18/05/11 Theory episode 1_ Driveshaft universal joint

Roughly 12 degree of anglular movement

When checking the flank check the spine, cuz the shaft is like a sound magnifier
Binding, shaft will lift the transmission.

CV Constant Velocity can give 100% of the drive whereever the angle. allow to extend or retract the shaft

Other types of joints
Layrub Coupling is similar to a  CV Constant Velocity, it can deliver 100% of the torque applied at various angle. Whereas a cross joint varying velocity with angles, the more angle the less velocity. Also it allows the shaft to be lengthen and shorten. That means when the suspension goes up and down, the driveshaft is in correct motion.

Rubber trunnion joint
Absorb vibration due to the made of rubber, only works on limited angles, use for low power vehicle.

The doughnut joint
Normally larger in diameter 150mm- 250mm. Everything applied same as the rubber trunnion, still small angle, absorb vibration, but can operate @ greater horse power.

Universal joint yoke phasing
To obtain the variable velocity characteristic within the driveshaft, it is critical that the yokes on each end of the driveshaft "in phase" i.e both yokes are in line, and turn through the same angular distance together.
Most car driveshafts eliminate any possibility of being out of phase by having the sliding spline or "slip joint" on the input yoke to the driveshaft

When you get 2 univerasal joint, the angle problem is elminated becasue the ang;e is lessened.

Major causes of drive shaft vibration:
Out of phase driveshaft yokes, out of balance(will cause the bush behind the shaft to wear out),=> twisted driveshaft
Shaft run-out, bent

How to get rid of the noise: vibration=freq=wave=sound=harmonic of the car.

CV joint lubricant
most molybdenum disulphide greases from reputable oil suppliers are suitable eg castrol ms3 grease; however however some vehicle manufacturers specify a particular product for their equipment and these recommendations must be followed.
Worn universal joint.

25/05 Theory episode 5

Clutch control systems

Mechanical control : cable operation; lever operation

Cable: more flexible

Power Hydraulic opertaion: manual; power assisted

Causes for clutches slipping

Poorly adjusted causing thrust bearing to be applying presssure to diaphragm , stops full pressure to be applied to dics.

Riding the clutch( driver rest foot on clutch pedal) applying pressure to diaphagm, stops full pressure being applied to disc.

Oil leak out of the front of the transmission,( soaks friction material with oil 

Clutch Shudder can be caused by two main problems: +incorrectly aligned clutch when clutch has been replaced (installer has to wriggle transmission around to align dics assembly flexes splined section which damages(bends) disc.

Excessive slipping of clutch causing beat 

20/05/2011 Theory episode 3

Backlash: is the clearance between moving parts, more clearance, reduce friction, reduce the heat.

Preload: initial load placed on bearings during set up or adjustment, allows for bearings to bed into the cup and prevent free play after the bearing is seat

Helical diff: fWD

LSD Types:
Mechanical LSD
Clutch and cone type LSD
Viscous LSD overcomes the difference between front-rear wheels diameter

Purpose:
Reduce wheel spin
Improve traction
reduce tyre wear
to permit normal slow rate differential action on good surfaces, during low to moderate power operation.

LSD allows diff action under normall cond. Not normal, limited slip prevent diff action. Each clutch pack, absorb load on them, 4 pinion, right angle, meshed with the side gears, 4 extra load carry.

Visco=modern vehicle, front n rear end
4WD: ENgine n Tran are longi,

The advantage of the viscous unit iver the mechanical type is a smooth operating slip limitting unit that provides for lower type wear easier steering and less stress on the driveline components alowing for improved durability.

Third diff systems some 4 wheels drive part time four wheel drive vehicles should not be used on a hard surface in 4wd becasue transmittion

19/05/2011 Theory episode 2_ Drive, diff n Clutch

Final drive is the last section of the gear train and forms part
There are 3 gear set lyke
 Worm drive: extremely low, underneat the diff, 2 low, or over the diff, too high, expensive to produce.

Spiral Bevel goes right on the center line

Hypoid gear set: goes down low on the crown wheel, the pinion hooked 2 the driveshaft, coming out of the gear box, normally pinion/crown 3.8:1, PRO: tooth contact, height of the drive shaft.
Provide a good

RWD DIFF
Banjo diff type
Salisbury diff type: solid case with axle housing sticking a side, no adjustiing nut to adjust the side bearings.

Conventional 4WD'
No good on tarseal road

18/05/2011 Inspecting, dismantling, cleaning and greasing the universal joint

The Universal Joints

I. On the theory side         

 1. What is it? 

First of all, it's a joint type of a drive-shaft, which transfers the torque/drive from the transmission to the final drive. The universal joint is one of the most popular drive-shaft joint type that mostly used in RWD vehicle. Many are one-piece construction, but longer longitudinal length cars use 2 pieces, with a support bearing mounting the front shaft to the body. 

