Shuddering SVX

My SVX with 117,000 miles on the clock recently had a new gearbox & torque converter fitted. Before this, the car had developed a strong vibration (after about 12 miles of travel.) It isn't felt through the steering - the whole car shudders. The vibration happens at 1500-2000 rpm when easing off the throttle to cruise at 50-60 mph. Dropping into 3rd gear whilst maintaining road speed increases the revs to about 3000 and the vibration stops. If neutral is engaged, the vibration also stops, but of course road speed drops as well. Accelerating also seems to stop the vibration. There is sometimes a lag in throttle response, but it is difficult to define when this occurs. Suggestions have been - a sticking calliper, all 4 were checked and Ok; electronic ignition; fuel injection system; & from the local Subaru dealer a noisy rear hub bearing! This was replaced and needless to say did not cure the vibration. Ignition & injection have not been ruled out, but probably they are best checked by the main dealer, however I don't want to pay their prices for a hit and miss diagnosis. Any ideas would be gratefully received.

1 possible cause could be your rear abs speed sesor catching the notched ring. When I did a drum to disk swap on my 1997 Impreza OBS I came across this issue. I attributed it to the sensor being from the OBS & the rear hub/brake assemblies being from a 1992 Legacy turbo. I later found out that it was just that in cleaning the surface to get the sensor in... I milled away enough (didn't take much) to cause them to interfer on some tight lowspeed corners.

This however isnt likely your problem... but could be a last resort to look at.

I would have your wheels/tires check for balance. what kind of condition are your struts/springs in?

Just some things to look at. sounds like it could be drive train related also.

[thumper_svx]

Funnily enough, Halistan's car has recently begun suffering from a similar vibration... though it's there all the time... not just after the car's warmed up.

His local shop suggested perhaps a slightly bent driveshaft... the sound is RPM-related though rather than speed (right around 1900 rpm... kind of the speed you're suggesting in your post), so I started to doubt a driveshaft (a driveshaft should be spinning at a different rate dependent on wheel speed... not RPM)

After driving his car, I surmised that it could be caused by cavitation in his transmission fluid.

He took his car to Jiffy Lube and had them flush the tranny... it didn't eliminate the problem but did make it less overbearing.

It has now been suggested that he might have an air leak in the fitting for his transmission temperature guage (aftermarket) that's letting air bubbles into the transmission. This seems reasonable to me and he is going to try disconnecting it sometime in the next couple of weeks.

Might be worth checking to see if the vibration is RPM related or wheel speed related. Try revving in neutral to around 1900 RPM to see if it occurs.

[Earthworm]

I had this shudder caused by having low ATF in the power steering reservoir. It only happened at around 60mph. I thought maybe the o-ring as the pump was making noise but changed my mind when I noticed no oil on the dipstick.

Looks like I'll be shopping for new power steering hoses as well.