Hey Guys, im thinking about getting 3.90 gears, for those of you that have them please chime in and let me know what kind of 1/4 mile time difference you got. (really looking for M6 only).

If you dont have them, please refrain from speculation.

Thanks in advance

Daren

 

Wasn't there another thread about 3:90's before?

Oh yea, here it is, have hours of fun:

http://forums.corvetteforum.com/show...ght=3.90+gears

 

OK, then. When you want to know about 4.10s I'll chime in with my .02.

 

thanks...didnt know that wast there

 

cliff notes
Z-51 get 3.90s

Base get 4.10s



end of story

 

I have the base 6 spd. I am having 3.90's installed this saturday,
So i'll let you know soon. For those who worry about retaining some hiway gear. Here is the speeds @ 2k rpm's in 6th

stock 93.6 mph @2000
373 85.3 mph@ 2000
390 82.1mph@ 2000
410 78.1 @ 2000

Z-51 tranny stock 82.1 mph @ 2000
373 75.3 mph @ 2000
390 72 mph @ 2000
410 68.5 mph @ 2000

This is where I look at my gearing. I drive cross country couple times a year so I want to retain the low rpm hiway cruise.
I'm going 390
If I had the Z tranny it would be 373's if any.
other wise gas mileage would suffer to much. Any lower gear than stock will reduce Hiway mileage.

 

In my expirience so far with 4.10's

Cruising on the highway in 6th is getting me 24-26mpg @70mph. Cruising at 65mph is getting me 25-27mpg.

So those couple hundred rpms with 3.90's are not gonna make much differance at all on a Z51 car in 6th gear in terms of fuel economy.

With stock gears 6th would get me nearly 30mpg at 70mph......but the rpms were down near 1600, the sweet spot for economy with the stock cam.

 

Rock'n Blue 08

Thanks! Good details.

 

I assume you do not have the Z51 option as it is not mentioned, so here's a little tide bit for you. Your final drive ratio with 3.90s in first, second, and third gear will be almost identical to the final drive ratio of the Z51 car with a 3.42 rear end.

BJK

 

Which brings in the question of why the overwhelming majority of Z51 owners with 4.10's are very happy with them. I think the ratio is like 50 yeses tot he Z51 with 4.10's to a single no. Getting 3.90's on thebase transmission is like the Z51 transmission and stock gears so why do so many Z51 guys want more than the stock gears?

I think it more important to choose a tire first and think about gears based on trap speed or application. Many people have for too much power for the tire they insist on running and will pay thousands for more dyno sheets rather than get a tire that works well.

I think the best advice for you would be to go to a tuner or forum members and go for a ride or even drive a car with the gear set you want and the one above it to see the differences. Keep in mind if you are a track guy that you should gear for your intended trap speed and get the tire and power requiements in line before you choose more power.

I have a Z51 with 4.10's an r-compound tire and nearly 500rwhp all motor plus a nitrous shot that can go as high as 175more HP. I am firmly staying with the 4.10's and have all the traction (and acceleration) I will ever need.

Cartek ran 3.90's on a Z51 with 650rwhp on their R&D car with plenty of traction. They also have numberous all motor cars in the 10's with 4.10's so choose based on the tire and power you will run for track situations. Road track guys repeatedly say they like 3.90's.

I get 28 MPG and do 2000 rpms at 65mph. Mileage is also dependant on other variables. Having the proper compression on my head/cam motor, it loses nothing to cam only cars which have a drop in mileage as a result of lower dynamic compression. Stock cars will see a 2-3 MPG loss with 3.90's or 4.10's and rpms vary only slighly with the two gear sets. At 100 mph the 4.10's are at 3000rpms with a Z51 and at 2850rpms with 3.90's.

Anyone in the NY area that wants to go in my car for an example of the 4.10's on the Z51, feel free to shoot me a PM. I would be happy to help out.

 

IMO, I think some of the reason people w/ z51 option want gears, is because 4th, 5th and 6th are identical or near base gearing. So the guy with the 3.90 base gears would be close in the 1,2,3 but ahead (gearing wise) in 4,5,6.
I agree about the tires. But how much gear is too much (base and z51) on run flats? Which is what most of these people will be running on.

 

I drove 3.90s back to back with another car with 4.10s (both base gearing) and both of us agreed the difference is barely discernible. By back to back I mean got out of my car and hopped in his and off down the road. Im not sure how the often repeated but seemingly tried by very few rumor that 4.10s feel "much" better started. It is often repeated here though and its false.

My experience tells me that most folks are not giving up much of anything or gaining much of anything either way since few go on a road course or will have the power and traction needed to require a shift into 5th on the straight pipe. Out side of those few at most you stand to gain a very slight edge in acceleration against a very slight loss in mileage.

