Car vibrates when Tachometer is between 1 and 1.5 in Automatic Transmission. Idles below 1

My 2010 Hyundai Elantra GLS has 167k on it. I actually had a new transmission put in at 38K because of a factory defect. Havent had any problems since.

When I am giving the car gas and the tachometer is between 1 and 1.5 the entire car vibrates. When the car idles it does so below 1.

I didnt think anything of this until my friend was teaching me how to drive manual this weekend, and the same feeling I feel in my car is the same vibration i felt if I let up off the clutch too much before her manual would stall. Its not a violently shake - its that vibrating that happens right before the violent shake and the engine stalls out in the manual. (She has taught me that the ‘sweet spot’ to shift is right before said vibrations happen)

This transmission has not been touched since it was put in and has 129k on it. I am wondering if I need to get a transmission flush but I was reading if there are already problems with the transmission, a flush might exacerbate those problems.

Any help would be greatly appreciated.

Here are some specs that might be helpful:

Engine: 2.0L in-linefour-cylinder DOHC with variable valve timing and four valves per cylinder
Unleaded fuel
Fuel economy: EPA (08):, 26 MPG city, 34 MPG highway, 29 MPG combined and 406 mi. range
Multi-point fuel injection
14.0-gallon fuel tank
Power(SAE): 138 hp @ 6,000 rpm; 136 ft lb of torque @ 4,600 rpm

With that many miles, it could be engine miss or tranny. Does it idle poorly? Normal idle is below 1k rpms. I would not flush it. Just drop the pan and replace the filter and refill. I like dealers for tranny service. That way you know you’ll get the correct fluid. Also, I would have it test driven at the dealer or a reputable independent mechanic listed in the Mechanics Files link.

This tranny may be beyond help. Putting on 130’000 miles without any service to the tranny is just plain neglect on your part.

Because it is the tranny that you think is giving you problems, have you even checked the tranny dip stick to see if it’s low. The fluids abitity to do it’s job has been weakened and the fluid may just be worn out.

Avoid a flush, but ask for a total fluid exchange and filter…if it has one. You may get lucky.