AL SS590 M6

Background. Car worked great all last year. Added a little power, took out a little weight, changed fluids this spring and just got the car together last Friday. Wouldn't shift to 3rd at WOT at all Saturday until I let off of the go pedal. Had Sean at C.A.R.S. touch up the shift points and do a sim pull on the dyno to see if it worked OK, it did.
Went to the track at Stanton,MI last night and 2 of 5 passes it shifted.
1st pass right out of the trailer, 25 psi in the rears, spun to a 1.69 60' and ran an 11.51 @ 120ish.
2nd pass after dropping the tires to 23 psi from the 27 that they had climbed to, 1.55 60' no shift to third. WTF
3rd pass after a long cool down to see if it was temp related, dropped the tires to 21 psi cold, 1.51 60' no shift to 3rd again.
So I went right from the ticket booth out onto the street and ran up to the next little town slowing and speeding up and ramming on it in 3rd to see if it was the 3-4 clutch pack going out. Pulled hard in third with no signs of slippage. On the way back I slowed to 30 a couple of times dropping the shifter into second so that it would hold second, nailed it then pushing the lever to third and it shifted fine, right when it was supposed to.
When I got back to the track I went right up and ran a pass. 1.51 60' 11.12 @ 120.73.
Let it cool down for a bit and went for pass number 5. 1.507 60' and no shift to 3rd.
Is there anything in the PCM that would cause an intermittent problem like this?
I'm thinking no and looking towards a bad 2-3 shift solenoid in the trans.

Any helpful hints will be greatly appreciated.

Pro Built Automatics

I have seen this occasionally, when with a fairly good 60 foot time, the transmission filter opening can get uncovered, allowing air to get in the system, and this can cause your problem. Most of the time adding about 1/2 - 2/3 quart will solve this.

AL SS590 M6

But I pulled 1.48-1.53 sixties all last year without it ever not shifting to 3rd.

12SCNDZ

Probably not a shift solenoid, unless your "B" solenoid is hanging up. Could be a bad 3-2 down solenoid, though. May be a valve trying to hang up. Is it kicking any "SES" lights? Would be nice to see if the computer is commanding the 2-3 shift when it doesn't occur.

Frank
CPT

Pro Built Automatics

What I have suggested (the easiest) is just one of the things that need to be checked out here. If it does not work, then try what Frank suggested. We are offering ideas of what to do because you asked what the problem might be.

AL SS590 M6

Oh I'm going to try everything suggested and really appreciate the ideas. I need the help.
But I need to feed you guys back info too, like the fact that the 1.5 60's are the norm.

AL SS590 M6

No SES light, I wish it would set one then I'd scan it and have a starting point.
I'm working on getting a battery solution for my laptop or maybe borrowing my daughters laptop to monitor the trans commands and such.

Thanks for the ideas.

AL SS590 M6

Ok I added a 24oz. bottle of Lucas Stop Slip to the trans making it overfull. Made 3 passes at the Pinks All Out race and it shifted right every time.
But the weather was very simular to my last outing where I ran a 11.12 @ 120.8 on a 1.51 sixty foot and this time I ran a 11.01 @ 122.31 on a 1.504 sixty foot.
That increase in ET and MPH when adding the Stop Slip sdditive tell me that my trans was/is slipping do it's time for a freshen up.

Pro Built Automatics

"That increase in ET and MPH when adding the Stop Slip additive tells me that my trans was/is slipping do it's time for a freshen up."
Not necessarily, it could be now your fluid level is correct. The Stop Slip additive probably did not do anything either way. If you have no more problems here, be thankful. What is the condition of the transmission fluid?

AL SS590 M6

You just seem to keep missing the fact that this trans has been working and shifting correctly for 7 years and the last 3 at ~ the same power level with the fluid at the full mark. Then an all of a sudden this year it doesn't work right problem.
It's hard to tell anything from the trans fluid as I run the car about a 100 miles a year and change the fluid every year.

thunderace31

What trans fluid are you using?? Dextron or Type F???

blue 79 Z/28

yes but you said it worked right on the money or not at all which leads to question how is it slipping then? and how did adding 1qt of fluid fix that? has the tranny been run for 7 years without a rebuild? id do it then, but you asked for suggestion and people are giving it, hopefully you will find what is causing it upon teardown. if it runs fine now with the added fluid then see if it comes back while running it some more.

thunderace31

Dextron

AL SS590 M6

I bought a built trans and set mine aside for now. I'll dredge this thread back up when I have it rebuilt for a backup.