Reflashing the PCM for gear change
Thread Starter
Registered User
Joined: Apr 2010
Posts: 6
Reflashing the PCM for gear change
I had 3.73 gears but didn't really like them for highway so had 3.23 installed. I know most people go the other way, high --> low gears.
The PCM has not been reflashed yet (will have it in a week). Now the tuning person tells me there will be no damage driving like this but it does shift weirdly, and I think too high/ late?
Would I get any smoother performance when it's correctly tuned for the gear? I don't expect LT1 / 3.23 / mild cam / 2400 stall to be a speed demon, just moderate performance on the street and still get good MPG.
The PCM has not been reflashed yet (will have it in a week). Now the tuning person tells me there will be no damage driving like this but it does shift weirdly, and I think too high/ late?
Would I get any smoother performance when it's correctly tuned for the gear? I don't expect LT1 / 3.23 / mild cam / 2400 stall to be a speed demon, just moderate performance on the street and still get good MPG.
Registered User
Joined: Nov 2007
Posts: 910
You PCM is still shifting with you speedometer reading which is now 13.4% off (reading low). EG: if it shifts 2 >3 at 30 you are actually traveling at 34.6 MPH so it feels like a late shift from what you are used to. It won't harm anything.. What's your year and model ? Since you need a tune anyways there are some good mail order tunes available that could help your performance and possible MPG for a little extra $$.
Thread Starter
Registered User
Joined: Apr 2010
Posts: 6
Well, I have a 1996 B-Body (Buick Roadmaster) but I thought I would ask here given the wealth of knowledge.
It's a cammed LT1 (Comp Cam 1000-5000), 2000-2400 stall from Transmission Specialties 12LS torque converter, etc. I had 3.73 Motive gears and they were very fast but the MPG was consistently about 17MPG on the highway and I was hoping to get more like 20. The MPG dropped like a rock between 70-80, I got 16.5MPG one time.
The other thing that bugged me about 3.73 was noise on the highway, not uncommon to turn 2500-2600. 3.23 is is much quieter.
Now I know B-body is big and heavy, 4400 lbs in a wagon but still I hear reports of wagons with 2.93 or 3.08 gears get 23-24mpg. Don't expect huge performance however, but I don't race or anything.
I do wonder if 3.42 gear is the best compromise between MPG and performance. My LT1 has this mild cam so I cannot really go too high, I think 3.08 is high of a gear for me.
I have a tuner who already worked on it and can reflash it... I was just trying to understand the mechanics of it. It does run but not as smooth or responsive, even compared to a stock B-body with LT1/3.23.
It's a cammed LT1 (Comp Cam 1000-5000), 2000-2400 stall from Transmission Specialties 12LS torque converter, etc. I had 3.73 Motive gears and they were very fast but the MPG was consistently about 17MPG on the highway and I was hoping to get more like 20. The MPG dropped like a rock between 70-80, I got 16.5MPG one time.
The other thing that bugged me about 3.73 was noise on the highway, not uncommon to turn 2500-2600. 3.23 is is much quieter.
Now I know B-body is big and heavy, 4400 lbs in a wagon but still I hear reports of wagons with 2.93 or 3.08 gears get 23-24mpg. Don't expect huge performance however, but I don't race or anything.
I do wonder if 3.42 gear is the best compromise between MPG and performance. My LT1 has this mild cam so I cannot really go too high, I think 3.08 is high of a gear for me.
I have a tuner who already worked on it and can reflash it... I was just trying to understand the mechanics of it. It does run but not as smooth or responsive, even compared to a stock B-body with LT1/3.23.
Thread
Thread Starter
Forum
Replies
Last Post
Lt1son
Drivetrain
1
Dec 31, 2014 01:35 PM
chevroletfreak
LT1 Based Engine Tech
202
Jul 4, 2005 05:00 PM