Major mystery with two 6L80s

[Darin Morgan]

Never asked for help on this board before but I really need it now!

A friend and I recently purchased a complete rebuild kit with the Red Eagle double bonded clutches and Alto steals. I was the first to rebuild and after wards I encountered a problem. When you first start the car, put it in drive and take off, multiple clutch packs ratchet ( engage and disengage) about five to seven times with an addible clicking sound (when heard from outside the car). You can then drive the car around all day with out this happening but as soon as you shut the car off and let it sit for about five minutes it will do it again on initial take off. I thought it was my shitty rebuild effort so I took it to a pro and he rebuilt it. On inspection he siad I had done nothing wrong and the rebuild was fine. My friend just got done with his rebuild using the same kit and now has the same problem. We have both messed around with different tunes and volume presets trying to eliminate the problem.

Anyone have any insight?

[wreckwriter]

Interesting. Mine goes in for rebuild tomorrow............ I'm using Raybestos clutches.

[Darin Morgan]

Interesting. Mine goes in for rebuild tomorrow............ I'm using Raybestos clutches.

They Are called Alto red Eagle clutches but they may very well be produced by Raybestos.

[Waker]

Hey Darin, I've been working with Mike and getting some inside scoop from other parties. The tranny is designed to cycle all the pcs solenoids after initial startup. Being that you have increased your clutch surface area, you are now feeling something GM built into the tranny. You can log most if not all 6L80Es doing this. I have a built trans, but I don't run Altos and have not encountered this problem. It appears you just have too much surface area in there for the tune. I'm sure it can be fixed with some serious time in tuning the base tables and maybe the presets, possibly setting a level that appears to be less than desirable. Or, you can pull the tranny back out and remove one clutch from your problem area (2/3) and try that. Good luck

[Darin Morgan]

Hey Darin, I've been working with Mike and getting some inside scoop from other parties. The tranny is designed to cycle all the pcs solenoids after initial startup. Being that you have increased your clutch surface area, you are now feeling something GM built into the tranny. You can log most if not all 6L80Es doing this. I have a built trans, but I don't run Altos and have not encountered this problem. It appears you just have too much surface area in there for the tune. I'm sure it can be fixed with some serious time in tuning the base tables and maybe the presets, possibly setting a level that appears to be less than desirable. Or, you can pull the tranny back out and remove one clutch from your problem area (2/3) and try that. Good luck

Yep, thats the problem. below is what I posted on another forum stating what we did to fit the other 2 clutches in the packs. The trans hits hard and firm now.


The stock clutch clearances are .045 to .065 normally. Because the double bonded clutches have a much higher coefficient of friction they need more area between them to set up a hydrodynamic wedge. The 6L80 transmission will cycle through the solenoids on first start and if the clutches are to tight, the car will jerk VIOLENTLY 6-7 times when first started and put in drive. Installing the clutches with .080 clearances on ALL clutch packs will eliminate this problem and give the pressure purge some where to go but not apply the clutches violently 6-7 times. In order to accomplish this clearance you must precision grind the clutch backing plates. Other wise you wont be able to get the clearance to .065. The real kicker here is, the directions tell you to put them at .045-.065! but .065 is not enough.

Special thanks to Mike at Century Transmissions for lending his expertise and getting me out of this jam.