Guest coolmesser Posted July 27, 2005 Share Posted July 27, 2005 would it be worth my time to seek out an 81-83 zx (non-turbo) rear end for the 3.9 differential? Pretty sure if I looked long enough around here I could find one. is that one limited slip? I know I am full of questions. You guys are just so smart! Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted July 27, 2005 Share Posted July 27, 2005 I know I am full of questions. You guys are just so smart! probably because we know what forum to look for the answers in... Try the drivetrain section... Quote Link to comment Share on other sites More sharing options...
Tim240z Posted July 27, 2005 Share Posted July 27, 2005 Moved from ChevyV8 Forum..... Quote Link to comment Share on other sites More sharing options...
Leith280zlt1 Posted July 27, 2005 Share Posted July 27, 2005 The only LSD nissan ever made and put on a stock car was a 3.7 out of the 87 - 89 300zxt. None of the 3.9's will have an lsd. You can install lsd's in them but you won't find one with a lsd already in it. You will definitely notice a difference with the 3.9 gears versus the 3.7's or 3.5's. Dunno what you have. If you really want a kick in the pants, get the 4.11's out of a 85 - 86 200sx turbo's. They really make a difference and it gives the car a whole new attitude. If you do find a 3.7 lsd, you can swap the carrier for the limited slip into the new gears no problem. Hope this helps. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted July 27, 2005 Share Posted July 27, 2005 would it be worth my time to seek out an 81-83 zx (non-turbo) rear end for the 3.9 differential? Pretty sure if I looked long enough around here I could find one. is that one limited slip? I know I am full of questions. You guys are just so smart! Depends on which engine you are using. N/A might benefit from a 3.90 or 4.11, but a turbo I6 benefits from lower ratios like 3.54 or 3.36. Quote Link to comment Share on other sites More sharing options...
2126 Posted July 27, 2005 Share Posted July 27, 2005 Depends on which engine you are using. N/A might benefit from a 3.90 or 4.11, but a turbo I6 benefits from lower ratios like 3.54 or 3.36. I don't think it matters if your engine is naturally aspirated or has forced induction, on what gearing is better or not. I think appropriate gearing is a matter of how you intend to drive your car! JMO. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 27, 2005 Share Posted July 27, 2005 Turbos build boost faster with more load. So by putting low gears in you reduce the load on the engine which can make the turbo not spool as well or as fast. This is also why NA transmission gear ratios are best kept close and turbo gear ratios are spread farther apart. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted July 27, 2005 Share Posted July 27, 2005 I don't think it matters if your engine is naturally aspirated or has forced induction, on what gearing is better or not. I think appropriate gearing is a matter of how you intend to drive your car! JMO.I was considering "appropriate" gearing as what makes the car accelerate faster. Quote Link to comment Share on other sites More sharing options...
savageskaterkid Posted July 27, 2005 Share Posted July 27, 2005 i have a 3.9 in my car, and it hauls sum ***, especially with a 3 speed, it still has getup and go. Quote Link to comment Share on other sites More sharing options...
2126 Posted July 27, 2005 Share Posted July 27, 2005 I was considering "appropriate" gearing as what makes the car accelerate faster. I would say, based on your statement, that lower gears would be the ticket for you. Example...4.11 gearing will allow a car to accelerate faster than 3.90 gearing given that everything else remains the same. It's the basic laws of physics coming into play. Quote Link to comment Share on other sites More sharing options...
datsunlover Posted July 27, 2005 Share Posted July 27, 2005 Just to throw in my $.02 here, My 280z had the stock 3.54's last summer, and it was.. ok. Fun anyway.. This winter I instaled a 3.90 I pirated from an 81 ZX and let me tell you, it makes a WORLD of diffrence! (I'm sure some of this is due to the 240sx 5 gear I installed, but afaik, the KA has the same 3rd and 4th ratios as the stock 4 gear) Its definatly got more 'pull' with the 3:90's out back. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 27, 2005 Share Posted July 27, 2005 I would say, based on your statement, that lower gears would be the ticket for you. Example...4.11 gearing will allow a car to accelerate faster than 3.90 gearing given that everything else remains the same. It's the basic laws of physics coming into play. That's non-turbo physics. Quote Link to comment Share on other sites More sharing options...
Pyro Posted July 27, 2005 Share Posted July 27, 2005 I never really understood the belief that turbos build boost faster with a load so they run better with higher gears (lower numeric value). Well, maybe in first gear when the overall gear ratio is over 10:1. But once my turbo car is in 2nd gear, it builds boost very quickly with a overall gear ratio of around 7:1. So in a Z, at or before an overall ratio of 7:1 is enough load on the turbo for it to build boost quickly. I mean my turbo makes full boost at the same rpm in 2nd gear as it does in 3rd, 4th or 5th. So where is the load effect on the boost? So, I really feel a turbo Z, in say 2nd, 3rd, or 4th gear with a 3.90 diff gear would accelerate faster than the same car in the same gear with a 3.54 diff gear based on just mechanical advantage. Quote Link to comment Share on other sites More sharing options...
zguitar71 Posted July 27, 2005 Share Posted July 27, 2005 The transmission you have will make a difference too. I have a 3:90 R190 with a `83 5 sp (11.9 1st gear ratio), I like it, but I prefer to use a 4:11 (12.57:1 1st ratio) but I do not have a LSD for that diff. at the moment. I used it (3.9) with a `74 4 sp and the gearing was too low, 1st gear was in the basement (14.01:1 ratio), I prefered to use a 3.54 (12.7:1 1st gear ratio) with that trans. The close ratio trans starts out with higher gearing so the 3.9 compensates. The 3.9 with an older 5 sp is like the 4:11 with the close ratio. Quote Link to comment Share on other sites More sharing options...
HeatRaveR Posted July 28, 2005 Share Posted July 28, 2005 Can someone clarify something for me? Does a 3.54 diff mean that for a given speed, that the rpms are slightly lower than a car with a 3.9? Quote Link to comment Share on other sites More sharing options...
Sparks280zt Posted July 28, 2005 Share Posted July 28, 2005 yes thats correct heat raven Quote Link to comment Share on other sites More sharing options...
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