Thicker oil than synchromesh fluid?

[Chris142]

5th gear in my jeep is pretty rattly. I would like to try a thicker oil just for giggles.

Reading about synchronesh fluid it seems that it's designed to handle water contamination. Thats not something I have to deal with.

Any recomendations for an oil that's thicker that would replace synchromesh fluid?

 

[Sequoiasoon]

Which synchromesh?

@MolaKule has that covered for us. https://bobistheoilguy.com/forums/threads/updated-list-of-mtfs-may-1st-2026.383388/

 

[Rygrego]

5th gear in my jeep is pretty rattly. I would like to try a thicker oil just for giggles.

Reading about synchronesh fluid it seems that it's designed to handle water contamination. Thats not something I have to deal with.

Any recomendations for an oil that's thicker that would replace synchromesh fluid?

3 years ago I stopped using Synchromesh fluid in my 2002 Wrangler NV3550, 5 speed and switched to RedLine MT-90 and could not be happier. The transmission is quieter, not notchy when shifting and just a pleasure to drive. I believe Synchromesh fluid was for fuel economy as it's like the consistency of water. 3 years later I would never go back to Sychromesh. It's not cheap but worth it.