Grinding into 4th gear
Thread Starter
Racer
Joined: Sep 2004
Posts: 368
Likes: 0
From: Melbourne FL
Grinding into 4th gear
I was crusing yesterday, doing a little spirited driving when I noticed a grinding noise while making the 3 - 4 shift. The clutch is not sliping, fluid is clean and the level is fine in both the trans and the clutch booster.. It will hold power in any gear even 4th, it just grinds into 4th from 3rd. Syncro?, I don't think fork sicne I have no problems going into 3rd and it does go into 4th it just has that grind. Also, I notice it is easier into 4th at lower RPMs. Sugestions?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
My 98 had the same issue and I changed the tranny fluid and the problem went away. You can up-grade from a standard ATF tranny fluid to a synthetic ATF for a better shift performance!
I used Mobil 1 Synthetic ATF.
I was so impressed in the improvement, I changed the fluid in my new at the time 02 ZO6. It also improved in shift feel.
BC
I used Mobil 1 Synthetic ATF.I was so impressed in the improvement, I changed the fluid in my new at the time 02 ZO6. It also improved in shift feel.
BC
Le Mans Master
Joined: Feb 2002
Posts: 6,937
Likes: 21
From: Waldorf MD
On my 1998 C5 I changed my transmission fluid to Mobil 1 ATF at 49,000 miles and then to Amsoil ATD (you can also use ATF) at 100,000 miles when it started grinding going into sixth gear. Amsoil fixed the grinding.
I hear that these transmissions are sensitive to dirty transmission fluid and GM never recommends changing it, go figure ?
I have heard conflicting reports whether early C5's have "paper" blocker rings in the transmission. They say most synthetic fluid is not good for these EXCEPT Amsoil. I would, and do, use Amsoil. Synthetic makes the transmission easier to shift, especially in cold weather.
I hear that these transmissions are sensitive to dirty transmission fluid and GM never recommends changing it, go figure ?
I have heard conflicting reports whether early C5's have "paper" blocker rings in the transmission. They say most synthetic fluid is not good for these EXCEPT Amsoil. I would, and do, use Amsoil. Synthetic makes the transmission easier to shift, especially in cold weather.
Last edited by Oldvetter; Jul 1, 2007 at 11:32 PM.
Thread Starter
Racer
Joined: Sep 2004
Posts: 368
Likes: 0
From: Melbourne FL
True, I have not tried sync yet, but my shop did pull all my fluid and it was clean without debris. Moreover, if the fluid was the issue, wouldn't I have problems in ALL GEARS? This is just 4th and from the 3 to 4 shift. I can down shift into 4th from 5th without issue. (Forgot to mention that). I am thinking maybe the 3-4 forks they may just be slightly bent in one direction?
Burning Brakes
Joined: Jan 2004
Posts: 896
Likes: 1
From: Overland Park KS
I had *exactly* the same issue, and then it eventually stuck in 4th gear and required an act of God to get it out. The tranny had to be rebuilt.There's a GM TechLink report covering this issue -- my tranny repair ended up being covered by GM:
http://www.corvetteactioncenter.com/....php?qstId=533
Had warranty not covered it, I would've had RPM do the work.
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Race Director
Joined: Jun 2004
Posts: 19,459
Likes: 48
From: Schaumburg IL
CI 7-8-9-11 Veteran
St. Jude Donor '06-'10, '13
The T56 is notorious for synchros going bad. Mine are toast from 1-2nd. In my 99Z28 5th-6th went.
There is always that glimmer of hope in ones mind when this happens that it's just the fluid...but if you checked yours and also had a shop look at it and it's fine, it's your synchros.
I am actually headed to see Rodney at RPM this Friday
Pro
Joined: Jan 2006
Posts: 716
Likes: 1
From: Bay Area CA
Its definitely the syncro. Actually the same syncro is used for 3rd and 4th gears in tha transmission. About 9 months ago I had the same problem but with 3rd gear. You will most likely want to replace the syncro along with 4th gear as well, sicne the grinding is actually wearing the gear down.
Good luck. At the dealer this is approximately a $2000 job.
Warranty Warranty Warranty!
Good luck. At the dealer this is approximately a $2000 job.
Warranty Warranty Warranty!
