Restoration Difficulty Level

[andyburns]

I ended up making a new tool for getting the nut off.  Measure it up and determined I needed a 37mm OD socket.  Figured that a 29mm ID socket would be about perfect so trundled off down to the local auto shop with my calipers.  Discovered that they only had 28 and 30.  Neither would work so I went through all the imperial until I found a perfect size.  I got it all the way home to discover that the shaft bottomed out in the socket before I had even contemplated cutting the notches.  This would only make matters worse.  So back in the car and swore at myself all the way back to the shop.  If your going to make one of these make sure it starts off as a long reach socket.

Only took 20 minutes to cut the new tool out of the socket with an angle grinder and a hand file.  On the end of the impact driver and with a few second the nut came off closely followed by the back plate.  I popped the old seals out and as expected it was also, like the front seal, in pretty damned fine condition.

Spent another 20 or so minutes on the wire brush prepping the body for paint.  Will probably do this tomorrow.  Took all the bits I had taken off down to the blaster.

[andyburns]

Now all I need to do prior to assembly is sort out the change arm seal and the speedo worm drive spindle seal.  Both have me a bit flummoxed at the present.

I cant seem to figure out how either come out.   Nothing in the BBB eludes to it either.  If anyone cant steer me in the right direction with either of these I would be most grateful.

[mbzse]

.../...the speedo worm drive spindle seal..../...I cant seem to figure out how either come out../...

Among other postings you may find with the "search" function, our very own M-B Doctor (DanC) as well as George Davis have written these useful guidelines:
http://www.sl113.org/forums/index.php?topic=6182.msg38737;topicseen#msg38737
/Hans in Sweden
.

[andyburns]

Thanks Hans,  that is a very helpful post.  Thanks to Dan as well for putting that up.    I am pretty bad at picking the correct words for searching on I guess.   Or just really buggered and grumpy after working all day with a bad back on stuff I dont really understand. 

So sincerely thanks for your help,  even these small tip bits are really really useful to me and keep my spirits up.  I am incredibly out of my comfort zone with the mechanicals on these old girls so a pat on the back and a steer in the right direction comes as a breath of fresh air from time to time.   Hopefully the daily posts have a least some entertainment value to you.

[andyburns]

Hans, any tips on search words for that top seal.  I tried 'gear change rod seal' and didn't get far. 

I am a bit worried about the speedo seal after reading the post you found.  Sounds as if its a mongrel to get out unless you have special gear.  My battery drill probably isn't going to cut the mustard!

[GGR]

You should measure the clearance between the syncros and the pinions with gages. I don't remember what is the lowest acceptable clearance. But basically, the less clearance you have, the earlier the syncros are going to fail. If you can't engage any shim while pushing the syncro onto the pinion, then the syncro is shot.

[DaveB]

Hi Andy,

The shifting shaft 'radial sealing ring' is listed as 006503 04100 (A14 x 26 DIN 6503). I can't see the speedo drive shaft seal listed as a separate part in the book.
But why replace them if they're not leaking?

Interesting that the top case is a 198 (300SL) part.

[andyburns]

Hi Dave, thanks for the part numbers.  I have a complete seal kit for the box including these seals.  I started off just wanting to reseal the front and back main seal but as I have discovered you have to take apart quite a bit of the box to get to these.  So lucky the kit came with all the paper gaskets.  I honestly dont know if it was leaking or not.  If you go right back to my initial post in this thread a year or so ago I had the delema of not knowing if all the muck in the bell housing was from the transmission or the engine.  The engine and the gearbox were dirty so I had a bit of a delema on my hands.  The diff leaked on the concrete and also two separate puddles under the bell housing area.  Given that the box is out it just seemed prudent to do as much of a careful reseal job as I could.  Trust me, if I put it all back together and it still belches oil I will loose sleep.  Another member in here has pointed out that the speedo shaft seals also give problems.  Makes sense as its quite low down the housing and would get saturated with oil.  Not so worried about the top shift shaft seal as it has gravity on its side.  But if I can get to it I may as well.  The devil you know as they say.

[andyburns]

Was looking forward to putting the gearbox back together this afternoon... but it just wasn't to be.

I phoned ahead to the electroplaters to make sure the nuts and bolts were ready.  'Sitting on my desk'.  When I got there, 30 minute drive, discovered the reception lady had mistaken my job with another and mine hadn't in fact even be started.  Off to a good start.

