Mark42
Fleet Admiral
- Joined
- Oct 8, 2003
- Messages
- 9,334
You may have seen a post a little while ago about a 98 Pontiac Firebird V6 Coupe I bought with just 28K on it. Now its up to 34K and I desperately needed a limited slip differential to drive in the snow. So while the LSD is being installed, its a good time to change gear ratios. Seeing as the factory 3.08 gears gave rather sluggish performance, and wanting to make the car a little more spirited to drive, I opted for a set of 3.73's to go with a new Eaton Tracloc differential. The Tracloc is cool because it has no clutches or friction material to wear out like conventional "posi" rears have. Check out this great video on how they work: http://www.youtube.com/watch?v=lZmsY2YvVsc
Anyway, I got the gears and Trackloc installed by a local trans builder and followed the 500 mile break in period for the gears. I have to admit this came out much better than I imagined. First off, driving in the rain the tires stay planted to the pavement where before, one wheel would always be spinning on take off, especially while turning. And in the snow, now the car can make the incline in my driveway where before it would get stuck half way up and slide back. Driving in the snow is much safer because the car goes when it should and doesn't get stuck spinning a tire on the slightest incline.
On dry days, the car is so much more fun to drive. The engine is running at a higher RPM, so its always in a higher hp range. This allows the car to scoot along with mild throttle, and passing in overdrive is just a slight press of the gas pedal. Downshifting and heavy doses of gas really make the car get up and go. A real thrill compared to before. Feels like another 50 hp were found somewere.
And of course, the obligitory "peal out" is effortless. A quick stab at the gas from a stand still locks up the Eaton and both tires are spinning in a seconds notice. Roll on the throttle and the car grips and accellerates like a scalded cat!
Ordered a "tuned" PCM (computer module) to replace the factory PCM so that the speedometer will be correct (its off by about 21%) and the tune also modifies the fuel and spark curves giving about a 10-14% claimed hp boost on the 3800 v6. This should be here Friday so I'm really looking forward to having the speedo corrected and see what sort of performance increase it affords. They also claim 1-3 mpg improvement depending on performance accessories (exhaust, etc).
I like this change rather than bolting on stuff to the motor to boost the HP. Its just making better use of the available HP without stressing the motor or trans, and I don't have to worry about add on's messing up the emissions for inspection.
So far my MPG has only dropped 1.5 mpg on average, which is a small price to pay for such a performance increase. And it will probably improve as I back off on the jack rabit starts.
Next a trans cooler and engine oil cooler and remote filter will be added to keep things cool, and help offset the added wear from running at higher RPM. For example, with the old 3.08 gears 60 mph was at 1900 rpm. Now with the 3.73's 60 mph is at about 2300 rpm. The engine is making 33% more hp at 2300 vs 1900 rpm, giving the expected performance boost right throught the entire RPM range.
This was by far the best "bolt on" modification I've done in a long time!
Anyway, I got the gears and Trackloc installed by a local trans builder and followed the 500 mile break in period for the gears. I have to admit this came out much better than I imagined. First off, driving in the rain the tires stay planted to the pavement where before, one wheel would always be spinning on take off, especially while turning. And in the snow, now the car can make the incline in my driveway where before it would get stuck half way up and slide back. Driving in the snow is much safer because the car goes when it should and doesn't get stuck spinning a tire on the slightest incline.
On dry days, the car is so much more fun to drive. The engine is running at a higher RPM, so its always in a higher hp range. This allows the car to scoot along with mild throttle, and passing in overdrive is just a slight press of the gas pedal. Downshifting and heavy doses of gas really make the car get up and go. A real thrill compared to before. Feels like another 50 hp were found somewere.
And of course, the obligitory "peal out" is effortless. A quick stab at the gas from a stand still locks up the Eaton and both tires are spinning in a seconds notice. Roll on the throttle and the car grips and accellerates like a scalded cat!
Ordered a "tuned" PCM (computer module) to replace the factory PCM so that the speedometer will be correct (its off by about 21%) and the tune also modifies the fuel and spark curves giving about a 10-14% claimed hp boost on the 3800 v6. This should be here Friday so I'm really looking forward to having the speedo corrected and see what sort of performance increase it affords. They also claim 1-3 mpg improvement depending on performance accessories (exhaust, etc).
I like this change rather than bolting on stuff to the motor to boost the HP. Its just making better use of the available HP without stressing the motor or trans, and I don't have to worry about add on's messing up the emissions for inspection.
So far my MPG has only dropped 1.5 mpg on average, which is a small price to pay for such a performance increase. And it will probably improve as I back off on the jack rabit starts.
Next a trans cooler and engine oil cooler and remote filter will be added to keep things cool, and help offset the added wear from running at higher RPM. For example, with the old 3.08 gears 60 mph was at 1900 rpm. Now with the 3.73's 60 mph is at about 2300 rpm. The engine is making 33% more hp at 2300 vs 1900 rpm, giving the expected performance boost right throught the entire RPM range.
This was by far the best "bolt on" modification I've done in a long time!
![4188_1136065450739_1500424835_30346659_2277857_n[1].jpg](/data/attachments/39/39219-9d8c18586b0a9ffc1169f598e6983ea4.jpg)
