722.118 Automatic transmission rebuild (Monster DIY) - Page 2 - PeachParts Mercedes-Benz Forum

Stretch · #16 09-09-2011, 04:56 AM

The input shaft (which runs through the hollow one) is held in place by three cross head screws. These should be have been glued (Loctite) in place. If they haven't been glued then the chances are that there has been a monkey visiting this 'box before! As they should be glued in place take your time undoing them and make sure you don't burr the edge of the fasteners. A cross head screw driver bit in a socket and a ratchet handle can often give you a bit more control.

With the screws out remove the cover, the shims, and the input shaft. You might find that the cover is a bit stuck – be careful if you decide to prise it off. Don't damage it.

Remove the little circlip on the end of the intermediate shaft

You can now remove the B3 brake drum

Stretch · #17 09-09-2011, 04:57 AM

Examine the splines in the front planet gear assembly. I think it is quite likely on a 722.118 transmission that they will be worn or wearing.

More information about this problem is contained in this thread http://www.peachparts.com/shopforum/showthread.php?t=299729.

Don't loose the shims that sit between the sun gear on the front sun and planet assembly. These are luckily a different size from the other shims in the gear box but just to be sure keep them safe and label them clearly.

Pull out the sun cog from the “top” of the B1 brake drum.

From now on you'll see a what will be familiar method of holding bits together. Most of the gear set is held together with spring rings that fit in grooves. If like me you are being bad and using screw drivers for a purpose for which they were not designed (!) please be careful not to knacker anything.

Take your time removing these bits; you don't want to bend them out of shape – heaven only knows if you can buy new ones... don't refit these spring rings if they are bowed or distorted as that will mess up the clearances that you need to check later on. The chances of this are probably small, but if you are unsure check them on a flat surface. Ideally you need a surface plate or a surface table. Not all DIY mechanics have these so at a push you can test for flatness on a modern sheet of glass. If you detect any signs of distortion “on glass” you may have to visit someone who's got a surface plate (machine shop) or attempt to buy new spring rings...

When you've removed the spring ring you can start to dismantle the K1 clutch.

Stretch · #18 09-09-2011, 04:57 AM

Remove the B1 brake drum and set to one side – we'll be coming back to that in a bit.

Remove a bearing race from the intermediate shaft...

...and the oil supply tubes to the K1 and K2 pistons.

Tip the gear set onto its side and remove the spring ring and withdraw the intermediate shaft. Jealously guard any shims that you find on the intermediate shaft.

Tip the gear set back up on its end as you had it previously and clamp the B2 drum as shown in the picture below to release the pressure on the spring ring. Remove the spring ring in the “top” of the B2 brake drum to get to the K2 clutch pack.

Stretch · #19 09-09-2011, 04:57 AM

When you have removed the cover for the K2 clutch pack you'll find several return pressure springs.

I don't think it really really matters exactly where the springs go – they need to be grouped into three large groups and evenly spaced around the circumference of the brake drum. Even so I stuck a bit of paper around the outside of the drum and marked the positions of the springs.

I also marked the position of the teeth of the end cap (shown by the circles drawn on the paper in the photo above) but that turns out not to be necessary as it only fits one way.

Take out the k2 clutch pack...

...and the free wheel which attached to the hollow shaft.

I didn't take this to bits. I chickened out.

Stretch · #20 09-09-2011, 04:58 AM

The K1 and K2 clutch packs are pretty similar in the way that they consist of a set of steel plates and a set of friction discs. The combined thickness of these parts that make up the clutch pack needs to be correct for your transmission. Don't swap and change these bits between different gearboxes and then expect the clearance to be good when you come to reassemble.

I couldn't see any “real” wear marks on the steel plates in either of the clutch packs in my gearbox. I guess this indicates that the recorded mileage of 100,000 is more or less correct – matching numbers blah blah blah...

The ATSG manual states that any clutch parts that show badly burnt spots, distortion, or wear should be replaced.

The thickness of my used friction discs is shown here...

...and the thickness of the new here.

