Final Drive - Differential

The assembled diff.

For this week, we are studying final drives in practical class. We have Gary for a tutor.
The differential that we are are taking apart and measuring is a banjo type diff. This type is where the diff gears come out of the body of the diff. As opposed to a salisbury type where we have to spread apart the body to get the gears out.
It is the hypoid type, where the centre line of the pinion gear is below the centre line of the crown wheel. This is opposed to the spiral bevel type, where the centre line of the pinion gear is on the same line as the centre line of the crown wheel.
It is also a non limited slip type, which opposed to the limited slip type which has clutch packs and springs which are used to lock the two axles together.
There was no visible identification on the final drive.

Marking the teeth with the
teeth marking solution.

There are centre punch marks on the diff housing caps for alignment, to ensure they go back in the correct way.

There is also a white painted mark on the crown wheel and carrier to ensure that gets lined up the correct way. Starting to dismantle the differential, we first removed the diff case assembly. While pulling the carrier out, be aware that the bearing caps will fall out.
Next we removed the bolts off the crown wheel and removed the crown wheel itself.
Then we were to remove the pinion gear. We first had to remove the pinion nut and flange, and then push the pinion out through the case. We then used the handle of a hammer to remove the seal and the pinion bearing.

Now comes the inspection part of the process.

The crown wheel, adjusting nuts,
and bearing caps.

We checked the condition of the crown wheel teeth. It was relatively good, apart from a very small chip in one tooth, and very slight wear on the teeth due to the wrong type of oil used. The chip on the tooth could have been caused by the cross shaft coming out and hitting it.
The condition of the crown wheel bolts are all good for service.
The condition of the threads in the case were also all good and ready for service.

Next was to remove the cross shaft, spider and side gears and thrust washers.
We tapped the roll pin out and then removed the cross shaft. We were then able to remove the spider gears, and then remove the side gears. Also the thrust washers came out.

The diff housing with the
crown wheel carrier removed.

We then had to inspect these parts.
The side gears had pitting on the teeth. This is where there gets rust spots on the teeth. This oxidises and turns blackish and it wears through the hardening of the teeth and then excessive wear is caused.
The side gear thrust washers are in good condition and ready for service.
The spider gears and spider gear thrust washers are in good condition and ready for service.
The cross shaft has a bit of where on the shaft where the spider gears run. This is a black colour. This is caused by the diff sitting around not being used and water in the oil.
The roll pin had a slight bend in it. However this is alright as the bend can apply tension to help hold the pin in, however a bent roll pin can indicate that the cross shaft has moved.

The crown wheel bolts removed.

The next step in this task was to calculate the final drive ratio. The pinion has 9 teeth and the crown wheel has 41 teeth so the calculation is 41/9 which gives an answer of 4.56 and a ratio of 4.56:1. This means that the crown wheel will turn once for every 4.56 turns of the pinion.

We then had to measure the side gear backlash clearance. We measured this with a DTI  and got .18mm and .09 mm for the two gears. This is clearance is good for service as it is within the specifications of .05 to .2mm.
If this clearance was to great or small, this could indicate that new thrust washers would be needed. This backlash is there to allow for the metal to expand under heat.
Note 1: When clamping the carrier in the vice, do not clamp the mating surfaces as the cross hatching on the vice jaws  can dig into the surface and cause it to expand minimally and then cause the mating part to be off balance.

Undoing the nut to get the
pinion gear out.

Note 2: When assembling gears, damaged thrust washers can cause the gears to jam up and not turn.

We then refitted the crown wheel, being sure to align the wheel to the carrier by paint marks. We torqued down the bolts in a star sequence to the manufacturers specs of 97Nm. (actually 35 because its half to protect threads).

We then inspected the condition of the pinion gear. The teeth, splines, thread and bearings were all in good condition. But because this diff has a collapsible spacer, it can only be used once and would need replacing, but for the purpose of the exercise, that one was not replaced.
The next task was to re assemble the pinion into the diff housing. We oiled the bearings and put it in place with the collapsible on the shaft. We then put the washer and seal in and wound up the nut. We then had to set the pre load on the pinion bearings using the inch pound torque tester. The pre load was set to 7.8 inch pounds, which is manufacturers specification. If we were using a new collapsible spacer, we would not have had to wind the nut up so much, as it would be a fresh, new spacer.

The driveshaft flange.

