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6.9 Transmission woes

Started by daantjie, 05 November 2014, 11:22 AM

TJ 450

If you really want to try adjusting it yourself by feel, you can turn the key in the modulator valve clockwise to firm up the pressure. Do it one notch at a time and test drive.

Only do this after you have made sure the pin is in place though.

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

daantjie

Daniel
1977 450 SEL 6.9 - Astralsilber

daantjie

OK here is a pic of my modulator, pulled it tonight.

Daniel
1977 450 SEL 6.9 - Astralsilber

TJ 450

As long as that pin is secure in there, all is fine. How did you go dialing up the spring pressure with the key?

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

daantjie

Thanks Tim.

Did not get back to it yesterday, will try and have another look see tonight.  Tempted to crank it up quite a bit to see if I can firm up the shift.  I did a half turn clockwise on the weekend, and it made no difference whatsoever.
Daniel
1977 450 SEL 6.9 - Astralsilber

daantjie

OK, so I pulled the Vacuum Modulator again tonight.  The steel pin is completely loose, I can pull it clean from the sleeve without any drama.

So, next step is Loctite that bugger in, and say a little prayer to the 722.003 gods :o
Daniel
1977 450 SEL 6.9 - Astralsilber

TJ 450

That could be an issue, try gluing it in then dialing up the spring tension with the key if you need to.

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

daantjie

Thanks Tim
Now seems like when I test pull vacuum, the pin does not move at all.
I can see movement down in the bore, around the sleeve where the pin sits in, but that pin housing itself does not seem to be moving under vacuum :o
Daniel
1977 450 SEL 6.9 - Astralsilber

daantjie

OK, I guess the modulator was already cranked up pretty high, thus the vacuum had pretty much no effect on diaphragm movement.

I turned the key way down, and I saw movement on the pin, though very slight.  I am guessing the movement of the pin under vacuum is not very noticeable?
Daniel
1977 450 SEL 6.9 - Astralsilber

daantjie

Hi guys

OK so I installed the new vacuum modulator last night, will take her out later today and she how we go.

Before I screwed it in, I took a snap of the hole where the modulator goes into.  Saw a funny type of bar inside the hole, I will attach pic.  Looked kinda out of place?

Daniel
1977 450 SEL 6.9 - Astralsilber

TJ 450

I'd say that's fine, but couldn't say for sure without seeing another trans for comparison.

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

daantjie

Thanks Tim

So the new vacuum modulator has made no difference, even after I cranked up the pressure with a few clockwise turns.

Ken (Koan) gave me the tip to check tha ball valve on the aux trans cooler.  So I pulled it last night, and indeed there is no spring or ball inside the check valve where the bypass line connects to the case :o

Guessing (hoping) this is part if not all of my problem :-\  Unless the previous dude who worked on it tried to "fix" some other issue at the time by omitting these parts?
Daniel
1977 450 SEL 6.9 - Astralsilber

daantjie

Guys, just to close the loop on this one, happy to report that I have managed to get my trans issue sorted (I hope permanently ;D)
With lots of help from various sources, talking me off the ledge and such, I managed to pull the valve body and take a good hard look at it.
Seems as if the control pressure valve was binding in the bore a bit. After some careful honing by hand, I got the sleeve to move again in the bore.
Also cranked up the modulator nice and high, so now I am getting that nice and tight, firm MB shift again! How I do like tight and firm 8)
As well I had another good look at all linkages. Micro adjustments here does indeed make a big difference!
Thanks to all for the tips.
Honourable mention to Frank Reiner in California, he is a member on another forum, very knowledgeable and he helped me a lot!

Cheers
Daniel
1977 450 SEL 6.9 - Astralsilber