SS #670 Modifications: Clutch

At some point I started having trouble with my clutch hydraulics. First I tried a new master cylinder. That helped for a while but eventually it became obvious I needed a new slave cylinder. Since that requires removing the transmission I decided to do the clutch at the same time. After enlisting help from my buddy who was a heavy truck mechanic I started ordering tools and parts.

Clutch Parts

GM	Description
12570806	LS6 flywheel/clutch
12565144	Master cylinder
24264182	Slave cylinder
14061685	Pilot bearing (needle bearing)
19299818	DOT 3 brake and clutch fluid (Delco 10-4090)

Installation Notes

• From day one my car leaked transmission fluid out the tail. The dealer even replaced the rear seal twice within the first three years. While prepping to do the clutch job I noticed that the area where the yoke and seal make contact was dry but there a drop of fluid on the integrated balancer. This caused me to a little research and I found that the yoke has a pressed-in metal seal that sometimes leaks. I had bought a spare yoke (GM 26061475) years before and decided to use it. This was not cheap as my driveline shop charged over $150 to replace the (still good) u-joints and install the new yoke but it definitely fixed the leak.

  

  I suspect it might be possible to fix the leak by tig welding the seal.

• Getting the clutch master cylinder out the first time can be a bit of a pain due to "star washers" that are used to keep the master in place during assembly at the plant. These are sandwiched between the firewall and clutch bracket. I found it necessary to loosen the four bolts on the bracket and two nuts holding the bracket to the steering column to get them out.

• Relevant sections of the service manual:

  • 3-7-54 Transmission replacement
  • 3-7-400 Clutch pressure plate and clutch driven plate 5.7 L

• At my buddy's suggestion, I made alignment pins cutting the heads off of two M10 x 1.5 x 100mm bolts. These worked great when we reinstalled the transmission:

  

• I used a Keyser Manufacturing 100-7414 clutch alignment tool. It is 1-1/8" in diameter with 26 splines and is made out of steel.

• The factory service manual says to remove the bell housing and transmission together. We found it easier to remove the transmission first and then the bell housing.

• We used an OTC 4581 blind bearing puller kit to remove the pilot bearing and it worked great:

  One thing you do not want to do is use a grease gun to push the bearing out using hydraulic pressure; LS motors have a seal similar to a freeze plug in block at the the end of crank that you do not want to push into the engine.

• I bought a Performance Tool W83151 hydraulic clutch line disconnect tools but never used it as I was able to remove the complete old hydraulic system intact. When we separated the transmission from the bell housing it was easy to remove the two bolts that hold the slave cylinder to the transmission and then just let it hang until removing the master cylinder.

• I wanted a remote clutch bleeder and used a Hinson remote clutch bleeder (TPSBL). Attaching it to the new slave cylinder was not straight forward. It uses a modified -4 AN to M10 x 1.5 adapter that is supposed to thread into the slave cylinder and seal with a copper crush wash. The problem is that the threads on the adapter aren't cut very close to the mating surface. This means when it's threaded all the way there is still a 0.100" gap so the surfaces don't even touch the crush washer which was about 0.030" thick. I'd since read that many folks have used these bleeder kits and have had them leak and I suspect this is why:

  

  With no time to source a better adapter (for example M10 to -3 AN adapters are available from ebay but ship from China) I used my drill press to clearance the first small part of the threaded hole in the new slave cylinder.

• The Tremec T-56 spec sheet says dry weight is 115-129 lbs.

• I used a Harbor Freight 60234 800 lb hydraulic transmission jack:

  
  It has a lift range of 8 to 24.5 inches. The platform has handy tilt adjusters and adjustable brackets but they didn't work well with the T56. When it was time to reinstall the transmission I cut up some scrap wood so that the transmission could be securely chained to the platform:
  

• After getting everything back together I found I could not engage the cruise control. This was because I used a LS6 clutch master cylinder which has a shorter stroke. This was easily solved by adjusting the clutch anticipate switch.

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Craig Leres