Preload on the pinion bearings, is there to stop the pinion gear from moving in and out of mesh.
Once the pre load was set, we were able to replace the crown wheel carrier into the housing.
We refitted the bearing caps along with the adjuster nuts. When fitting the bearing caps, it is essential that the adjuster nuts are free to rotate in their threads, otherwise they will not rotate when the caps are torqued down.
We then tightened up the adjusting nuts so that were was no sideways play in the crown wheel.
Next we had to check the backlash of the crown wheel. At the four different points around the crown wheel, we got readings between .38 and .40 mm. The specifications are between .13 to .18mm. Our readings were to high, so we adjusted the adjusting nuts, moving the crown wheel further into mesh. We then took the readings again, and got readings between .13 and .16mm. This is within specs so this is ok and good for service. If there was not enough backlash, there would not be enough clearance for the gears to expand, and the teeth would bind up and stop turning.

The pinion bearing, washer and spacer.

We then had to do a tooth marking test. We found that the pinion was meshing too close to the toe, so we needed to put thinner shims, or less shims to move the pinion out of mesh.

The pinion.

The last task was to check the driveshaft flange for runout. We set up the DTI and got a reading of .08 mm. We did not have any specs for that so that is the differential fully inspected and assembled.

Clutch assembly

Checking for flywheel runout.

The clutch that we were inspecting was off a toyota 3k engine. It is the cable operated type.
After un doing the cable, and un doing the bell housing bolts, we were able to remove the transmission. After the tranny  was removed, we were able to remove the pressure plate bolts and then remove the pressure plate and the clutch plate. After we removed these, we were able to inspect and measure the components.
The face of the pressure plate was in good condition.
The clutch plate was fairly worn and would need replacing.
the release bearing was fairly worn and would need replacing.
The release fork was in good condition.
The release linkage was in good condition.
The spigot bearing was in good condition.
The clutch housing was in good condition.
The input shaft was in good condition.

A clutch friction plate.

The flywheel face was in good condition, but after checking for flywheel runout, we found there was .05mm of runout. However, this amount is acceptable because the specification is .15mm.
If the clutch plate was worn down to the rivots, the rivots would then score the face of the flywheel and pressure plate which will cause excessive damage.
We then had to identify which way the clutch plate goes in on re-assembly.
We concluded that the raised side of the plate goes against the pressure plate.

A clutch assembly.

when putting the clutch and pressure plate back in, we used a dummy shaft to align the clutch plate while we bolted the pressure plate to the flywheel. Once the clutch assembly was bolted down we were able to re fit the transmission. We had to make sure that the weight of the tranny was not hanging on the clutch assembly while we were bolting it to the engine.
We then had to fit the clutch cable and adjust it correctly with the correct amount of free play. If there was not enough freeplay, the release bearing would be constantly pressing against the diaphragm fingers and cause and excessive amount of damage. Also riding the clutch will cause an excessive amount of heat and wear to the clutch plate.

A flywheel

A pressure plate.

we adjusted the clutch linkage accordingly and checked operation and it all worked fine.

Driveshaft and UJ (universal joints)

Un doing the bolts at the centre
flange.

For the driveshafts, we had to dis assemble the UJ's which require a lot of hammering. we had to write a list of equipment that we would require for the job. This includes A big hammer, a big punch, wooden blocks, a DTI, screw drivers, spanners and pliers.
We first had to check the phasing of the UJ's. The phasing of our driveshaft was correct and is unable to be changed so nothing could be done here anyway.
Drive shaft balance needs to be checked. This can be done in various ways. One way is to put it in a lathe and use weights in a trial and error method to see when the driveshaft is balanced.
To check driveshaft runout, we use a DTI on the driveshaft sitting in Vee blocks. We then turn the driveshaft to see how much runout we get. The manufacturers specification is maximum of .6mm. At the front we got .49mm, middle was .44mm and rear we got .32mm. This is within specs so this is ok.
Next was to check the UJ's. They operated smootgly and there was no axial movement.

Using the DTI to check the driveshaft
runout.

To dis assemble the UJ's, we first had to remove the snap rings. We then had to hit the cross down to remove the cups. This required alot of force, but we got there in the end.
We then removed all of the grease from the components so that we could inspect them. We found that all of the caps, yokes and journals, rollers and seals were all in good condition.
We then had to re assemble the UJ's, we made sure that we put grease into the caps and yoke surfaces. After hammering the caps into position, we re fitted the snap rings and then checked that the UJ operated smoothly.

The UJ with the cups removed.

There were no problems with the UJ so no new parts were needed. Once we re assembled it, the UJ operated smoothly.

CV (constant Velocity) joints.

The outer CV joint where we can see
the cage and the balls.

For this week, we are working on the clutch, CV joints and drive shaft.

CV (constant velocity) joints:
On each drive shaft, there is an inner and an outer CV joint. The inner joints are often the tripot type, and the outer are often the birfield type. The inner joints are able to slide in and out because of the suspension movement.
Before we pulled the CV apart, we had to check the joints for play, roughness or binding. These problems are often caused by lack of grease which gets thrown out when the rubber boots get worn out.
Our CV joints operated smoothly

The tripot which slides along the race
of the inner CV.

