G56 3rd Gear Grind

[cumminbighorn06]

When I shift up from 2nd to 3rd, there is a consistent grind. I can double clutch to alleviate the small grind but the truck still doesnt shift smooth regardless. Down shifts no problem. Any ideas much appreciated. She's a 2006 / 68K miles / EFI on 40HP tune / no towing / Stock Clutch /

 

[Regcabguy]

From new mine and a friend's 2007 manufactured in late '06 exhibit a very slight "grind" on the 2-3 upshift especially when cold. He's got the stock clutch and mine is an SBC.
Hesitating a dab or shifting extremely quick eliminates or minimizes the effect.

 

[Motorhead]

My LATE, G-56 is real notchy when cold and the first shift or two when it has been in the thirties at night, is almost impossible to to get it into gear. Looks like a trend! I have the Delvac 50 in the trans and once the trans is good and warm, it is smooth. I have 87,000 miles on mine. How many miles on yours Dave?

 

[Regcabguy]

My LATE, G-56 is real notchy when cold and the first shift or two when it has been in the thirties at night, is almost impossible to to get it into gear. Looks like a trend! I have the Delvac 50 in the trans and once the trans is good and warm, it is smooth. I have 87,000 miles on mine. How many miles on yours Dave?

77K. Mine goes into gear well enough on cool mornings. The deal with mine ever since the smf conversion was installed is the difficulty getting it out of reverse on the first try. I nearly always have to recycle the clutch and it slides right out. After it's warm no issues.

 

[Motorhead]

Dave, did you put in the South Bend clutch master and slave assembly? They are adjustable at the clutch pedal which sets where the clutch engages or dis engages.

 

[Regcabguy]

Dave, did you put in the South Bend clutch master and slave assembly? They are adjustable at the clutch pedal which sets where the clutch engages or dis engages.

Yeah it's adjusted fine. Stopped in neutral it shifts between gears effortlessly. The only issue is after backing out of the driveway when cold I usually have to recycle the clutch.
The rest of the day it's fine.

 

[Motorhead]

The only issue is after backing out of the driveway when cold I usually have to recycle the clutch.
The rest of the day it's fine.

Okay, Mine does the same when cold. Try pulling it out of reverse while still rolling if possible. Blip the throttle a bit then pull it out of reverse. Up here in the Paso Robles area, it freezes at night in the winter. My truck parks in an enclosed car port with the one end opened. When it is real cold and I have the time, I back out of the car port, put the transfer case in neutral and the trans in 3rd or 4th gear and let the clutch out. I have the fast idle feature enabled and I pull my exhaust brake. I let it run for a minute or two then back into 2wd high range and go.
Dave, You have to try the turbo set up that Tom did for me. I kept the stock Holset and the stock compressor wheel. Tom modified the turbine side (exhaust side) and installed a stock Holset turbine wheel for the 6.7. This is how our stock, 5.9 turbos should have been set up. The truck just RUNS! Very, very hard to exceed 1150 EGT. Is is real responsive with the G56. Come up this way and drive mine!

 

[jgillott]

Mine has 111K on it now. It really shifts well at this point. I really felt a difference as it got close to 100K.

 

[Motorhead]

Mine has 111K on it now. It really shifts well at this point. I really felt a difference as it got close to 100K.

What oil have you run it the trans?

 

[jgillott]

Factory ATF+4

 

[Regcabguy]

Factory ATF+4

Stock clutch?

 

[Regcabguy]

Chris,that turbo mod sounds great.
Hopefully,I can swing it someday.

 

[jgillott]

Stock clutch?

Yes, original stock clutch.

 

[RVTRKN]

When I shift up from 2nd to 3rd, there is a consistent grind. I can double clutch to alleviate the small grind but the truck still doesnt shift smooth regardless. Down shifts no problem. Any ideas much appreciated. She's a 2006 / 68K miles / EFI on 40HP tune / no towing / Stock Clutch /

There is a distinct possibility that the syncro has worn. Then there is "was it there from new," if not, then syncro is probably bad. Double clutching will help, but its probably time to pull it and have it rebuilt. There are many faults the G56 has, so its a good time for a rebuild. Change the oil to a heavier oil like Delvac 50, unfortunately if you have the OEM ATF4 in it, you wont see the golden glitter from excessive wear of the brass syncro's. If the heavier oil works, then no need to rebuild.

 

[cumminbighorn06]

There is a distinct possibility that the syncro has worn. Then there is "was it there from new," if not, then syncro is probably bad. Double clutching will help, but its probably time to pull it and have it rebuilt. There are many faults the G56 has, so its a good time for a rebuild. Change the oil to a heavier oil like Delvac 50, unfortunately if you have the OEM ATF4 in it, you wont see the golden glitter from excessive wear of the brass syncro's. If the heavier oil works, then no need to rebuild.

I bought her used, didn't really notice it when I bought it with 49K miles on the clock.

 

[RVTRKN]

Do you want to convert to a SMF? If so, then it would be a good time to pull the trans and have it rebuilt and converted to a SMF. The front bearing housing tends to wear enough to have to be reshimed. When you pull it, check the end play on the input shaft.

 

[cumminbighorn06]

If the syncro is bad wouldn't it grind for the up shift and the down shift??

 

[RVTRKN]

Depends on RPM at point of shift.

 

[RVTRKN]

Here's a animation on the basic auto transmission I've posted before, it'll help in understanding the workings of synchro's. https://youtu.be/wCu9W9xNwtI

 

[DClark]

There is a distinct possibility that the syncro has worn. Then there is "was it there from new," if not, then syncro is probably bad. Double clutching will help, but its probably time to pull it and have it rebuilt. There are many faults the G56 has, so its a good time for a rebuild. Change the oil to a heavier oil like Delvac 50, unfortunately if you have the OEM ATF4 in it, you wont see the golden glitter from excessive wear of the brass syncro's. If the heavier oil works, then no need to rebuild.

I just replaced my G56 with a ST rebuild. They informed me that the newer GT56s don't have brass syncro's. Gone to fiber, which does not wear as well. ST recommends Amsoil. My year is up and I'm going to Delva 50. I had good success with Pensoil synco-mesh. I liked the way it shiffed. It gets cold here in MT. Maybe I should stick with the Pensoil.
DClark