I have a new full roller c6 built by Jim @ JPT. He used one of his non transbrake, fully manual, reverse pattern valve bodies. Well, 2 weeks ago, I finally got my Strange axle, so I could take the truck for a spin. 2nd gear hit hard, shifted into 3rd and it flaired. Under very very light throttle, its a quick, hard shift. But medium throttle or above, it flairs (shift @ 5500, it'll flair to 6500 and then shift firm). It feels like I jab the clutch for a touch too long. I called Jim last Monday and he said to check pressures. If idle is at or above 200 and rev up is 225 or above, its good. Well, I have 220 idle, 240 revved up. Also said to check band. Band was loose, but still didn't fix the problem.
The bad part was, I was on vacation last week so I wasn't able to look at my truck until this last weekend. Friday was Jim's last day for two weeks. So he won't be back until the 14th of July. I even switched servo springs just to make sure that wasn't the problem. Its gonna drive me nuts to not be able to really go out and race it or anything. I was going to chassis dyno it Sunday, but didn't want to mess anything up in the trans. It doesn't feel like it slips at all in 3rd, just that initial flair when its shifted. I know some of you know transmissions pretty well, so I was hoping someone could maybe give me an idea. My guess is that something in the valve body is messed up and I'll have to swap one out once he gets back???? I have a couple forward pattern v/b's, but no reverse pattern, otherwise I would've swapped it out to see if that was the problem.
I re-adjusted the band to 120 in/lbs and backed it off 1 full turn. I also tried different servo springs just to make sure that wasn't the problem too.
A "flair" is a delay and resulting rise in RPM as it shifts from 2nd when releasing the band and before rev/hi clutches apply in my understanding.
This mostly happens with lighter throttle input. I have had this issue with several C-6's and have corrected it with a longer modulator pin (or adjustment) to increase pressure. You have good pressure.
As you said "It feels like I jab the clutch for a touch too long" maybe this is what is happening. Does it slip on hard acell in reverse? This will confirm that maybe the drum piston seal is leaking. An air pressure check would confirm this maybe others will chime in now with their ideas. Good luck.
Hate to say it but your Vb's Junk !150 psi is enough for 800hp. I run mid 7's at 180mph with a 2700lb car and run 170psi .call me in November after farming season and I'll build you a Vb
Frank
This message has been edited by fmerkl from IP address 208.70.58.79 on Jul 3, 2008 8:13 PM
So, you don't think there is excessive clearance in the direct drum clutch pack? Why would the high pressure of that valve body cause the trans not to shift right?
exessive pressure can and will warp the separater plate in the VB and blow out the gaskets and wearout the sealing rings on the pump real fast
Frank PS in race applications make sure you use teflon salng rings not the cast
press too high!! probably blew out sealing ring vb gasket or something ----maybe too much clearence in the direct pack but doubtful would almost have to be miss-assembled!
re-adjust band to spec. too tight will kick 2nd out too early
