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EDIT: Read post: http://ericthecarguy.com/kunena/8-Service-and-Repair-Questions-Answered-Here/41968-86-volvo-740-turbo-vibration-and-noise-issues?start=70#83381
Greetings all the way from Norway!
I have an issue with my 1986 Volvo 740 Turbo Intercooler that I can’t find any solution to. When driving past 60 km/h the car start to vibrate. I have had my car to a couple of different workshops, but none have managed to get it fixed.
Thought I could mention some technical specs about the car.
Engine – B230ET (134kW, turbocharged)
Injection system – Bosch Motronic ML 1.0
Gearbox – M46 (manual 4-speed + electric activated overdrive)
Rear axle – 1031 (torsen differential)Here is a runthrough of what I’ve done so far:
* Replaced every bushing on the car.
* Replaced engine mounts and gearbox mount.
* Replaced bushing and bearing for the driveshaft.
* Replaced the gearbox with one driven approx. 100.000km
* Replaced the differential and had the rear axle at the Volvo dealer to check for slack. Found well within tolerance.
* New tyres and rebalanced them.
* Changed wheel bearings.
* Changed rubber coupling (hardy coupling) between the gearbox and driveshaft.There have been vibrations since I bought the car 10 months ago. It is a common problem that the bushing for the driveshaft goes bad (which causes vibrations), so I didn’t really see that as a problem. After changing it I also realized that the driveshaft had a loose piece inside it that were impossible to remove. I then bought a used driveshaft. The vibrations were now less intensive, but very noticeble. I then replaced much of the things mentioned above, without any luck. Had it at a workshop to get the issue sorted out, the driveshaft were then replaced again with another used one. Got the car back as “fixed”, but there were still vibrations. Turned out the workshop installed it wrong (splines mismatched the balance markings. I corrected that, now the vibrations are almost gone, but are still there. Doesn’t look like any workshop know how to fix a RWD car anymore. None have equipment to measure angles etc.
Any suggestions on what to do here? This have been bugging me for a long time and won’t give up until it is fixed!
– Frank
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Your right.There should be no vibration. Sucks
for the games we must play.If it does go kaput
and the shop does not cover it.I think your idea
with finding a good used rear is your best answer.
keep us posted on your progress. 🙂All the bushings are replaced. I even went as far as using polyurethane bushings. Another common problem is that the torque rods tend to get oval holes where the bushings are. That isn’t the case either. The issue is simply too much slack inside the differential housing.
I’ve bought my self a dial gauge to measure with. Now I’m just missing the special paint. No car part dealers around my area sell that. Guess I’ll have to look at eBay.
I was going to refer you to some places that sell the gear marking compound but saw your in Norway :/
Let us know how bad the preload and backlash are. I can probably find the specs for you if needed.
If indeed the differential is shot and not rebuildable, are you going to find a used stock replacement or upgrade the rear end?
I’ve bought gear marking compound from eBay. Actually a lot cheaper than buying it here in Norway. It will take a week or so to arrive, that’s the only catch.
I just realized that the service/repair handbook I own don’t have any specs. It states that it must be brought to an authorized Volvo workshop. The problem here is that the specialist refuse to do the work… If anyone have the specifications for the backlash etc, please provide them.
My goal with this is to bring back hard evidence that there is a problem with the differential. The workshop that did the overhaul last year should replace it if needed.
This car have been a restoration project where I’ve tried to use all original parts if possible. A lot is brand new parts as well. If I were to upgrade, I’d use a original “anti-spin” rear axle. The type that have LSD. I would think that would be a great advantage in the winter, although not a big requirement.
A G80 locker from a 940 would work if you want to change the ring gear.
I can get you the specs from work Monday or try that Volvo site I referred you to or try a Google search if your after those specs before I can get the for you.
I’ve done some measurements on the differential. I’m a bit uncertain how to interpret the tooth pattern. The dial gauge gave a reading of about 0.2mm backlash (assuming I set it up correctly). If I interpret the pattern correct, the pinion gear should be moved slightly backwards?
The oil didn’t look too good either. It’s driven about 1000km (about 621 miles). The oil is metallic black/grey and I can’t see through it.
It also might look like the pinion bearing is bad? The differential housing is hot to the touch towards the back. The flange on the back have a very slight slack up and down. I can hear a weak “singing” noise while driving.
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No input or suggestions on this? Would this be sufficient evidence that something is wrong to bring back to the workshop?
To be honest the backlash you listed and the pictures of the contact pattern look good. Mind you I don’t have the specs off the top of my head. It’s also common for that oil to be dark and have some particulates in it. That said, you might have an issue elsewhere and not in the differential.
I have now replaced the rear axle. All the clunking and bearing (singing/squealing) noises are gone now. Most of the slack I felt is also gone, so the drive train feel a lot more tighter now than it did. The handbrake doesn’t stick on the right side anymore as well. BUT the slight vibration I feel at around 60 km/h (~37 mph) is still there…
I had the car at a workshop a few days ago to have a few other things checked like alternator charging, the turbocharger etc. While they test drove my car they felt the vibration and had a quick look at that as well. They told me that something else is wrong, as it shouldn’t vibrate like that. Finally a workshop that agree with me! The dealership have tried to convince me that rear wheel drive cars are supposed to vibrate and make noises. Anyhow, they suspected the drive shaft to be the issue and thought I had incorrectly assembled it while changing the rubber coupling. Since I’ve tried several different shafts and been very careful to assemble them correctly, that can’t be the issue. They got quite puzzled as well when I listed up everything I’ve done.
This got me thinking, and I started reading my workshop manual again. I found an illustration of the drive shaft (see image below). I can’t remember the item “A” on the picture, called Centre sleeve. That sleeve might be missing, so I’m going to disconnect the shaft and check. If it is missing, then the shaft would have the possibility to flex out of balance while driving.
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Glad you are finally getting this resolved. I take it you
found another rear to replace it? When you do take the drive
shaft apart. If the sleeve is missing. make sure there is no
play for the new sleeve.Also the the rubber coupling. Been a
long road to this point. Well done on your progress. 🙂Yes, I bought and imported an overhauled rear axle from Sweden. Couldn’t find any that provided that service in Norway. Also used the chance to get one with LSD.
I could also mention that I came across a service manual from Volvo. The spec there is that the backlash should be 0,13mm. I measured about 0,2mm, so clearly that was out of spec. I also inspected the gears and found signs of wear, what the service manual call “binding gears”. So the gears were slowly eating each other.
Did you go back to the workshop that did the rebuild?
I saw all the metal in the oil from the last time.Alignment angles can affect vibration, but mostly only if there are any old u-joints involved. A u-joint transmits rotation smoothly when it’s straight, but with an increasing wobble as the angle increases. The wobble is a combination of increased rotational speed, lowered rotational torque, and a sideways torque too, varying at twice the driveshaft speed. You can model this with a u-joint extender on your wrench.
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