Heavy vibration and trans noise

Jardon · Dec 20, 2025

Hey yall! Back again lmao. So, today (12/20/25) I had replaced the gear oil i put in my transmission unknowingly with Mercon V. I had also replaced the ancient trans mount with a urethane mount. While under my car, I noticed the front U joint for my drive shift has a good bit of play on one plane. After doing all the maintenance (oil change included), I noticed a very heavy vibration at 80mph, along with transmission noise on decel with no load (in neutral). Im really concerned whether or not my trans will have to be rebuilt. As for the U joint I know it'll have to be replaced soon anyway. My stang still drives and has all gears, but is noisy and kind of sucks to drive now. Any help or advice is very welcome. This is my first RWD car and my first time diving this far into really any car. Recent maintenance includes oil change (no oil came out of old filter and am confused about that), trans mount, clutch, trans oil drained and refilled (after I put in wrong fluid)

cobrajeff96 · Dec 20, 2025

If the u joint has play then it surely needs immediate replacement. It's not hard, either. Loads of youtube vids on how to do it. Or just replace the entire driveshaft.

Jardon · Dec 20, 2025

cobrajeff96 said:
If the u joint has play then it surely needs immediate replacement. It's not hard, either. Loads of youtube vids on how to do it. Or just replace the entire driveshaft.

Im honestly thinking thats most of the noise I hear when coasting in neutral to a stop. And after adding a much stiffer trans mount (old one was extremely loosy goosy) now i feel vibrations throughout the car that gets progressively worse with speed. Ive found some full assemblies on marketplace but i also like the idea of an aluminum drive shaft. Only issue is cost unfortunately