I can't find the numbers on the rear end on my 69 SS. I looked underneath the passenger axle housing. There seems to be no #'s there. It's a 12 bolt and I can make out a casting number. It's upside down and on the passenger side of the differential. It is: 67 89 0 I lifted up one tire and put the car in neutral and spun the tire twice- the driveshaft went around 3.25 times. Does that approximate my ratio since I was turning only one tire? It surely couldn't be half of that eg. 1.67 could it? Any help will be appreciated. You guys are so helpful with all my questions.
Thanks,
John

Take a look at the pics in my link below to see where the numbers were on my car. They are not on the bottom of the axle but on the face of the axle about half way between the differential and the wheel on the passenger side. Facing the front. Probably covered with dirt, paint etc. you have to scrape sometimes to find them but they are there. If you have posi, then that 3.25 turns might be a 3.08 posi, again the numbers should tell you if the gears have never been changed.
Also visit www.camaros.org (http://www.camaros.org) for great info. on numbers and locations. Good luck.
click http://www.camaros.net/forum/smile.gif

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69RS 350/255 LM1, Balanced, TRW forged pistons, .30 over, TH-350 auto.,
Dover White,Blue Vinyl top, F&R spoilers,pdb, close ratio ps,am/fm,3.08 Posi., A/C, fold down rear seat
My RS www.brainerd.net/~knudsen/69RS (http://www.brainerd.net/~knudsen/69RS)

Thanks Click-I went out and degreased some more and found the stamped numbers. CC BM 0911G1.
In my book that shows to be 3.31:1 ratio. Does that sound right?
Thanks,
John

Yep sounds right and much closer to the 3.25 turns you had with the tire vs driveshaft.
Im still not sure if its a posi or not. Im thinking there should be another letter an inch or so below the string of letters and numbers you found already if its a posi. Im sure someone else better versed in gearing will jump in and clarify the posi or nonposi question.
Neat to find old numbers http://www.camaros.net/forum/smile.gif
click

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69RS 350/255 LM1, Balanced, TRW forged pistons, .30 over, TH-350 auto.,
Dover White,Blue Vinyl top, F&R spoilers,pdb, close ratio ps,am/fm,3.08 Posi., A/C, fold down rear seat
My RS www.brainerd.net/~knudsen/69RS (http://www.brainerd.net/~knudsen/69RS)

If it was originally a posi, there would be a stamped 'E' below your other numbers. This letter represents Eaton, the posi supplier.

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Dave
'69 Z11 Pace Car, 350/4 speed, manual top, console w/gauges, tilt rosewood wheel, AM radio

Thanks guys! I'll do some more degreasing and find out if there are any other letters. Would one tire turn with a posi? Or wouldn't the letters be different in the code? My book shows BM=3.31:1 and BS=3.31:1 posi. Would that be conclusive or could a BM be posi?
Thanks,
John

Non posi only spins one wheel whereas posi spins both.