Driveshaft balancing saga - Page 2 - PeachParts Mercedes-Benz Forum

Diesel911 · #16 02-22-2012, 11:38 AM

Quote:

Originally Posted by vstech

nope...
there are 32 positions the driveshaft yoke will assemble on...
and the flex disc bolts are one time use... so... that's a LOT of flex disc bolts to replace... I understand what you are thinking, but no the yoke ends are totally independent from the center connections. all of the splines are even, and if no markings are found, it'll need to be balanced.

While the Yoke can fit anwyere in the splines what I was thining was once the Yoke was assembled with the part that the Flex Disc attaches to (another part you need to match mark if you remove it to change the U-joint) that it should be indexed to match the Flex Disc on the other end of the Diveshaft so as to balance the load on the Flex Discs.

martureo · #17 02-22-2012, 11:48 AM

Quote:

Originally Posted by Diesel911

While the Yoke can fit anwyere in the splines what I was thining was once the Yoke was assembled with the part that the Flex Disc attaches to (another part you need to match mark if you remove it to change the U-joint) that it should be indexed to match the Flex Disc on the other end of the Diveshaft so as to balance the load on the Flex Discs.

I can't remember where I read it, whether it was a technical article or just some guy's opinion. But you are correct, the front and rear yokes should be aligned, clearly making only three positions possible for proper balancing.

mach4 · #18 02-22-2012, 11:59 AM

There is a 99% chance that on any given day, any given drive shaft, procured from any given junkyard would have been in balance on the day it it was scrapped.

Perhaps I'm dense, but I can't figure out what the obsession is with finding a shop that will balance an existing drive shaft when countless ones lie in silent wait for the crusher and would just love to have a second chance at a useful life happily providing a smooth and reliable connection between a transmission and rear end for transmitting motive power for a happy families beloved vehicle.

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andrewjtx · #19 02-22-2012, 12:00 PM

I just received my driveshafts.com replacement last week or so. First, they no longer reman most of the MB driveshafts anymore. They have a outsourced company that has a few warehouses across the country. Also, the current ones do not have their greaseable U-joint. The unit I received looks very nice. German parts were used on the boot, bushings and center bearings.

To me, this is one of those things that I'd just as soon spend the money on. It's probably going to last another 25 years. Well worth the $375 IMO.

Left Coast · #20 02-22-2012, 12:08 PM

Quote:

Originally Posted by martureo

As an update:
...The two options that I am still pondering over are buying a new rear section of the driveshaft from Mercedes or getting a custom one from Portland Driveline. Has anyone ordered and installed one from Portland Driveline?

I have a rebuilt from them installed on my '79. It is almost 4 years old, with nearly 20K of mostly stop and go on it. No problems. The warranty is 5 yr. / 50K. They are the first choice around here, being a local outfit, and I'd buy from them again.

rs899 · #21 02-22-2012, 12:14 PM

I would agree with Mach4 about a used one, but I don't think these are so available anymore in many parts of the country (other than his).

I don't see why some trial and error with hose clamps would be so hard. Just mark as you fail so as not to duplicate the error.

JB3 · #22 02-22-2012, 12:25 PM

Ive mailed at least 4 MB driveshafts to Powertrain Industries in Springfield MO. Shipping is way cheaper than you would expect, and driveshaft broke down is not a huge, or heavy box.

I include a note with dimensions with whatever custom length I want and on what part, and several times they have installed a new carrier bearing (provided my me) and staked in a replacement U-joint sourced by them.

Most I paid for a custom front length MB driveshaft with installed carrier bearing and new u-joint was about 220-240. Least I paid just to have something custom lengthened and balanced was about 120. Worth calling.

martureo · #23 02-22-2012, 12:33 PM

Quote:

Originally Posted by mach4

There is a 99% chance that on any given day, any given drive shaft, procured from any given junkyard would have been in balance on the day it it was scrapped.

The eccentricity and runout of these "99%" of junkyard driveshafts are almost without question quite a bit different than what came out of the factory. And I'm not just talking about dirt and grime.

Quote:

Perhaps I'm dense, but I can't figure out what the obsession is with finding a shop that will balance an existing drive shaft when countless ones lie in silent wait for the crusher and would just love to have a second chance at a useful life happily providing a smooth and reliable connection between a transmission and rear end for transmitting motive power for a happy families beloved vehicle.

If it weren't a driveline part or a rapidly moving and necessarily balanced part I would and do agree with you. But as an Engineer I can already mentally picture the vibrations, torsion and wobbling of used driveshafts of questionable condition and unknown history used on a vehicle today.

I don't want any avoidable issues on a vehicle that I'm restoring, not simply a just a beater to drive. And more significantly I don't want to have to keep buying junkyard driveshafts continually to replace ones with failed u-joints. Reusing old components that can be newly manufactured to "save" quite old and original components of unknown history is just insane.

Quote:

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mach4 · #24 02-22-2012, 01:17 PM

Quote:

Originally Posted by martureo

But as an Engineer I can already mentally picture the vibrations, torsion and wobbling of used driveshafts of questionable condition and unknown history used on a vehicle today.

I'm not an engineer... and I'm not arguing, just trying to understand.

My non-engineer logic and observation would tend to indicate, that if driveshafts as a matter of course became unusable through vibration, torsion, wear, corrosion or whatever, it would seem that we would be replacing/rebuilding driveshafts in the same way we replace timing chains, flex disks, motor mounts or cooler hoses.

