I'm looking at a rearend that came out of a 79 camaro z28... i have an 81 z28...i know it'll fit but it hasn't been used in about 8yrs andthe fluid drained out... it has a posi and he thinks it has 4.11's but not sure....is there an easy way to find gear ratio without taking it all apart because i don't even wanna buy it if its above a 4.11 thaqnx

 

Only way is to pull the cover off and count the teeth. Since the gears arent factory, the engraving code on the front of the right axle tube won't mean anything. That is (to the best of my knowledge) the only way to tell.

 

Try this, as long as your speedometer is accurate, this will work perfect. No counting teeth, no pulling differental covers


http://www.idavette.net/tech/ratioc.htm

 

but if the rear end isnt in a car, that wont work

 

Sorry, didnt read the Post too carefully. Then yes the only way to check is to pull the cover off...whats the big deal? a few bolts

 

Then try this:

Turn the pinion, and count the number of turns it takes until you get ONE full turn of the axles. You'll need to pick a mark on the axle to gauge by, and as well have a "relatively" accurate means of counting the turns of the pinion (usually easiest to have it horizontal, or vertical, then you can count each 90 degrees easily). This may be easier if you've got someone there to keep track of the axle while you concentrate on the pinion so that you don't mis-count. I know you can't accurately pin-point 4.10 turns, but you'll know if it was 4 turns "and a bit".

That's the only way I know without pulling it apart. Knowing that the common ratios are 2.56 / 2.73 / 3.08 / 3.23 / 3.42 / 3.73 / 4.10 / 4.56, it's pretty easy to say it took "rougly" 3 and 1/2 turns (for 3.42) or 3 and 3/4 (for 3.73) or 4 and a little (4.10).

HTH.

 

dont forget 3.90's thats a ratio for them too lol, that can make it hard. just pull it off and count. are the gears in it aftermarket? or stock cuz if they are stock they came in 3.42 and 3.73's on some of them.

 

The number of teeth are usually engraved on the edge of the ring gear. It will have " 41 11" which would be 3.73:1. I know with my posi, it was very difficult to actually see the pinion gear and count the teeth.

 

thanks for all the help... i ended up pullin the back off and it said 42-13...which is 3.23... haha 4.10 my rear end and i done bought it... but i guess its better than the 2.73 it has now...it was in good shape on the inside so now i have the low 1st from the th700 and a 3.23 posi(which i got for $250) so i guess my gears aren't to bad for the initial take off... n e ways thanks again for all the help