Some shafts have a sliding spline( which is quite common) that allows the drive shaft to extent and retract on its own length.

Hooke's joint /Cross joint are universal joint, they function the same way that there is a trunnion/or cross credited the two joined yokes 90 degree out of phase with each other, allowing both horizontal, vertical angular movements of the shafts.

2. Characteristics:

Universal joint has a "variable velocity" characteristic, that the drive shaft angular speed varies between the input yoke and the output yoke, but from the transmission to the rear axle, the speed remains constant throughout. This is because the yokes and the trunnion which are responsive for bisecting the angle at which the shaft spins are limited in their own ability to completely transferring the torque without the affection of any fixed angle. Therefore the drive varies between different angles particularly that when the angle displaces further from straight condition, the transferred speed varies more. Hence, it is designed so that the change of speed in output shaft always eliminates the change in the input shaft. So, although the wheels are driven at a constant speed, the drive shaft itself is alternately changing speed.

 II. On the practical side.

  Visual check for clearance: cracks or torsion or bents etc... help identifying the problem straight away if it's too obvious.

  One of the most critical step I should remember when servicing a universal joint drive shaft after cleaning and preparing for inspection is phasing. Phasing is the alignment of the cross yokes in the center section of the drive. With the incorrect phasing it will result in severe vibration when driving because the output yoke is 90 degrees out-of-phase with the input yoke, hence when driving, it does a painful job of lumping over 90 degrees to catch up with the input yoke, this can seriously causes heavy twisting. But shafts that have a sliding spline attached to the input yoke don't suffer from any incorrect phasing because they can correct the error by sliding back and forth. 

  In my situation, my both yokes on the shaft are welded with the shaft, so there is only one way to reassemble the phasing. However, when putting it back, we still have to distinguish where is the input(to transmission) and output(to final drive). I notice that on the 2 ends of the shaft, there are 2 different sized emerged pad of weight. So I guess they are balancing method of the shaft, which can also be used as match marking.

  Next, i have to check the drive shaft runout. By putting it on a V bench and set up the dial test indicator, i have to make sure that the probe is at right angle to the drive shaft. Then, identifying the runout by slowly turn the shaft 360 degrees to inspect the change in the probe meter, then collect the highest reading and compare it to manufacturer specification. A higher reading indicates that the balance is not good hence when driving we'll feel abnormal vibrations, since its not straight enough.

  When disassembling the cross joint, remember that the trunnion needs to be knocked out of the yoke first. So I have to remove the bearing cap retain ring first to free the caps from locking, by using a hammer and a long, flat tip screw driver. Once a rollers cap is taken out, the other can be disassembled easily with out any tool. As for the input shaft, the trunnion is disengaged with the driven yoke first, then we disconnect the trunnion from the driving yoke. As for the output shaft, the trunnion is disengaged with the driving yoke first, then the driven yoke.

  When everything is dismantled, before putting back, they need to be re-greased. All moving parts, surfaces are cleaned, removed from the old grease and re-greased. The roller bearings need grease to maintain the cap pressurized shut with the trunnion, so i pay attention to these.

  It is practical to match marking all alignment before disassembling. And thanks to this, our shaft were put back in no time. In the instruction, instead of hammering the trunnion back into the yokes, a relevantly smaller bolt can be used with the bench to press the trunnion cap back into the yokes, at a point where both the retain rings can fit into their trenches. Phasing is also checked when performing reassembly.

 

  

24/05/2011 Theory episide 4

Clutch systems

purpose : engage or disengage the power from engine to transmission as and when necessary
Most application: CLamping a friction disc in between two rotating metal dics
Name: Single dics/plate dry clutch
Friction disc is held against a heavy spring load.
Mainly 2 types:

Clutch plates: Diameter=torque capacity but increased pressure spring.

Pressure plate assembly
Sheet metal cover: smth that supports everything
Diapham spring(applies pressure)
Pressure plate
Spigot bearing supports the input shaft 4 the gearbox in the flywheel-can be a bronze bush or bearings(bull bearings or needle rollers)
There must be a freeplay between release bearing and the diaphragm spring

WHy? Diaphragm

Low maintenace
Low weight, low engine powerloss
less effort to operate
Cost effective
Smoother operation
Can be used in a large range of vehicle.

Beginning of a new ERA!!!

     Hi this is Tung Nguyen aka Tommy Alpa Shepard. In this blog I'll record everything in both practical and theory, in a self-reflecting manner, about everything, anything involving automotive transmission and driveline. This is an INTRODUCTION POST, not introducing what "transmission and driveline" is. So, in the future, i assume that you would like to visit my blog and expect hellova brain storming overthere.
Cheers,
Tung