Fixing the M6……for good! Using this article as a guide that I printed out for Tim, I had Tim at Toms Oates Chevrolet upgrade my M6 into a higher performance transmission.
The transmission was getting worse. I couldn’t use 5th gear for 2 weeks before Skyline Drive because it would grind most of the time on the upshift from 4th (it would not downshift to 5th from 6th at all). I suspected it was bad synchros causing this. Then it started to not want to come out of 3rd or 4th. It was most likely a bent 3rd/4th-shift fork, since this is the only fork made from Aluminum (the other 2 are steel). Why is that? It would also pop out of those gears, usually when the car wasn’t under load (accelerating or slowing down) but in between (freewheeling).. Since the transmission was under warranty, it shouldn't cost me much or anything to have the upgraded high performance replacement parts installed instead of the standard GM parts. I also wanted them to do the drill mod to open up the restriction in the hydraulic clutch line. I got a price on the parts and placed an order on 6-23-03, $61.04 for the stronger shift fork (Rockland only replaces the 3-4 shift fork), $233.65 for 11 of the carbon fiber lining synchro rings, $31.30 for the Silicone Bronze "no walk" extension housing bushing. I got the prices from Cindy (ext. 113) at Rockland Standard Gear.
After explaining the above transmission problems with a tech support (George) at Rockland Standard Gear, he told me- 1. My transmission already has the carbon fiber lining synchro rings (they’re black, with no slots around the inner circle. The paper ones are brown with slots. 1st gear had paper, the rest were carbon fiber rings). So I will be returning the 11 carbon fiber lining synchro rings that I purchased since any damaged ones will be covered under warranty. I do want the steel fork and silicone bronze bearing install per the Rockland Standard Gear article. 2. It is a clutch problem. The clutch isn’t releasing when the petal is pushed in. He was quite certain about this and said that GM has been going around in circles with these common problems with the M6. When I asked about the “drill mod”, he said that MAY help but the biggest factor in making the transmission work well is the detail to the tolerances when putting it back together. 3. The fine teeth on the 5th gear may be damaged (they were), along with the synchos. He said that while the M6 is a good transmission, (it’s used in the Corvette and Viper) it will not stand up well to a couple of missed shifts. 4. I thought the 3rd/4th gear problem was due to a bent shifting fork, but he’s convinced that it is also the clutch not releasing that causes it to resist coming out of 3rd or 4th gear. He also said the roller cone bearings may be damaged by being pushed in too far.
These parts were replaced: 3rd, 5th, and 6th gear, throw out bearing, slave cylinder, gear select interlock plate, 5th-6th shift fork, most of the synchros and synchro rings, 2 cone assys., and some of the fork pads. The 3rd-4th steel fork and longer silicone bronze bearing from Rockland were installed and the drill mod was done. My clutch disk was normal for 20K miles, so I decided not to upgrade to the $518 Z06 clutch assy. All of this was done under warranty except for the labor involved with the drill mod. The car shifts much better then when new and I plan on installing the LSS very soon and removing the rubber insulator along with the factory Hurst shifter. I would like to thank Daniel J.(hawk_eye), Doug N. (Doug 97SS #1499), Tim C., and Rockland Standard Gear for their help in making this happen! Tom Oates Chevolet also loaned me a 2000 Malibu for 10 days at no charge.
Posted by DaddySS (Member # 848) on :
Thanks for write up.
Posted by Kevin V 2002 SS (Member # 1025) on :
![[Big Grin]](biggrin.gif)