Clutch bearing may be going out on kompressor.
Most times it is an out of balance tire, but if balancing does not fix it check out the wheel bearings and suspension parts, a harmonic distortion will cause a shudder at a certain speed. Basicly the vehicle makes a sound or vibration at that speed that amplifies into what you feel.
Warped rotor(s).
The actual removal of the thermostat will not cause this condition but if you possibly disconnected a vacuum hose white changing the thermostat, WOULD cause that problem. Check all of the vacuum hoses to make sure they are connected and tight.
A bad transmount or transfer case .
The blower motor resistor/power module has failed.
A bad alternator will cause a battery to go bad. It does not have an effect on the air conditioner.
There are many ways for a Hyundai tiburon's air conditioner to mulfunction.
Without knowing what "shudder and skip" means, but knowing that it occurs at a specific speed at all times, I might look to a gear noise issue. All gear sets have a noisy speed - They are generally engineered to occur at speeds that are not expected to be used as constant speeds of travel. In other words, they are designed to occur when you will only experience them for a short time, as you move through the 'noisy' speed. The shuddering and skipping might suggest that you have depleted or insufficient lubrication in the differential. Of course, this is an answer most applicable to a rear-wheel-drive system. ________________________________ If you have a front-wheel-drive vehicle: Is there a shift point near this speed? If so, then you may have a transmission 'dropping' into a gear that the vehicle is not 'ready' for? This could cause the engine to 'lug' and could generate a "shudder and skip" sensation. The problem would lie in the transmission.
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a very specific range for a shudder is either from worn front end parts or unbalanced tires. The tires should be speed balanced and the front end should be checked for worn parts.
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possible motor mount problem, when you turn the steering wheel- the wheels line up at a differant height and if the motor mount is totally shot then this cause the motor to bind with the tranny and or front axels depending on the car