373 or 411 ring and pinion?

[87vettevert]

I'm thinking about changing my stock 87 automatic 700 gears with either 373 or 411 gears has anyone done it? Was it worth it? Will i feel a big difference in low end torque? What are the pros and cons? Where do you suggest i buy the part? Thank you for all your help this is a great site.

 

[toptechx6]

Unless you do a LOT of drag racing I think you will find either gear too low for a stock automatic car. Many guys with the L98 find the factory performance ratio of 3.07 to be about right, if your car already has the performance gears and you want more low end, I'd suggest nothing steeper than 3.54.

 

[vetteoz]

I'm thinking about changing my STOCK 87 automatic 700 gears with either 373 or 411 gears has anyone done it? Was it worth it? Will i feel a big difference in low end torque?

Why?
Waste of time with stock TPI , the engine does not rev enough to use those gears.Only guys with big intake / cam mods or LT1's run those ratios.
3.07 is the only ratio to have with TPI ,
Some reading
Anyone Upgrade from Stock 3.07's to 3.73 or 4.10's ? - Corvette Forum

luv the new 3.07s - Corvette Forum

Will i feel a big difference in low end torque?

You won't be using 1st gear , will run out of revs before you can shift

 

[TedC]

toptechx6 and vetteoz are right on. Gearing and engine should be propely matched. The optional 3.07 high performance axle is a decent match with the low rpm torque curve of a stock auto L98. The 2.59 is another story. Traction can be an issue running the 3.07 and anything less than 1/2 tank of gasoline.

 

[87vettevert]

Thanks for your help what do you mean by the 2.59 being a different story? Will I feel a big improvement changing from 2.59 to 3.07? Is it worth the change? Anyway of telling what gears are in the car?

 

[toptechx6]

You will notice a substantial improvement in the launch going from 2.59 to 3.07, but your standard gear ratio could be 2.73 in a convertible which will make the change less dramatic.
There are several ways to determine the ratio in the car now, assuming it has not been changed. You should find a list of RPO codes under the center console lid or one of the compartments behind the seats, it should look similar to this picture.

The standard ratio is indicated by the code GM1, the high performance ratio is code G92. The one illustrated has 3.07 which was the only optional ratio for automatics, the problem is that GM1 can indicate 2.59 or 2.73, I believe 2.59 is standard in coupes and 2.73 is standard in convertibles.

If you raise the car the ratio should be stamped on the lower part of the differential pumpkin, if for some reason that is not legible you can resort to good old math. With the rear wheels off the ground and the transmission in neutral place a chalk mark on one half shaft and one on the driveshaft, now rotate the halfshaft one complete turn while counting the number of times the drive shaft rotates, just over 2.5 and you have 2.59, almost but not quite three and it is 2.73, if it is over 3 you likely have 3.07 or someone has already changed to something even lower.

 

[TedC]

I had a 88 with 2.59, and now a 89 with 3.07. Both under 60K. The difference was night and day. 89 pulls very hard from a dead stop. In a 1/8 mile run, no Camaro, Mustang GT, GTO (5.7), Vette (LT1 or LS1), Charger (Hemi) or Ricer has ever walked me. It is expensive to switch gears, that is why the high performance axle was a must have option for me the second time around. After the 1/8 mile the L98 will give ground to the higher RPM engines. This is why a 3.73 doesn't make sense unless you modify the engine and expand the RPM range.

 

[pologreen1]

I had one with 3.07's it was fun., I test drove one with 3.54's it was a blast, depends what you use it for, my car has the 2.59's and I bought the lowest I can go 3.75 for an auto, but I have a hogged out SR and other things to flow way better up top. I have not installed them yet, I'll let you know how I like them, I only hear good things about them from those who have them.

 

[87vettevert]

Polo why is 3.75 the lowest you can go can you do 3.07? What is SR?

 

[pologreen1]

Polo why is 3.75 the lowest you can go can you do 3.07? What is SR?

the car had 2.59 series 2 , in an automatic that comes with anything in the 2's is a #2 carrier. if it comes with 3.97 it is a #3 series carrier. automatics have a dana 36 which is weak compared to the manuals with the d44 so the lowest gear they make for an auto is 3.75.
if you have a manua (d44) you can put 4.11s.
SR is a lingenfelter super ram intake.

 

[vetteoz]

the lowest you can go can you do 3.07?

Higher number = LOWER gearing
3.73 is LOWER gearing than 3.07

 

[pologreen1]

yeah if you put in 3.75's it will accelerate quicker with less top speed.
if you put or have 3.07 you get less acceleration and more top speed.

 

[87vettevert]

I dont understand why i wouldn't be able to change my automatic from 2.56 or since i have a convertible as toptech pointed out i may have 2.73 to 3.07? I was under the impression i could. Well I do thank everyone for the feedback

 

[toptechx6]

While you certainly CAN change to a lower gear ratio, most members are trying to explain that going lower than the factory performance gear (3.07) will likely be unsatisfactory unless you also make drastic engine modifications.
The torque curve of your L98 engine is best suited for gears that keep RPM during acceleration under 5000, lower gears will make the engine turn faster at any given road speed. Very low ratios such as 3.73 and 4.11 will cause RPM at freeway speed to be much higher than stock and reduce fuel economy, most people find that unacceptable in cars used for everyday transportation.
Cars modified for drag racing can often reduce ET by using such low gears since the engine changes made raise power output by increasing RPM and raising the torque curve above stock. Acceptable noise level at freeway speed and fuel economy are not an issue on such vehicles.
To improve the performance of street driven cars you need to strike a compromise, (a ratio lower than the factory yet not so low that the car is obnoxious at freeway speed or a gas hog), for your vehicle that ratio is likely 3.07.