98PontiacTA10s

Hello i have a 1998 Pontiac Firebird with an LS3 swap BTR ls3 stage 4 v2 (233/25x .636"/.636" on a 113LSA) cam and supporting parts 85mm MAF, 4l60e with a transgo shift kit and a 4000-4200 stall TCI converter with a ford 9" rear end 4.10 gear on a 275 MT drag radial. i upgraded the rear end after breaking the spyder gears at the end of 2022 and ran great for the 2023 season the car slowed down a little in the 1/4 mile due to my guess of weight gain and parasitic loss between the loser converter, larger steel drive shaft and 9" rear end. spring of 2024 i upgraded the cam to a BTR ls3 stage 4 v2 from a GMPP ASA (226/236 .525"/.525" on a 110LSA) cam and i basically gained the hp back from the parasitic loss when i put it back on the chassis dyno (different dyno). while on the dyno it appeared i ran out of MAF at around 5600rpm or so. the tuner tried rescaling the MAF to "Cheat" it engine runs great but since the dyno the car has only made 5-10 successful passes as it will not 1-2 shift and sometimes 2-3 shift unless i let off the gas pedal. pulled the transmission everything looks good leads me to believe the trouble may lie in the MAF scaling. i have read that the ECM uses the MAF to calculate torque and could potentially be causing an issue my question is how does it calculate torque when running a SD tune? and is it worth switching to SD? should i be running out of MAF at this point or no? GB logs are on a prepped track the others are in Mexico. Thanks for any input

NicD

iTrader: (7)

Just took a quick look at the tune itself and I see your WOT shift MPH has literally no lead on them and you are going to need a good amount of lead with 4.10s and a high stall converter. I would start by pulling 10 mph out of the WOT shift MPH tables and drop your WOT shift RPM down to like 5500 rpms across the board. Being a 98 PCM makes this even worse as it's very slow. Start low and work your way up to extend your shift points.

I would also put some torque management back in it being a 4L60, right now it's totally gone.

There is already additional line pressure added in the tune which should compensate for the minor torque differences from scaling, but I'm not seeing engine torque in the log file. However airflow is pretty high which tells me it's probably fine.

98PontiacTA10s

this revision is a fairly recent change with the shift scheduling… I’ve lowered the shift rpm and mph in both small and large increments with literally no change in the outcome. ive had it as low as 4500rpm. it shifted fine last year with higher rpm and similar mph only change was the camshaft

NicD

iTrader: (7)

Well I can tell you that changing the cam isn't going to cause what is happening, especially if it was fine before. If it shifted fine last year then you have a mechanical problem with the trans.

jmilz28

iTrader: (13)

I tend to agree with Nic. Get a quality HP rebuild on that tranny from someone who knows. There are a few, like Circle D, here is another one and why: https://www.motortrend.com/how-to/ho...andle-1000-hp/

98PontiacTA10s

I would tend to agree.. at this point i have already had the transmission out and back in. very minimal wear on the 2-4 band, slight mushrooming of the servo pin replaced both parts while inside no evidence of any other wear. my concern based off of some reading is the rescaling of the MAF as i have read it uses the MAF to calculate torque somehow based off of air flow. while on the chassis dyno the MAF was being maxed out at 11,800Hz at only like 5600rpm. its a 85mm MAF. i noticed those logs do not have MAF frequency going to try and reduce the shift mph and log again