mikesz Posted April 13, 2009 Share Posted April 13, 2009 Just curious because i was thinking about changing my 3.90 gears to 3.54.I would just install a whole new diff with the 3.54 gears already in it.Should i stick with my current set-up?I'm asking because the rpm's real get up there in 1st gear and i thought maybe the 3.54 would make the turbo spool up faster.Any advice would be much appreciated. Quote Link to comment Share on other sites More sharing options...
dexter72 Posted April 13, 2009 Share Posted April 13, 2009 I did the same thing as you and with the 3.90 diff in mine, it made first gear almost useless. When I accelerated hard, I had to shift out of first so quick I hated it. I put a 3.54 diff in and it made a world of difference. I could stay in first longer and it pulled harder since the turbo had more time to boost. So with the 3.54 diff you can stay in first gear longer, Boost should feel better because the turbo has more time to spool. You will like 3rd gear a lot. 3.54 diff was in them from the factory for a reason, is how i feel about it. From having both diffs in my car, I liked the 3.54 a lot better. If this is a street driven car I would do the 3.54 diff swap. Quote Link to comment Share on other sites More sharing options...
Savage42 Posted April 13, 2009 Share Posted April 13, 2009 Wait a second, your title said N/A 5 speed, but then you mention "turbo" in the message. Anyway, I took the 4.11 out of my VG turbo powered 510 and went with a 3.70 (nearly identical jump you are referring to) and it totally transformed the car. It was much more streetable and it does work better when you can keep your foot down and create more boost for a longer period of time. It depends on what you ultimately use the car for and want to get out of it. I'd love to have a 3.54 or 3.36 R200 LSD (instead of the 3.70 LSD) for the 280Z-06, but I'll live with it for now and possibly swap it later. Hope that helps. Quote Link to comment Share on other sites More sharing options...
mikesz Posted April 13, 2009 Author Share Posted April 13, 2009 Yes, I have the l28et motor installed.Thanks for the input.I'll have to look for a r200 with the 3.54 gears. Quote Link to comment Share on other sites More sharing options...
ShaggyZ Posted April 13, 2009 Share Posted April 13, 2009 I vote 3.15 R200.... oh wait, I have one! Reading this thread makes me feel a little better about getting read to run it with my project. Quote Link to comment Share on other sites More sharing options...
mikesz Posted April 13, 2009 Author Share Posted April 13, 2009 I did the same thing as you and with the 3.90 diff in mine, it made first gear almost useless. When I accelerated hard, I had to shift out of first so quick I hated it. I put a 3.54 diff in and it made a world of difference. I could stay in first longer and it pulled harder since the turbo had more time to boost. So with the 3.54 diff you can stay in first gear longer, Boost should feel better because the turbo has more time to spool. You will like 3rd gear a lot. 3.54 diff was in them from the factory for a reason, is how i feel about it. From having both diffs in my car, I liked the 3.54 a lot better. If this is a street driven car I would do the 3.54 diff swap. Are you using the N/A transmission? Quote Link to comment Share on other sites More sharing options...
Gritz Posted April 13, 2009 Share Posted April 13, 2009 I vote 3.15 R200.... oh wait, I have one! Reading this thread makes me feel a little better about getting read to run it with my project. How much hp are you aiming for... Quote Link to comment Share on other sites More sharing options...
Challenger Posted April 13, 2009 Share Posted April 13, 2009 My 78 has the 3.54 and I have a really nice NA five speed thats pretty much ready to go. As mentioned I bet its really nice with a turbo motor to have really long gears, Itll also keep RPMs down on the highway. My question is how much of a change in the rear end will be beneficial, at some point if you go to to high of a gear youll loose most of your ability acceleration. It would be nice to know where that point is... Quote Link to comment Share on other sites More sharing options...
