HCI2000SS

iTrader: (2)

I'd definitely do the 3.73's if it were me. The gas mileage between the two is going to be so small that you probably won't even notice it

BWZ_2k2Z28

that's what I was leaning towards. If I'm gonna go through all the trouble, I don't wanna end up wishing I went with 3.73's. Hell, my dad is trying to persuade me to go with 4.10's lol

Carguy8888

iTrader: (1)

I am about to do this exact swap (2.73 to 3.42) including Bilsteins. My used 4 channel dif is on the floor waiting to go to the shop to get installed. I'm smart enough to know I can't do the install. I can't wait to feel the difference, it will be perf for me. Not sure about mpg.

HCI2000SS

iTrader: (2)

Exactly man 4.10's would be fun, but I think the 3.73's are a better fit for what you are wanting from the car

Kingc8r

iTrader: (21)

A stall converter will help more than just on launches.

That being said gears will help slightly. With a stall they help more with tightening up a stall, more so than overall performance.

If I had to choose I'd take the stall every time over gears. They make stalls that will drive like or close to stock. Swapping a converter is easier than gears too

FirstYrLS1Z

iTrader: (4)

Dad wants 4.10s',he's old school,like me,LOL. I ran 4.56s' with my auto for 4 years,incredible on the street.I'm back to 3.23s' for now,gonna build a rear with 3.73s'.
MPG in an automatic for freeway legal speeds(65-70) would be:2.73-25.9,3.23-24.5,3.42-23.8,3.73-23.0,4.10-22.2,4.56-21.5. City driving is too much fun to be concerned about mpg.
Each step up in gearing would net about 1/8 of a second improvement in 1/4 times.
Stall changes for improvements in 1/4 mile times is much greater. Seen reports of as much as a full second. AND a stall(because of lock-up capability) won't change freeway mpg as a gear change will.
Most popular combo is a 3600-4000 quality stall and 3.73 gears.

99 Z28 camaro

I'm doing my 99z28 this Friday she runs 8.50 1/8 now (all stock)but my 60 feet is 2.028 with the 2.73s.can not wait to put in 3.42 BC every one say it is like going day to night

BWZ_2k2Z28

man if it wasn't my DD I'd go 4.10's in a heartbeat but I'm just gonna go 3.42's because it'll be a little easier on my rear end. Plus I'm gonna go with the thick gear for my 2 series carrier and my dad told me he could never get a thick 3.73 to set up right.

LQ4Supra

iTrader: (1)

I have a 1999 Z28 M6 that I just converted to 4L80 and here is what I've found. It's just my opinion, but I thought I'd throw in my $0.02.

On two back to back hwy drives I got 29 and 31 mpg with the M6 and 3.42 in 6th. In 5th (0.75:1 like the 4L80 OD ratio) I got 22mpg on the same drive.
I was getting 18 in town.

After the swap, retaining my 3.42 rear, the car gets 16.5 mpg on the same commute to work. My 2005 6.0 VHO Silverado gets 15 for the same drive. I'm getting 20ish hwy and the VHO gets 18mpg. The 4L80 probably soaks up more MPG than the 4L60 would.

At 75mph with a 0.75:1 OD a 2.73 rear is appx 2000rpm and a 3.42 is 2500rpm. 500rpm cruising for a long distance makes for a pretty big drop in MPG. My M6 was 1700ish.

3.42 gears are very fun for acceleration from a roll but mean very little for 1/4 times comparatively. If you DD the car and commute a long distance, you may like a stall better than gears. If you drive 9 miles to work like I do, you won't worry as much about having the lower gear ratio.

My pinion seal is leaking again and I take just enough HWY trips that I am contemplating swapping my M6 axle for an A4 or having a 9" built with a 2.75 or 3.00.

FirstYrLS1Z

iTrader: (4)

a 2.73 to 3.42 change will be a 25% increase of torque to the axles/tires. will make a 325hp car FEEL like it has 405hp.

BWZ_2k2Z28

well my overall daily commute is 20 miles, give or take a few miles. I drive down to the beach about 4-5 times a year, which is about 120 miles. So I'm thinking the loss in mpg's isn't gonna be that bad to me. And if my car instantly feels like it has 400hp then f*** gas mileage lol

I still see some of you guys talking about stall converters on here. So maybe you all know something that I dont. My understanding is that stalls are used for two things, launching and helping out the idle with bigger cams. I don't go to the strip or launch on the street often and I have a stock cam. So what exactly would the stall converter help me with?