Last night I took the new gearbox speedo shaft seal to bed and pondered for a couple of hours how I could get it out of the casting without doing any damage.  After studying the seal and the casting I discovered that there is a quite a pronounced steel lip on the front of the seal.  You cant get a screwdriver through and on it due to angles not working in your favor through the pins shaft which has a narrower OD by about 4mm. 

I thought about pushing something in that might turn and then lock on the lip and then knock it onto the lip with a bolt.  Then I came up with the idea of a dynabolt.  The only reason I thought of this is that I am currently involved in another project at home bolting down some large gate posts to concrete pads.

The dynabolt would have to be smaller than the pin which is about 8.75mm.  The pin spins freely in the shaft so the shaft is probably about 9mm at a guess.  The dynabolt needs to also be 80mm long to reach through the ali housing.  I initially thought that there would be no way of obtaining such a long bolt given such a small diameter.  I was pleasantly surprised this afternoon when I stopped at the hardware store to find a 8mm x 95mm bolt.  Absolutely perfect.

Before I started the removal process I used a screwdriver to grind out all the rubber over the lip to give the dynabolt tip maximum surface area to rest on.  The bolt slid in and I only had to do the bolt up by hand until I could feel it sitting on the lip of the seal.  The bolt was still not even tight enough to prevent it from being slid back in the seal.  I was a bit worried if I did it up tightly that it might do some damage.  Also if you cranked it up it would only increase the friction between the seal and the housing.

A few taps on the head of the dynabolt and the seal just popped out.  I was over the moon... until I inspected the housing.  Inside it I found a crack which I followed all the was back out and back along the exterior.  I was gutted to say the least.  I couldn't figure out how I had done it as I hadn't used any force but just assumed that the light knocking of the seal with the hammer must have loaded it up and done the damage. 

The rest of the afternoon has been terrible.  I priced a new housing at 400USD and then got on the phone and rang around my second hand sources.  Kev at startech went down to his stash of complete boxes and one at a time replied with, damaged,  broken house, rooted.  He has about 8 boxes and all bar two of them had the same type of damage in the same place.  Kev told me that most of them just had huge chunks of the sheath the cable get clamped into sheared off.  It must be a weak spot of the box.  Am picking that people over tighten the clamp and the housing just gives way.

Anyway I have another one which was a huge relief.  Still going to cost me a couple of hundy for the box.  My mood got much better after this news.  At least I can obtain it tomorrow and get on with the job.

It wasn't until about half an hour ago when I was reviewing my photos that I looked carefully at the very first photo I took with the dynabolt lying on the casing.  If you look carefully you can see the external crack.  I feel sooooo much better that my method of removal didn't cause the damage.  I was really happy with the technique and the second I thought it had damaged the casting I lost all of my mojo.

So the day hasn't been a total write off.  I have even wondered if I should just slam the new seal back in and use heaps of sealant to prevent any seeping.  But after thinking about it the crack could totally give way leaving the seal useless and also the cable then couldn't be clamped up properly so best I just persevere and fix the problem properly.

[WRe]

Hi Andy,
I would repair this crack with plastic metal with aluminium, e.g. from Weicon ( www.weicon.com/pages/en/products/adhesive/2c-adhesive/plastic-metal.php). For small repairs as repair stick. It gets hard like steel. Just open the crack a bit and fill it in. It's cheap and it works very well.
...Wolfgang

Video: http://www.classic-car.tv/know-how/werkstatt-gussmetall-reparaturen/

[andyburns]

Hi Wolfgang.  Thanks for that suggestion.  I thought of repairing it yesterday.  Its always an option if the new plate is flawed as well. 

If I did repair I would probably grind carefully 3/4 through the wall thickness from the outside and then get it properly tig welded.  I would elect to add additional material to the outside shell as well to strengthen it.  But the crack on the inside is what worries me.  It would be difficult to get a tig rod, or the paste you have suggested, in as its such a confined area.  Even if you could you would then have to machine back the surface perfectly as its the mating seal surface.  If I leave the inside and only deal with the outside then I would guarantee that oil would track down the crack on the inside and seap. 

Just heard back from the classic center this morning.  The part is NLA.  Given I have access to a good undamaged second hand part for a couple of hundy,  I would be crazy not to take up the offer I think.  A proper repair would far exceed this cost.

Am heading through this morning to pick up the box and the plated nuts and bolts.  I have agreed with Kev I will strip his box down for him and clean up all the parts in exchange for keeping the price of the plate down.  So have another full 'gear box' day ahead of me.

