Bad06vette

I am entertaining the idea of switching my 3.42s on my z51 06 to some 3.90s. I have done some searching but still, just want to get some opinions about this. Is it worth it? Will switching to 3.90s require any other moding in the future, ie built rear end or anything? Also, how much MPG will I be giving up by going to the bigger gears? Will I feel a difference in power/drivability?

Also, are 3.90s okay for a DD? Would 4.10s be too much?

Furthermore, who is a good vendor to get gears from? And how much am I looking at for install?

Smitter

I am thinking the same thing. Look for some of Spinmonster's threads he seems to be very knowledgeable about gears. DTE had some good prices a while back and say they are always open to talking to customers about what gears best suit your wants and needs. Let us know what you decide

Bad06vette

Thanks for the input! It is hard to find all the good threads... there are just so many threads! lol.

Also, what is the DTE website?

stinky

go here: http://www.dynotech-eng.com/

Ben Diss

Wicked Weasel

3.90s and 4.10s are close. If you are not planning on other mods in the future I would go straight to the 4.10s and skip the 3.90s. If you plan on HP mods in the near future than you will have to make a decision to see which one will fit you better.

The another thing to consider is if you are going to start to road race the car than you might want the 3.90s over the 4.10s, but for general street driving and 1/4 mile driving the 4.10s are nice.

Gas mileage is minimally changed.

4.10 gears will decrease your 1/4 mile ET by at least 3 tenths and yes you will feel it right away.

ECS charges $1395 to swap your 3.42 and put in 3.90s or 4.10s. If you want a hardened output shaft that will be an additional $295.

ECS uses Cryo Treated / Micro Polished Ring and Pinion Gears for all gear swaps.

Silver05GTO

I have 4.10's on mine. Lot's of fun. With mixed driving I average about 23mpg combined so my total fuel usage hasn't changed too much. I don't think they are too much for a DD imo.

Bad06vette

Good information guys. Thanks!

I plan on doing a cam next year, maybe even H/C. So yes, I do plan on doing more power. Would the 3.90s be better for more power in the future? Why are they better than 4.10s?

blackfd

I plugged in the numbers and like where 4th ends with the 3.9 vs. the 4.10 (because i'd like to be trapping upper 120's with bolt ons/cam)

RPM Transmissions will do it with C6Z diff/shafts and gear for 1595$ installed

SpinMonster

It isnt the power that causes the need for 3.90's in the rare circumstances some wanted them. While it could be argued that road racing courses mandate the need to shift on a straightaway, the fact that a good shifter and 4.10's may have better time as a result of the steeper gears would be the reason to get 3.90's. Not wanting to shift isnt a well grounded reason to not get 4.10's for a road course if the car is in fact faster with 4.10's in that application. That distinction hasnt been commented on but by a few people.

For the rest of the regearring candidates, the only reason to get 3.90's is if you need the extra trap speed at the end of the 1/4 mile. If your car is going to be a street car only and will never see the track the vast majority of people get 4.10's and wouldnt give them up after getting them. There were three (3) people that swapped out the 4.10's to a taller set. The 3.73 car is now a mid eleven second car and the other 2 swapped to 3.90's, one because he didnt like seeing high rpm's on the hiway (at 140mph where the 3.90's would be 3700rpm instead of the 4.10's 3975rpm) and the other reason is that he swears the 3.90's restored his gas mileage concerns which cant possible be true. 3.90's were 2/3 of the gearing from 4.10's and therefore would still have 2/3 of the gas mileage loss of 2 mpg. The last man was for a road race set-up and I cant comment on that.

Getting back to your car, you need to see what application you need here. My car is a head, cam, nitrous car, and I have 4.10's and wouldnt give them up for anything. Most people that are anti gear think power and gearing are replacements for each other and that isnt true. My car has all the power needed for a 10 second run and the thing that makes me fast is the tire choice. I solved the traction issue with the things discussed in this thread:

http://forums.corvetteforum.com/show....php?t=1923715

I repeatedly hear people say, I have too much power and the wheels spin so I cant get gears. This approad results in very poor street performance. When you spin the tires its from too much power for your chosen tire. For a street car that will rarely if ever see a track, the tire you chose dictates the power level you can go to. The best advice I can give you is to chose your tire and max the gearring since it costs the same for any gear set and simply stop adding power when you cant get it to the ground. Tall gears arent a band aid for a poor tire/power combo. There are many overpowered cars running 12 second 1/4 mile times.

