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I just replaced my prop shaft, and was also concerned about whether my noise originated from the viscous coupling, bevel gear, or prop shaft. I spoke to the guys at Colorado Driveshaft, and they said they'd test it for $40 or so (I'm within driving range, so could take it over). I stopped by and the guy there (Dave, I think) needed all of about 5 seconds to diagnose the problem.
Be sure to check the center u-joint very carefully - that was my problem and it was _so_ obvious when pointed out. But easy to miss because the prop shaft is so floppy that it may not be obvious that one of the bearings is binding in just one direction. The shaft was in my garage for probably a month, and I asked several of my friends to check it out - none of us caught it. Both end bearings on my shaft were very tight (front one recently replaced), and the carrier bearing was tight but Dave pointed out that it sounded 'dry' - i.e. spun freely, but sounded as if there wasn't much (or any) grease in it. He figured the carrier bearing would also fail in the not too distant future. You'd need a lot more experience than I have to pick up that sort of thing. But with 150 k you gotta be suspicious.
On the viscous coupling - there's a service bulletin on testing this, which involved getting a front wheel off the ground and turning it with a torque wrench. I don't have the bulletin at hand but I think it's supposed to take at least 50 ft-lbs to turn the rear wheels. I thought I saw another post that the torque specs on this were incorrect, but I can't relocate it.
I'd also be interested to know why this noise indicates a viscous coupling rather than prop shaft (unless you've been running different sized tires). I gotta trust JRL though - he's been correct in very response to my problems.
Finally, I replaced my sway bars (2000 xc) with the IPD heavy duty one. I can recommend the beefy ones - they really help but the are a bit of a PITA to install. I have the old bars and if they'd fit your car you're welcome to them for the cost of a 6-pack and shipping from Colorado.
It turns out that the VC I 'found' had bolts that were rusted so badly that the owner was unable to remove them. In the meantime a friend has given me a good prop shaft so I'll put this new shaft in next week sometime and see what happens.
Here's another issue, however. When I had the original shaft in, along with the clunking noise was a sort of metallic sound that was like some sheet metal rubbing on something but only when it wasn't under load. When I gave it some throttle the noise would disappear. Now, the noise is constant but more quiet. It's obviously not the shaft but clearly still related to the drive train near the center in the rear. (From the driver's seat I first thought it was a vacuum leak back near the fuel pump, but after riding back there myself I discovered that it's a metallic sound somewhere under the rear seat.)
As time moves on I'm guessing that it will become more and more difficult to keep these old Tractors AWD as the parts will become more and more rare and expensive.
With over 1200 views on this thread I thought that I'd better add the most recent news regarding this issue. Been driving the XC sans prop shaft and finally got the chance to stop by an indie shop we have here in the area that specializes in Volvos. I spoke with the owner briefly and told him the scenario and he almost immediately responded that there is likely a bad mount bushing on the VC housing where it attaches to the bottom of the car. I knew immediately what he was referring to. There is an arm on the housing that goes diagonally back and upwards to the body and mounts there. Gonna attempt to get the prop shaft reinstalled (will be a project since one of the mounting bolts on the center bearing twisted off- naturally ) hopefully sometime this coming weekend and get that bushing swapped out as well. Stay tuned...
check the bushing at the front of the viscious coupler they have been an issue on these cars
YLStaffer - What bushing was bad? a body mount bushing or a busing specific to the VC. Do you happen to have a Volvo part number? If you replaced it did that fix your problem?
Very interested in knowing the ultimate outcome....
I have my Driveshaft out and have driven 1000 miles with no noise or adverse effects in Front Wheel Drive. I really want to get this back to AWD but don't want to throw money or parts at it....
There are now 3 possibilities and I am trying to figure out how to narrow it down.
1. Propshaft
2.VC
3. Bushings.
Any further enlightenment would be appreciated from ANYONE who has resolved this problem.
Thanks
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My build thread: http://www.nastyz28.com/forum/showthread.php?t=276139
Hey 8pack I haven't had the opportunity to get to the shop yet so I still don't know the outcome, but I'm guessing the noisy bushing is where the bracket mounts on the body (over the rear axle). Hopefully I'll know more later this week! Stay tuned...
Also noticed the Z28 in your signature... I've owned 2 '68 and 2 '69 GTO's back in the day. Sweet cars!
Some time back I had a problem with the VC on my 98 XC. It had a rubbing/metallic noise and I thought it was the rear wheel bearing. Volvo checked it for me and for once got it spot on! It was the front 'nose' bearing just behind the flange that connects to the prop shaft. When I removed the viscous coupling, the bearing balls fell out!
Once the bearing was replaced all was well.
The viscous coupling 'tube' has a bracket arm cast into the housing at the front which has a rubber bush in it to stop the VC whipping. These are known to fail and will cause a 'clunk' when you accelerate/decelerate.
If you are lucky it is the bush only which I believe can be fitted without removing the VC.
I have a 97 850 AWD prop fitted to my 98 XC and it also has the same VC.
Good luck. Hopefully one of these is your cars problem as neither are bank breakers!
Thanks Hogie, and I believe both issues you mentioned are present in my car and my indie shop guy concurred as well. He can't get at it for another 2 weeks but that's OK I'm not in a huge hurry. I'll post the results of that session as soon as they are available.
So I just got the XC back from the shop and sure enough, it was that sneaky little bushing where the VC housing mounts to the body. Sounds nice and quiet now (no more clunk). As for that 'rubbing' sound, I'll hafta get it out on the highway to hear that again. So my buddies at the shop replaced that bushing, put my prop shaft back in, (they had to come up with the 12 bolts, I couldn't find them ANYWHERE ) topped off all the fluids in the drive train and diagnosed another oil leak (oil cooler lines) for $150. Anywhere else would have been twice that or more. But in any event, case closed!
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