[andyburns]

Picked up the new box and plated nuts and bots.  Stripped new box and extracted the backing plate.  Made quick work of getting the seal out with a new dynabolt.  The one I used yesterday was not usable again.  The tangs get bent and wont seat that well again.   The new seal sailed back in with no issue.   The front seal sailed back in with no issue.  Then I tried to knock the pin back through the gear.  Big mistake.  The tolerance between the two is very tight and it take a massive amount of pounding to push the pin through.  I ended up knocking the pin right through and staring again.  This time heating the gear with a heat gun until it was probably a couple of hundred C.  This made the job much much easier.   Not doing this cost me at least an hour of grief.

I managed to get the pin back to within .01 of a mm from when it came out.  I then took the plate and checked everything was ok by installing the cable up to ensure everything was the right length and seated correctly. 

Trying to figure out what the numbers are on my box and if its the original unit that shipped from the factory.  On the input shaft of the box there are some numbers that are hand engraved on a polished surface.  They don't correspond with any of the numbers on my dog tags.  Does anyone know what they are and the significance.

Tomorrow I will  torque everything back up and move onto the engine. 

[andyburns]

I couldn't sleep last night so got up at 3am and went out into the garage to start the install.  I have hit a few issues.  The first was getting the shims to sit in the recess in the alloy for long enough to bolt everything up.  The are very light and on one of the shaft there are 5 of them that have to be perfectly stacked.  If one slips off the stack your starting again.  In the end I sandwiched them against the alloy housing with some very thin plastic and then just slipped out the plastic when everything was lined up and bolted in.  Worked a treat.  The run up to figuring out how to do this cost me two hours of frustration.

The top plate was no issue.  I did lightly lubricate the shift mechanism as it had gone quite stiff after I clean it thoroughly washing off all traces of it former lubrication.

Then onto the front plate and bell housing.  The steel front plate has a recess cut into it for the front main seal.  You have to take the plate off to get access to the seal.  Essentially its an internal component which is a bit of a bugger from a maintenance perspective.

Anyway the seal seems to seat with the lip facing outwards which to me seems unusual.  I have deduced this from the tell marks on the shaft and the approximate position of the plate.

The problem is how do you knock the seal in with the lip facing you?  I am guessing you have to have a tool which has a ID and OD exactly the same size as the seals.  Has anyone done this that can steer me in the right direction.  I really dont want to bugger the seal at this point as it would put me back considerably until I sourced a new seal.

[andyburns]

HELP ME RHONDA... or at least JA, Stick or Dr Benz or any other gearbox expert

Gearbox is turning into a complete nightmare and I am stressing big time.

Other than the issue outlined below I now have another much more worrying problem.  I went to do up the grooved nut on the rear output shaft to around 130nm.  Even when I tighten this nut by hand its seem to be loading up the bearings to the point where its barely possible to turn the shafts.  Loosen the nut and its all good again.  Something is wrong.  I am 100% certain that I did everything up in exactly the reverse order so just can understand whats going on.  The box is completely dry which wont help things but I would have still expected it to turn freely.

Only having 3 hours sleep last night hasn't helped matters.  I would really appreciate some help here.  *current status Sinking rather than swimming* 

[GGR]

All parts can't be machined with exactly the same clearance all along production, this is why the shims are there to fine tune clearances. The housing you replaced mat have tighter clearances and may require less shims. Try removing a few and see how it goes. Axial play needs to be according to specs but for sure binding means you don't have enough clearance.

[andyburns]

Hey GGR thanks for your reply, much much appreciated.

Will obliterate the paper gasket getting it all apart I suppose.   Guess I will have to somehow make one or buy another entire set.

I dont quite understand why the shims would have a bearing on things.  Do they slide the shaft one way or another in the casing?  The grooved nut seem to tighten down on the brass worm drive which in turn clamps down on the inner race of the bearing.  It seems that no matter how many shims you would either take away or add the nut would always be able to be tightened and load up the bearing.   What am I missing.    What stops the nut from exerting a **** load of force on the bearing.  Does it hit a shoulder on the shaft?

If the clearance is too tight and the shims determined it wouldn't I add them rather than take them away?  

Should I try the shims that came with the new housing?  If the only thing that determines the number of shims is the housing then this might be logical.

[GGR]

My experience is with the later side shift models. Though similar, they may not be the same, so I guess you'd better hear from people with direct experience with these trans. Don't take your housing off before diagnosing properly what's going on, especially if you fear to tear the gasket apart. Is the front cover/bellhousing in place? If not try fitting it, it may put pressure on the other side and help a bit.

