flex disc alignment

Dear MB friends:

(74 280 M110, AT)

How critical is the reassembly of the front flex disc/driveshaft link?

When my motor was re-installed, my helper simply went ahead and bolted the pieces together, using the original bolts, but not paying attention to any specific orientation of the bolts or radial orientation of the flanges, etc. They just fit up nicely, so...Now there's a vibration that causes me to suspect that things are now out of balance there. Should I go back and look for alignment marks and re-fit?

Thanks,
Will

[psfred]

Loosen clamp nut on driveshaft and push car several feet back and forth a couple times, then re-tighten. If the shaft is fractionally too long, it will "orbit' on the center bearing support, causing vibration.

Also, the washer goes against the rubber.

It's best to get the driveshaft and tranny flange back in original alignment, too since the shaft is balanced in the car, I think.

Peter

[kpb]

I recently started a thread here while replacing my flex disc. The responses were quite helpful. The thread may even still be visible on this first page. When my disc was disintegrating the oscillation went from subtle to scary within about three weeks. I did not see any alignment marks on my drive shaft but I marked everything when disassembying just in case there was a balance issue. I have a '72 280SE 4.5.

Good luck. There are a number of very knowledgeable folks here who will be able to assist with your questions.

[300SDog]

Tranny mount replaced too, along with center support bearing on driveshaft?? .......these are items that need replacing on the 114/115 at least each 20yrs along with flex-disc. Center support vibes can be felt from putting your hand on the driveshaft tunnel while driving the car. If tranny mount was replaced it could be slightly off in position too - good idea to check it anyhow, after it settles, if its new.

Peter's idea of loosening the driveshaft clamp nut sounds like a winner..... hell, you might even try jackstanding both rear wheels.... loosening the clamp nut and tranny support very slightly..... then idling at very low rpm's in reverse and forward with rear wheels raised - for the drivetrain to "find" where it belongs before retightening.

Otherwise yeah sure, MB is always braggin about paintmarking driveline components - but just how critical is it? I know one mechanic who's been specializing in automatic/stick shift tranny conversions on 123's for 10+ yrs..... and the dude never ballances the flywheel to the crankshaft - and has had no vibration problems....... sacrilege i'm sure in they eyes of dealership recommendations.

Great cars the early 70's 114/115 - imho, the most maintenance free that MB has built in the past 30 yrs.