tmartin01Z28

The past two times that I have gone to the track my car will over shoot the 2-3 shift, peg off the rev limiter twice and then shift. When I try to get the car to duplicate this on the street it will not do it and shifts perfect. Does anyone have any thoughts on why this would be happening at the track only? The only thing that i can think of is at the track i am running 18 PSI in my MT drag radials and on the street i am running 28 PSI and thus the OD on the tire would slightly change. Also to note that on the street i am unable to launch the car like i do at the track for obivious traction reasons and need to do a roll on in drive from about 35 MPH to hit the 2-3 shift at WOT. Is there something in the tune that would cause the car to shift differently between a roll on and a full out strip launch? Thank you for any help in advance

PBA

If you cannot duplicate the problem on the street, then I would suspect the fluid is slightly low and you are picking up air on hard acceleration. Add 1/2 -3/4 of a quart when at the drags and see if this solves this, it should.

waterbug1999

iTrader: (3)

raise the rev limiter a few hundred rpms and see if that will do it.

tmartin01Z28

I will have steve (frost) look at the tune today while he is in town and see what he can do. I still dont understand why it only does it at the track and not on the street

PBA

" I still dont understand why it only does it at the track and not on the street
" I just gave you the most logical answer.

tmartin01Z28

The fluid level is spot on.

transam19

iTrader: (1)

Once your at the track it changes how hard you launch the car vs the street. Like waterbug stated. Raise the rpm a few and see if that will help. Happend to me all the time where it would shift fine on the street and hit the revlimiter at the track. So have someone look at the tune and have them adjust it.

PBA

I give up.

PaSteLaSo4U

iTrader: (-2)

o.p add about 1/4 to 1/2 quart o tranny fluid, I know u said its spot on but at the track it will prevent in some cases hitting the rev limiter

mrvedit

I recall that one trans sponsor suggested that too in an old thread.

79TAKid

iTrader: (1)

do you run the same tire at the track, or switch, tire size will affect your Tune and shifting

01ssreda4

iTrader: (96)

Run in D or OD at the track?

PBA what's on your mind?

silverz28camaro

iTrader: (20)

Running it in D can starve the 2-3 shift of oil if the trans is stock or mild build, I am also a fan of the truck "stepped" pan with the level 1/2 quart overfilled...If you feel confident enough you can drop the valvebody and drill 3rd gear feed hole to .120 or so with the servo release checkvalve installed...may help for a bit

mrvedit

Just to reduce confusion, as discussed in other threads, running in [D3] can starve the 2-3 shift of oil UNLESS the Sonnax 2-3 shift valve is installed (which requires an irreversible valve body mod). Therefore run in [D4] or [OD].

I also run the "deep" truck pan which holds 1 quart more. This reduces the chance of oil starvation under extreme conditions; a slight overfill might help too as has been suggested. (You must run the "deep" filter with the deep pan.)
I also recommend the Sonnax servo release checkvalve and drilling the 3rd gear feed hole to .120 (or 1/8" which is .125).

However, I also suspect your shift RPM is too close to your rev limiter. What is your rev limiter set to now? Do you have stock or aftermarket or dual valve springs?

silverz28camaro

iTrader: (20)

Yeah, i like that 2-3 valve ...one of my favorite parts...also takes alot of load off that sprag

PBA

With the transmission being stock, I would not use "D" shifter position to race in. Use "OD" or manually shift the transmission 1-2-3. The adding of fluid is to prevent the 2-3 WOT shift problems caused by the filter getting uncovered. If this solves it, then "remark" the dipstick with the "new" full mark.

Philip Pugeau

Man, this 2-3 limiter bounce happens a lot. I had the same thing. It was solved by dialing back the 1->2 shift. Some people don't like this idea, but it worked.

After messing with the 2->3 many times, adding 1/2 quart more ATF, running a built 4L60E with a full compliment of Sonnax servos, it started to behave itself ONLY when dialing back the 1->2. Give it a shot, you have nothing to lose.
_______________________________
2001 NBM Formula A4 T-Top DailyDriver
383ci b&b | 230/236 114+4 | AR 1-3/4" LT | AR 3" Y-pipe | FTI 3500 | Built 4L60E | BMR k-member | BMR F&R U&L control arms | torquearm | panhard | PST 3.5' | S60 4.10 | 315/35R17 555R
393rwhp / 377rwtq

RonSSNova

iTrader: (3)

Gets confusing listening to Camaro talk when it comes to OD vs D.
The C5 Vette has the following:
1 Low only
2 2nd only (want to slow the car by 6 tenths? Start in 2!, but it sure won't spin)
3 Shifts 1-2-3
D All 4 gears

I started having the 2-3 shift skip, so I set it up with the spread sheet in this post from HPT forums.

http://www.hptuners.com/forum/showthread.php?t=27981

Takes into account converter stall, slip etc.

The changes to my shift tables were subtle, but it worked. Maybe you have seen this.
After resetting the tables, I began running in D, and it worked great. I had been running in 3.
My perception is that the shifts are much less violent......
I have 1-2 and 2-3 set to 6600.

FYI, adding a half quart to a C5 to overfill is a nightmare. You have to own one to understand. But in simple terms, there is no dipstick. You fill from under the car, with it running, from the big fill/drain plug in the side of the pan. Basically, impossible to overfill, but you do get a nice hot ATF bath in the process while trying to get the ATF to go uphill.

Tmartin, you didn't come back and report progress. Don't leave us hanging.

Ron

01ssreda4

iTrader: (96)

My trans has never missed a shift in OD. It misses like crazy over the years (not all the time and its not predictable) and takes a long time to complete the 2/3 shift with in D3 (commanded 6250, actual shift ~6700). I'm gonna try running a little more fluid. My builder advised my to race only in D3. He built the trans, I trust his advice.

RonSSNova

iTrader: (3)

That makes no sense. You trust his advice, but D3 is unpredictable and doesn't work sometimes. What am I missing?