Rebuilt my own 722.6

[DieselPete]

After having shift flare from 3-4 and changing the conductor plate and seal conector on the trans i got fed up and decided to pull the transmission out and hopefully find out whats going on. Its a 2000 ml 270 thats not worth alot so im not going to get a gearbox company to sort it as it would cost way to much. Taking the transmission out is very easy they are quite nice to work on and once out i stripped the transmission and couldnt find much wrong if im honest, conserdering its done 110,000mls all the clutch plates where in speck so i orderd a seal kit and the k1 and k2 sprags so i know it should be good for many more miles. I think my fault is definitely in the valve body now so thats off to a specialist on monday to be bench tested. I must say the 722.6 is a very nice trans to work on and a workshop manual is freely available on a google search. I have picks of the trans but i cant upload for some reason. Total cost for the rebuild is £250 including seals and bearings. After talking to gearbox wholesale parts suppliers it sounds like most parts never get replaced on a 722.6 rebuild so they only car seals and a few bearings for them! Il keep the page updated on progress but all being well should be back on the road Wednesday at the latest fingers crossed it should be back to normal

 

[DieselPete]

Here are a few photos, i wanted to do a bit of a step by step as iv never stripped an autobox before but it was really easy only the oil pump bush needs pressing in as its looks very delicate

 

[LTD]

I'll hold my hands up and admit that stripping anything like that is way beyond my skills.

Congratulations fella !

 

[DieselPete]

im not joking if you take your time, buy a decent socket and bit set from say halfords you could do this and save yourself a fortune. here is the parts break down, this is also where i got all my parts from. If anybody requires the shop manaul pls send me your e-mail and il send it to you its very good.

http://www.jpat.co.uk/60 Mercedes 2A 722.6.pdf

 

[KillerHERTZ]

Brilliant work, any more photos?

 

[DieselPete]

no sorry i just didnt have time im sorry, il try and get some tomoz as il finish the build tomorrow so i il take some more. just got to wait for the valve body, now and we will see if my idea of saving money has paid off

 

[noogieman]

722.636 trannies up to 1999 had problems with valvebodies, did MB update this part?

 

[neilrr]

I'll hold my hands up and admit that stripping anything like that is way beyond my skills.

I reckon just about anyone could strip one.

Putting it back together so it works is a different matter.

 

[Trickythemerc]

The most critical thing when rebuilding auto boxes is cleanliness,the smallest amount of contamination will cause havoc. Everything needs to go through a proper wash plant before you start to ensure all traces of old fluid,swarf etc are removed. For reassembly new fluid should be used for lubrication where required,never build them up dry.

Pay particular attention to seals and o-rings on the shafts,they need to be well seated in the grooves or they may get dislodged during assembly,this happened to a Borg Warner 35 that someone built for an XJ6. They stripped it twice and couldn't see any problems, I stripped it and found a very fine o-ring had pushed up inside one of the clutch servos.

 

[brucemillar]

im not joking if you take your time, buy a decent socket and bit set from say halfords you could do this and save yourself a fortune. here is the parts break down, this is also where i got all my parts from. If anybody requires the shop manaul pls send me your e-mail and il send it to you its very good.

http://www.jpat.co.uk/60 Mercedes 2A 722.6.pdf

I will hold my hands up to you here in salute.

I am great at taking things apart, usually when that was never the intention. The worst sound known to man is "beeeooing". I hear that sound a lot.

Cir-clips become aeronautical marvels in my garage. Small nuts and screws have mastered the art of camouflage to the point of stealth. My cars undertray has more tools lying on it than Harlfords on a Sale day.

To me a gear box is where miracles happen. Like a woman's vagina it looks good from the outside only.

 

[Druk]

Like a woman's vagina it looks good from the outside only.

Don't change the subject Bruce.

 

[Nasco12]

And to think Edd China won't touch the things (gearboxes not vaginas) with a bargepole.

 

[bob6600]

I used to do this for a living (not MB) so can appreciate the work involved especially for a first timer. Well done!

 

[french]

The Regulating Pressure Control Valve Spring has been a problem with these in the past, they snap about 3/4 way along ,then bind into the remains causing a slow change etc, but are different after 1999.
The Overlap control sleeves wear & can have scoring on this can cause judder & slow gear changing, some here instantly say TC, but this is worth checking 1st. I would buy a Sonnax overlap valve sleeve kit, the new kit has 'O' rings on that stop the ATfluid going around the sleeve & causing a pressure drop hence the slow change,judder & slip, while its out & a new conductor plate,pilot bush etc, & remember ,cleaner than a plastic surgeons table,
good luck.

Automatic Choice LTD. They are agents for Sonnax, Farrington Gurney & a branch in UK in Essex ?
https://www.automaticchoice.com/
HTH

 

[DieselPete]

ok i was back in the work shop today putting the finishing touches to the trans,


as you can see every pack of seals tells you whats its for this pack is for the b1/k1 clutch and piston. Some of the seal are only slighty different in size so you got to be careful the right one gets fitted.



you have to compress the pistons slighly to remove the snap rings i had to crack the welder up and make this tool using a bit of pipe the od as the piston to compress it



this piston i managed to get away with using some deep sockets and little ofcuts of alloy to get at the cerclip.



i aint got any "trans gel" so use lots of Vaseline to coat the o rings.

once the pistons back in use a airline to send pressure to check the piston pops out and retracts as it should



if you look in the middle you can just see a bearing this is a sprag bearing it should turn one way but not the other it should "lock to the clock".


well just the valve body to come back from test now and il let you all know if id do this again lol

 

[DieselPete]

just for reference as im not majorly clued up om Mercedes the error codes i got from my problem trans where as follows,

110 rpm comparison n2 to n3 implausible
147 gear implausible or transmission slipping
146 inadmissible transmission ratio

like i said with the original post it was fine when cold but when hot had a really bad flare from 3-4 would pop into neutral on steep hills or when really gunning it and would lock out as well, it was very annoying

 

[shorty]

I had an 2001 E 220 cdi did the same flaring between 3 n 4 when hot. I never did get it sorted, some said the clutches where worn but I always suspected the valve body.
Good work stripping the box yourself.

 

[Mrhanky]

Fantastic work and a great read.

 

[DieselPete]

Well got the valve block back from repair and 2 valves where apparently worn causing them to stick, i refitted the trans tonight, just the drop box and props to go on now and fingers crossed it should drive sweet as nut. Total cost of the valve block repair and test c/w new conductor plate was £320 so not to bad. Add this to the £250 for new bearings and seal kit for the transmission iv done a complete overhall for £570. Next post should after the test drive

 

[DieselPete]

One thing somone may be able to help me with there is a little rubber gromit/bush that the selector rod goes through on the side of thr trans does anybody know the OE part number pls?