fryenretards Posted June 17, 2011 Report Share Posted June 17, 2011 im looking for a pre 83 720 rear end preferably the longer gear ratio somewhere around the portland area. there is one, count it one, at u pull it in the area. and before i go spend the outlandish amount of money they want for it and since there isnt any on craigslist or on the for sale section on ratsun (unless im blind) i figured i would see if this turned anything up let me know Link to comment
datzenmike Posted June 18, 2011 Report Share Posted June 18, 2011 Just the 3rd member gears or the whole thing? Just the gears should be $50. Take them out yourself. I know the 4x4 diffs had a change in flange size around '83. Not sure if the 2wd did or didn't. The later ones may work. If you have a 4X4 forget this. Link to comment
fryenretards Posted June 18, 2011 Author Report Share Posted June 18, 2011 Will the gears just straight swap over into my axle. Link to comment
wayno Posted June 18, 2011 Report Share Posted June 18, 2011 Will the gears just straight swap over into my axle. Yes the pumpkin will transfer into your stock 521 rear axle housing. The 83 720 rear axle is wider than your 521 axle, that can become a problem if your dropping your 521 depending on your wheels. I suspect you have 437 gears now unless some switched them out already, what gearing are you looking for? I forget what engine you have now, that can also be an issue depending on what your going to use the truck for. Link to comment
datzenmike Posted June 18, 2011 Report Share Posted June 18, 2011 The gears come out in a 'pumpkin' or 'bum' or '3rd member' and just bolt in without disturbing the gear settings. Your 521 should have 4.375 ratio. The 720s ranged from 3.364 through 4.375 so look on the passenger side inner fender below the hood hinge. There will be a small credit card sized aluminum tag with the gear ratio stamped on it. They look like this... Look on the lower right side. Here it says HF38. 38 stands for 3.875. An HF41 would be 4.11 and HF38 would be 3.889 and so on. . Link to comment
fryenretards Posted June 18, 2011 Author Report Share Posted June 18, 2011 i think i know (lol) the mid and late 80's axles are wider but will the gears swap into my axle housing even though their overall wider Link to comment
wayno Posted June 19, 2011 Report Share Posted June 19, 2011 i think i know (lol) the mid and late 80's axles are wider but will the gears swap into my axle housing even though their overall wider Yes they will, you just pull your axles out far enough to remove the existing pumpkin, and put the new set of gears in, and push your axles back in. The gear ratio you put in will depend on the engine you plan on running, 3.364 gears just won't work with a L20b, 389 gears are pushing it if you plan on hauling loads a lot, or pulling a trailer. Link to comment
datzenmike Posted June 19, 2011 Report Share Posted June 19, 2011 The 3.364 gears were used in the 'Milage Option' 720 with a Z20 engine!!! It used a lower than usual 1st gear truck 5 speed and ran 9.5 compression. Naturally it would ping so a knock sensor and ignition retard system was employed. Link to comment
dvboth Posted June 19, 2011 Report Share Posted June 19, 2011 will a 3.54 gear work on a L16 with a 82 Z car 5 speed and low profile 13's? Link to comment
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