Re: comp cam xr274r vs 288ar BB
Sorry checked my rear axle code and i have a 3.31 ~ 12-bolt Positraction rear end...a little bit better
FYI,just because the code on the rear states it was 3.31 gear when built new means it still has a 3.31 ring & pinion in it 35-40+ yrs later.
A quick & dirty chk that will get you somewhere close is to jack up rear of car and then put on jack stands.
Then mark a tire and also drive shaft using masking tape.
Now put trans in neutral & turn the driveshaft to see how many times the d-shaft spins fully artroun to make 1 full turn of the tire/wheels.
For ex if the d-shaft turns approx 3.4 times for 1 full turn of the wheel/tire then you likely have a 3.42 or maybe 3.55 ring & pinion.
Another example 3.75 (3 & 3/4) turns of d-shaft vs 1 tire rotation = approx 3.73 ring & pinoin.
But also keep in mind cond of posi unit /posi clutch slippage if in bad cond can affect results when doing this quick/dirty rear gear ratio chk too.
The only real way to nail it exactly is to remove the cover on the rear end and count the teeth on ring & pinion .
1969 CHEVELLE SS396,ORIGINAL #'S MATCH,GOT IN 1978,(In 2001 rblt/bored original 396 .030 to 402)/M20/12BOLT/3:31'S
2006 YAMAHA 1700 ROADSTAR SILVERADO (1 owner ,GOT in 2009,4,700 miles/WK end fun)
1977 KAWASAKI KZ1000 (AM ORIGINAL OWNER ,GOT IN 1977,NOW has 29k miles/WK end fun)
2002 MAXIMA (DAILY DRIVER/1 owner,GOT 3/2013 w-44k miles)