1st Gear Grinds
Thread Starter
Melting Slicks
Joined: May 2001
Posts: 2,186
Likes: 7
From: Evansville, IN The GOCC, rebels without a clue.
St. Jude Donor '06
1st Gear Grinds
A friend's '06 Z51 had a disasterous problem with his diff a month or so ago. It caused a catastropic failure that sheared the teeth off the couter shaft in his tranny. The transmission has been out of his car for service twice now, and is still having some problems.
The symptoms are when sitting at a light with the transmission in neutral if you push the clutch in and try to shift into 1st immediately you get a horrendous grinding sound. It does the same during a downshift from 1st to 2nd when rolling to a stop. If you sit at a light and push the clutch in and wait for about 5 or 6 seconds you can shift into first OK.
We went through the service manuals over the weekend trying to figure out the power flow and what may be at fault here. We think it's the synchronizer for 1st and 2nd. We can't figure out why it would only affect 1st gear if it is the synchonizer. I'm thinking it may also be a bent or worn shift fork. Anyone have any ideas? The car is still under warranty and he's waiting to hear from GM what they're going to do.
The symptoms are when sitting at a light with the transmission in neutral if you push the clutch in and try to shift into 1st immediately you get a horrendous grinding sound. It does the same during a downshift from 1st to 2nd when rolling to a stop. If you sit at a light and push the clutch in and wait for about 5 or 6 seconds you can shift into first OK.
We went through the service manuals over the weekend trying to figure out the power flow and what may be at fault here. We think it's the synchronizer for 1st and 2nd. We can't figure out why it would only affect 1st gear if it is the synchonizer. I'm thinking it may also be a bent or worn shift fork. Anyone have any ideas? The car is still under warranty and he's waiting to hear from GM what they're going to do.
Le Mans Master
Joined: Jul 2005
Posts: 5,328
Likes: 405
A friend's '06 Z51 had a disasterous problem with his diff a month or so ago. It caused a catastropic failure that sheared the teeth off the couter shaft in his tranny. The transmission has been out of his car for service twice now, and is still having some problems.
The symptoms are when sitting at a light with the transmission in neutral if you push the clutch in and try to shift into 1st immediately you get a horrendous grinding sound. It does the same during a downshift from 1st to 2nd when rolling to a stop. If you sit at a light and push the clutch in and wait for about 5 or 6 seconds you can shift into first OK.
We went through the service manuals over the weekend trying to figure out the power flow and what may be at fault here. We think it's the synchronizer for 1st and 2nd. We can't figure out why it would only affect 1st gear if it is the synchonizer. I'm thinking it may also be a bent or worn shift fork. Anyone have any ideas? The car is still under warranty and he's waiting to hear from GM what they're going to do.
The symptoms are when sitting at a light with the transmission in neutral if you push the clutch in and try to shift into 1st immediately you get a horrendous grinding sound. It does the same during a downshift from 1st to 2nd when rolling to a stop. If you sit at a light and push the clutch in and wait for about 5 or 6 seconds you can shift into first OK.
We went through the service manuals over the weekend trying to figure out the power flow and what may be at fault here. We think it's the synchronizer for 1st and 2nd. We can't figure out why it would only affect 1st gear if it is the synchonizer. I'm thinking it may also be a bent or worn shift fork. Anyone have any ideas? The car is still under warranty and he's waiting to hear from GM what they're going to do.
Thread Starter
Melting Slicks
Joined: May 2001
Posts: 2,186
Likes: 7
From: Evansville, IN The GOCC, rebels without a clue.
St. Jude Donor '06
It sounds like the 1st gear synchro has failed. The 1st/2nd synchronizer is actually two synchros on one ring. One side of the ring is for 1st gear and the other side is for 2nd gear. When the 1st gear synchronizer fails, the 2nd gear synchro is not affected (usually). Tell him good luck with repairs!
Don
