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1986 280 GE lwb
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210 Posts
Discussion Starter #1
have has the front drive shaft rebuilt with toyota LC u joints. When i got it back from the dyanamic balacer shop the offset between the 2 u joints was changed. Shop says shaft is perfectly balanced.
Will this affect the drivetrain in anyway?? Should I take it back and ask them to rebalance it with the correct offset??
thx
 

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1980 LWB 280GE
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3,504 Posts
The shaft can be balanced no matter how it's assembled. So it's not surprising they say they were able to balance it perfectly as it is.

The offset of the two U-jonts is used to offset the vibrations that are induced when the flange at the front diff and the one on the transfer case are not parallel. In the rear, the axle flange can be set to be in a plane that is very nearly parallel to the plane of the transfer case flange, so there's no offset of those U-joints. Same is true of the short shaft between transmission and transfer case.

The front is a different story though. Due to the arangement of the various parts up there, the front axle's input flange has to be tipped upward a little and is not parallel to the transfer case flange. Due to the way the U-joints work a vibration is induced in the shaft if both U-joints aren't at the same angle (both are automatically at the same angle if the flanges are parallel). You can see by looking at the front shaft installed in the vehicle that there's more "bend" in the u-joint at the transfer case than there is in the one at the axle.

The stock 88 degree offset of the U-joint angles in the front driveshaft is helping to minimize the vibration that is caused by the different "bend" at each end of the shaft.

In my opinion, you should definitely have the shaft reassembled with the proper phase angle between the two U-joints. You may be able to "live with it" the way it is, but it's not right, and the angle is definitely important to proper (as designed) functioning of the system.

-Dave G.

PS - you're right, it will also need to be re-balanced after the the U-joint phasing is corrected
 

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1991 300GD, 1990 560SEC
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15 Posts
That's a very good and easy to understand explanation, Hipine. Can only add here that I've experienced the same problem in practice. After replacing the U-joints my shop mounted the drive shaft with wrong offset and balanced it that way. I tried to convince them that it doesn't work that way but we ended up trying it out under the car. The car had really bad vibration starting already from 35 km/h. Mounting it with the correct offset and rebalancing solved the problem.
 

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1980 LWB 280GE
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One of these days....

For a long time now I've wanted to put together a little spreadsheet that will calculate what the offset angle should be based on the angle that the front axle flange is away from vertical. If you use springs to accomplish a chassis lift without bending the radius arms or dropping their mounting points, then the front and rear pinion angles change, and U-joint phasing could be changed a bit to help offset vibes.

Like the Subject says, "One of these days...."

-Dave G.
 

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280ge
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574 Posts
would the offset problems not be solved if you used double cardon joints regardless of how much you raised spirngs[?]
 

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230 G BGS 300G TDI
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Brilliant explanation Dave, when you look at a front prop correctly set up it doesnt look as if it should work, but it does, as you say if properly off set.
 

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1980 LWB 280GE
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ianwatsoni - 5/10/2005 5:24 PM
would the offset problems not be solved if you used double cardon joints regardless of how much you raised spirngs[?]
Not really. Well, at least not in and of itself. Especially not in the front axle.

The double cardan joint is in effect two U-joints that are back to back with the same angle in each joint, so within the DC, the vibes talked about above are cancelled out internally. This leaves the problem of the joint at the differential end of the shaft (the DC is usually placed at the transfer case end). That single U-joint at the axle end will induce vibrations in the shaft if it is at anything other than a zero degree (straight) angle.

When fitting a DC at the TC end of the drive shaft, the diff housing has to be tipped so that the flange points as nearly as possible straight at the transfer case flange. This is easy enough to do if the two flanges are directly in line with respect to where they sit in the WIDTH of the truck. If the drive shaft travels a little bit ACROSS the truck in addition to front to rear, then there's no way to point the axle flange toward the transfer case flange, since that would mean angling the whole axle to one side or the other.

I know I'm probably not being too clear here, but maybe you see what I mean.

-Dave G.
 

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85 300GD 83 300TD
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I think you are being very clear here Dave. These are the issues I have been working on with my truck and why Q's offset bushings are so interesting. I made DC shafts for the front and rear of the truck but without the ability to point the diff flange directly at the t-case flange, loosing the vibrations is difficult. I got it close in the rear and with the offset bushings I think I can now make them go away I hope. The front in my truck is a greater problem as the diff flange points up too much. The offset bushings in offset sleeves will likely get it into the target zone. I have the bushings and now need some time to get sleeves machined to get it right. The solution may require some offset phasing as well to deal with the fact that there is left to right offset as well as up down out of alignment. Tricky stuff.

-Dai
 

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Hey everyone, I have a 2002 g500, the drive shaft crapped out and the car was vibrating like crazy, A mechanic put on a new dorman driveshaft. We had it installed, and it still vibrates quite a bit. Not like before... maybe 20% as much... The original mechanic couldnt sort out where the vibration is coming from. I took it to another mechanic and he said its because of the driveshaft installed does not have an offset. Ofcourse the original mechanic says thats not the problem, dorman says this drive shaft is built for this car... and meanwhile my car is still vibrating.
Any ideas? Is there a way to retrofit this drive shaft to create an offset? Do i need another driveshaft altogether?
 

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96 G300DT
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The factory shaft has markings on it to show how the two halves should be offset. I'm guessing that you could try to match the offset and get pretty good results. Changing the offset is accomplished by pulling apart the sliding joint, reclocking the spline interface, and pushing it back together.

That being said. I don't think I've heard of an aftermarket W463 drive shaft.
 

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2003 G500, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
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I have seen the Dorman drive shafts for sale for the W463 in various places and have wondered whether they are built with the proper u-joint offsets since the G uses some very unusual offsets. There is also another generic brand that often appears on ebay. If you still have the old drive shaft, I would compare the two to see if the offsets appear correct. If they are, while it's a bit of a long shot, you may want to have the mechanic rotate the flanges 180 degrees relative to each other. Somewhere there is a procedure from MB about doing this for vibration issues, but I can't seem it find it right now. I have done it on my G and strangely, it does make a difference. BTW, is it the front or rear driveshaft?
 

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Sold .....1987 U1250 Unimog
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Can someone explain this offset? I keep thinking the shaft is offset by some reason but that can't work, so I'm lost in what we are talking about.
 
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