chazzvette

Can I tell what rear end ratio I have by the VIN, and if so, what is the # it is on the VIN. Thanks

AWW2BAD

Give me the vin number and I will find out for you

simpleman68

You can also check RPO codes. Mine are on the inside of my glove box door. Not sure if '98 is the same.
If you have an auto:
G92 is the performance ratio axle 3.15
GU2 base ratio, 2.73

If 6 speed:
GU6 3.42 ratio. I don't think any other ratio was available for M6 cars.
Scott

6spdC6

[QUOTE=simpleman68]You can also check RPO codes. Mine are on the inside of my glove box door. Not sure if '98 is the same.

98s are located on one of the small storage compartment lids in the trunk

chazzvette

Na na na..... ..thanks anyway

chazzvette

[QUOTE=6spdC6] Thanks 6sp and simpleman.. I will check it out.

rkerr1234

Whats the big deal, anyone can walk up to your car and get it.

chazzvette

Not on mine....... a small piece of black plastic has been placed over the VIN, easly removable.

Vetteman Jack

No, the VIN does not tell you the rear end ratio. Look on your RPO tag and it will give you the ratio (G92 is the performance ratio for automatics (3.15) and if you have a manual, it is 3.42). You can also look on the differential plate and see if the tag is still there.

donnyonee

All factory C5's with the manual transmission came with the 3.42 axle ratio, there was no other option available. But the A4 equipped models had two choices of axle ratios. The standard equipment was the 2.73. An optional "performance ratio" G92 was available as an option; this being a 3.15 ratio.



For those with A4's not knowing which ratio is installed in their C5 Corvettes, you can:

A. Either crawl under your C5 and read the printed ratio on a metal tag located at the fluid fill location (not the bottom drain plug) of the rear carrier.

B. Or, look at your option list. If you look in your glove box there is a sticker with all codes on the inside of the glove box door. The 3.15 performance axle ratio option is code G92. For '99 and earlier it should be listed on the underside of the left-hand storage well cover:


GU2 2.73 ratio

G92 - 3.15 ratio

GU6 - 3.42 ratio (maunal tranny only)

C. Or... place your A4 into third gear and get on the highway. At a constant 75mph (making sure the TC has locked) read the rpm value; then divide it by 1000.(This also works with the six speed manual transmission using 4th gear):



examples:

2730 RPM........ you have a 2.73

3150 RPM........ you have a 3.15

3420 RPM........ you have a 3.42 (not a factory available ratio with the A4)

3730 RPM........ you have a 3.73 (not a factory available ratio)

3900 RPM........ you have a 3.90 (not a factory available ratio)

4100 RPM........ you have a 4.10 (not a factory available ratio)

(assuming rear tire height has not been altered from the factory height)



The key is third gear, driving at a constant 75mph. AND, you must be using the same rear tire height as the factory installed tires. It may be up to 100rpm off depending on the amount of slip your TC has when locked.

With this method, you don't need a chart to compare your rpm/mph to. Just divide the RPM by 1000. This also works with the six speed manual transmission using 4th gear (again with identical tire height as from the factory).



FYI: individual overall ratio of an automatic A4 C5 in each gear:

2.73 - 3.15 - 3.42 - 3.73

8.35 - 9.63 -10.4 -11.4 (1st gear A4)

4.42 - 5.10 - 5.54 - 6.04 (2nd gear A4)

2.73 - 3.15 - 3.42 - 3.73 (3rd gear A4)

1.91 - 2.20 - 2.39 - 2.61 (4th gear A4)

LoneStarFRC

donnyonee: Good info except for the part about the location of the RPO codes on the '99's. Mine's in the glove box too.