The driveshaft is pretty well defended at least compared to 4WD trucks and traditional American cars of the same vintage, so getting damaged would seem to be pretty rare. And the torque that a stock engine puts out appears to be pretty well matched to the design specifications of the driveshaft. So if it comes from the factory balanced, what is it that makes it unbalanced over time?

I just don't see how a used driveshaft is a problem... with one exception, and that would be the U-joint. But you could feel whether the U joint is good before you ever bought the used drive shaft.

Again, not being argumentative, just trying to understand.

martureo · #25 02-22-2012, 04:38 PM

Quote:

Originally Posted by mach4

I'm not an engineer... and I'm not arguing, just trying to understand.

My non-engineer logic and observation would tend to indicate, that if driveshafts as a matter of course became unusable through vibration, torsion, wear, corrosion or whatever, it would seem that we would be replacing/rebuilding driveshafts in the same way we replace timing chains, flex disks, motor mounts or cooler hoses.

The driveshaft is pretty well defended at least compared to 4WD trucks and traditional American cars of the same vintage, so getting damaged would seem to be pretty rare. And the torque that a stock engine puts out appears to be pretty well matched to the design specifications of the driveshaft. So if it comes from the factory balanced, what is it that makes it unbalanced over time?

I just don't see how a used driveshaft is a problem... with one exception, and that would be the U-joint. But you could feel whether the U joint is good before you ever bought the used drive shaft.

Again, not being argumentative, just trying to understand.

The main issue is not that a used driveshaft won't work, but that it is more than likely to fail to operate at par in a short time span and because of the unknown history of the operation and care of the vehicle (or vehicles) it was installed on we have no clue as to how it will function. In my experience junkyards and PnPs are rarely, if ever places of pristine, rust, dirt and damage free parts. Many places cars are move around on front loaders, which often damage side panels, tie rods (one would wonder why you would want one from a JY), transmissions and ... driveshafts.

You will have no clue if the PO (or the one before him...or the one before him..) just drove it around not caring about the humming or tried to unsuccessfully repair the bearings or u-joint before possibly taking it to a shop that crudely "fixed it". Yes, some things are quite apparent upon visual inspection, but some aren't.

The biggest problem for me is that you are going to spend money on something that will not give decent return. Even IF you found a driveshaft with only 100k documented miles on it, do you really think that a 25+ year driveshaft is going to be error free for the next 25k miles? Has the u-joint been spared by some miracle?

The entire issue of using load-bearing, rotational, safety related parts and those receiving cyclic loads, from a junkyard when there are suitable remanufactured, NOS or new replacements in my eyes is akin to debating which brand of junkyard acquired brake pads will last longer. For me, I would rather use something rolling (driving) then test, repair or replace it than take something taken off the road (for whatever unknown reason). There's just too much unknown and as I see it, too much to lose.

jt20 · #26 02-22-2012, 04:47 PM

I would suggest that you look very closely at each end near the splines. On an '84 there should be cast alignment markers (part of the casting). They are hard to find on a rusty u-joint and are not close to each other.

One side has a female looking pointer (two triangles with a space between them), and the other side is a male pointer. The male aligns with the female space.

jt20 · #27 02-22-2012, 04:53 PM

2 characters

mach4 · #28 02-22-2012, 05:04 PM

Quote:

Originally Posted by martureo

The entire issue of using load-bearing, rotational, safety related parts and those receiving cyclic loads, from a junkyard when there are suitable remanufactured, NOS or new replacements in my eyes is akin to debating which brand of junkyard acquired brake pads will last longer. For me, I would rather use something rolling (driving) then test, repair or replace it than take something taken off the road (for whatever unknown reason). There's just too much unknown and as I see it, too much to lose.

Makes sense. Thanks for the clarification.

For my money, in a similar situation, I would most likely take the chance on used parts sourced through a PnP, knowing that there is a risk all the things you describe as potential problems could happen. But that's just me.

In every situation there are a set of values, beliefs and experience that guide our decisions. Neither is "right" or "wrong" but rather an outcome of the application of the guiding principles we employ.

I completely understand your views and in light of that, your approach is exactly the proper one. Certainly minimizes a set of risk factors that you nicely defined.

Wish I had a driveline company to refer you to.

Thanks

Paul

martureo · #29 02-22-2012, 05:34 PM

Quote:

Originally Posted by mach4

Makes sense. Thanks for the clarification.

For my money, in a similar situation, I would most likely take the chance on used parts sourced through a PnP, knowing that there is a risk all the things you describe as potential problems could happen. But that's just me.

In every situation there are a set of values, beliefs and experience that guide our decisions. Neither is "right" or "wrong" but rather an outcome of the application of the guiding principles we employ.

I completely understand your views and in light of that, your approach is exactly the proper one. Certainly minimizes a set of risk factors that you nicely defined.

Wish I had a driveline company to refer you to.

Thanks

Paul

No problem. And I sincerely apologize if I came off too strongly or argumentative, neither was my intention. Immediately prior to my first response to your question I had ended a very frustrating phone conversation with an auto shop that I have trusted for years.

mach4 · #30 02-22-2012, 06:54 PM

Quote:

Originally Posted by martureo

No problem. And I sincerely apologize if I came off too strongly or argumentative, neither was my intention.

You didn't at all. I hope I didn't either. I'm relatively new to the world of Mercedes and still learning. That's why I was really interested to hear your thoughts and ideas and get a new set of data points with which to think about drive trains.