Why when you put the gear select into first, it still shifts into second?
The car limits the speed to 98 mph in second, which is close to red line,
but when the gear selector is in third the car will only do 108 mph.
With the gear selector in drive, I have run the car up to 120 in third.
Would these things be addressed with a new PCM?

Thats the 3rd gear rev limiter (4000 rpm?) cutting in and yes a custom pcm will remove that. so to get to the 128mph top speed you have to ease off and let it shift into 4th then ease back into letting the engine rpm climb softly.

When you put the shifter in 1st the car will downshift to first if you are just crusing down the road, but even with a reprogrammed PCM it will panic shift into 2nd at 5200rpms (lower than it would normally shift) just because that is how GM programmed it. It is a safety feature GM installed.

In second it will hit the rev limiter (which stock is 5800rpms), but this is helpful at the track because you can hold it in 2nd and shift at 5800 instead of the 5500 it will shift into 3rd at if you just put the shifter in 3 or D.

In 3rd it his the limiter at 108 because GM doesn't want people putting the car in 3rd (on purpose or by accident) and cruising down the freeway in 3rd at 120mph for hours because this will easily blow the engine up, costing them big $$$ if the car is under warranty. But in 4th gear, the car won't be revving high rpms for long periods of time so GM lets you go 128 because the speed rating on ghte stock tires is 130mph.

Make sense???

A reprogrammed PCM will fix the 3rd gear limiter and 4th gear limiter, but the car will still panic shift out of 1st (just at a higher rpm, like 5500). However the car will shift at higher rpms (5950rpms out of 1st & 2nd) and you can hold the car in 2nd until the 6200rpm limiter if you want to.

Shawn

Pontiac Dad:
If the gear selector is in third, I hit the speed limiter at 108 mph.
When the gear selector is in drive the transmission is still in third at wot
at 120 mph, about 4800 RPM. i never have taken the car past 125,
but it was in third at 125 mph .

ps. the car goes through the lights in 2nd gear at 96 mph

You need a chip, it will fix all your performance bugs.

I seriously doubt you were in 3rd at 120 on a stock PCM. Do you have a scan tool to verify? In D at WOT the car will not shift into 4th at 108 you have to let off the gas, let it shift then get back on it to continue to climb. In Manual 3 the car will not go beyond 108 on a stock PCM.

I think that this guys PCM is just fudged up a little. The fact that he supposedly hits 96mph in 2nd gear seems very odd to me. Our GTP hits a rev limiter at 6200rpms and IIRC it only hits like 95mph before hitting that limiter in 2nd. So this guy would have to have some REALLY tall tires to be able to hit 96mph under 5800rpms in 2nd. Thats what makes this whole thing seem really odd to me. And there is no way, unless his PCM is screwed up, that he hit 120 in 3rd gear.

Shawn

I hit mid 90'* 95-97 on my second gear dyno pulls to the limiter so that may not be to far off.

gtp cars have a lower gear ratio than bonnevilles
thats why i can hit 98 mph in 2nd gear my tires are
stock 235/55/17 27.2" tall
maybe i should see if i have a speed limiter at 128?
we have rain showers right now will have to do
it later

GTP'* have the EXACT SAME gear ratio as SSEi'* do. The only difference is in the tires. The tires on the Bonneville are slightly taller, but I doubt that it would make that much difference. Maybe I will just have to "borrow" the SSEi for a 2nd gear top speed test.....

Maybe I just dont remember the autotap logs from the GTP correctly. Its possible that it went like 98 and it looked like 95 or something. But I would think if the SSEi did 96+ in 2nd gear at 5800 that the GTP would do at least 100 in 2nd gear at 6200.

Shawn