The difference in thickness (0.03mm) between new and old (that I have measured) on both clutch packs and all friction discs was the same. From the information I have available about my car it seems as though this wear is evident after about 100,000 miles of use. It is difficult to say for sure that friction discs wear of 0.03mm is equivalent to 100,000 miles of use but this suggests to me that if you are experiencing K1 or K2 clutch related problems it is less likely to be because of wear on the friction discs. I would start by looking at the K1 / K2 actuating system even though this observation does not rule out the situation of burnt out or damaged by foreign bodies friction plate clutch problems.

Please note according to the ATSG manual the friction discs are considered to be worn when they are less than 2mm thick.

I decided to change the friction discs anyway as I'd gotten this far. The cost of new friction discs was surprisingly low – about 7 Euros each (price good for the date of this post).

Before you fit new friction discs soak them in clean ATF for at least an hour before fitting them. I was told the longer the better so I left them soaking over night.

If you are re-fitting old ones (arguably not a smart move) make sure at the very least you have cleaned them and re-soaked in clean ATF. Any muck that you leave inside the gearbox could eventually find its way to the valve body. If (hopefully when) you take the valve body to bits you begin to understand why Mercedes recommends that you only clean the filter housing and you wipe your transmission dip stick on rare breed super soft hunted by Zulus chamois leather...

Stretch · #21 09-09-2011, 04:59 AM

Easy – just put it back in the same order you took it out!

Make sure you've got the correct order of friction discs and steel plates. Also make sure you buy new friction discs from a supplier who needs your chassis number to make sure you get the correct friction discs. The ATSG manual does state that some parts are not compatible – apparently there was a change in design. For more information see page 79 (in the ATSG manual).

The cover for the clutch pack – which is actually a piston – has two seals that should be replaced. It is easy pulling the two parts of this piston assembly apart but it is pretty difficult getting them to go back together once you've fitted the seal.

Note the position of the lip of the old seal before you remove it for replacement. You'll notice that it goes in a direction that makes it especially difficult to get the two parts back together.

I don't have any snazzy tricks for getting this stubborn bit back together other than to use lots of ATF to lubricate it; and to take your time. Do not force the seal. Do not try and push it in with a sharp object such as a thin screwdriver. You will probably rip the seal or worse damage the piston assembly.

The ATSG manual states that the circlip used in the “bottom” of the B2 brake drum is different in diesel engine gearboxes (such as the 722.118) than the petrol engine gearboxes. The diesel gearboxes have a rigid circlip; the petrol gearboxes an undulated. If you are chopping and changing parts you might come a cropper – so watch out.

Before you reassemble the return pressure springs in the B2 brake drum you need to check the clearance of the K2 clutch pack. This needs to be between 0.7mm and 1.2mm.

Place the clutch pack in the B2 drake drum and measure the depth (with your depth gauge) from the “top” of the B2 brake drum to the “top” solid plate in the clutch pack...

...make a note of this measurement and call it “measurement A”. Then measure the thickness of the K2 clutch piston assembly...

...make a note of it and call it “measurement B”. Then place the K2 piston assembly in position and measure from the “top” of the B2 brake drum to the “top” of the K2 piston assembly...

...make a note of this measurement and call it “measurement C”.

The clearance is A – B – C This value should be between 0.8mm and 1.2mm – and can be visualised as the gap between the “bottom” of the K2 piston assembly and the “top” of the K2 clutch pack.

Adjustment of the clearance is made by introducing different steel clutch plates with different thickness’s.

Please note:- the information shown above is the clearance for a 722.118 K2 clutch =>

From the information in the ATSG manual other transmissions look somewhat different. If you know that other transmissions are different please let me know as this chapter in the ATSG manual just looks confused and not in the correct order to me.

Fit the return springs on the pins positioned around the inner circumference of the B2 brake drum. I decided to fit them back in their original positions although the ATSG manual says to distribute uniformly. I'm in no position to recommend one way or the other so it is up to you to choose what you want to do.

Place the K2 piston assembly on top of the return springs and push it into position with the help of a woodworking clamp. Please note the K2 piston assembly only fits on one way. Compress the woodworking clamp so that you can fit the circlip ring in position.

Stretch · #22 09-09-2011, 04:59 AM

This last bit of the K1 clutch assembly is the return spring mechanism.