A word about forced induction:

There are FI cars that run low 9 second 1/4 mile times with 800rwhp and yes they need 3.15 gears because the trap speed dictates it, not because its faster. Most FI cars that are under 550rwhp dont perform better than a 480-500rwhp N/A car with gears. I was just talking to a guy last night at dinner who was telling me he thinks he will get a smaller pulley for his ATI sincce he ran a 11.69 with ET streets. He didnt want gears because he thought the new power level would make it spin the tires too much. I ran through all of this with him and the time slip he had with him told the whole story. He had a 1.81 60' and a poor 1/8 mile performance. On the street the 1/8 mile run more accurately shows the typical race set-up. Its less than 0-100. This is where mile FI cars with stock gears show the poor side of performance. Most FI cars make up the poor 1/8 mile in the second half of a 1/4 mile run. Max the gears for a great 60' and with the tire you choose stop adding power when your tire cant get the power to the ground anymore.

I have to put in a disclaimer for the sill responses I get from tyime to time about 900rwhp FI cars being an exception to the rule so here it is:

None of these comments are for the guy that runs huge HP (700-800rwhp) for drag race applications. It isn intended for the application the OP has suggested which has no plans for anything beyond a H/C job. Since the fastest H/C car is currently in the 10.8's and a 4.10 gear set with a 28" tall tire will run a 10.6 - 10.7 at or near 130mph. I suggest the gears be maxxed. On the street my car and its tire have no issue with a nitrous shot on top of a 480rwhp car and have no tractio issues. Comparing apples to apples states that maxxing the gears is his best choice.

One last point is that the ratio of those who like 4.10's after theyre installed compared to the people that swapped them out is like 50:1. This isnt an exaggeration. while 3 people say they werent for them, ther are 100 that say they love them.

In the end you should go in a car with the mod you are thinking about getting and dont take advice on a mod from people that dont have it. My car is here for anyone who wants to see the truth about what 4.10's can do on a street car with all the power you will liklely ever use.

Most people with 4.10's report 2mpg at best lost and they are fine for a daily driver.

3 Z06ZR1

I feel a big difference with 3.90's compared to the 3.42's Choose 3.90's or 3.73's if you like hiway driving along with good lower gears. With the 2.97
First gear of the Z tranny your plenty low. Two people that switched out 4:10's ended up faster.The Z manual also has a .57
6th gear vs .50 of the base.Raising rpm's when you want to save gas and cruise. Only 68 mph at 2000 rpm. I went 100-110 mph per hour for two hours.With 3.42's seeing only 22-2300 rpm's.Trust me with the Z tranny and 4:10's that would be no fun looking at 3k rpm's plus.Probably would have used some oil.For sure not the 24.9mpg. I got ( yes I filled up drove at least 100 or more for two hours and checked the mileage)Thats one of the reason's 4:10's can be too low to some. The shop I had do my gears does more
of the other ratio's than the 4:10's. Another shop that didn't get my gear job.Said the 3:90's make the best overall package. My tuner said do 1 or two ratio's lower. With the base tranny 3:90's is perfect,
Mostly likely not quite as quick as 4:10's is the short run,but better in all other respects. If that Kind of overall performance is not what you want,and you just want max (till u raise the power)at the strip. Get 4:10's
The 50-1 is such crap.

kaislick

i have gone to a little smaller tire and with my 1/4 mph at 126 am afraid i'll have to shift into 5th. any thoughts on how tire size affects gear choice? am torn between the 3.90 and 4.10 also, i do drive 50% highway. i'm not trying to hijack the thread but i hven't seen tire size mentioned in these decision trees.

Bruno0825

I have 3.90 with Z51. They are perfect 1-4th pull great 5-6th are like OD.

Braciole

Max from Cartek told me 3 tenths in the 1/4 mile
I thought it would be more

3 Z06ZR1

Tires affect gearing also,They have tire size gearing calculators for tires as well as ring and pinion.

k0bun

485rwhp with Z51 and 4.10s. 100% daily driver with absolutely no complaints about gas mileage, rpms, etc. A beast on the street from a stop or a roll.

LS1LT1

I bet from a roll in like any gear your car is downright nasty Frankie.

Bad06vette

That sounds hot. That is what I am looking at... hopefully just shy of 500 with a H/C combo. What H/C did you go with? Very interested in your setup!! Are you on a stock ported intake or ported fast? Those are nice numbers. Sounds like a beast!

06.Z51.MontRed.Vert

410's here with 554rwhp, I love the gears. Great mileage, and excellent on the highway, especially with a now useable 6th gear.

k0bun

Thanks. It's Cartek 4x/2x H/C with ported FAST and TB. Along with Kooks 1 3/4" w/cats, Borla Stingers UD pulley and VR. The car is nasty(like Marc said ) and the gears optimize the set up perfectly. You will not be disappointed with 4.10s.