Found a tag on my 8 1/4" differential cover

[Dibbons]

Re: '72 SSP--The shop that installed my used sure-grip last month cleaned up my differential cover but did not paint it. I crawled underneath to see what was needed to paint it myself and noticed through the recent surface rust a tag on one of the cover bolts "2.71". I had been wondering if I had 2.71 or 2.76, now I know.

 

[super-bee_ski]

ah,
Jack it up, wire brush it down....
Zinc primer
Let stand for a day
Then SEYMOUR Paints (Heavy solids) 60 degree black

 

[oldbee]

If I'm right you got a 'highway gear', lol.

 

[Dibbons]

For '72 BBody 318 automatic, the 2.71 was standard and 3.21 optional. The mystery remains why the odometer is 5-6% over and the speedo is 5-10% over depending on speed (the faster I go, the more it is wrong--in the faster direction). The tire diameter is about the same as stock. Transmission and gauges were both professionally rebuilt.
Some day I will have to examine the speedo pinion gear.

 

[oldbee]

I do believe ur pinion gear is probably wrong, just a couple teeth on it will make a difference, there's charts on the web.