My 97 XJ has a vibration at 65 mph and it gets worse faster. It is not a death wobble. I have a brace welded and bolted on by my steering box, but that didn't help. Tires have been balanced many times. Even different sets of wheels. It starts at about 2100 RPMs in drive. If I go 2100 RPMs in another gear, there isn't a vibration. So I don't think it's the driveshaft.

I went for an oil change and my mechanic noticed that on the short front axle (driver's side) there is a boot and he thinks the axle is for an ABS brake.
There is a gear looking thing by the boot. There isn't one on the passenger's side axle.

Could this be the problem? Anyone have such an axle?