i put a set of 3.73 gears in my 95 z28 a while ago, i got it tuned so the shiftpoints are set right, 1-2 is set for 35mph, didnt check what the 2-3 shiftpoint was

i run TTS Datamaster on each pass and i was bouncing the rev limiter occasionally on the 1-2 shift last thursday, it happened on my 2 time runs before the race on friday also

i checked datamaster and it showed the transmission in 2nd gear at 35mph, but the rpm's continued to climb to 6250 rpm up to about 42mph then droped, i also looked at the graph that measured trans slippage, theres no more slippage now than there was before the 3.73s

the only mods to the car are in the sig, slp cold air induction, catback, and the 3.73 gears

any idea whats causing this? i'm new to this stuff so i'm 100% clueless, tryin to learn it as i go

i'm takin it in this week to have it tuned, i just wanna know what the experts in this forum think about it before i take it in

 

Just tell whoever tuned it to move the rev limitor back or the shift points sooner.

 

^^^ exactly, your shifting too high, drop the 1-2 shift MPH by 1.

Also since our cars shift by MPH the RPMS are almost never consitant, Im fighting this in my car and its driving me CRAZY. I wish there was a way to shift by RPMs not MPH. They make a dedicated transmission controller but they START at $700

 

It was my understanding that the trans won't complete a shift until it reaches the mph in the kickdown tables and the rpm in the threshold tables. Why not lower the mph so that you're sure to be above it, and then control the shift points with the rpm threshold tables.
I have found a small fudge factor in this method though, as your shift event is probably going to happen 400-500rpm after what you set it at in the program for the 1-2 shift and right around 400rpm for the 2-3 shift.
I have found this to be fairly consistent though.

 

thanks for the responces i've had the shift points droped by mph a few times with the same result, i'll take dan k's advice on this one

thanks a lot

 

but hten what about the downshift ?

say your in overdrive at 50 MPH and you floor it, I would want it to go into 2nd gear. Wouldnt doing the above cause the downshift to barely ever happen ?

 

I understand what you're saying. I guess I should have been a little more clear. I'm not talking about dropping the 1>2 mph to 1 and the 2>3 mph to 2. Just drop them a little and take them out of the equation. And I've never had a problem with a car not downshifting in that situation.

 

So I should drop the 1-2,2-3 MPH lower then what I actually want, and set the Normal and Hot Shift RPMs to about 6600 for 1-2 ( i wanan shift at 7100) and 6700 for 2-3 ( i wanna shift at 7100) and this will make the PCM use the RPM to shift ?

Now I have an Art Carr Heavy Duty street/strip tranny that shifts fast. so would the 500 RPM fudge factor still apply ?

 

Sounds right to me.
The last file I did we wanted to shift at 6500 and have the rpm thresholds at 6100 and it worked perfect. This car has an FLP Level IV trans too...so it shifts quick. Fudge factor doesn't seem to be influenced by it. I think I've got the mph dropped around 10mph and that works.
If you look in a stock A4 file you will see that the rpm thresholds in that are around 5300-5400 and a stock car shifts at what 5700-5800rpm? Not sure why there is that delay, but it's there.

Try it and see if it works. It's worth a shot.

 

Thanks ! I will try this for sure.