What Happens When a Transmission Mount Breaks?

Transmission mounts help to stabilize and support the main engine driveshaft, which is an extension of the engine crankshaft that runs through the transmission and connects with the rear vehicle axle. The driveshaft spins in tandem with engine speed and meshes with the transmission gears to affect transmission operation. When a transmission mount breaks, stability is lost in the area supported by the broken mount. This loss of stability leads to increased engine driveshaft vibration and noise, which is often times transmitted into the passenger vehicle compartment, a condition that can be quite noisy at higher engine speeds.

In addition to helping stabilize a vehicle transmission, transmission mounts also help keep a transmission aligned properly in relation to the engine and the engine driveshaft. The entire transmission housing must be aligned properly to allow for the driveshaft to enter the transmission properly and to link up correctly with the inner transmission gears and spindles. A broken transmission mount can alter transmission alignment and cause an ill-fitting link to exist between the transmission and driveshaft, and in severe cases, cause damage to the driveshaft and/or transmission/driveshaft coupling.

Vehicle transmissions are heavy mechanical parts that require significant support to properly stabilize. Transmission mounts shoulder the brunt of the weight of a transmission; they help to distribute the transmission weight equally over the entire length of the transmission. When a transmission mount breaks, a large part of the transmission weight becomes unstable, and in severe cases, the strain of the unsupported transmission weight can cause parts of the transmission housing to crack, break, or become warped. If multiple transmission mounts break simultaneously, severe transmission damage, both to the outer housing and the internal parts, can occur.