4th gear grind

[dallenj]

Im havimg issue going in to 4th at high rpm. When I try to it will ho in but it makes an awful grinding noise. I took it to the dealer and they said when you shift quickly the synchros dont have time to synchronize to the transmission gears. That explanation kind of sounds like bull shit to me so they can get out of doing work under warranty.

My real question is, is this something that actually happens or should I fignt it to get it fixed. My other questions is what else could be wrong with my transmission.

[cdq85]

The year and mileage of car will be important in your case here. That issue should be covered under your powertrain warranty of 5 years/60,000 miles. Maybe push the issue with the dealer a little more because I can shift quickly just fine. Also, are you pushing the clutch in all the way when you are shifting?

[bababooey]

i recently had this begin happening over that thanksgiving trip. 3 to 4th gear crunch, only high rpm (WOT or 65% on gas pedal didnt change the crunch @ same rpm). i attributed it to too (tutu) quick a shift. but 1-2 & 2-3 with similar effort no issue. will keep aware of this condition, hoping it doesnt cause further issue.

EDIT--2014 with about 19K on the clock

[bababooey]

and that crappy thing is that 3-4 shift @ 6-7k rpm is merging on the highway speed settling into the flow of traffic

[Spartarus]

Originally Posted by dallenj

They said when you shift quickly the synchros dont have time to synchronize to the transmission gears. That explanation kind of sounds like bull shit to me so they can get out of doing work under warranty.

Aaaand Right you are! that explanation is bull shit!

Here's why. On an old-school Toyota W-series truck transmission, that would be true. But those transmissions are missing a critical part that ours has.

The Aisin Az6 derivative that sits in our cars has baulk rings in the synchros. If those are working correctly, the baulk ring and its associated components prevent gear engagement until the gear speeds match.

Old school synchros relied on spring pressure and a ball bearing to stop the synchronizer sleeve from sliding over the engagement teeth until pressure was applied. When you pull fast and hard, or the synchros are worn out, you can easily overpower that system, causing the gear to engage before it has had time to synchronize.

I attached a few semi-relevant pictures. The larger shows a super-old-school synchro. The smaller picture shows the three inserts and spring that form the baulk ring. It also depicts a triple-cone synchro. You can have a baulk ring without triple cone synchros.

For curious people, the following link has a good summary on how baulk rings work. http://www.cdxetextbook.com/trans/cl...baulkring.html

Incorrectly functioning or broken baulk rings are also responsible for shift lock-out, and other problems. If they are broken, the dealer should fix them, not lay on some horsesh*t explanaion that isn't true.

[humfrz]

WOW ...... that's a hard post to follow ..........




Remember, @dallenj a warmer transmission is a happier transmission.

I would suggest that when shifting, wind up the last gear pretty tight (4-5,000 rpms) before shifting into the next higher gear.

Also, when shifting, pull (or push) the shift lever slowly and firmly into the next gear.

It's not a toggle switch ..... the lever is moving heavy transmission parts.

I suggest you NOT "lazy leg" it ……. push the clutch pedal all the way to the floor.

If this technique doesn't help, you may consider changing the transmission oil.

If that technique or oil change doesn't work ...... I reckon, there is something wrong with your car's transmission.


humfrz

[bababooey]

Originally Posted by humfrz

If this technique doesn't help, you may consider changing the transmission oil.

If that technique or oil change doesn't work ...... I reckon, there is something wrong with your car's transmission.


humfrz

hesitant to change oil until making formal complaint with dealer and getting some paperwork on it. to attempt to avoid the theory 'oh u changed the oil, we deny that transmission any legitimate service".

[Ultramaroon]

What @Spartarus said. Total BS. If someone from your dealership won't go out on a drive with you, take it somewhere else. It will only get worse over time.

[Toyarzee]

Originally Posted by Spartarus

Aaaand Right you are! that explanation is bull shit!

Here's why. On an old-school Toyota W-series truck transmission, that would be true. But those transmissions are missing a critical part that ours has.

I actually have a w58 and w59 tranny opened up in my garage right now. I couldn't figure out why it was so impossible to keep them running on a motor with anything over 250 ft. lbs. torque... it's been a point of contention trying to swap into an r series tranny instead. Good read as always Mr. Spartarus.

