My 1990 is vibrating from underneath when I reach 50 mph. It gets really bad at 55 and then gets less at 60. I just replaced the rear transmission mount (easy job). But the problem continues. What's next? Center bearing or drive shaft? Is it true that the drive shaft joint has marks on it where it was supposed to be originally balanced?

I did have a problem with my "U" joints that caused a vibration.

Try this.....

See if the vibration is the same at the same speed in any gear to rule out the engine and most of the transmission. If it doesn't matter what gear but the vibration is the same at just the right speed then I would try swapping the tires around or maybe just have them balanced.

Be sure to tell the guy that is balancing them to check for out of round or excessive weight to balance them.

I did have a 79 245 that had frozed end caps on the u joint bearings that caused this type of vibration.

Good luck.
Kyle 245

240 driveshafts are marked with both and arrow punch on the front and rear shaft and with a paint blotch, but it usually has to have the undercoating removed to find them, use a rag with gas on it and wipe off both shafts near where they connect. But I agree with ola the wheels are my first thought, especially since it starts and ends betweeen 50 and 60, very typical of wheel balance.

If it's an automatic tranny, the rear transmission bushing might be worn. It's not an unusual problem as the miles accumulate -- I've done several of my 240s at around 200k miles, or so.....

Any oil seepage at the rear tranny seal?

You can usually tell by shoving the d-shaft back-'n-forth at the tranny and listening for "clunks" or feeliung for excess lateral play where the output flange enters the transmission.

Driveshafts themselves almost never go out of balance. The last time I balanced a Volvo d-shaft was in 1977 when I shortened the stock shaft to mate to an OD transmission ('75 245).
--
Don Foster (near Cape Cod, MA)

I had the rear tranny seal and bushing and replaced about 3 weeks ago. The problem actually seems worse now.

Ah.

One cause of the vibration you've described is a misalignment of the two halves of the driveshaft. This can occur when someone removes the d-shaft for, say, a transmission bearing & seal replacement but then reassembles the splined joint improperly.

But a failing U-joint could have been exacerbated during the bearing & seal job, leading to the same vibration.

Just a thought.
--
Don Foster (near Cape Cod, MA)

Assume the driveshaft was balanced when installed, so it wouldn't be the driveshaft but the universal joints. Grip the shaft on opposite sides of the joint and twist in opposite directions. If there's play the joint needs replacing. You probably will be able to see the wear. Mark the driveshaft to keep everything inline and maintain balance before removal.

Perhaps a silly comment, but have you checked your wheels? You might have lost a lead weight which will cause this kind of symptoms.

Thanks, Not a silly comment. I had not thought about the tires. I guess I'm being pessimistic looking for the worst.

Mark

You might check the center bearing, if the rubber carrier is shot it might induce a vibration. As far as the driveshaft being marked, I don't think so. How did it come to start vibrating?

You are supposed to mark all of the driveshaft components upon disassembly so you can get them back together with their original orientation. If you have removed the shaft and not marked them you can always experiment with putting it back together with a different orientation and seeing if that helps.

Good luck,

Justin B.
83 Turbo

Vibration became noticable last year at relatively high speeds. I had the tail shaft bushing and seal replaced about a month ago. Seems worse now. I don't know if the shop took the driveshaft apart.