The circular cap that covers a set of 25 springs in the “bottom” of the K1 clutch assembly is held in place by a wire circlip. To remove the circlip it is necessary to push the cap and compress the springs with clamps...

...there is a special tool for this but it is easy to replicate it with some wood and three woodworking clamps. I used four blocks to push down onto the cap as with three it seemed as though the cap would bend out of shape. Here's a picture showing how my springs were distributed.

With the wire circlip removed and the spring pressure released you can gain access to two seals buried within. Here is the big one – sorry the picture shows the actuating piston in an upside down position...

...and the small one.

Stretch · #23 09-09-2011, 05:00 AM

Replace the seals shown in the two pictures above. Note which way round they go. I found the best way of getting the actuating piston back into the B1 brake drum was to get hold a glossy magazine and fit it as shown.

Oil up the magazine with ATF and you'll have a much easier time pushing the piston into position. Make sure that you can pull the magazine out of the actuating piston – do not leave any paper in there.

Position the return pressure springs and clamp back down the cap so you can refit the wire circlip.

Fit the steel stator and friction rotor disks finishing with the “top” cover. Fit the big circlip ring.

To measure the clearance of the K1 clutch pack use a depth gauge to measure from the “top” of the B1 brake drum to the “top” cover when the clutch pack is in a lightly compressed state – just push down until you feel the resistance of the return pressure springs. Call this measurement “A”. Repeat this measurement when the clutch pack is uncompressed. Call this measurement “B”. The clearance is calculated as A – B and it should be between 0.8mm and 1.2mm. As for the K2 clutch pack the clearance can only be adjusted by adding or removing steel plates of different thickness's.

Stretch · #24 09-09-2011, 05:00 AM

Inside the B3 brake drum you can find the front planet assembly. If the splines are worn you might want to take a look at this thread for the solution I came up with http://www.peachparts.com/shopforum/showthread.php?t=299729.

There are no seals to be replaced in the B3 brake drum.

Stretch · #25 09-09-2011, 05:01 AM

If you are a professional transmission re-builder you will probably have a dedicated transmission stand for this bit. As a DIY mechanic you will have to make do with a clean work surface and a roll of tape.

As DIY mechanic set a roll of tape on your clean work surface and then position the intermediate shaft on top of it. If you had a dedicated stand you could assemble the output shaft and the intermediate shaft (with the two sets of bearings!) in one go. Without the stand it is a bit awkward...

Next slide the assembled B2 brake drum (with the hollow shaft) on to the intermediate shaft. Make sure you've not forgotten the bearing or the shims that were previously fitted to the intermediate shaft...

...you don't really need the roll of tape just yet – you just need to position it later on to push the intermediate shaft high enough through the gear set (and up inside the B2 brake drum).

Slide on the K1 and K2 clutch oil feeder assembly.

Replace the four rubber grommet like seals that fit on each end of the connectors that run from the K1 and K2 clutch oil feeder assembly to the valve body. I'm in two minds whether to say fit this now or not. On the one hand the copper clamps that hold these connection pipes in place are much easier to manipulate when you haven't fitted the B1 brake drum yet; however, on the other hand these connection pipes tend to get in the way of installing the assembled gear set into the main casing...

Continuing with the assembly; fit the re-assembled B1 brake drum...

...and fit the roller bearing.

Stretch · #26 09-09-2011, 05:02 AM

Remove the B3 brake drum from the centre planetary assembly if you have not already done so.

Fit the sun gear onto the intermediate shaft.

Measure dimension “a” from the top of the centre sun and planet assembly (the planet part which is going to be fitted into the B3 brake drum) to where the thrust washer will be fitted.

ATSG recommends that you position the thrust washer prior to making this measurement. I found these measurements to be pretty tricky mainly because the foot on my depth gauge was too wide... in my work around I found that the thrust washer got in the way. I'll continue the explanation as though I used the correct tools! Here's a photo showing it again to make it as clear as possible.

Next measure “b” from the top of the centre sun and planet assembly to the shoulder of assembly that goes over the hollow shaft.

Calculate value “c” by subtracting “b” from “a” (c = a-b).