The joints did not have any excessive play. If this axial play was excessive, the joints will make that knocking sound and won't be smooth to rotate.
All rubber seals and boots were checked and no cracks in boots or worn seals were found. If the boots and seals are worn, the grease inside the joint will escape, causing the joint to dry up, and will then fail.
To disassemble the CV joints, we first had to remove the rubber boots. The next step was to remove the joint from the shaft. Our joints had a snap ring on it that presses down as the joint moves over it. So we applied force with the hammer to remove the joint. It came off fairly easily.
After removing the ball cages, and balls, we were able to remove all of the grease from the components so we could inspect them for damage.

The inner CV where we can see that
the tripot is able to slide along the race
inside the CV.

The outer and inner races, where the balls sit in, were smooth and free of scratches or scarring. The ball cage and balls of the outer CV were in good condition.
The tripot in the inner CV, however, as numerous dents and marks on the rollers and should be replaced.
All of the splines and threads were all in good condition also.
The last step was to re assemble the CV joint. This went smoothly and the CV joints operated smoothly and as it should once we re assembled it.


The circlips and circlip grooves were in good condition and operated as they were supposed to.

manual transaxle day 2 / 3 / 4

Day 2.

The assembled transaxle.

Today, after disassembling the transmission on tuesday, we took measurements and inspected the components of the transaxle.

The first components we inspected were the bearings in the transmission.
There are a few types that are present.
Taper rollers, in which the rollers are tapered and roll around on a tapered cone. These were found on both sides of the crown wheel, part of the final drive assembly.
Another type was the normal cage supported roller which were located at the rear of the input and output shafts. This type of bearing uses rollers or balls which roll between two shells and are supported by a cage.
The needle roller bearings are are type of bearing that uses needle shaped rollers which are supported by a nylon type cage. This type of bearing are very thin and are found on certain driving and driven gears in the transmission. The fifth driving gear has this type of bearing in two pieces.

we removed the top cover.

Another type is a bush. It is fixed in place and for lubrication, the bush has grooves in it which let oil in between the bush and shaft. This type of bush was used in the transmission on the reverse idler gear, and as it sits over the shaft it needs lubrication, so the grooves allow oil to get in between.

Another measurement we had to take was the side clearance of the non fixed gears. Side clearance is the sideways movement of the gears. These clearances are measured using feeler gauges. The clearance between most of the gears was about .3mm, which is normal.
While checking the side clearances, we also checked the condition of the teeth and gears. We had to check that the hardened face wasn't worn, make sure there were no teeth chipped off. We also checked the condition of the syncro dog teeth. Everything was in good condition.

Removing the selector mechanism

The syncromesh system also needed to be inspected for damage and clearances. Cracks on the baulk ring need to be checked for, wear on the inside of the baulk ring and wear points on the teeth. We also need to check for the clearance between the baulk ring and the engagement ring. If this clearance is too small, then this will mean wear on the inside of the baulk ring. Again, this clearance is checked using a feeler gauge. The minimum clearance is about .5mm, anything less than this will mean insufficient pressure can be put on the engagement ring, and will be unable to slow the gear down. Our clearances were good, ranging from .5 to .9 mm.
Also as part of the syncromesh system, the shift plates, wire springs, syncro hubs and shift sleeves had to be inspected for wear and damage. All of these on our tranny were in good condition and no further action had to be taken.

using the gear pullers to remove
the fifth gears.

Next we had to inspect the selector mechanisms for damage. The detent systems, the interlock system, the selector forks and shafts had to be inspected. The detent springs were stiff, the selector forks had no visible signs of damage and the selector shafts were smooth, also with no damage.

Next we had to measure the diameter of the different shafts. We had to measure the input and output shafts, the reverse idler shaft and the 3 selector shafts.

We then had to check the condition of the cir-clips, splines, housings and covers, breather, seals and thread holes and bolts. All of these were in good condition and no further action was needed.

We removed the gearbox housing

The last step was to calculate the gear ratios of each individual gear. After counting the teeth on each gear, we used the formula Driven/Driving to calculate the ratio. E.g. The third driven gear had 38 teeth, and the third driving gear had 29 teeth.. We then use the formula so 38/29, which we get 1.31, therefore the ratio is 1.31:1. This means that the input shaft will turn 1.31 times, and the output shaft will turn once.


Day 3.
On day three, we reassembled the transmission. The most difficult part of this was assembling the selector forks. This was a very fiddly task but we got there in the end. Once we got the transmission assembled, all gears were selected and it was as good as new.

The selector forks and shafts.

Day 4.
Because we had finished assembling the transmission, it was unnessecary for us to be at class. I went home and worked on this blog and revised some automatic transmission material.

