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240 car is making a rumbling noise

Jul 19, 2020
alright so i have a 1988 Volvo 240 sedan that i love but lately it's been annoying me. i keep hearing a rumbling noise when I'm inside the car coming from under the center console. i know it's something under the car and i thought it was the tail shaft so i pulled it out and replaced the bushing, seal, and gasket plus new transmission fluid (not a fun job). before i did this a month a ago i change the center driveshaft bearing. i notice this sound a lot when i start to drive then it goes away and then when i come to a stop and then go it comes up then goes away. any idea what i else i should be looking for. i just want this to be my daily why does this car hate me lol.
So if I understand correctly:
1. When stationary, engine on: No rumble
2. Drive away from stationary: Rumble
3. Get up to speed: No Rumble
4. Slow down to a stop: No Rumble

If you had anything in the line from flywheel to wheels that was directly bad, the rumble should be independent of accel from a stop or slow down to a stop. It would also continue to occur and change note with speed. Does the sound, when it happens, change proportionately with speed?

Since I am running with the idea that the sound only occurs when accel from a stop, there's something about acceleration that's causing it. Potentially your exhaust is almost/touching a crossmember so when you accelerate the increased engine load causes twist on the mounts and it grinds/slaps exhaust on the crossmember. Once up to speed or in different load/rpm zones, the forces are different and the grind/slap doesn't occur. By vehicle sort of does that because the replacement exhaust was done while the mounts were bad, so once mounts replaced, exhaust hits. RPM and load dependent noise though.
It sounds like a bad u-joint to me. If they're okay check the torque rod bushings. The pinion angle can change a lot when they're bad.
When the driveshaft bearing was replaced. Did you make sure the support spring and washer were in the rubber driveshaft support? If it's not there the driveshaft flops around and can cause a take off rumble.
If that is all good. I'd have to go with hiperfautos suggestion. I recently had a bad ujoint on my friends 244. It made a slight vibration on takeoff and was smooth otherwise. But once we had the driveshaft off you could feel the play in the ujoint.
It may be that the new bearing that was installed on the driveshaft wasn't a very good one. Would not surprise me if it's bad a year later with the lack of quality control on parts now.
Ah. That heavy duty driveshaft support is stiffer and would not surprise me if there is a bit more vibration from it. However, it's an over kill choice for a stock car. A bad trans mount can give you vibrations right where you describe. Hopefully you got it on the run.