3.90 gears on a 12-bolt. Good choice?

I'm pretty much set on a set of 3.90 gears for my Moser 12-bolt. Right now I have 3.73's in them. One thing I appreciate a lot about my 3.73's is the highway and street manners. It's just great. I do drag racing 6 months out of the year when I have the time.

With my current set-up, what you guys think of going 3.90's as opposed to 4.11's like most of you may suggest?

I wanted to add something for my 1/4 mile runs. I've been losing most of my bracket races between the 330' mark and just past the 1/8 mile marker. I can get good launches and run strong on the top-end. Just being caught hafway down the track.
Anybody with 3.90 gears that can give his opinion on what gains seen or benefits with it?
Thx-Goose :)
I figure a little bit more gears, may help there.

I have heard that the 3.90's were noisey vs other ratios. Even says that on Moser's site. Guess it all depends on what kind of times and what rpm range your running in, especally where your running rpm wise going through the traps. I used to have 4.10's in my 10 bolt with my 6spd but had to drop to a 3.73 to stay away from a 5th gear shift right before the traps. I'm still close to that right now so will probably have to move up to a 28" ET street vs a 26" and that should buy me a little. But if your bracket racing, does it really matter? Your talking bracket racing as in racing your own dial in?

Ken R.

I have heard that the 3.90's were noisey vs other ratios. Even says that on Moser's site. Guess it all depends on what kind of times and what rpm range your running in, especally where your running rpm wise going through the traps. I used to have 4.10's in my 10 bolt with my 6spd but had to drop to a 3.73 to stay away from a 5th gear shift right before the traps. I'm still close to that right now so will probably have to move up to a 28" ET street vs a 26" and that should buy me a little. But if your bracket racing, does it really matter? Your talking bracket racing as in racing your own dial in?

Ken R.Yeah, bracket racing dialing-in my own time, but I'm always looking to go faster. :)
There's a place here that sells Richmond 3.90's, and I know how noisy they can be.
What's you mph and rpm at the top of your 4th gear before you have to shift into 5th?
I have my rev limiter set at 6500rpm. Is it less than 6500rpm?
I may consider 4.10's if 3.90's don't get enough favorable votes here.
Thx-Goose :)

Yeah, bracket racing dialing-in my own time, but I'm always looking to go faster. :)
There's a place here that sells Richmond 3.90's, and I know how noisy they can be.
What's you mph and rpm at the top of your 4th gear before you have to shift into 5th?
I have my rev limiter set at 6500rpm. Is it less than 6500rpm?
I may consider 4.10's if 3.90's don't get enough favorable votes here.
Thx-Goose :)

Hmmm, not sure of your traps or anything but let me try to help. with 4.10's and a 26" tire, you can go 123 @6500 RPM's in 4th gear. The same gear with a 28" tire would net you at 132@6500 in 4th.

3.73's w/ 26" tire@6500 would be 134mph, and the same with a 28" tire would be 145mph.

3.90's w/ a 26" tire@6500 would be 129mph, and the same gear with 28" tire is 139mph

Look at the above post. If you think you will get the car to trap higher than 122-123 MPH w/ 26" tires (26" isn't always a perfect measurement + tire growth variable in there), then 4.11's are not for you. Higher RPM = higher speed per gear, of course.

I'd assume if you spent the money on AFR heads and building a 383, you've probably got some forged goodies in there. So it would be a safe assumption that there is a chance you'll spray that motor some time in the future. In that case, some 4.11's + 28" tire may be your best bet. Or if you are being more budget oriented, stick w/ 26" tires and 3.73's.

Me personally, I run 26" tires. I take my motor up higher (spray until 6800 RPM), and 3.73's are most definately holding me back, and are killing the car N/A. I definately need to step up to 4.11's, hence the reason there is a set sitting in my garage. :)

Look at the above post. If you think you will get the car to trap higher than 122-123 MPH w/ 26" tires (26" isn't always a perfect measurement + tire growth variable in there), then 4.11's are not for you. Higher RPM = higher speed per gear, of course.

I'd assume if you spent the money on AFR heads and building a 383, you've probably got some forged goodies in there. So it would be a safe assumption that there is a chance you'll spray that motor some time in the future. In that case, some 4.11's + 28" tire may be your best bet. Or if you are being more budget oriented, stick w/ 26" tires and 3.73's.