[dallenj]

Thanks for the help guys my car has 33k miles on it and is a 2013. When I do shift into 4th I do depress the clutch all the way and it still does that quick grinding noise. I have tried to take it to 2 different dealerships one said there was no issues and the other said what I mentioned before. I have done this when the car was warm to I had been thinking it could have been because of a cold transmission but I had drove it all day and decided to floor it getting on the highway and it still happened. I will try a dealership again and if that doesn't work I will try to change my trans oil to see if that helps.I ll keep this thread up to date to help anyone else with this problem.

[Trust86]

2 hello kitty band aids
1 on the reverse lockout for JDM points and 1 on the transmission
The band aids will aid with the 4th gear grind, and hello kitty will aid with heating up the transmission faster and keeping it happy

[Spartarus]

Originally Posted by dallenj

When I do shift into 4th I do depress the clutch all the way and it still does that quick grinding noise. I have tried to take it to 2 different dealerships one said there was no issues and the other said what I mentioned before. I have done this when the car was warm to I had been thinking it could have been because of a cold transmission but I had drove it all day and decided to floor it getting on the highway and it still happened. I will try a dealership again and if that doesn't work I will try to change my trans oil to see if that helps.I ll keep this thread up to date to help anyone else with this problem.

Changing your trans oil will not fix the broken parts in your transmission. It may mask the issue if you are very lucky. Even then, it will not mask it under all conditions. If it is grinding on normal engagement, something IS broken. Read my above post carefully. It was not a subject of speculation.

It is not because of a cold transmission. A cold transmission will cause different issues, not the one you have. A cold transmission with this synchro design will be very hard to shift, very notchy, and occasionally lock you out if you have poor technique. But it will NOT grind... If you drag the clutch and try to make it grind, it will lock you out of gear. If this doesn't happen, and it does grind, it is broken, and needs fixing.

You can make a transmission with correctly working baulk ring synchronizers grind, but it is a complicated process. Feel the shifter carefully, there are 2 separate and distinct "clicks" or "notches" (or whatever you want to call them) from neutral into each gear. If you move past the first click of the baulk ring falling into place and then hover on the edge of gear engagement, it will grind. Same goes to taking it only slightly out of gear and hovering.

I have taken apart more than a few transmissions because of this issue.

[dallenj]

Originally Posted by Spartarus

Changing your trans oil will not fix the broken parts in your transmission. It may mask the issue if you are very lucky. Even then, it will not mask it under all conditions. If it is grinding on normal engagement, something IS broken. Read my above post carefully. It was not a subject of speculation.

It is not because of a cold transmission. A cold transmission will cause different issues, not the one you have. A cold transmission with this synchro design will be very hard to shift, very notchy, and occasionally lock you out if you have poor technique. But it will NOT grind... If you drag the clutch and try to make it grind, it will lock you out of gear. If this doesn't happen, and it does grind, it is broken, and needs fixing.

You can make a transmission with correctly working baulk ring synchronizers grind, but it is a complicated process. Feel the shifter carefully, there are 2 separate and distinct "clicks" or "notches" (or whatever you want to call them) from neutral into each gear. If you move past the first click of the baulk ring falling into place and then hover on the edge of gear engagement, it will grind. Same goes to taking it only slightly out of gear and hovering.

I have taken apart more than a few transmissions because of this issue.

Thanks for the help I will try to post a video of my promblem to correctly diagnose it. I just want a second opinion on whats happening. When I post the video I will quote you to make sure you know I posted it. You seem pretty knowledgeable.

[zypher10]

Originally Posted by Spartarus

Changing your trans oil will not fix the broken parts in your transmission. It may mask the issue if you are very lucky. Even then, it will not mask it under all conditions. If it is grinding on normal engagement, something IS broken. Read my above post carefully. It was not a subject of speculation.

It is not because of a cold transmission. A cold transmission will cause different issues, not the one you have. A cold transmission with this synchro design will be very hard to shift, very notchy, and occasionally lock you out if you have poor technique. But it will NOT grind... If you drag the clutch and try to make it grind, it will lock you out of gear. If this doesn't happen, and it does grind, it is broken, and needs fixing.

You can make a transmission with correctly working baulk ring synchronizers grind, but it is a complicated process. Feel the shifter carefully, there are 2 separate and distinct "clicks" or "notches" (or whatever you want to call them) from neutral into each gear. If you move past the first click of the baulk ring falling into place and then hover on the edge of gear engagement, it will grind. Same goes to taking it only slightly out of gear and hovering.

I have taken apart more than a few transmissions because of this issue.

I'm having the same issue, 3rd to 4th gear grinding at high rpm. only happened after i installed a whiteline shifter bushing, would this cause this?