87Heaven

I don't know much about this stuff b/c my car has always been all stock. I'm considering making some mods now. From what I've read, changing the gears really does change the performance of the car quite a bit.

I have the stock 2.59 ratio now. If I went to the 3.54 and changed nothing else on my car:
What kind of horsepower and torque gains should I expect?
What about 0-60mph times and 1/4mile times?
How much would this cost if I had a shop do it for me?
Is it worth the costs?
What effect will it have on my gas mileage?

Thanks for any responses. This forum is great.

scorp508

I'll answer this one.

None.

Gears don't affect the amount of horsepower or torque you make, they simply affect how it is used. [img]http]//www.corvetteforum.cc/ubb/smile.gif[/img]

GlockLT4

Yup... it simply changes how many revolutions of the tire you get per every engine revolution. Of course the tranny alters this as well.

Ezgoin721

As stated above, you won't see any Hp or Tq gains, but you will feel a significant difference in how the car accelerates. You will however pick up lots of rpm's at every speed and fuel mileage will suffer in highway driving since the engine is turning faster to maintain the same speed. Look at it this way: With 2.59's, your engine is turning 2.59 times for every revolution of your wheel. With 3.54's, your engine turns 3.54 times with every wheel rotation. It's like jumping on your ten speed bike and starting off in 1st gear as opposed to 5th gear. You can take off a lot quicker, but you reach your max rpm level quicker. Good for a quick sprint, bad for top speed and gas mileage!

GUMPA

I went from 2:59 to 3:73 and it feels like a "rocket sled" and I know it's "Quicker".....and Never hunts for 3rd gear....my mpg is ok and it turns 2000 rpm at 60 mph......you might try 3:45 w/ your year car......

87Heaven

Gumpa,
How much of a gas mileage difference was it for you?


Anybody willing to share costs?

Thanks for educating me on this.

nickd

I also went from a 2.59 to a 3.54 gear, this is on a 94 LT1 car.
2.59 gear, 160° Tstat, & fans reprogrammed, BPP Vortex Rammer
13.823 @101.50 60': 2.037
13.942 @100.21 60': 2.083
13.938 @99.61 60': 2.144

3.54 gear, above mods, & Muff elims
13.418 @104.66 60': 2.141
13.315 @105.20 60': 2.051
13.258 @105.91 60': 2.051

I really have not noticed any change in gas mileage.
I bought the differential outright from Ed Portner at
http://partsforvettes.com
I kept my stock unit.
I believe I paid somewhere in the $1200-$1300 range for the rearend. It's a completely rebuilt unit, all new parts including the gear.
I think Zip products has the same 3.54 rear for about $875? The only difference is you'll have to ship them your stock unit.

scorp508

With an L98 engine, you won't see the kinds of results that NickD did.

Goody

I just bought the DANA44 package from a salvage yard out of LA for $1125 after shipping and tax. I'll be doing the install. I was advised against doing the gear swap to my DANA36 because with future mods planned I would most likely break it. If you wanted to have the entire deal done for you then figure in the $1200-1700 range. A better option for your stock engine package might be the 3.07 gears. But only if you will be staying stock. My stock Dana36 has lasted me 118K miles. Good luck.

J Z06

To the original post person...

You are going to LOVE The difference in feel and performance. 2.59's are G A R B A G E! God knows why they we're put in our cars. I have a Dana 44 3.45 out of a '91 ZR-1(Thanks ED!) and it was a Godsend. Resonance with the 2.59's lugging down the highway was un-bearable. Now with the shorter gear... the rpm's while cruising are where they should be. Be sure to get a 3 series VSS and the correct speedo gears from Jeff Kopp/Superior Chevrolet. 18carfan is what He goes by here. He'll set you up with the right parts.

samc

in a long tube intake (stock, ASM/TPIS, superram) L98 with 700r4 auto any gear above 3.07 is questionable. my 1/4 times went DOWN when i broke my 3.54's and went to 3.07's! and my MPG went up a little. the car felt more refined in general. 1st gear in the 700 is so low anyway, with anything above 3.07 gears you can't really use it at all.

even with the 2.59's, you might see more et improvement with a converter than gears. and of course the "free" mods like air filter lid, tb bypass, maf screens (87 have a maf?), and the cheap mods like k&n, adj, fuel pressure regulator, plenum porting, open up the exhaust.

plus, if you think you might make more serious mods, you would be better off looking for a deal on a used D44 with the gears you want in it rather than upgrading the D36. look where i am now. i had more in the 36 with gears, seals, bearnigs and labor than the used 44 cost me.