We removed the input and output shafts

The input and output shafts.

we removed the final drive.

The crown wheel.

Manual Transaxle

Day 1. This week we are studying the manual transaxle. Today we dissassembled the transmission into all of its seperate components.

The assembled transaxle.

After removing the end cap, we were able to access
the fifth gear set up. From here we could remove the
synchroniser and shift forks and then the gears themselves.\
The shift forks are operated by shift rails which are connected
to the selector leaver.

Removing the selector assembly which
selects each gear.

Using the gear pullers to remove
 the fifth gear.

The transaxle with the transaxle
case removed.

The shift forks and rails which are used to select the  ratios.

The clutch housing with the crown wheel
still in it.

The primary and secondary shafts , which
the power goes through.

The clutch housing with everything removed.

Automatic transmissions

For this week, we are working on automatic transmissions with Brian.
Day 1: On tuesday, we stripped down the entire rear wheel drive automatic transmission into all of its separate components.

The automatic, rear wheel drive transmission

Removing the oil pan

Here we can see the valve body,
servos, and oil pipes with the oil
pan removed.

The valve body controls the transmission. It directs
oil to the right places to allow for different ratios to be selected.

The transmission with the valve body removed.

This piece is what houses the output shaft
and the governer.

The transmission with the valve body and the servos removed.

The servos are hydraulically controlled by the valve
body and are what apply pressure to the bands which
hold the drums. 

This is the governer that senses the speed
of the output shaft. It feeds this information
to the valve body.

This is the oil pump which is driven by the impeller
part of the torque converter. It supplies oil for
lubrication and also pressurised oil to the valve body.

The front of the transmission showing the
input shaft after the oil pump has been
removed.

The input shaft removed with the front clutch
pack. The clutch packs are locked up by oil
pressure which flows through the shafts.

Looking inside the trans at the rear clutch
pack with the intermediate shaft inside it. 

The intermediate shaft inside the rear clutch clutch pack,
and has the 2 sun gears inside it, which mesh in with the
pinions inside the planetary gears.

This is one of the bands which are used to  hold the clutch
packs/ gear sets.

This is the planetary gear set.  The pinions that can
 be seen are what mesh with the output shaft ( on the outside)
and the intermediate shaft (inside).

Looking into the transmission with the output shaft
still in there. The output shaft is connected to the planetary
gear set by an internal ring gear on the output shaft.

The rear band, which is operated by the servo which
makes the band clamp down on the planetary gears.

The housing of the transmission as we removed
 the output shaft.

The output shaft which sends power out to the diff.

Day 2.

We had torque converters explained to us. It is there to couple the engine to the transmission. The torque converter works by the engine driving the impeller, and by the centrifugal force, and using the vanes, forces oil out and into the turbine side of the torque converter which intern makes that spin. This torque is then transferred down the input shaft to the transmission. There is also a stator between the impeller and the turbine. The stator is there to redirect the oil flow as it enters the impeller and is also there to increase torque. This is so that the oil enters the impeller in the same direction as the impeller is turning, which also assists in turning the impeller.

Day 3.
Today we were asked to do some work out of the workbook. What we had to do was to list the major parts of an automatic transmission and give a brief explanation of each part
1. Torque converter: This takes the place of a clutch and transfers torque to the transmission. It also increases              the torque.
2. Oil Pump: Provides oil pressure for transmission control systems and supplies oil for lubrication.
3. Planetary Gears: Supplies power flow through the transmission and to change ratios.
4. Input and Output shafts: Input supplies power to transmission, output supplies power from transmission.
5. Governor: Senses vehicle speed and and provides information to the valve body.
6. Front and rear clutch assemblies: Lock components to change gear ratios.
7. Bands: Hold components to change gear ratios.
8. Valve body: Brains of transmission, decides what gear to select.

What does the servo do in the transmission?
The servos operate the bands. The bands hold the drums etc. to provide different gear ratio's.

Give two advantages of using a 'lock up' torque converter:
1. Increase power (by about 2% ish)
2. Increase fuel economy.

Day 4:
On friday, Jiejun, Cody and myself, after assembling the rear drive auto trans, we took apart and reassembled    an automatic transaxle.

The assembled auto transaxle.

The valve body. This has a vacuum system to determine
throttle position. It uses vacuum from the intake manifold to
operate the valves.

The trans after the valve body has been removed

The bellhousing. We can just see the various shafts.
The small one in the centre drives the oil pump, the
middle one is the input shaft and the big one is the
stator shaft.

Here we can see the oil pump which is on the back of
the trans. It is driven via a shaft which goes through the
entire trans from the torque converter.

The housing of the trans after the  clutch  packs
and planetary gears have been removed.

The governor which sticks out the side of the trans.

The clutch packs and planetary gears  and bands etc.