ok so here is my basic understandings. First gear ratio is applied diffrently with every car, depending on tire size, transmission (auto or manual), and what your looking to do. with that said, if you wanted gears with a real low end and no top end you would want 4.11 or higher. and if you wanted something with a high top end and no low end you would want 2.73-3.42. and a happy medium would be around 3.42-3.73. am i close?

Second all 7.5" 10 bolt rear ends are 27 spline pinions, i was told there was no other option.
and axles splines are whats diffrent with 89 and older 7.5" 10 bolts are 26 spline. while 90 and up are 28 spline axels. is this true?


also didnt all automatics come with either 3.42(v6) and 2.73 (v8)? and the v6 and v8 had the same 7.5" just diffrent gears?

and finally is it drivable to use 4.11 for highways?

sorry for all the questions just need to clear some thoughts up.

 

example 4:56 is "lower" that 4:11, 4:11 is "higher" that 4:56

there are only 27 spline pinions for the 7.5 rear, no exceptions

i think you have the axle splines about right

4:11 would work on the street, but are a little overkill

3:42 are common as 3:73 are also pretty good

generally stick cars had lower ratios

 

i believe 88 or 89 was the switchover year for the 26-28 spline axles

Any 7.5/7.625 gear set will interchange ans long as they are mated with the proper series carrier.

2 series = 3.08 and numerically lower (higher gear)
3 series = 3.23 and numerically higher (lower gear)



4.11s wont be too painful on the highway as long as you have an OD tranny, you will still see a good drop in mileage though.

Like stated above, for the street you should keep it with the 3.23 or 3.73s. Kind of the best of both worlds there.

 

im looking for the best on a 1/8 mile run, but not too low. street performance and gas millage dont matter too much as it isnt driven alot. right now im looking at the summit 4.10 gears for $140.

 

From what I see, all your information is correct. 1990 is officially the changeover year from 26 to 28 spline axles. There may be a few 89's with 28 spline axles but it will depend on the exact build date. Assume they have 26 spline.

The gear ratios available for the third gens depended on a lot of options not just what type of engine it had. Except for the few cars that got the 9 bolt, they all got the same 10 bolt diff no matter what engine/tranny combination was in the car. There's no such thing as a V6/V8 diff.

My daily driver truck has 4.10 gears. It also has a 4L80E tranny for the OD. It also has 28" tall tires which help. I normally cruise down the highway at 120 kph with the engine rpm around 2900. Driving around town I have good acceleration but having a 454 helps. For a 4600 pound truck I get 10-12 MPG in the city. About 16-17 on the highway. I'd rather have 3.73 gears but the 4.10's give me a 10,000 pound towing capacity in a 1/2 ton short box truck.

 

but 4.10's should be better than 3.73 for a 1/8 mile run right?

 

You could get a ratio that's too deep. Lets say you have a 700R4 and 2.73 gears. The low 3.06 first gear helps to get you off the line to compensate for the 2.73 highway ratio and the OD combined with the highway ratio brings the rpms down for better fuel mileage. The torque multiplication factor for a launch is 3.06 x 2.73 = 8.35. Now you change the gears to 4.11. Your launch factor now jumps to 12.57 which will probably be enough to easily smoke the tires even with a V6. The OD will help on the highway but fuel mileage will decrease because of the higher engine rpms while driving the same speeds.

As a comparison, you change the tranny to a TH350 with the 4.11 gears. You lose the OD so highway mileage gets even worse but the 2.52 first gear ratio gives a launch ratio of 10.35. My car has a 1.76 first gear and 4.56 gears. My launch ratio is only 8.02 but I also have a lot more torque so I don't need a high ratio.

Somewhere in the mid to high 3.xx ratio is a good compromise ratio. It gives good performance and keeps the vehicle streetable. For drag racing, the car needs to be geared so that you're out of gears and out of rpm at or just before the finish line. 1/8 mile racing is a little different. Although the gearing should be the same as a 1/4 mile race, the car could be geared a little bit lower but going too low can create too much torque and lose traction. All the shifting is done in the first 1/8 mile and you should be in high gear, 1:1, at or before the 1/8 mile mark. OD is not a dragstrip gear.

 

That depends, do you have enough power to put that much torque to the ground coming out of the hole?

Will your engine fall out of its power curve before you cross the line?


Worst case scenerio: Your always spinning bad off the line and blow way past redline before you finish the race



Steph, whats this talk about a truck...? You dont drive the maro all the time?

 

i am getting a hurst dual gate shitfter in a few days so that should help out with the automatic. thanks for the help im gonna go order them 4.10's now on summit.

 

I've never owned a street legal Camaro. When I bought my car it was street legal but I didn't buy it to be a street car. The previous owner drove it to my house then took his plates home. I fabricated tow bar mounts to tow it to my work where I stripped it into a race car. I've never driven it on the streets, legally I've roared up and down the street in the industrial park testing things but that's it. My car hasn't been street legal since I bought it in 1999.

My daily driver is a 91 454SS pickup. I raced it in Street class for 2 years before building a real race car. It's not really a truck. It's a sports car with a 6 foot trunk.