newly acquired '97 S500 -update
 

Thought I'd post a quick update and a couple of questions for those kind enough to advise me on this on this acquisition a month or so ago.

She's running great; a real pleasure to drive. Still takes longer to turn over than I think it should, but only a couple of seconds longer and never fails to start up. Any ideas of things to check?

Maintenance so far; two oil changes in quick succession (500 miles apart). My indy put in ELF synthetic 0W-40 and advises that it can be left in for 7k miles. That surprises me; I'm used to changing oil every 3k.... opinions?

The tranny oil and filter were replaced without incident -pan was free of ominous debris and the transmission works smoothly. Question- I understand there is a set of needle bearings that are vulnerable to failure in the 722.6, later replaced by a more robust bushing. Mine, being a '97, is likely the earlier version. Anything I can do to prolong the life of these bearings? What impact on transmission life does starting in 2nd gear (setting "W") versus 1st gear ("S") have?

Replaced a set of amazingly worn spark plugs; I'm surprised she was running so well. Thankfully none were terribly seized.

Another final question; can ETA wear be reduced through use of the cruise control? Just a thought; so far, no ETA malfunction symptoms.

Thanks to this forum for great information!

Me too! I finally, after driving my S500 cpe for 10 years, decided to try synthetic oil; put in ELF 5 - 40W and it's is amazing. On a hot day (90F) after a high speed run going directly into stop-go traffic, the temp gauge hardly moves!! And the engine temp is lower than it's ever been! Runs around 85C and goes up to low 90s w/ A/C.
I guess we all know synth oil provides better lubrication and has less friction but this is amazing. Don't know why I waited so long to try it. Tech says 8k miles . .

Use your CC; it's one of the best ever made but I don't believe it will lengthen the life of your ETA. It will 'die' when it dies and you'll know it! :mad:

The early 722.6 had brass bushing between input and output shafts. Later (about 2000?) MB replaced it with needle bearing and seal. The problem with original design was that as bushing was getting worn the clearance would increase and as a result lubrication pressure was lost. It would cause oil starvation in the rear gearset and bearings. I have a very limited experience rebuilding 722.6 in my car (99ML430). The clearance in the bushing was about .040
I don't think you could prevent that, and don't think ATF change would help much. I've done two changes in 150000 and still had failure. Just enjoy your car and fix it when required.
See pictures here:
http://www.peachparts.com/shopforum/tech-help/198186-transmission-noise-park-neutral-99-c280.html
Mike

thanks
 

Old bearing design upgraded to a bushing, vs. a failing bushing later upgraded to a bearing; I seem to be seeing contrary accounts:

http://www.peachparts.com/shopforum/tech-help/180161-what-issues-722-6-transmission.html

I've never been inside a tranny, so I'll have to defer. But it seems to be agreed that there's nothing to be done pre-emtively, unfortunately. If mine makes it to 150k miles, I won't be too unhappy- that's 100k from now. Wishful thinking, but hoping that good maintenance and gentle usage may peen the bushing surfaces and make them last longer? (like the "glassy" surface of a worn-in cylinder bore?)

Thanks for the observation about the ELF oil, Jim! That's reassuring! I may chicken out and change it earlier, unless that dipstick looks REALLY clean.

My S 500 L have run synthetic oil (Mobil 15W40) since new. The local dealer uses only that on S classes. The recommended change schedule here is 10,000 Kms (about 6,250 miles), but you have to take into account that we are set in mountaneous region.

Don't use your 722.6 on the "W" setting unless really required by climate conditions. 722.6s start on third (3) gear at W mode, not second as most people believe. This would put higher stress on the transmission on regular weather.

A/C temp sensor aspirator
 

I should mention that I worked on this sensor yesterday. I've been setting the A/C manually since it didn't seem to respond to in-cabin temperature properly. The aspirator wasn't spinning up to deliver air to the temp sensor. The fan motor needed to be cleaned up and the spindle that it spins on pressed back into the fan. Now the A/C tracks and responds to interior temperature perfectly!

Thanks to Greg Baxter for his DIY and JimF for the diagnostic codes!