Bottom line its not that big a deal and sorry in advance to the fanboys.

 

Thanks for the long post
I always run Drag radials at the track (315/35/17) BFG (got a new set waiting for me to pick up tomorrow.). Right now, I Barely have to shift into 4th in the 1/4 mile on these tires. I would like to be accelerating more, instead of being at 4800RPM. I have the base transmission, (with a brand new stock clutch..thanks to GM) I dont really care about gas mileage, as Im only driving it here and there and to the track. No long trips where it really matters. I just do NOT want to have to shift into 5th before the end of the 1/4 mile. From what everything i have read so far, it shouldnt be a problem. Im pretty sure ive got all the bugs worked out, gonna go back one more time and have it re-dyno tuned next week, to try and pull just a little more HP and TQ out of it.


Thx again for all the information...Knowing is half the battle.!

Daren

 

http://media.putfile.com/Ed-33
Z-51w/ 4.10, 485rwhp/460rwtq

The car BARERLY crossed the traps hitting the rev limiter (7K) in 4th gear...car was driven by Doug@ECS. .....ET couldve been lower if the car wasnt bouncing off the rev limiter....

I drove the car (yes I know it takes seat time), I was bouncing off the rev limiter in every gear including 4th 30 ft before the traps...... the bottom line is, if you are not going to cut 1.85 60ft or less you will be shifting the car into 5th or having a ruined run by hitting the rev limiter right at or right before the traps....

I know you said you dont care about the gas milage & long drives, but do keep in mind, you are sacrificing top speed of the car by 40mph...

here's a chart that can help you make your own personal desision (set up for base tranny)
http://www.xse.com/leres/bin/gearrat...mference=84.04

-Ed

 

The car will do 200+ with 4.10's in 6th gear.

If you think you will have enough power to justify faster than a 10.6 1/4 mile then get 3.90's. Also keep in mind that if you are going ot drag race your car, get the equipment needed to do it right. Just dont be pissed off if your requirements change because you raise your power long after the gears are installed. If you have the correct equipement even 500rwhp will be able to run a 1/4 and not hit the rev limiter with 4.10's.

When making this decision, be sure to consult people with the right equipment who can run a 10 second 1/4 so you are guided correctly. Getting 3.90's so you can run the wrong tirs wont result in as fast a car as you can have otherwise. Good luck with your decision.

Since you will run drag radials which is not optimum and it will be a 25.7" tall tire, 3.90's will be best for any power level over 450rwhp and still not hit the rev limiter. A true 440rwhp and 4.10's would run a 10 second pass with slicks though. If you are barely running into 4th gear then a 4.10 gear-set would be best. You of course realize that if you raise the power level later on, you shouldnt whine like a sissy about the gear set as recomended since it isnt on the table now.

 

I love you guy, and agree whole-heartedly, but I'm really into spiney lobsters.

 

Wrong on a couple things, how did you lose 40mph of top speed??? So 4.10's mean the car won't go over 146mph???? Sounds WAY off base. A Z51 car w/4.10's means the car's new top speed gear is 6th, the differance is very little from 6th w/4.10's and stock 5th gear Z51 w/3.42's.

Also your not hooking well and driving crappy, you admit to banging the rev limiter on every run. If your 4.10's are so bad, start in 2nd gear and finish in 5th....you'll be making the same amount of shifts just staring in a gear that's longer.

Final point, your running stock tires, and the weather is cold still=no traction with stock runflats PLUS you have nearly 500rwhp. You NEED tires much worse then you think you do.

 

I'm confused. I don't see how hitting the rev limiter in every gear is the fault of 4.10 gears??

 

go to the track and let me know how you do....


gears wind out the tach lighting quick......as soon as you launch the car, you have to shift into 2nd......

I also went to Atco, we only ran 1/8 and out of 5 runs, twice I made it to the traps in 3rd, those two times I had 1.9 & better 60'ft.....3 times I hit the rev limiter in 3rd right before the traps and those were over 2.0 60ft.

My point is (once again) 4.10 will put your car in a sheeet zone near the traps.......

 

I have alot less power then you, and run at a track that isn't near sea level, those 2 things combined mean I won't be hitting redline in 4th (wont have the mph to do it).

It's all good though, at your speed (mid 11's trapping nearly 130) is it really worth it going to 3.90's just for the sake of a little better timeslip? Your car is running FAST as it is, you'll pull just about everyone and pull them HARDER in 5th now then you will if you drop to 3.90's. Based on what you've said before your into the high speed runs, you'll pull harder with the 4.10's once you make that needed shift to 5th......you'll still need to make that shift even with the 3.90's.

And as anyone will tell you, your still gonna wind out 1st gear lightning fast with 3.90's, if you want to stay in 1st longer might as well swap back in the stock 3.42's.