I have a Volvo s40 2007. My car starts vibrating when I hit about 10 mph and just gets louder the faster I go. No one can seem to figure out what is wrong with my car. You can feel the vibration on the passenger side but in the center (where you'd put your left foot)
So far on both sides I have changed the axle, struts, tie rod end, sway bar and wheel bearings.
When my axle was changed the guy said it came out dry and that the transaxle is dry so it'll need to be replaced. I asked another mechanic about this and he said to just put grease at the end of the axle that goes into the transaxle and that'll fix the problem. So I went and saw another mechanic and he said it's the wheel bearings so I'm getting those replaced again....
I was also told that the lower control arm has a lot of play on the passenger side. Could this be causing the vibration?
Has anyone else had this problem?

 

vibrations that change with road speed point to something that's rotating with the tires. If the axle has a torn boot, then its time to replace as you may have already damaged the CV joint or inner bearings (axles have inner and outer bearing joints). Other possible causes are the wheel bearing, brake rotor/caliper or could be related to the engine/transmission mounts. A worn control arm wouldn't cause vibrations per se, but could amplify a wonky axle's vibration. Brakes are the easiest to diagnose - simply put the car up and turn the wheel by hand and look/listen. CV joints may click when doing low speed turning like a K turn. Wheel bearings tend to moan and may change sound when turning left vs right. My experience with wheel bearings is they tend to be noisiest around 30-40 mph. Motor mounts can cause vibrations but will change as you apply or let off the gas. Axles will vibrate the most and change with road speed, particularly when its the inner bearing. Its possible it could be a bearing internal to the transmission but given you reported a torn axle boot, that's reason enough to replace the axle. Also note that replacement parts are often rebuilt and can vary in quality so buyer beware.

 

When you change the front axle is there supposed to be fluid or grease? I was told that there's supposed to be fluid and that the transaxle is dry

 

transaxle and axle are two different things. The transaxle is a reference to the transmission or differential. You didn't mention if your car was FWD or AWD. AWD has an extra "bevel gear" with its own fluid. the axles or "half shafts" are the rods that go from the transmission to the wheel hub. these shafts have rubber boots to keep the grease in and dirt out of the CV joints and bearings. If the boot is torn, this grease can run out and let dirt in - ruining the bearings.

 

I'm talking about the tip of the axle that goes into the center of the car (the transaxle) when they pulled it out it was dry. No fluid came out. So I guess my question would be how to I get fluid in there? The dipstick to the transmission shows that it's full (I don't know if that matters or not....) it's fwd

 

best talk to your tech again to have them clarify what they are talking about. I'm betting they were referring to the bearing or CV joint having lost its grease.

 

I've never had transmission fluid leak out when I changed either front axle. If the dipstick shows full then you are golden.

EDIT: Check the motor mount on the top pax side. Mine was split in half which caused vibration and noise during acceleration. If your vibration increases with speed but not engine RPM then it's something related to the driveline like a bad tire or unbalanced wheel or axle. Oh, don't assume a reman axle is good. They are sometimes crap right out of the box. BTDT