3.27 or 3.45 gears
01-07-2013, 04:04 PM
#1
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3.27 or 3.45 gears I need your opinion on which gears I should get.
My car has a stock L98 motor. I’ve got Hooker 1 5/8’’ ceramic coated headers and y-pipe with a single 3’’ high flow cat and Flowmaster 3’’ cat-back exhaust.
For the intake I’ve got Hawks Thirdgen ram air boxes, gutted factory air-box along with K&N air filters. I also have a 52mm BBK throttle body. I've also got a ported factory plenum, ported SLP intake runners and, ported Edlebrock TPI intake base.
I’m running a Bowtie Overdrives level 3 700r4 and one of their 2,400rpm stall converters. I’ve got it set up to have all the full throttle shifts occur at 5,500rpm and to allow full throttle shifts in to overdrive.
After I finish with the intake mods I’m going to leave the rest of my motor stock for a while.
My remanufactured L98 motor (I got from A/C Delco) only has 30,000 miles on it so I’m not in a big hurry to start tearing in to it just yet. I’ve had no problems with it since it was installed and I’m happy with the way it has performed so far.
The problem is the gears – I’m going to swap out my stock Borg Warner 9bolt rear with a 1989 9bolt rear with the PBR disk brakes and deeper gears. That way I'll get a brake upgrade when I swap rears.
That’s the only part of my drive train that I haven’t gone through yet. I saved it for last until I got my motor and transmission figured out. Currently I have 2.77 gears which really zap the performance.
I’ve heard from some people that moving up to 3.27 gears would be a good move. The 3.27 gear ratio was the G92 performance axle option from GM for the L98 cars with the 9bolt rear.
Other people that I have talked to say I would get more performance gains from the mods that I have done if I moved up to 3.45 gears.
I’m concerned about getting traction with the 3.45’s combined with the 700r4’s low 3.06 first gear ratio and what rpm’s I’ll be turning on the highway with those gears. My car is a 100% dedicated street car so I want to pick the right gear ratio that will be best for all around good street performance and won’t hurt me too bad in terms of fuel economy.
My car has a stock L98 motor. I’ve got Hooker 1 5/8’’ ceramic coated headers and y-pipe with a single 3’’ high flow cat and Flowmaster 3’’ cat-back exhaust.
For the intake I’ve got Hawks Thirdgen ram air boxes, gutted factory air-box along with K&N air filters. I also have a 52mm BBK throttle body. I've also got a ported factory plenum, ported SLP intake runners and, ported Edlebrock TPI intake base.
I’m running a Bowtie Overdrives level 3 700r4 and one of their 2,400rpm stall converters. I’ve got it set up to have all the full throttle shifts occur at 5,500rpm and to allow full throttle shifts in to overdrive.
After I finish with the intake mods I’m going to leave the rest of my motor stock for a while.
My remanufactured L98 motor (I got from A/C Delco) only has 30,000 miles on it so I’m not in a big hurry to start tearing in to it just yet. I’ve had no problems with it since it was installed and I’m happy with the way it has performed so far.
The problem is the gears – I’m going to swap out my stock Borg Warner 9bolt rear with a 1989 9bolt rear with the PBR disk brakes and deeper gears. That way I'll get a brake upgrade when I swap rears.
That’s the only part of my drive train that I haven’t gone through yet. I saved it for last until I got my motor and transmission figured out. Currently I have 2.77 gears which really zap the performance.
I’ve heard from some people that moving up to 3.27 gears would be a good move. The 3.27 gear ratio was the G92 performance axle option from GM for the L98 cars with the 9bolt rear.
Other people that I have talked to say I would get more performance gains from the mods that I have done if I moved up to 3.45 gears.
I’m concerned about getting traction with the 3.45’s combined with the 700r4’s low 3.06 first gear ratio and what rpm’s I’ll be turning on the highway with those gears. My car is a 100% dedicated street car so I want to pick the right gear ratio that will be best for all around good street performance and won’t hurt me too bad in terms of fuel economy.
01-08-2013, 02:23 PM
#2
first of all 2.77 to 3.27 isnt that big of a jump you need to look into some 3.73s at least. second the l98 tpi intake will not support a 5500 rpm shift peak power happens right around 4800 so you need to shift closer to 5000 rpm
01-08-2013, 06:28 PM
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A stock TPI intake won't support a 5,500rpm shift point but a modified one like the one I have will.
Stock the '85 LB9/700r4/3.42 geared cars shifted from 1st-2nd at 5,500rpm and the other shifts occured at 5,000rpm at full throttle.
When my intake was stock a 4,500 or 5,000rpm max rpm shift point was best but not with the modified set up that I have now. Holding that shift point higher helps reduce the rpm loss in to the next gear and keeps the motor in the power band.
Thats what I was worried about since there isn't a big change between 2.77's and 3.27's but TPI cars don't need a lot of rear gear to get good performance. Maybe I should look in to 3.45's.
Stock the '85 LB9/700r4/3.42 geared cars shifted from 1st-2nd at 5,500rpm and the other shifts occured at 5,000rpm at full throttle.
When my intake was stock a 4,500 or 5,000rpm max rpm shift point was best but not with the modified set up that I have now. Holding that shift point higher helps reduce the rpm loss in to the next gear and keeps the motor in the power band.
Thats what I was worried about since there isn't a big change between 2.77's and 3.27's but TPI cars don't need a lot of rear gear to get good performance. Maybe I should look in to 3.45's.
