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Triumph Repair/75 TR6 Metal Grinding Noise

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Question
Hi Howard,

My 75 TR6 developed a metal on metal grinding noise recently.  Here's what the symptoms are:

- Clutch rebuild 24 months ago with about 6000 miles on it since rebuild.
- 4 speed transmission, no OD
- normal N/A engine.  Nothing souped up.  
- looks like the front U joint on the drive shaft was replaced when the clutch was rebuilt.  Hard to tell if the U-Joint at the differential end was replaced.

Symptoms:

- engine running, tranny in neutral - all is good
- reve the engine (no load), - all is good.  No noise, no vibration
- depress the clutch with engine at normal revs, no noise
- put the tranny into first, definite metal to metal contact noise proportional to speed and highest when torque is highest and diminishes to nothing as the car accelerates.
- same thing after shifting to second but almost can't hear it
- 3rd and 4th same
-  once you are speed, no vibration, no sound
- if you stop the accel in any gear to torque up the engine, the sound returns.

So, before I take it into the shop, can you give me your thoughts?

My thinking is it's either something in the clutch, the U-joints on the drive shaft, or my tranny is starting to go. My gut says it's the clutch, I'm hoping it's just a u-joint and dreading it if it's a tranny.

Answer
Hi Nelson,

Sounds to me like a gearbox problem not a clutch problem. Keep in mind that 4th gear is direct drive and even though all the gears are spinning none are under load while in 4th. But a bearing noise can show up even in 4th.

I would have them closely examine the "U" joints and if they are ok you might as well open up the gearbox. Any noise that is noticeable will be easily spotted by any experienced mechanic once he is inside.

Howard

Triumph Repair

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Howard M. Fitzcharles III

Expertise

Triumph TR-4 up & Spitfire, and Engine theory

Experience

Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Organizations
Associate member SAE EAA member

Publications
Import Car magazine

Education/Credentials
ASE Master Auto with L-1 certification up to 2000

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