I never checked this cars rear end gear before so i went out there today and jacked up the rear end. I put a piece of tape on the driveshaft and a piece on the tire. I put the car in neutral I turned the tire one full turn and the driveshaft did not go around even twice? I started over and turned the tire 1.25 turns to make the driveshaft turn exactly twice? That is a ratio of 1.6:1 I never heard of 1.6 gears before I must be doing something wrong. Is there a different process for an open differential, that would make my ratio 3.2? that would make more sense but I dont see why it would matter. I never had a pumpkin open before, i take that back I did have a pumpki open before but I dont remember it was so long ago. can anyone illuminate me?
oh see, so then it would be just double what I got. So i have a 3.23. Thtas what I thought but didnt know why.
I have nothing to add other than I went through the exact same mental process a few months ago. Like you figured out it's just double the amount of turns. Just letting you know misery loves company.
Determining ratio by rotating the tire or driveshaft can be tricky. techG8s suggestion of rolling the car forward gives you the actual ratio without doubling but the car needs to be going perfectly straight. Because of the differential acts as a torque equalizer, with one wheel not spinning the other one spins twice as fast for the number of input revolutions. As you know when you go around a bend one tire spins slower and the other one spins as much faster as the other one is going slower. So take that a step farther to where one tire is not spinning at all such as when one tire is on ice and the other is on solid ground. The tire on ice is suddenly spinning twice as fast. In this case with only one wheel spinning, if your speedometer read 60MPH the wheel would actually be spinning the equivalent of 120MPH! So thats why the numbers need doubled when spinning only one tire with the other locked. With one tire locked, the driveshaft only has to spin half the revolutions to get the single tire to make one revolution. This is because the driveshaft/pinion is spinning the ring gear/carrier like normal, and with one axle & subsequently its side gear locked, it causes the internal small pinion gears to rotate and spin the side gear that is connected to the spinning axle twice as fast per input revolution. Clear as mud huh. o No:
thanks for the great explanation. one thing though was that the other tire was not locked. It was off the ground and nothing was holding it. But it just stayed motionless while I rotated the one wheel.
That's not unusual for what's termed as an "open" differential. Both Positraction and open differentials have gearing that allows one wheel to turn faster than the other while cornering. The posi units keep the gears well locked with springs and clutches until enough force is present to allow them to unlock, i.e. cornering. The benefit of the posi is that if one wheel sees poor traction (like ice) the other still gets some driving force. The other benefit is at the drag strip, so both wheels get a chance at pushing the car, where an open differential puts double the torque on the wheel that loses traction, leaving the other sitting still. The 3.23 is a great all-around ratio; if you're putting enough power to the ground that you're having traction problems launching the car (usually the left rear tire going up in smoke), having a positraction carrier installed is a nice next step. Devon
If the gears are not worn out, yes. Setting up your old ring & pinion on a new carrier will still require significant setup. When I say "have a shop do it" I'm not being condescending and an a s s like I was before, though! It really does take some exprience and precision measuring equipment to have it done right. Getting power to both wheels will be a big improvement. Devon
ya i hear ya, from what i read it looks intimidating. Id love to pull it off though. How did you learn how to do it, did you work in a shop or something?
Before I got into design & release engineering for (what used to be) the big three, I did autobody/paint work and Corvette restoration work. I learned about ring & pinion setup while I was there, using the shop's equipment. If you get specific questions about the rear axle improvements, we have a resident expert onboard named Jim (monzaz). http://www.v8buick.com/member.php?u=3880 Devon
I would be surprised to see a 3.23 in your rear end. I was thinking it would be a 3.08. The best way to tell is to get a look at the numbers stamped on the gear.
That's the only positive way.. Wanna ask Dustin about the 3.42 rear we got in a deal? Turns out it spun 3 1/2 times nearly...Only to be looked at and see it was a 2.73 posi.Good thing we traded old junky stuff for it..I have a 4.10 posi rear that sipns not quite 4 turns,but when the case was cracked open,I realized why the dude blew up so many 350's behind the 4 speed GS...
what if the r& p were stamped incorrectly? i have seen it once. the best way for a non-posi unit to check with no special tools is to see it with your own eyes.... park the car on a flat surface. chock the front tires. put the car in nuetral. jack one rear tire off of the ground. place a jack stand under the car for safety. count the driveshaft revolutions (i like to ziptie an angle gauge to the yoke when possible) as you turn the tire exactly TWICE. if you get just uner 3 1/4, the ratio will be 3.23-ish, a little over 3 1/4 will be a 3.31, a little over 3 will be a 3.08, a little under 3 will be 2.93, a little under 3 3/4 will be a 2.73 ... etc. etc. using the angle gauge can get perfect numbers. 3 times around and 29ish degrees =3.08 3 times around and 83ish degrees =3.23 .. since you have 3.6 of degrees to every .01 of rotation you can really hit it on the head.
COUNT THE GEARS TEETH...THE ONLY WAY TO BE EXACT..Guessing at the revolutions isn't smart or accurate...PERIOD!
there is no guessing when you use an angle gauge. its precise and much easier and faster than getting into the grease. try it.
I've seen these posts before and am puzzled? Why not pull the cover and read the ratio off the ring gear-check the backlash-change the lube and check that magnetic fill plug (you have one right?)for fillings and excessive metalic 'slurry'. You haven't spent much time or money and you've done some good as well as learned about the health of 'your rear'=a good thing-
B I N G O... lol. I second that... But have given up on this one too. lol. Jimou: :beer :blast: :ball: :laugh: :sleep: Take care guys...
