Gearbox rebuild

[celberg]

Is it at all possible to rebuild the automatic gearbox yourself if you have never done it before or even been involved and seen someone else do it?

[daantjie]

Having not done this myself, I cannot say from personal experience, however I would say it is possible IF you have at least a moderate level of DIY skills and of course the correct tools and ample workspace to do this.  You can find the Mercedes transmission manual which does show a step a step, but this is one of those jobs which I think the saying "a gram of experience is worth more than a kilo of theory" comes to mind.

Very important is to work with absolute cleanliness in all aspects, as any dirt stuck in any part of the transmission will cause you heart ache once assembled.  Another topic is of course the availability of the parts you will need such as the clutch packs.  I think these were only ever available from Benz so they may be NLA (no longer available) so this would all be items you would have to check off BEFORE you tear the whole thing down

[raueda1]

Daniel may well be right, but I'd never attempt it.  I saw mine taken apart and it scared the bejesus out of me.

[Nabstud]

Agree with the above, definitely a job for a professional. Tolerances and cleanliness needs to be perfect, and knowing how to measure/check parts to make sure they are in spec is necessary. If you have a workshop manual and are confident of the above then go for it!!!

[raueda1]

A further consideration is parts.  My tranny guy had a very hard time finding some of them.  Some were sent to specialty rebuilders for refurbishment.  This was the case for the torque converter and one of the bands, I think.  I also had a junk yard spare unit that had some useful parts.  Maybe it's just me, but I find transmissions very intimidating.

[rumb]

I rebuilt a TH350 and it bled like a stuck pig forever.  That trans fluid comes from everywhere for a long time.  That's why rebuilders work on a metal table with a drain built in.

Over here we have Sun Valley Transmission that rebuilds MB trans only and they charge $1700.  Well worth it to know you get back a fully to spec and tested unit with a warranty.

[w123wrench]

I celebrate your audacity. I think anything is possible given the individual and the resources at hand.

That being said, I have thought about doing this and backed off. I have good mechanical skills (I've DIY a lot of things) but I backed off and brought my trans to Sun Valley for a rebuild. Too many little parts to forget. And too much work to unload and load it if I had to do it two or three times as I learned. Is it possible?  Of course.  Nothing on these cars is rocket science, but everything had a learning curve.

Everything I've successfully rebuilt or engineered I've understood well before tearing into it. I was uncomfortable tearing into the trans because I just don't know what half of the parts do.  That seems to be a big determinant of success in these rebuild projects for me.

Marc at Sun Valley showed me some of their tricks during the tour.  As they assemble, there are points to use air pressure to test each function of the hydraulics as you assemble.  This is how you make sure a piston doesn't leak or you remembered a particular check ball.  If you don't do this you are just flying blind till you load and drive.  The second thing he had was a dyno.  It was just an OM617 engine in a diy welded stand with a brake to test shifting and shift quality. With these steps they are way ahead of a diy mechanic who follows steps in a the manual that comes with a rebuild kit. 

There were videos I've seen of 722 rebuilds on YouTube.  The big thing that jumped out at me is it was a big mess. Oil everywhere.  You need a big table with a pan or a lot of rags.  I never had the room to do it systematically.

That being said I think it is possible depending on the YOU factor.  There is a manual that comes with the rebuild kit. I suggest getting one and thumbing through it. You can get them from the transmission parts suppliers who sell the kits. 

[floyd111]

The answer lies within your own daily environment. Go visit the 5 or 10 best car garages in your city and ask them about a gearbox fix. Ask them whether they do it themselves. I have never seen or heard any professional garage refurbishing gearboxes. They may not like to admit it or tell you, but boxes are always take out by garages and then shipped to gearbox specialists.
No doubt there may be an exception along the line, I just never have encountered such.
I visited a lot of  gearbox specialists. That is a proper profession.

[celberg]

Thank You all for Your answers. I thínk I try to get another gear box first. Then, when I see that it works as i should, I might try to build up the courage to rebuild the old gear box...

[daantjie]

It's a pity you are not in US (take that as you wish ) as Sun Valley in California is a great resource for an exchange unit.  Not sure if they would ship to you in Sweden and then the shipping cost would likely be astronomical.

[ptashek]

I've heard good things about this place, much closer to Sweden: https://www.goherrmanns.de/

[Taha]

Is there any online source to buy an overhaul kit for a 722-110 (280S) transmission? As much as I know most of the W114s, W115s and W123s with 4 and 6 cylinder engines have almost the same transmission. Thanks in advance.