Decoding rear gear ratio

[Dawg]

I just recently bought a 1984 Regal 2 door with the 3.8 V6/3 speed auto combo. I also have the factory window sticker. I was hoping by looking at the sticker it would say what the rear gear ratio was but it didn't. I would like to know if there are any codes anywhere on the car that I can look it up? I know some GM cars have an actual RPO sticker. Thanks.

[guyopel]

Dawg , Look at the spare tire cover ( on the top or bottom ) and under the trunk lid and sometimes in the glove box looking for a white sticker app.2.5 by 4.0 " HTH Guyopel

[Dawg]

Thanx. I know what you're talking about, but unfortunatley I didn't find that tag.

Any idea on what ring and pinion ratio normally came on '84 Regals equipped with the 3.8 litre/3 speed auto?

[rcull]

Maybe these calculators will help you get close


http://www.buicks.net/shop/reference/calculators.html

[Syndicated]

I can't tell you for sure, but your car probably has highway gears, probably in the area of 2.81:1 or something. I would bet my bottom dollar that you dont' have anything higher than a 3.20:1 gear set. Usually non-overdrive cars have low rear end gears so the engine rpms are way too high when driving at highway speeds, its an emmisions thing.
If you're really interested and can't find out without tearing the cover off, you could always count the number of teeth on the ring gear and divide that by the number of teeth on the pinion gear. :-)

[guyopel]

If you take the rear cover off the gears are stamped with the ratio and the number of teeth . HTH Guyopel

[Dawg]

Yeah I know I can count the teeth or look for the stamped number on the gear set.....really didn't want to have to remove the differential cover though.

I look over on the Grand National board.....it says it would have a either a 2.73 or a 2.41 depending on if the tranny was a TH200C or a TH250C (what's the difference anyways??).

Thanx fellas.

[bob k. mando]

this page over at 442.com might help, they have a section for 1978-1988's towards the bottom, outside the boxes. http://www.442.com/oldsfaq/ofdif.htm...ential%20Codes
you know how to do the junkyard calc for diff ratio, yes? from a little further up the same page:
"You will have to put the rear up on jackstands, put the transmission in neutral. Make sure that the car is quite stable, get under the car, and TURN THE DRIVESHAFT. Count the number of turns of the driveshaft it takes to turn one wheel one time. If you turn a wheel, instead of turning the driveshaft, you will only turn the other wheel (not the driveshaft). It also works better (more accurate) if you turn the driveshaft enough times to turn one wheel ten times, and count the number of times you turn the driveshaft. This is because it may be difficult to tell if the driveshaft goes around, say, 2.56 or 2.78 times for one turn of a tire. But if you turn the driveshaft enough times to turn a wheel ten times, you will have 25.6, or 27.8, or 41.1 (or whatever) turns of the driveshaft. Then just divide by ten to get the ratio of the rear."

[rcull]

The 200C should have 11 bolts on the pan, the 250C should have 13. The angled corner on the 250 is also shorter than on the 200, but you won't be able to do a comparison.