722.9 box service questuon

[IFFY100]

Just about to do a trans service on the 7g tonic box. I'm planning on following this guide

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(followed it before without issue) but this time I'm wondering whether I should drain the tq as well? My thoughts are that it isn't needed as the fluid from the pan will push through old fluid anyway? And lastly, how much fluid would be held in the pan, tq and lines? My pan drained about 3.5l. Oh and I forgot to put tranny in N which again I think ain't an issue unless turning the engine over for tq drain alignment

 

[Petrol Pete]

OP , I'm a bit confused . You say you did this job once and got 3.5 litres out of the transmission ? It holds over 8.5 litres and this guy used 10 Litres during this flush.

Mercedes-Benz 7-Speed Transmission (722.9) Service Walkthrough

To ensure long life and peace of mind in your seven-speed (722.9) Mercedes-Benz automatic transmission, periodic service is a must. Many manufacturers, including Mercedes, claim that their transmission fluid is for life, but that's simply not the case. Instead, follow this service procedure to...

www.fcpeuro.com

Transmission Oil Drain & Flush Kit - CTA Manufacturing 7650

Transmission Oil Drain & Flush Kit - CTA Manufacturing 7650

www.fcpeuro.com

The FCP kit will get most of it out , but they do admit it's best to use the TC drain plug if you have one . Why would you not ? I wish my 72.6 had a drain plug on the TC.

 

[IFFY100]

Thanks for the reply mate. So something odd happened - when I drained the tranny I got around 4 litres actually(spilt some oil). Now during the job a more important task came up so I stuck the pan back on and left it to the next day. When I went back about 1.5 litres appeared in the pan. Now how long that took to get there I don't know.
With the method in the video, that will in my opinion push fluid through the box tq, cooler and lines - in that order. Provided that being the case, tq gets drained anyway.

 

[geoffus]

I got 9 litres out of my 722.9 gearbox including draining the torque converter.
If you have the TQ drain plug then its very easy to drain from there.

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[IFFY100]

I can't understand how I got so little fluid in my first go. In any case though, the fluid is only ever going to be a little over the guide stick in the pan. The pan prob can only hold 4 ish litres. Could it be that I didn't have the trans in N? If I go down the route of draining the tq, I take it the tq will fill with oil first befote tjr pan gets to fill level? I ask this because I still will flush lines and cooler.

 

[OneForTheRoad]

It all sounds a bit iffy to me .

 

[Petrol Pete]

Most tutorials show all wheels off the ground with the car level, engine running and cycling through the shift positions and checking the fluid level . Defiantly 8/9 litres required .