Transmission Grinding in 4-Lo

Hey Guys,

The past few times I've used 4-lo I've noticed my transmission (6spd) feels like it's grinding when I shift, particularly from 1st to 2nd (I made a conscious effort to make sure the clutch was depressed all the way).

I've also noticed that even in regular 2wd driving sometimes it's hard to get the transmission into 1st- it physically won't go into gear until I partially depress the clutch. Are these problems related? Any suggestions for things to check/ how to fix?

Thanks!

 

Are you saying that you have been shifting withOUT depressing the clutch? Doing so will, unless you are VERY precise with shifting, be extremely hard on the transmission's synchronizers, causing excessive wear. When the synchronizers wear out, it will no longer be able to... synchronize the gears, causing an increase in grinding while shifting.

 

No, sorry that was unclear. When I try to shift into 1st from a dead stop, occasionally I can't get the transmission in gear without letting up on the clutch partially (I do this without giving it any throttle). In other words, I can't force the stick into first with the clutch all the way down, I have to let up slightly before it will go into gear.

 

I have a 2015 6 speed and only some times have trouble getting into 1st from a stop. I usually just pump the clutch a couple of times or shift into 2nd and up into 1st. What rpm's are you shifting in 4low?

 

Yep, that's the same problem I have. I notice the grinding when shifting at higher rpm's... not exactly sure but I'd say between 3 and 4k.

 

That's normal.
What do you have in the unit, in terms of gear oil? While I can't speak specifically about the 6-speed, I can say that the 5-speed is incredibly sensitive to the fluid. Crap gear oil like mobile 1 will make it grind gears terribly. Had that in mine for about 3 days before switching it out to amsoil MT, which brought it back to smooth.

 

I'm still running the fluid from the factory (25k miles) is it time to drain that and fill with something like the amsoil?

 

That's because the parts (dog clutch) isn't aligned, shifting to 2nd then to 1st should also work. When you let up on the clutch a bit it spins the transmission so the parts line up. Shifting to 2nd then to 1st also reduces wear on the 1st gear synchronizer ring by stopping the transmission. The 1st gear synchro is the only one I've seen worn out on a manual transmission (not on a Tacoma).

 

Wouldn't hurt. 25kmiles is probably a good time for a first gear oil change. Get all the manufacturing crud out of it. Subsequent changes can be at much longer intervals since gear oils don't get the combustion byproduct contamination like engine oil does.

 

Shifting a manual trans in 4lo is always more difficult than when in 2wd or even 4hi. So much more torque you have to make sure you time each shift perfectly otherwise it feels rough. It's normal.

 

Make sure you're always pressing the clutch completely in and I always try to shift nice and slow when doing so in 4lo.