N20Jeep Posted December 10, 2008 Share Posted December 10, 2008 so, i finally decided to put the 280 in the air and check the gearing in the axle...i used the spin the tire and count the revolutions method. i know its not exact, but i wanted a ballpark figure... after checking and rechecking about 6 or 7 times, i had my boss come over and get a second opinion... it came out to be just about 2 driveshaft revolutions to make one tire revolution... so its saying i have around a 2.00:1 gearing!!!! this cant be right, someone tell me im crazy and that they never made a gearset that low.... because with that gearing ill be shifting into second at 88mph, into 3rd at 145mph, and 3rd will run out of gear at 240mph...noooooway this can be right Quote Link to comment Share on other sites More sharing options...
johnc Posted December 10, 2008 Share Posted December 10, 2008 Hold one of the tires still while doing the rotation thing. You can also remove the rear cover and read the ratio on the ring gear. Quote Link to comment Share on other sites More sharing options...
N20Jeep Posted December 10, 2008 Author Share Posted December 10, 2008 i did hold one of them still...the ratio just doesnt seem right to me Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 10, 2008 Share Posted December 10, 2008 The figures for a ZX should be all over the drivetrain section. If it was an NA 5 speed it should be a 3.90. A turbo would be 3.54. An auto would be a 3.54 R180. That's from memory, but it shouldn't be hard to verify with a little looking around. Quote Link to comment Share on other sites More sharing options...
zgeezer Posted December 10, 2008 Share Posted December 10, 2008 As a rule of junkyard wisdom: hold one wheel solid [not a problem when it's mired in the mud] Scratch a line on the carrier housing to mark the location of one ujoint bolt head or nut. Rotate the free tire one complete rotation, while counting the turns of the driveshaft. Multiply the driveshaft turns by 2. In your case you would get "4" which would be either a 3.90 or 4.11. If it is just shy of two turns it is a 3.90 if it completes two turns it is a 4.11. This is an approximate reading and you must know what ratios are available. Estimate the fractions. If all else fails, pull the cover and do the long division from the pinion/ring gear tooth count engraved on the edge of the crown gear. g Quote Link to comment Share on other sites More sharing options...
Mike C Posted December 16, 2008 Share Posted December 16, 2008 Holding one tire works OK if you have a 2:1 spider gear ratio. You can then do double the turns and that should give you the ratio. If your spider/side gear ratio is different, will give you different results. Easier would be to find an internet gear ratio calculator. Plug in your RPM, MPH, and tire diameter and get #. Or if the diff is out of the car, just pull the cover. Going to need an oil change, gear lube, and axle seals while it's out. Chances are your 2 to 1 is really closer to 4:1 which would be a 3.90 gearset, but that's just a guess. Quote Link to comment Share on other sites More sharing options...
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