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Transmission Rebuild, 6.9

Started by TJ 450, 03 January 2009, 07:56 AM

TJ 450

Indeed, although I did in fact test some, just not all of the of the servos properly. ;)

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

koan

That's good news and its good to know getting the box out is easier the second time.

What was the problem with the clutch?

Fill us in on the compressed air testing procedure and what went astray with it.

koan 
Boogity, Boogity, Boogity, Amen!

s class

Awesome dude - I saw your postings over at M100 and I could feel your pain. 

I'm glad to hear the tranny can come out the bottom - I was going to ask that because the Webasto block heater project car has a leak second to none at the radial seal where the torque converter meets the tranny. 


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

TJ 450

Yep, that was me posting on the M100 site. In the end, there was a fault with the valve body, but it didn't change the operation of the trans at all.

The most difficult part of removing the trans in that way is removing and reinstalling the exhaust system. As long as the car is supported on jack stands so the huge bellhousing will clear the floorpan, it's not particularly difficult.

After unbolting the torque converter (three pairs of bolts), the trans only has to be moved back a couple of inches and it can be lowered directly downwards.

The front shaft seal can be replaced in situ, but the front pump o-ring requires removing the bellhousing to unbolt the pump from the rear. It's all very straightforward when the transmission is removed.

The problem with the clutch was that the 6.9 version piston is smaller and the flange that it fits into is modified accordingly. The original flange out of my 6.9's transmission was all chewed out where yet another bearing had failed, so I swapped it with the 450 version. Even though the manual states that the 6.9 version's hollow shaft and intermediate shaft is longer, it was not the case here. The difference was in the piston and I wasn't aware of this.

The manual doesn't mention any testing procedure for the clutches, but it is done by attaching an air hose to the two fluid ports on the gear assembly, that lead to the valve body, one at a time. Applying a very small amount of pressure should activate each clutch and it can be clearly heard and seen if they are functioning properly.
In my case, there was no resistance and air just passed straight through the port for K2. K1 was pressurising and activating.

I used one of the fluid pipes from my spare 450 trans parts, with the rubber seal on the end attached to a hand pump with a rubber hose. I used a hose clamp on each end to make it airtight. It was then just a matter of pressing the end firmly in the fitting and using the pump to pressurise the clutches. The pump with this fitting can then be used to test each of the servos through the ports into the casing when the valve body is removed.

The servos are tested in the same way. Servo B2 has two ports to test with. One is for lift, one is for shift position. The port for lift position will move the piston outwards. The port for shift position will move the piston inwards tightening the band. If it doesn't move at all, then there is a problem that must be fixed as in my case.

Servo B1 only has one testing port, for shift position. It is held in lift position by its spring.

Servo B3 similarly has a spring and can only be held in shift position through its port. If it doesn't move it has a leak.

Unfortunately, I didn't take any pics of the testing procedure, although I still have the testing apparatus and can demonstrate which ports are which with the spare 722.004 casing and oil feeding sleeve. I'll get something organised.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

TJ 450

Here's a pic of the engine bay now. There's still a lot of detailing and small things that need to be attended to.
I also need to sort out the fuel system and get the rest of the car functioniong as it should. The engine is quite sluggish and cold start enrichment is non existant. It's a real step backwards in that regard, as there was no problem before with cold starting.
The suspension is behaving itself nicely and so far I'm impressed.


Here's the vid:
http://www.youtube.com/watch?v=ifBzO_VU-Cw

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500