[andyburns]

GGR,

I had exactly the same thought when I first struck the problem.  I have now clamped up the bell housing but havn't put in the front boss as I havn't managed to get the seal in (the other problem).  Perhaps this is required to exert the correct and opposite force.  Will this potentially move the shaft backward in relation to the position of the bearing and provide the extra clearance?

I suppose I can try bolting on the boss without the seal to see if its the problem.  Perhaps your on to something.  Will try it and report back.  In the mean time have you got any idea how I can get that seal in without stuffing it.

Cheers

Andy

[andyburns]

GGR,  that didn't work either.    Running out of easy solutions.  Either the shims are the problem or I have done something to the box accidentally while it was apart.

[GGR]

Can you loosen the back housing a bit to see if there is any improvement?

[andyburns]

I can loosen the back housing but it will definitely pull apart the paper seal.   I am wondering how much of an impact it has having a completely dry box?   

[andyburns]

Went out and decided to half fill the box with ATF to see if the extra lubrication made any difference.  It did a little but the lock up issue still present.  Festered around for over an hour trying to free it up and then out of frustration decided to wack the end of the input shaft with a brass drift.  Immediate result.  Knocked the back shaft and then the front shaft a couple more times to settle whatever problem was present.   Seems much much better.  Still some resistance through the box.  Can spin it in any gear with two fingers but definitely feel some resistance.  I just have to figure out if this is normal/acceptable.  The old box with the rear plate off spins with much less effort.  Dont know enough about the workings to know what to expect

Just need to figure out how to get this front seal in.   In the absence of any suggestion here I am going to try and head the boss and put the seal in the freezer overnight.  A bit of a long shot but will give it a crack and hope it will go in with just finger pressure.  Feel free to chime in if you have successfully done this before.

[tel76]

Andy,
I would suggest that you are trying to fit the seal the wrong way around, just because it came off that way does not make it correct, the previous mechanic could have fitted it incorrectly.

[andyburns]

Hey Eric,  that was my first thought as well but the machined surface where the seal runs is only 4-5mm wide before the shaft tapers off toward the engine.  If you installed it the other way around it would be running way off where it should on part of the shaft thats considerably narrower. Also I have stripped the front plate off the second gearbox and its seal has been installed in exactly the same orientation.

I have actually just had a good friend of mine around this evening to give me his opinion.  He is a factory trained Mercedes mechanic who did his time in the 70 and 80's.  Even though he is not a expert on gearboxes he certainly has a much better feel for them than I have and I really respect his opinion on these types of issues.

First up he addressed my concern that the box had more overall internal resistance than the second hand one.   His opinion is that it feels almost perfect and pointed out that it could be a cumulative combination of new seals, a lack of lubrication and unsettled gears could well be contributing to the difference.   He chuckled when I told him about my fix for the binding rear nut ie the mallet belting the input shaft.  He told me  that it wasn't the first time he had seen such tactics used to good effect in his time and that more than likely the shaft had been somehow moved on the bearing and need a bit of gentle persuasion to move ti back to where it wanted to be.  More than likely after its in the car for a while it would free up considerably.  Fingers crossed.

He also agreed with me that the seal goes in the weird orientation.   I am going to try and get the seal out from the second box and use it as a tool to drive the new seal in with.  Eric have you overhauled one of these before.   If you are 100% certain its around the wrong way I will investigate again tomorrow morning.  I am open to all suggestions.  Take a look at the screen shot below of the parts breakdown.

So the good news is that I am certainly in a better space than 12 hours ago.  Really dont want to linger on the gearbox any longer.  Its been a week now.

[Tomnistuff]

In my 34 years of automotive engineering, I have never seen a seal that did not have the small end of the rubber seal cone in the direction of the oil that was intended to be retained in the reservoir.  That normally means that the flat metal part of the seal is opposite the retained oil reservoir (gearbox).  In this case, what makes the installation difficult is that the seal is not installed in the transmission case, where the oil is, but in the end cover.  The way you show it is, in my opinion, exactly correct.  Installation should require a really thin wall tube or, better yet, the old seal with the rubber removed, butted up against the new seal outer diameter end.

Andy, please remember your front steering idler arm seal installation.  The BBB described the reason for the direction of its installation.  It was installed so that the grease could escape if too much grease caused the pressure in the "idler arm shaft housing" to get too high as the shaft screwed itself back and forth in the housing.  Installing it in the opposite direction would have trapped the pressure in the housing and caused the seal to rupture (like mine had).

In your transmission situation, there must be something other than the seal that is not right.  Trust your instincts and keep looking.

By the way, your experience has convinced me to leave my gearbox alone and live with the occasional weak synchronizer.

Good luck.

Tom Kizer