Noisy transmission

[Layne]

If an E9 4 speed (G262) is noisy when using Redline MTL, is there another fluid that might make it quieter? I know the MTL is kind of thin, but most thicker fluids are not compatible with syncros. (I know Redline has MT90, but the difference between MTL and MT90 is very marginal) The noise is mostly in 3rd gear, sounds like a rumbly bearing. It's not drastic, but noticeable.

 

[lloyd]

If an E9 4 speed (G262) is noisy when using Redline MTL, is there another fluid that might make it quieter? I know the MTL is kind of thin, but most thicker fluids are not compatible with syncros. (I know Redline has MT90, but the difference between MTL and MT90 is very marginal) The noise is mostly in 3rd gear, sounds like a rumbly bearing. It's not drastic, but noticeable.

You have a number of lubrication choices, but if your transmission has significant wear, it is doubtful that any of them will cure the problem.

If you are only trying to increase viscosity, you could try adding some of the viscosity improvers commonly used in engines, e.g., "STP" or "Wynns Friction Proofing." To the best of my knowledge, these additives do not contain extreme pressure lubricants commonly found in hypoid lube that attacks yellow metal "GL5." Another option is replacing Redline with one of Amsoil's transmission lubes that are also GL-4 rated and therefore yellow metal compatible. LubroMoly also offers a GL4 75W 90 alternative. Another alternative is engine oil (see below).

https://www.e9coupe.com/forum/threads/oil-for-manual-gearbox.4518/

Can I use STP® Oil Treatment in my manual transmission?
STP® Oil Treatment has been used successfully in manual transmissions, gearboxes and differentials at a 10% treat-rate by volume (i.e., 90% oil and 10% Oil Treatment by volume). Do not overfill.

 

[pat cooks]

Probably worn layshaft bearings, 3rd gear puts the most load on the layshaft, 4th gear does not use the layshaft at all, try engine oil and pick up a spare 4 speed box, easy to change as you do not need to remove the bellhousing just the four bolts holding the gearbox to it, Pat