Quick ? About GEARS

[slrvette]

I have just a quick question
What are the stock gears in the 84, are they 2.59 or 3.07. Looking at going to the 3.07 if the stock is 2.59. Thanks in advance.

 

[Jeb]

Manual or auto?

 

[slrvette]

sorry about that. It is a Automatic

 

[Radar]

I think they are 2:59. I know that in 89, that is what the auto's had. But there was a "perfomance option for the 3:08's. You may have to get under the car and count the number of driveshaft turns to 360 degrees of the wheel. Remeber to have both wheels free to turn. If you only jack one side, the internal differental action will change the results

Hope this helps,

 

[3dale1]

Look at your RPO codes under the rear box lid behind the seat. On my 85, code G44 indicates a 3.07, which was an optional gear for the automatics. I think the 2.59's were GM1 or something like that. Willing to bet that the 84 codes for the rears are the same as 85. Of course this is assuming the rear is stock and nobody's changed the ratio over the last 20 years.

Look in the tech center tab at the top of this page and it will better help you to decode your 84.

 

[Jeb]

RPO G92 would indicate that you have 3.07:1 gears.

 

[Black Bart]

Unless you bought the car new the rpo code tells you nothing.
How many people change the ratio on their car I know I have and the code won't reflect that change. Jack the car up place a mark on the tire and on the drive shaft. Turn the shaft until the wheel makes one revolution and count the number of turns the drive shaft turns.

 

[slrvette]

Thanks for all your input, guys. I think I'm gonna have to jack the car up and rotate the tire. I have a feeling the rearend has been changed. After looking at it I noticed that there is some writing on the bat wings and has "1994" hand written on it as if it were a junk yard part.
Just so I know when I rotate the tire one full revolution and count the amount of times the driveshaft turns can I assume that if it turns 2x that its a 2.59 and 3x- 3.07?

 

[Black Bart]

Thanks for all your input, guys. I think I'm gonna have to jack the car up and rotate the tire. I have a feeling the rearend has been changed. After looking at it I noticed that there is some writing on the bat wings and has "1994" hand written on it as if it were a junk yard part.
Just so I know when I rotate the tire one full revolution and count the amount of times the driveshaft turns can I assume that if it turns 2x that its a 2.59 and 3x- 3.07?

2.59 ratio= 1turn on the wheel and 2.59 turns on the shaft
3.07 ratio=3.07 turns of shaft to 1 turn of the wheel.
Use a piece of chalk to mark it.

 

[85vette]

The '84 and '85 automatics had 2.73 rear gears.
First year for 2.59 was 1986.

 

[Black Bart]

The '84 and '85 automatics had 2.73 rear gears.
First year for 2.59 was 1986.

What it had in 84 and what is in it now very well may be different.
Like I posted earlier the only way to know for sure is to jack it up and check it. Otherwise you are just speculating.

 

[85vette]

What it had in 84 and what is in it now very well may be different.
Like I posted earlier the only way to know for sure is to jack it up and check it. Otherwise you are just speculating.

Possibly, but the original question was did the '84 have for stock gears.

 

[Black Bart]

Possibly, but the original question was did the '84 have for stock gears.

Sorry the way I read it he wants to improve the performance.
He stated that if it was a 2.59 then he was going to change to a 3.07
Sounds like he wants to increase the performance to me. Before one can decide on what to put in you must know what it has now.
Whatever his intention was he has the info to do with it whatever it is he had in mind.

 

[WhalePirot]

speedo?

Know also, that you are limited, assuming that you wish your speedometer to be accurate, how much you can change the RE ratio before getting into the tranny. Unlike the 'old days', you cannot merely change the externally-accessable gear for changes more than about 10%, I believe.

You can, however, get an external box to alter the pulses sent to the dash.