I dont feel like crawling under the car but I thought that all 89's had the 9 bolt with 3.27 gears. The guy who sold me the car said it was a 10 bolt with 3.23's. But I dont think it was an option in 1989. Could he be right?

 

If it's a non G92 car, it's a 9 bolt 2.77. If it's a G92 car it's a 9 bolt with 3.27s.

10 bolts came on non G92 LB9s and all L03/V6 cars.

 

Thanks a bunch! I KNOW FOR SURE ITS NOT A 2.73 OR 2.77 AXLE CUZ AT 80 MPH I WAS SPINNING LIKE 2,500 RPM'S. SO I FIGURE IT IS A 9 BOLT WITH A 3.27 BASED ON THE INFO YOU GAVE ME.

 

You can also determine rear end ratio (assuming the speedo is calibrated properly) by driving 70 mph in your 1:1 gear (in a 700R4 it's 3rd gear, in a T-5 it's 4 gear) with your foot lightly on the gas keeping load on the motor, but not so much it's accelerating.

Check your RPM at 70 mph in this manner - if it's 2770, you have 2.77s. If it's 3270, you have 3.27s. And so on..

 

Whoah, sweet trick, thanks for sharing that.

Dumb question: will non-stock tire sizes throw off the accuracy of this method i.e. tires that are taller or shorter than stock?

 

Yes, they will throw it off a little, but you should still be able to figure it out if you know what ratio you're looking for, i.e. 2.77 or 3.27.

 

Ok, thanks again. I'll be trying this on my cars.

 

FROM the factory, ALL FORMULA 350's & LB9/M5 cars have the performance gear, its not an option like on the Trans Am and the Camaro.

Therefore you Should have the 3.27 B&W (9) gear, unless someone swapped the rear.

The B&W axel was used from 1985 - 1989

 

[QUOTE=urbanhunter44]If it's a non G92 car, it's a 9 bolt 2.77. If it's a G92 car it's a 9 bolt with 3.27s. QUOTE]


Untrue. My NON G92 Formula came with the 3.27's

 

Want proof of your axle ratio without having to rip off the diff cover? Here is how. Oh and sorry you will have to climb under the car and you will need a helper.

1. Put the car in neutral. Chalk the front wheels for safety.
2. Jack up the back of the car on both sides. Use jack stands to be safe.
3. Put a chalk mark on the sidewall of one of the back tires.
4. Climb under the car and turn the drive shaft exactly 1 turn. Watch the rear u-joint for reference.
5. Have your partner count the revolutions of the chalked tire.

Following this method if you had a BW 3.27:1 rear the tire would make 3.27 turns. So if your buddy yells to you under the car that it turned about 3 and a quarter times you know what you've got. Likewise if he said it turned about 2 and 3 quarter times then you've got a 2.77.

 

hmm i didnt know that about formulas. wierd.

I've seen PLENTY of 2.77 non-G92 L98s (infact my best friend has one), but i think they were all camaros.

 

No flame intended--but good grief!

JamesC

 

You have to turn the tires one revolution and count how many times the driveshaft spins. Both tires, at the same time, or this method is useless (very important, you don't want the diff multiplying things). Turning the driveshaft one turn will result in less than one revolution of the tires and would be far harder to measure.

Now, you could also count how many times you have to turn the driveshaft in order to turn both tires (at the same time) one revolution.