Flexdisc wear observations - PeachParts Mercedes-Benz Forum

Mister Byrnzoil · #1 12-15-2006, 07:52 PM

During the test drive when purchasing this vehicle, the OE PO mentioned that he liked to downshift instead of braking, he asked me what I did, and I said that "brakes are cheaper than clutches" and I used the brakes when I wanted to slow down.

Fast forward 1 month while doing some unrelated brakework...

Well the flexdiscs appear to be in good shape @ first glance, no blatant cracks or loose reinforcement material.

But if you grab the driveshaft and twist, it will move almost an inch! Then I saw the spot where it had contacted the muffler a few times, then I saw where the bolts and grommits were loose in an oval wear pattern that used to be a tight grommited holes in the flexdisc, then I saw how the boot for the center driveshaft bearing was completely torn...

What I learned from this... Forget clutches, Brakes are much cheaper than your entire driveline

Stevo · #2 12-15-2006, 08:12 PM

Quote:

Originally Posted by Mister Byrnzoil

Brakes are much cheaper than your entire driveline

And way easier too. How many miles on the car. Maybe none of that stuff had ever been replaced.

Mister Byrnzoil · #3 12-15-2006, 08:25 PM

its the 84 w/ 123 on the clock and a broken (rusted) odometer cable.

The flexdiscs looked newish upon casual inspection, not at all dried out or weathered looking, I doubt they were OE...
(BTW another important piece of the puzzle.... Clutch was replaced @ 100k!?!)

Stevo · #4 12-15-2006, 08:46 PM

Oh, on the Euro, 5 spd, nice, yah, thats not allot of miles, seems a clutch should go longer than 100K. You figure it was all the down shifting of the PO which caused the excissave ware then? Replacing the flex disc (s?) and ctr bearing isn't a big deal, just be sure and mark that drive shaft

justinperkins · #5 12-15-2006, 08:52 PM

I thought everybody downshifted. Never really thought about the whole "brakes are cheaper" thing, but you've got a point there.

arcticathlon · #6 12-15-2006, 09:48 PM

hehe, you think 100k is a little for a clutch? my first car was a '99 nissan altima manual. i needed a new clutch at 54k!! ya i am not proud of my early driving, and love the "getting there happy and in style" style i have come to enjoy with my 300D.

vwbuge · #7 12-15-2006, 09:51 PM

I think the "brakes are cheaper" thing is a bunch of crap. The flex discs in that car are more than likely the original and would show that kind of wear regardless. Downshifting when done properly will not only save a little on brakes but is actually much safer way to drive.

Mister Byrnzoil · #8 12-16-2006, 07:36 AM

Quote:

Originally Posted by vwbuge

I think the "brakes are cheaper" thing is a bunch of crap. The flex discs in that car are more than likely the original and would show that kind of wear regardless. Downshifting when done properly will not only save a little on brakes but is actually much safer way to drive.

I disagree, I believe that they were more than likely changed when the clutch was replaced maybe 30k? (probably more) ago. Furthur I believe that agressive downshifting was the culprit. I personally favor a more balanced approach of braking and downshifting.

The center brearing boot DID appear to be OE, it was cracked and rotting.

Of course I immediately checked the FDs on my '80, although the rubber appeared older and considerably more weather-checked, they were tight with no play in the driveshaft.

I don't know what normal wear is supposed to look like on a FD, are longish oval holes normal? Anyway, folks can make a more informed decision when they see the FD pics after I change them this week.

#9 12-16-2006, 08:03 AM

This is how the Flex should look.

Personally, I avoid downshifting whenever possible except when I anticipate accelerating again. Look at it this way,
Brakes- 30 minutes, $65, expected life of 20-60k miles.
Front pads: $35
Rear pads: $30

Clutch- 4 hours, $321.06, expected life of 100-250k miles with good driving skills.
Disc: $172.64
Pressure plate: $118.42
Resurface the flywheel: $30
Also, let's not forget the added wear/tear on the synchronizers in the tranny.

I can do my brakes over my lunch period but I would have to plan my weekend around doing the clutch.

Diesel Giant · #10 12-16-2006, 08:21 AM

Flex disc failure is oh so damaging.

Get both of those out of that car and go gently on the old girl.

http://dieselgiant.com/Mercedes%20flex%20disc%20failure.htm

I just found both of them cracked on my '79 which will be done next week.

vwbuge · #11 12-16-2006, 08:41 AM

regardless of your opinion on the downshift thing, make sure you look REALLY good at your FD.

I developed a thump in the center of my car only around a certain speed. I looked at my FD and they looked OK. I was able to grab my shaft (haha) and move it quite a bit. After I took off my heat shield I was able to see that my center shaft support was torn. I decided while I had it down to replace everything. Both front and rear FD were bad. In fact, I was missing more than one bolt in each. I also could not see the nylon ? fibers coming out of the front FD.

Inspect everything closely!

miamirex · #12 12-17-2006, 02:37 PM

I look at it very simply, the ultimate life of an engine is directly perportional to total revolutions. I drive easy enough so that braking is not a big deal. Down shifting just puts more wear and tear and stress on your engine, why bother when it is totally unecessary. Just drive easy and if you must do all the enery it requires to downshift and slow tjhe car, maybe you should rethink your driving habits. My engines go forever with this philosophy. Brake sysytems are easier and cheaper to repair. Funny, I had this exact conversation 20 years ago, that guy could not take care of an engine whatsoever.