Differential Ratio

[korvetbill]

How can I tell if I have a 3:07 axle on my '88 AT?

 

[Ken]

If the axle is still factory-issue, there should be a tag attached to the housing somewhere. Automatics came with a Dana 36 differential, while the manual transmission cars were equipped with a Dana 44, a slightly larger and beefier unit. I don't know how to tell you what ratio you might have with your personal Corvette, but you might want to check the option code list in your storage compartment area (under the lid). If that sticker is missing, or doesn't answer your questions, you can order a build sheet and window sticker for your car from the National Corvette Museum.

The following is a list of axle specifications, courtesy of Mike Antonick's Cor-Vette Specs book.

• AXLE:
• Type: Rear
• Description: Overhung pinion gear
• Limited slip differential type: Standard, disc clutches
• Drive pinion offset: 1.50" (8.5" ring gear), 1.125" (7.87" ring gear)
• Drive pinion type: Hypoid
• Number of differential pinions: Two
• Pinion/Differential bearing adjustment: Shim
• Driving wheel bearing: Tapered roller
• Lubricant capacity: 3.75 pt
• Lubricant type recommended: GL-5 gear lubricant
• Lubricant SAE viscosity: 80W or 80W-90 summer, winter or extreme cold
  
  AXLE RATIOS:
• 2.59:1 ratio: 17 pinion teeth, 44 ring teeth, 7.875" ring gear outside diameter
• 2.73:1 ratio: 15 pinion teeth, 41 ring teeth, 7.875" ring gear outside diameter
• 3.07:1 ratio: 14 pinion teeth, 43 ring teeth, 7.875" ring gear outside diameter
• 3.07:1 ratio: 14 pinion teeth, 43 ring teeth, 8.5" ring gear outside diameter (manual transmission)

 

[korvetbill]

What am I looking for on the "option code list"?

 

[Ken]

Option code G92 would indicate a "Performance Axle Ratio." (3.07:1)

_ken

 

[vader86]

You should be looking for G44 code for 3.07:1

G92 does not necessarily mean you got 3.07. G92 itself is a worthless code to have, since it means nothing.

You could order the 3.07 in some years with the auto, and not get the G92, like in 86. My 86 AT has Z51 which triggers the 3.07 but doesnt have the G92.

G92 verts usually got 2.73 instead of 2.59.

 

[Ken]

I got G92 from the Black Book.

 

[muddywaters]

Ratio

Korvetbill, If you can raise your vehicle and rotate the drive line, mark a rear tire at the 6 o'clock position with chalk and mark the drive shaft at the same position. Rotate rear wheel one full revolution while counting the revolutions of the drive shaft. One full turn of the tire will equal just over three turns on the shaft if it is a 3.07. If it is a 3.54 the shaft will turn three and a half times for one revolution of the rear tire and so on.