What rear gear
#1
What rear gear
I'm in the middle of my build and I'd like to know what everyone is running for gears so I can make a good educated guess on what will work best for me. 72 nova 5.3 LM7, little Johns turbo cam, twin 61mm ON3 turbos, th400 and a 9" out back with a 28" tall tire. It will see the track a lot but I also want to drive the crap out of it on the street. Is 3.50 gear to low or should I be in the 3.20 or 3.08 range?
#2
Restricted User
I have a 3.55 with a 4L80e and regret not going with the 3.23 when I had the option.
I'd probably go 3.08 with a TH400 if you ever plan on driving it on the highway.
I'd probably go 3.08 with a TH400 if you ever plan on driving it on the highway.
Trending Topics
#8
Like I said. It will see a lot of time at the track. Maybe I'll do a 3.20s for the happy medium. I'd just hate to be wrong. I'm a baller on a budget and I already know the 4.56s in the car won't work so I only want to change them once
#9
8 Second Club
iTrader: (4)
Need to figure out how much power you’ll likely make and factor in weight. Then decide if ET or cruising is more important… can’t have both with a TH400.
I went with a 3.10, then a 3.25 on a 30” tire. Great for cruising… but I really think it’s hurting my ET a ton. Also harder on the motor (rods) being closer to peak torque most of the time. I’m only at 6200ish thru the traps at 160ish. Around 1000crank HP near as I can figure. If I was closer to 7k I think I’d pick up a lot.
Also need to figure in that TH400 has a short 1st gear, so without some sort of power management you’ll likely be very traction limited if you install the gear for the best ET. And better off traction wise with a super tall cruising gear.
I went with a 3.10, then a 3.25 on a 30” tire. Great for cruising… but I really think it’s hurting my ET a ton. Also harder on the motor (rods) being closer to peak torque most of the time. I’m only at 6200ish thru the traps at 160ish. Around 1000crank HP near as I can figure. If I was closer to 7k I think I’d pick up a lot.
Also need to figure in that TH400 has a short 1st gear, so without some sort of power management you’ll likely be very traction limited if you install the gear for the best ET. And better off traction wise with a super tall cruising gear.
#12
Originally Posted by Forcefed86
Need to figure out how much power you’ll likely make and factor in weight. Then decide if ET or cruising is more important… can’t have both with a TH400.
I went with a 3.10, then a 3.25 on a 30” tire. Great for cruising… but I really think it’s hurting my ET a ton. Also harder on the motor (rods) being closer to peak torque most of the time. I’m only at 6200ish thru the traps at 160ish. Around 1000crank HP near as I can figure. If I was closer to 7k I think I’d pick up a lot.
Also need to figure in that TH400 has a short 1st gear, so without some sort of power management you’ll likely be very traction limited if you install the gear for the best ET. And better off traction wise with a super tall cruising gear.
I went with a 3.10, then a 3.25 on a 30” tire. Great for cruising… but I really think it’s hurting my ET a ton. Also harder on the motor (rods) being closer to peak torque most of the time. I’m only at 6200ish thru the traps at 160ish. Around 1000crank HP near as I can figure. If I was closer to 7k I think I’d pick up a lot.
Also need to figure in that TH400 has a short 1st gear, so without some sort of power management you’ll likely be very traction limited if you install the gear for the best ET. And better off traction wise with a super tall cruising gear.
#14
8 Second Club
iTrader: (4)
Without knowing the rest of the combo 15psi doesn’t tell us much power wise. You’ll about double the NA hp at 15-16lbs.
Figure out what speed/rpm you consider comfortable cruising at and gear it as short as possible IMO. You’ll need it at low boost levels. A 3.50 with a 28” tire will put you around 150ish at 6500 rpm. (155 assuming zero converter slip.) Figure out your vehicle weight and we can tell you about how much power you need to go 150ish.
Figure out what speed/rpm you consider comfortable cruising at and gear it as short as possible IMO. You’ll need it at low boost levels. A 3.50 with a 28” tire will put you around 150ish at 6500 rpm. (155 assuming zero converter slip.) Figure out your vehicle weight and we can tell you about how much power you need to go 150ish.
#15
With the aluminum headed big block, me, and 12 gallons of fuel I was 3220 last time across the scales. It's a LM7 stock bottom end, china head studs, little Johns stage 2 twin turbo 225/235 cam, air to air intercooler, 3000rpm converter(might change that) and twin 61mm turbos. TH400 with a transbreak. I don't know what it will make for power. I'm about a month maybe two from getting it running and tuned
#17
9 Second Club
iTrader: (10)
I run a 3.90 gear with a th400 right now. 1.3 60' on old mt 275s and I've ran 9.17 @ 147 mph at 7200 rpm but I'm out of gear. I'm going to a 3.40 gear soon but if I only ran 1/8 I would not change. Guys with 3.08s dont realize how much they are leaving on the table and how much heat / slip they add to the converter by low rpm at the finish line. You either pick lower cruising rpm or a more efficient track car.
#18
I run a 3.90 gear with a th400 right now. 1.3 60' on old mt 275s and I've ran 9.17 @ 147 mph at 7200 rpm but I'm out of gear. I'm going to a 3.40 gear soon but if I only ran 1/8 I would not change. Guys with 3.08s dont realize how much they are leaving on the table and how much heat / slip they add to the converter by low rpm at the finish line. You either pick lower cruising rpm or a more efficient track car.