RickB Posted October 26, 2000 Share Posted October 26, 2000 Hey All, I am new to this particular swap and would like to identify the rear end AND the gear ratio in my 76 280. I take it that the stock rear for this car is a R180? From what I've read obviously the best choice is the R200 and I may be interested in that route (got one for sale?). I am primarily interested in straight line acceleration, i.e. drag racing..though i like the way this car handles so I'd rather not go with a solid axle. How about upgrades to the stock rear end (assuming that's what is in it?). Spicer U-joints or? thanks in advance... ------------------ RickB 280V8 350/700R4 12.77 w/radials & pump gas so far... http://photos.yahoo.com/bornabov Dallas, TX [This message has been edited by RickB (edited October 25, 2000).] Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 26, 2000 Share Posted October 26, 2000 The gear ratio is stamped on the edge of the ring gear as X:Y x and y being the number of teeth on the ring gear and pinion gear, just divide. You can't tell from the outside what the ratio is(Other than guesstimate by counting revolutions). I don't know when they switched to r200s... but look at the 'mustache bar' thing. If it's flat in the vertical transverse plane then it's a r180, if it has a slight curvature in the vertical transverse plane then it's a r200. I think that is true, but don't quote me on it! The diff housings are visibly different also, but I can't remember where I saw a nice side-by-side picture of them. ------------------ Morgan http://z31.com/~morgan/s30 http://carfiche.com Quote Link to comment Share on other sites More sharing options...
Guest Fast Frog Posted October 26, 2000 Share Posted October 26, 2000 Your '76 Z should have the R200 rearend. That's the one that the half shafts are bolted on the outside of the pumpkin. Stock diff gear ratio for the '76 is 3.54. I'm running 400HP+ with a 383 in my '76Z and have had no problems with the rearend-but I don't track race a lot! [This message has been edited by Fast Frog (edited October 26, 2000).] Quote Link to comment Share on other sites More sharing options...
RickB Posted October 27, 2000 Author Share Posted October 27, 2000 thanks guys...I want to be able to track race once or twice a month anyway. Have fun! RickB 280V8 Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted October 27, 2000 Share Posted October 27, 2000 quote: Originally posted by Morgan: The gear ratio is stamped on the edge of the ring gear as X:Y x and y being the number of teeth on the ring gear and pinion gear, just divide. You can't tell from the outside what the ratio is(Other than guesstimate by counting revolutions). No guesstimation involved, it's an easy fact to obtain exactly. Checked out many diff's in yards, can't imagine pulling them all and yanking rear cover just to know gear ratio. I only pull rear covers to check diff condition. Here's an old archive of mine on checking/ascertaining the ratio: Take a buddy, and just turn it to find out. should be able to by rpm's but the tried and true is...to hoist one rear tire in the air (need two people) and mark the driveshaft and tire relative to some position, turn the tire exactly 10 times while the driveshaft rotations are counted, you'll get a whole number and a fraction (like 17 3/4 driveshaft turns per 10 halfshaft turns) double this divide by 10 and it's your diff ratio....so 17 3/4 doubles to 35 (as far as you need to go but some get picky) so /10 and it's 3.5 ie. 3.54.... whammo its your diff ratio. 17.5 then a 3.54 18.5 then a 3.7 19.5 then a 3.9 Each difference is at least a whole number (except 3.36->3.54, but still 16 or 17?) so this always works for us. Don't forget to grab the speedo gear out of the tranny (one 10mm bolt), even though you don't need it (w/ your 700R4), if you ever sell it it'll help out a datsun dude. Others reccomend removing the rear cover plate and reading the ring gear, but the diffs I look at are still in the cars so... may variations all accomplish the same thing, this one's stuck with me and works easily IME (you can go 20 tire revolutions and simplify the already straight forward math if you like but I"d guess the longer you take the greater the chance is one of you falls asleep and loses count;^) Quote Link to comment Share on other sites More sharing options...
RickB Posted October 27, 2000 Author Share Posted October 27, 2000 OK! thanks all... RickB 280V8 Quote Link to comment Share on other sites More sharing options...
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