Next measure “d” by measuring from the upper surface of the sun gear to the shoulder of the hollow shaft (that encases the intermediate shaft)

Calculate end play S by subtracting “d” from “c” (S=c-d). The end play on this side of the sun and planet system should be between 0.2 and 0.3mm.

To adjust the end play you need to change the shims. Once you are sure that the end play is correct use a bit of grease to hold it in place and fit the planetary part without the B1 brake drum onto the rest of the gear set.

Now you need to measure the clearance on the other side.

This is where a dedicated transmission stand would be handy - due to budget restrictions I placed a roll of tape under the gear set to push the intermediate shaft into position.

If you have a small foot on your depth gauge you will be able to measure the distance “a” from the top of the intermediate shaft to the shoulder on the intermediate shaft.

Measure “b” from the top of the intermediate shaft to the top of the thrust washer.

This second clearance is calculated by subtracting “a” from “b” (S=b-a).

Again this value should be between 0.2 and 0.3mm. This clearance is adjusted by shims.

I had a bit of a nightmare checking these clearance values – partly because my depth gauge was a bit too big and chunky for the job. I found it very easy to convince myself that the Mercedes technician who had built the transmission was obviously a daft monkey and that I needed several 10mm thick shims to get the clearance anyway near to the ball park figure.

Unsurprisingly this turned out to be utter nonsense.

If you think you need a shim bigger than 0.1mm I would check your measurements again and again... think about it... it probably isn't going to wear that much if anything at all... if the clearance was set that badly from new the transmission wouldn't have made it once round the block...

Stretch · #27 09-09-2011, 05:02 AM

After you have satisfied yourself that the clearances on both sides of the planetary part of the centre sun and planet assembly are correct, remove the planetary part of the assembly and refit it with the B1 brake drum. Even though you have been gluing the thrust washers and shims in place with grease (as described above) make sure that the thrust washer is positioned correctly.

Fit the large locking ring and the circlip on the end of the intermediate shaft

You might have to jiggle the bits about a bit to get these bits to fit.

Leave the gear set assembly at this stage – so don't fit the input shaft just yet. There is one more gear set clearance to check when the gear set is back in the main case, but as this measurement needs to be made with the tail cone section of the transmission in place, it is best to carry on with the other bits that need to be dealt with first.

Taking the governor to bits and putting it back together again

All I did for this bit was to take it to bits – clean it – check for damage / wear – reassemble.

If the rings look worn you need to unclip them from their grooves.

Stretch · #28 09-09-2011, 05:03 AM

At the very least make sure you've cleaned the inside of the casing. Make sure that the gasket sealing surfaces are clean.

Remove clean and replace the small parts that fit in the casing

If you are replacing the output shaft bearing; fit the new one in place by tapping on the outer part of the bearing race with a copper punch. When the bearing is seated fit the circlip. Fit the output shaft seal.

Refit the speedometer drive, the secondary pump cam, and the governor.

Fit the secondary pump piston and make sure you align the hole for the securing bolt correctly.

Do not fit the secondary pump spring and cap just yet.

Stretch · #29 09-09-2011, 05:03 AM

Again the inside of the casing must be clean clean clean. The mating surfaces of the casing must also be clean and ready for the new gaskets.

Clean up the modulating pressure housing. Check it for wear before you put it back together.

Place a new gasket on the rear end of the centre casing and fit the modulating pressure housing in position whilst making sure that the new gasket is suitably aligned; so that when you come to fit the tail cone section you're not going to have any trouble pushing the mounting bolts through.

Fit the seals for the static brake band stays and if you haven't done so already the seal for gear selector input shaft...

...and the seal on the B2 piston housing.

Stretch · #30 09-09-2011, 05:04 AM

Fit the static brake band stays from the inside of the centre casing – lubricate so that they slide nicely into the new seals...

…and fit the retaining clip to hold them in place.

Fit the parking pawl and the gear shift selector if you have not already done so

Here's a picture of the centre casing ready for the gear set.

Please note the plastic holder for the gear set should NOT be fitted now – I was just playing about psyching myself up for it! (This picture will be revisited in a bit)