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I am double posting this here and in the S90 Forum.
I need some expert advice, I am out of my field of expertise here. The vehicle is a 1998 Volvo S90 (964) with 81,543 miles with a driveline vibration.
- There is a clunk in driveline (felt and heard) when shifting from R to N or R to D
- At speeds above 55 mph the gearshift lever rocks forward & rearward (worse when the accelerator is pushed harder, less when off the accelerator).
- No unusual noises at that speed when the shaking is worst and the gearshift lever is rocking.
- Vibration can be felt in the accelerator pedal
- Vibration is not felt in the steering wheel
- Replaced both motor mounts – No Change
- Replaced auto trans crossmember mount - No Change
- Tires and wheels have been changed out – No Change
- Vehicle has an independent rear suspension with the rear differential rigidly mounted (via bushings). Can’t detect much play at that end by trying to move the driveshaft.
- Even with new mounts the trans tailshaft does have some movement in it but it doesn’t seem excessive.
- I can move the driveshaft at the center bushing but don’t know how much play is normal. I’ve never had a car with a 2 piece driveshaft and center bushing before so I don’t know how to diagnose it other than what I have already done. The more miles I put on this the worse it seems to be getting.
Please advise.
Thanks in Advance, DEWFPO
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1998 S90 077,400 and 1995 964 154,100
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Well, I had a problematic central support bearing and the symptoms were clunkiness when starting off from a dead stop. Perhaps there are other symptoms of a worn central bearing, but my symptoms disappeared when at speed. A replaced bearing and now the car does ride much smoother. Again, I just offer this to offer an alternative opinion to what others point to as a central bearing issue. good luck.
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1991 745 & 1993 965 /// RIP: 86 764T; 79 262C
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Thanks for the info, my issues start at about 55 mph and above, nothing below that.
DEWFPO
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1998 S90 077,400 and 1995 964 154,100
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You should find that if you keep the foot brake on when you go from R to D or vice versa etc. ect.... you will not get the clunk....but if no brake is on you will get the clunk as all the tolerances are taken up....which is normal. But i had the same vibration as yourself....and it was one of the coils that fit to the spark plugs. Depending on which one is faulty....or whatever cylinder is not firing properly....alters the vibration quality....also lumpy tickover and revving was hardly noticeable. Your car has done no miles at all....and nothing should knock out that early.... so therefore i think maybe you are looking in the wrong place? Hope this helps?
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Dear dewfpo,
May this find You well. Here are a couple of things to check:
(a) Does the shift lever have play in it, when the vehicle is not moving? If so, the shift linkage bushings may have failed. The shift lever should have, perhaps, 1/8" play, when the vehicle is parked. These bearings are plastic, and fail with time/use. The linkage is on the driver-side of the transmission, easily accessible from under the car.
(b) check the bolts, that secure the drive shaft support bearing assembly to the floor pan. If these bolts are loose, tighten them. Usually, play in the bearing will produce a vibration - rather than a clunk - felt most when slowing-down or accelerating.
Has the tranny been flushed recently? If one of the valves is sticking, that could produce a brief "hang-up", which gives rise to a "clunk".
Has anyone worked on the driveshaft? If so, the bolts may have been put back in other than the factory-original positions. Driveshaft bolts must stay in where put at the factory. The reason: bolts of different lengths are used to balance the shaft. If the bolts are not put back in the factory-original positions, that can unbalance the driveshaft.
Hope some of this helps.
Yours faithfully,
Spook
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Thank You for you comments Spook, I appreciate them.
Today, I verified that the shifter is firm in it's mounting in all positions and only rocks forward and back when I reach approx. 55 mph or higher. If I back off the accelerator once it is rocking, then the shifter stops rocking and I can no longer feel the vibration in the accelerator pedal. There really isn't any sound when I shift from R to L, but it does feel like there is play in the driveline, virtually none when I move from P to R. I don't know how else to describe it. The trans is in good shape with regular synthetic atf changes and no one has worked on the vehicle other than myself and not for a while. There is no noise or vibration when the trans is shifting up or down when driving. I will lift the car again and see how much play I can measure various parts.
Again, Thanks, DEWFPO
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1998 S90 077,400 and 1995 964 154,100
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Dear dewfpo,
May this find You well. The symptoms point to the central support bearing or to the universal joints. When you accelerate: (a) the engine may shift position slightly; (b) the driveshaft turns more quickly.
If the bearing has failed - or is loose - the additional centrifugal force will move the driveshaft. As soon as the speed stabilizes, the driveshaft settles into a new position.
Does the tranny move, if you step hard on the brakes? That, too, should shift the driveshaft's position.
It seems as if this problem does not involve the tranny's internals.
It might be worthwhile to put the rear of the car on jackstands, and briefly run the engine up to 55 mph, while someone looks at the center support, to see if it shifts. The movement might not be enough to be visible.
It might be possible to put a string through the center support's foot. If the string is tensioned by pulling on it, and the holder feels a tug, when you accelerate, that would indicate a loose center support. Care must be taken to ensure the string does not contact the driveshaft.
While the car is on jackstands, and the engine is not running, can you shift the driveshaft front-to-back, by grabbing it, and tugging hard on it? There should not be much give, certainly not enough to allow the tranny to move.
Hope this helps.
Yours faithfully,
Spook
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Thanks for the ideas Spook, I will give the undercarriage a thorough inspection when I can get under there. I am wondering if the rubber bushing (not necessarily the center bearing) has too much play in it if it will allow the driveshaft halves to move too much and cause them to go out of alignment, thus causing the vibration?
Thanks, DEWFPO
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1998 S90 077,400 and 1995 964 154,100
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