Hi all,

I’ve been posting a lot lately since I just took possession of my ‘05, but just trying to get things sorted out. I’ve noticed that the shifter **** vibrates (almost like a grinding, but no noises) when I shift into third from second and sometimes when I shift into second from first. It appears the fluid in the trans was replaced about 15K miles ago with 80W-90 (I don’t have any more information about the fluid that was used - but with 80W-90 seems to be gear oil, not necessarily MTF). Would this issue potentially be rectified by changing to something like the Motul or Redline fluid I’ve read so much about?

Thanks!

 

It could be many things, but you should consider switching to a proper GL-4 fluid. First off, 80w90 is the wrong viscosity; it should be 75w90. But more importantly, if that is gear/differential oil, it can reduce the effectiveness of your synchros and possibly lead to grinding. Some are also slightly corrosive to the brass synchronizers as well.

Start by changing to a good GL-4. I've used Redline for a few years and would recommend MT90 if you are in a warm climate, and MT85 if you are in a colder one.

 

+1 on MT90. Had 3rd gear grind from both directions (and its probably the most worn synchro anyway) and it magically fixed this issue. 75w90 is too thick and the Redline fluid is "less slippery" or it says on the bottle. This helps make the cones match up. You need a little friction for it to work properly.

 

I'll probably be doing this fluid swap since I also have 3rd gear synchro issues as well. But, I find it more than funny that redline is being marketed as "less slippery". Who sells lubricants and makes a point of it being "less"?

 

Because without certain friction properties, things like synchros and clutch packs can't work. There are more than a few good videos out there on how synchronized transmissions work that explain it better. There are two "smooth" surfaces that rub each other that in essence, brings the teeth of the synchro to match the teeth on the gear (I guess its the hub). When you grind gears, you're grinding the synchronizer dog teeth, not the helical "driven" gear teeth. There are a number of things in these transmissions that can make shifting notchy too. Detents on the shift rods, keeper pins on the synchros and general slop in the transitional points that allow you to put pressure on a shift **** which ultimately pushes a shift collar.

Its still 100 times simpler than an automatic.

J

 

Thanks for the excellent explanation udelslayer!