I have a 1987 firebird with a 700R4. Can anyone tell what the colors should be for the drive and driven gears in the trans. for the speedometer drive with a 2.73 rear axle ratio. Or maybe the teeth for the drive and driven gears.

 

Okay, this is out of a 86 firebird GM service manual but should be basically the same as the 87.

 

This is great! An early 1987 and 1986 are the same. A late 1987 uses an electric speedometer and has a sending unit. The problem is I have a 2.73:1 gear ratio. I know this was the original factory ratio on this axle because I rebuilt it 2 years ago and found a cracked tooth on the pinion gear and replaced with a US Gear set that is 2.73:1. The original gear set said on the side of the ring gear "GM 2.73:1". I know what everybody is going to tell me that the decoder says it should have 3.08:1, but it did not and does not because it is an open road race car. The car presently has 235/60-15 tires and wheels.

 

Also, 3.077(3.08), 3.273(3.27),3.455(3.45),& 3.727(3.73) are 10 bolt ratios. 3.417(3.40)& 3.70(3.70) are 9 bolt ratios. I have a 10 bolt rear axle.

 

my 9 bolt has a 3.08, so the above is incorrect...

 

To Forshock 85TA,
If you need it, here is the listing for the 85 TA and firebirds. You will notice that there are quite a few more options for the 85 than there are for the 86 models. Does any one need it for the 82 & 84 models?

 

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