LQ4Supra

iTrader: (1)

I can tell you, your car will not really feel like it has 400 hp. It's a lot of fun but it will still feel like you have 325 hp and are in the peak parts of the RPM range more often (because you will be). You won't really be much, if any faster, but you'll pay for a gear change and more fuel to not be faster. If I was driving 50 miles a day, the difference would about $700/year. It's not a ton, but it still a consideration depending on what you'll spend on the gear change.

I happen to like it, whether it feels like 400hp or not.

murphinator

iTrader: (2)

BWZ_2k2Z28

well I know that it feeling like 400 hp was an exaggeration. But I am lost as to how "it's a lot of fun" and its brings me closer to the powerband yet it wont make me faster?

LQ4Supra

iTrader: (1)

It FEELS faster, but your power to weight ratio didn't change so you're actual acceleration isn't much different. Lower gears make no additional power, they just move around what vehicle speeds you see the the same power at. Your 1/4 wont change by more than a couple tenths. You FEEL your power band come in harder (earlier) when you're rolling but if you have 325ft-lbs of torque at 5000 rpm that won't change. If you were getting 325ft-lbs at 40mph in 1st, now you're getting it at 35 mph so you feel it come in lower, but you don't really accelerate that much faster. You are just changing at what mph (wheel speed) your engine hits 5000rpm in the same gear.

Carguy8888

iTrader: (1)

Wow, that much? I don't go to the track & try to limit burnouts lol. I just want the car to have a little more snap w/o getting crazy or breaking parts.

BWZ_2k2Z28

LQ4, I aint saying you're wrong. But I have a hard time believing that what you're saying is accurate and yet all these people have gone through all this trouble to swap gears out just for them to FEEL like they're faster.

LQ4Supra

iTrader: (1)

Gears can help your 60' time, especially in a standard. Stall helps 60' times more than gears in an auto if you are stock. You said you were not worried about the 1/4 mile so much, so the lowering of 60' times to improve ET isn't as important to you. There is a list of stickies at the top of this section of the forum and the one that talks about the results of changing gears has a discussion on how much of a difference a set of gears makes. You will see a more improvement in your actual acceleration from performance mods than gears because they actually increase your engine output.

There are times when changing ratios will benefit your ET because of where you are at in the RPMs as you cross the finish (lower half vs upper half). On a stock car, or nearly stock car you won't see a huge difference in 1/4 mile which means you aren't accelerating that much faster with the ratio change. This is a discussion that has been done often on every forum and some guys have tranny and engine combos that benefit from a ratio change, and some go up from 3.73 to 4.56 and might see 0.2 in the 1/4. I won't say you won't gain, but depending on the cost, there may be better options for the small increase you would see.

In my case, I already had a 3.42 rear so I didn't spend anything for the gears but I don't think I would have spent the money to change if I had the 2.73s.

I went from 3.54 to 4.08 in my 2003 M6 350Z when I had it and I went from running 13.6 to 13.4. It felt stronger in corners and throttle response was great, but the acceleration numbers never really showed that I gained anything with the money I spent, but I was still near stock for HP.

SSellers

It can be hard to wrap your head around why increasing torque to the ground doesn't always equate to a gain. The reason is that at whatever engine speed you are at to compare, the higher geared rear (lower numerically) is at a higher speed than the lower geared rear.

Say you're comparing a 2.73 to a 3.42 and running to 80mph in your 1:1 gear and leave out tire effect (tires are also a part of the actual torque to the ground equation). With say 300 ft lb you're putting 819 lb ft to the axle of the 2.73 and 1026 lb ft to the axle of the 3.42. Now, the car with the 3.42 should've gotten there way faster but it didn't. Why?.....

Well, the engine of the 2.73 car only had to accelerate to about 2850 RPM to hit that speed but the 3.42 geared car had to accelerate to about 3600 RPM. Did the 3.42 feel like it was accelerating faster? Well hell yeah but it took another 800 RPM to get to the same speed as the 2.73 and that does take time so the torque advantage of faster engine acceleration is offset by the fact that it had to accelerate further RPM-wise. You got to 2850 faster than the 2.73 rear but if you'd let off then you'd be doing 64mph. So essentially the 3.42 felt like it was accelerating faster (which it was) but it had to get to a higher RPM than the "slow" feeling acceleration of the 2.73 so the result is they both might take the same amount of time to reach the same speed.

Gearing is used to get a vehicle into it's intended RPM range for best performance whether it be quarter mile or economy. If you just change gearing and nothing else then it can go either way.

BWZ_2k2Z28

I understood it the first time but it almost seemed like LQ4Supra was tryna persuade me into not getting gears lol. I dont really care about the numbers because my car will probably never see the track. I dont street light race either. I just figured that gears were a pretty good bang for your buck.