# Transmission Mount Replacement in Upland > Clunk when shifting into drive? Route 66 Auto Repair in Upland checks transmission mounts under load, replaces broken ones and road-tests for vibration. Source: https://route66autorepairshop.com/transmission-services/transmission-mount-replacement Updated: 2026-09-17 Business: Route 66 Auto Repair, 1775 W Foothill Blvd, Upland, CA 91786, (909) 608-7699 Hours: Monday to Friday 8 AM–5 PM, Saturday 8 AM–2 PM, Sunday closed **TLDR:** A worn mount causes **clunks and vibration** on shifts. We test it **under load** and check the engine mounts at the same visit. A transmission mount holds the transmission to the frame and soaks up its movement, and Route 66 Auto Repair in Upland replaces mounts that have cracked, collapsed or leaked. A bad mount lets the drivetrain shift with every gear change, which you feel as a clunk or vibration. Our ASE-certified technicians check mounts with the engine under load, because a worn mount often looks fine at rest. ## What are the signs of a bad transmission mount? - A clunk when shifting from park into drive or reverse - Vibration through the floor at idle in gear - A bang when you accelerate hard or let off quickly - The shifter moves or shakes more than it used to - A visible crack or sag in the rubber - Fluid oozing from a hydraulic-style mount ## How do we test a transmission mount? With the car on the ground, a technician holds the brake and shifts between drive and reverse while another watches the drivetrain. Excess lift or twist shows a worn mount. On the lift we look for torn rubber, separated metal and oil soaking that softens the rubber. Transmission and engine mounts share the load. When one fails, the others work harder, so we check them together and label each one need-now or need-later. The [engine mount replacement](https://route66autorepairshop.com/engine-services/engine-mount-replacement) page covers the other half. A clunk can also come from a worn [U-joint](https://route66autorepairshop.com/drivetrain-and-additional-mechanical-services/u-joint-replacement) on rear-drive vehicles, and we rule that out too. A mount that let the drivetrain sag can also pull the [shift linkage](https://route66autorepairshop.com/transmission-services/transmission-linkage-adjustment) out of position. ## Our mount replacement process 1. **Load test:** We watch drivetrain movement while shifting under brake. 2. **Inspect all mounts:** Engine and transmission mounts are checked and photographed if damaged. 3. **Support and replace:** The transmission is supported safely while the old mount comes out and the new one goes in. 4. **Torque and road test:** Bolts are torqued to spec and we drive the car to confirm the clunk is gone. ## What's included in transmission mount replacement - Load test of all drivetrain mounts - Photos of cracked or separated mounts - Replacement transmission mount as quoted - Fasteners torqued to spec - Shift linkage and cable check after install - Road test for clunks and vibration ## Can a worn mount wait? **Need now:** - A mount that is fully separated - Drivetrain movement that pulls on shift cables or hoses - Loud bangs on acceleration **Need later:** - Small surface cracks with normal movement - Mild idle vibration only - An engine mount that shows early wear ## What sets the price of a mount job? Most transmission mounts are reachable from under the car, but some need a crossmember or exhaust part lowered. That access time is the main cost difference. If more than one mount is worn, the written estimate lists each separately so you can choose. Mount replacement is often done the same day when the board allows. ## After a new mount A new mount is stiffer than the old worn one, so you may feel a little more engine feel at idle for the first days. That is normal. A clunk that returns means another mount is worn, and it comes back to the front of our line. ## Frequently asked questions ### Is it safe to drive with a broken transmission mount? For a short distance, usually, but a fully broken mount lets the drivetrain move enough to stress hoses, cables and other mounts. We recommend replacing it soon. ### Should I replace engine and transmission mounts together? Only if they are worn. We test each one and label them separately so you only pay for what needs it. ### What causes transmission mounts to fail? Age, heat, oil leaks that soften the rubber, and hard launches. Engine heat in Inland Empire summers speeds up rubber aging. --- Call (909) 608-7699 or visit https://route66autorepairshop.com/contact for a written estimate.