LUDS 96

I went from the stock 2.59s to the 3.54 Dana 44 I bought it from Contemporary corvette in bristol PA. They shipped it ups to my repair shop. I Gained .4 in the 1/4 lost 2 miles to a gallon on the highway. Top end not forseeable on American highway. Could be 150 Plus.Cheap performance factory stock rear should be bullit proof with the auto. Love IT. Total swap Installed approx $1800

nickd

Hey Scorp, didn't you read my disclamier ? -LOL
I did mention what car it was on. [img]http]//www.corvetteforum.cc/ubb/wink.gif[/img]

aklim

I know older people move slower but this is from July 2001. Took you that long to type the response ?

aklim

Just saying that the OP's question was probably answered 20 years ago and hasn't been active since 2016. Just laughing at the long dead posts that have been resurrected. Stick around. Resurrect another long dead post and someone will mention it like I did. No harm intended

You were the one that mentioned old. I just used it as part of the ribbing.

JCrock

Howdy Frank. Fellow old guy here. I remember putting a built 401 in a '64 skylark convertible that was a 4 speed manual. It unfortunately replaced the 300 ci engine with aluminum heads and intake that was in it when we bought the car because the previous owner had warped the heads. Anyhow, that was a real kick to drive. Now, we can let the kids get back to their yapping.

aklim

What next? My underwear size and brand.

Here's my response "Shocked that you take a comment so seriously".

fredk

My 93 ran 14.0's stock. Headers and 3.54 gears 13.7.

KyleF

None, gearing does not affect HP or Torque output from the engine. What changes is the mechanical advantage at the tire. Since speed and Force are inversely proportional in the HP equation, the HP curve at the tire doesn't change. Force (Torque) will increase at lower speeds (RPM of the Tires). All else equal, the ratios you have chosen will make it feel as if you have added roughly 30% more torque at the motor.

This will depend on a lot of factors, mainly how good of a driver you are. From the 2.59 ratio I assume you have an automatic so we can take shifting out of it...but the biggest factor on Time, 0-60 time, 0-100 time, 1/8th mile ET, 1/4mile ET is traction and launch. The first 60ft. So, how good can you get the car off the line with just a bit of tire slip and not get out of control. Your car will have the potential to do much better. While it is a very dynamic system, the basic equation is F=MA. Force = Mass * Acceleration. If the Mass is constant, when Force goes up, so must your rate of acceleration, but only if your traction is also equal. The car will be able to accelerate faster but will have a shorter time before it hits it's red line. I like to look at HP as energy available (HP is the rate of which mechanical energy is used -ft-lbs/sec). HP being the ability to produce Torque (Force) at speed (RPM) . The more HP you have the more torque at RPM you have... the more area under the curve to do work. I could expand on this further with high HP peaks, race engines that run to 8000 RPMS and etc, but you are not changing the potential of the engine, just changing how it is used. Too much gear and you run out of power band, but you are not asking about going that low, but just want to note that going to a lower gear is not without it's losses. As I said, it is very dynamic and as speed increases, air resistance starts to become a larger force acting against the car than the inertial forces from mass. Engine output isn't perfectly linear either, and at each gear change the force at the tire also changes. So, while your acceleration rate will go up, the time of each step of acceleration rate (1st is higher than 2nd, 2nd is higher than 3rd), you get less time at each rate (again, not perfectly linear rate in each gear because the torque curve isn't perfectly flat and your HP curve as a result isn't a perfectly linear plot either). As long as you are not reaching your terminal velocity (red line) before crossing the traps in a 1/4 mile a lower gear should help if your tires and suspension can hold the additional force. Tire smoke is just power that didn't get to the ground, but puts on a good show. Obviously, ultimate top speed will be decreased. What I would expect to see on your time slip would be a .25-.4 second decrease in ET and very little change in MPH, 1 -1.5.

Having discussed this one the board a few times, with a full kit (pinion, gear, bearings, seals, fluid) and labor expect $1500-$2000 depending on shop rates in your area. Not just any shop should be trusted to set up a differential. Tolerances must be correct not only for life of the gear but to run quiet.

Yes! I have changed gears in multiple cars I have owned, never been disappointed. It makes the car feel much stronger in most street driving situations. You get the benefit of a stronger engine without having to upset what already works well together. Not that I am against engine modification.

Again, this depends a lot on you and your driving habits. If you mostly drive at 75mph on the highway, expect to see a drop of about 2mpg. On the other hand, if you are driving around at 45-55mph, very little will be affected. If this is primarily a fun car you go out and hot rod around in I will just say it won't be enough to worry about.

KyleF

Hahaha, I didn't look at the date of the first post

OP is probably long gone.