how to put back in my spider gears!