Vibration at 1800 and 3800 rpm

So at 250,000 miles I just had to replace the factory CV axle passenger side (the longer one). Since I'm in Mexico I don't have tons of choices and had to go with an Autozone axle Ever since the replacement I get a light vibration right at 1800 and 3800 rpm. Doesn't matter the speed or gear I'm in, just at that rpm. Doesn't happen tho if I'm just sitting in neutral and revving the engine. Best way I can describe it like if the engine was bolted directly to the frame and you can feel the harmonics of the engine. But it smoothes out above & below that rpm. The new axle is a solid bar type, not the larger hollow OE style, so maybe it doesn't dampen harmonics as good as the OE axle?
It's annoying but I've gone over 2,000 miles now like this and its still the same, but doesn't seem to affect anything else and hasn't gotten worse or better.
Nothing else was replaced or changed so could it just be this axle causing the vibration?

Axles run at road speed, not engine speed, so the axle rotation should not be the problem. I think engine mounts would be more important sources of engine vibrations being transmitted to the frame. I am not sure what is involved with the axle replacement. Did everything get tightened up correctly?

This has come up a few times and the fix has always been to go back to OEM tube style axles. Think of it this way: solid axles transmit more engine vibrations to the suspension and body than tube axles at every rpm. If your engine has small vibes at 1800 and 3800 they’re going to be felt in every gear. Don’t chase other theories. You didn’t have this problem before the axle swap...


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Cheap solid RH axle usually. Does not matter whether A4, A5, Auto or manual trans.
I pull them off regularly and can identify the sound after the first rev of a test drive.
It is always 1800/3600 rpms. That is where is all resonates.