Me personally, I run 26" tires. I take my motor up higher (spray until 6800 RPM), and 3.73's are most definately holding me back, and are killing the car N/A. I definately need to step up to 4.11's, hence the reason there is a set sitting in my garage. :)Yeah, I have forged everything on my motor.
A little bit of nitrous might be in the future. Right now, I have a set of BFGoodridge Drag Radials 245-50-16
I run at over 5500' altitude. My 1/4 miles times based on my best is 12.2 at sea-level estimated. This is how my car is set-up. It's full trim. and I kind of have it set-up for all around performance, not just drag racing. At 3800lbs with me in it it's not what I call drag racer :)
The kind of trap speeds you guys are talking about, I doubt I'll ever get that high, not with this car, anyway. Again, tne sea-level trap speeds of my car is calculated at 109-111mph as is right now. It's not as fast as it can be, because I haven't spent or wanted to spend the money on a suspension set-up for drag racing, skinnies, shocks, lighten weight more, etc...
I was looking at a change on gears just to keep it on the same line of what I already have done on this car.
There are two things I have left to do. Going true-duals, and 4.10's. I want to lower my e.t from 13.4 to low 13.1 or better at altitude. (11.88-12.00 sea-level roughly)
Altitude sucks. :D
-Goose :)

This is my time slip from Friday...

R/T......... .041
60'.......... 2.057
330.........5.745
1/8......... 8.760
MPH........ 82.07
1000....... 11.328
1/4......... 13.488
MPH........105.44

My 60' times are usually 1.92 for some reason, I couldn't hit it Friday. I'd like to get 1.8 60's at minimum with my set up. Hopefully, the 4.10's will do the trick.
-Goose :)

This is my time slip from Friday...

R/T......... .041
60'.......... 2.057
330.........5.745
1/8......... 8.760
MPH........ 82.07
1000....... 11.328
1/4......... 13.488
MPH........105.44

My 60' times are usually 1.92 for some reason, I couldn't hit it Friday. I'd like to get 1.8 60's at minimum with my set up. Hopefully, the 4.10's will do the trick.
-Goose :)
Whoa.....you've got other problems to deal with other than gears. I was expecting trap speeds in the high teens to lower 120's (depending on the exact combo); there are bolt-on LT1's w/ higher trap speeds than that. It's not the 3.73's that are holding you back.

Whoa.....you've got other problems to deal with other than gears. I was expecting trap speeds in the high teens to lower 120's (depending on the exact combo); there are bolt-on LT1's w/ higher trap speeds than that. It's not the 3.73's that are holding you back.Hehe! Not at this altitude. :D
Just to give you an idea, stock Z06's trap around 105-107mph and run 13.6-13.7 range up here.
Bolt-ons LT1 trap around 95-98mph uphere. My car stock ran 15.1 :eek:
People from Alburquerque can perhaps relate to what I'm saying. Racing at altitude it's a different ball game.
That's why I posted the estimated sea-level times, should I race it at Houston, per-se.
-Goose :)

Hell yeah. This dude from albuquerque can relate. I'm at 5300ft. Altitude kills Joe. My corrected ET's should be in the mid to low 10's, but not up here. Kills off your HP, ET's and trap speeds. zhevy-1 has times that are about right for where he's at. Add about a second to that ET and thats what he'd probably run at sea level with traps in the low teens. You could improve that 60ft a bit though. What kind of tires you running? I think you could get away with a set of 4.11's and get even more improvement with some ET streets and some higher rpm launches. Shouldn't be a problem with a 12 bolt though.

Ken R.

Hell yeah. This dude from albuquerque can relate. I'm at 5300ft. Altitude kills Joe. My corrected ET's should be in the mid to low 10's, but not up here. Kills off your HP, ET's and trap speeds. zhevy-1 has times that are about right for where he's at. Add about a second to that ET and thats what he'd probably run at sea level with traps in the low teens. You could improve that 60ft a bit though. What kind of tires you running? I think you could get away with a set of 4.11's and get even more improvement with some ET streets and some higher rpm launches. Shouldn't be a problem with a 12 bolt though.

Ken R.
I need to get me some new drag radials. When mine were new, I was pulling 1.9's consistently, as they wear out a bit, I've lost just a bit. Maybe, I need to lower the tire pressure more. My drag radials are 245-50-16 BFG. They're pretty good imn my opinion. I could definitely get better tires and set-up, I guess.
Thanks for your input on altitude racing! :D
-Goose :)

at a mile high your trap isnt gonna be anywhere near sea level status so you can get away with a lot more gear
with 245/50/16s
3:73's in 4th at 6700 is ~ 137
3:90's ~ 131
4:11's ~ 124
4:30's ~ 119
4:56's ~ 112.....just a thought on these :p