Dudeman Posted July 29, 2009 Report Share Posted July 29, 2009 So I understand that that a 77-79 280z/zx trans is a direct swap for my 620 5 speed, but after a bit of research I still have some questions. Will either clutch work, and are there any differences between the two? I know that both are 225 mm, but a z car makes about 50 extra horses over my pickup, and I would think that would translate to a beefier clutch/trans. And along the same lines, are there differences in the trannys themselves aside from gear ratios? I found a few tranny's pretty cheap on CL and think it would be nice to gear the truck up a bit. Thanks! Quote Link to comment
Bleach Posted July 29, 2009 Report Share Posted July 29, 2009 an L-series 225mm clutch kit is just that. No differences. The truck has a beefier 225mm vs 200mm in the cars due to its carrying capacity not horsepower. Quote Link to comment
72240z Posted July 29, 2009 Report Share Posted July 29, 2009 It would be more tq not hp that would effect clutch choice too imo. Quote Link to comment
datzenmike Posted July 29, 2009 Report Share Posted July 29, 2009 So I understand that that a 77-79 280z/zx trans is a direct swap for my 620 5 speed, but after a bit of research I still have some questions. Will either clutch work, and are there any differences between the two? I know that both are 225 mm, but a z car makes about 50 extra horses over my pickup, and I would think that would translate to a beefier clutch/trans. And along the same lines, are there differences in the trannys themselves aside from gear ratios? I found a few tranny's pretty cheap on CL and think it would be nice to gear the truck up a bit. Thanks! The '77-'79 280 z/zx 5spd is identical to the '77-'78 620 tranny. Your '79 will have a much wider ratio gear set so putting one of these closer ratio trannys in may make it a little harder taking off with a load on. They also have a slightly taller over drive 5th gear than your '79. Put your speedo cog in what ever you get. Quote Link to comment
Dudeman Posted July 30, 2009 Author Report Share Posted July 30, 2009 Your '79 will have a much wider ratio gear set Are you referring to the final gears? I've often heard that 79s had 4.11 gears rather than 4.375s, but my truck has a silver colored sticker on the underside of the hood that reads "1979 HL620 Final Gear Ratio Final gear ratio of this vehicle is 4.375 Nissan Motor co., ltd." I can take a picture of this tomorrow, but now it's dark and I'm tired :D Or do you mean the gears in the tranny were different in 620's between 78 and 79? Either way the truck feels undergeared (I think I could pull taller gears), and I hope a 280z transmission will do just the trick. Thanks again everyone, I always appreciate advice and input Quote Link to comment
Bleach Posted July 30, 2009 Report Share Posted July 30, 2009 http://www.bleachgarage.com/620tech.html Well, all the 1979 manual transmission trucks should have come with a 4.11 rear diff. I suppose your hood may have been swapped or it was an early 1979 truck or for some reason a 4.375 was put in and that was not normal so the sticker was put in place. 1979 for the trucks should have an even shorter 5th gear than prior trucks and the Z. A 1979 Z-car transmission won't be a lot of difference. I'd suggest you find a non-turbo 280ZX 1981-83. Those have the tall 5th gear. Leave your 4.375 in place. The gearing should be just right then. I tried a 4.11 diff and the tall 5-speed but it was too high for the underpowered L-series. Quote Link to comment
Dudeman Posted July 30, 2009 Author Report Share Posted July 30, 2009 It looks like the 79 five speed 620 came with shorter transmission gears than the 77-78, probably to offset the change to a 4.11 gear. I wonder if my transmission is a real 79 or one from a 77-78. I'd suggest you find a non-turbo 280ZX 1981-83 That may be my best option, but I would really like to be able to use my speedo cog, and I've read they only swap from 77-79 280s. or can I use the Z car cog/cable on my speedo? Quote Link to comment
datzenmike Posted July 31, 2009 Report Share Posted July 31, 2009 37/9 (4.11) diffs were installed on all '79 trucks starting in 07 '78. 35/8 (4.375) diffs were installed on the '79 Camper option trucks starting in 07 '78. If it's a '79 and has a tag saying 4.375 then it must have the camper option and also the 5spd to match. The 5 spd. used in the '79 with 4.11s would have: 1st... 3.592 2nd... 2.246 3rd... 1.415 4th... 1.000 5th... 0.882 The 5spd used in '77-'79 with 4.375 would have 1st... 3.321 2nd... 2.077 3rd... 1.308 4th... 1.000 5th... 0.864 Quote Link to comment
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