ShaggyZ Posted April 13, 2009 Share Posted April 13, 2009 How much hp are you aiming for... Right now, my goal is 400WHP with a fairly early-spooling turbo - probably a T61 - and stock USDM cams; if the funds permit, I may choose something like the GT35R. I want to avoid nitrous and methanol injection. Hopefully, with what I have in mind I'll be able to hit full boost somewhere around 3200RPM. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted April 14, 2009 Share Posted April 14, 2009 The 3.54s make 4th gear amazing for highway fun and you still have 5th to for crusing. I did that in my maxima but ran 215/50-15s. Quote Link to comment Share on other sites More sharing options...
Pyro Posted April 14, 2009 Share Posted April 14, 2009 yes, turbo cars came stock with 3.54, but the transmission gears in the T5 are set up for 3.54 gears. T5's have higher numeric gears in 1st and 2nd as compared to late model NA 5 spd. so really, the later model NA 5 spd with a 3.90 gear has about the same ratios as a T5 turbo trans with a 3.54 gear. And that is about the same as an early model NA 5 spd with a 3.54. Therefore the T5 and the early model NA 5 spd are wide ratio transmissions. when comparing rear end gears, the trans gears must also be considered. I say, stay with the 3.90 gear if you have a later model NA 5 spd. Gears are good for acceleration (turbo or not). A 3.54 gear with a later model 5 spd will slow you down, but will lower rpms 10% as compared to the 3.90. The question is, what year NA 5 spd do you have? if you have an early 5 spd (77 to 78) then a 3.54 gear will be just about where the stock turbo set up is. If you have a later model 5 spd (81 to 83) then the 3.90 gear would work nicely. Quote Link to comment Share on other sites More sharing options...
rwdawg2 Posted April 14, 2009 Share Posted April 14, 2009 Do the 80-83 N/A 280zx's have a r180 or r200? Varies? Mike is your stock one a r200 or what? Quote Link to comment Share on other sites More sharing options...
Pyro Posted April 14, 2009 Share Posted April 14, 2009 check out this site. http://www.geocities.com/z_design_studio/ early 5spd gears: 3.321, 2.077, 1.308, 1, 0.864 later 5spd gears: 3.062, 1.858, 1.308, 1, 0.745 turbo T5 gears: 3.500, 2.144, 1.375, 1, 0.78 max speed with 215/60/15 tires and 6,000 rpm early 5 spd w/ 3.54= 38, 61, 97, 127, 147 later 5 spd w/ 3.90= 38, 62, 88, 115, 155 turbo T5 with 3.54 = 36, 59, 92, 127, 163 later 5 spd w/3.54 = 41, 68, 97, 127, 170 Quote Link to comment Share on other sites More sharing options...
Mike C Posted April 15, 2009 Share Posted April 15, 2009 My experience is a little different since I have an NA motor with the T5 and a 3.54 diff. I find the combo near ideal with nearly as much first gear as the lower numeric NA trans and 3.90 gears (12.95 first with the early 5 speed 3.90 rear and 12.4 with the T5/3.54) For comparison, the BW Super T10 2.54 first gear in my Camaro with 4.10 gears only has a 10.4 overall first gear. And SUCKS on the highway even with the 28" tall tires. The same benefits of the T5 and 3.54 are true with overdrive. The late 5 speed and 3.90 gears has an effective final drive of 2.9 while the T5/3.54 setup is 2.76. This is the best of both NA 5 speeds IMO. I can cruise on the highway 70 mph at about 2400 rpm with my 205 55 16 tires. It also allowed me to dump the Nissan shifter for a Hurst Competition Plus which is amazingly slick compared to the OEM POS. Quote Link to comment Share on other sites More sharing options...
dexter72 Posted April 15, 2009 Share Posted April 15, 2009 Mikesz, Yes I am still using an 83 N/A 5spd. The difference with my setup is I have an 83 N/A engine with a turbo added on. My compression ratio is higher and I have like no turbo lag when I accelerate. During hard acceleration I was in and out of first so quick it made that gear almost useless to me. Now with your turbo engine you will have some lag and what Pyro pointed out may be better for you. You asked about a 3.54 with an n/a 5spd and that's what I ran for a few years and Liked it a lot in my car. I have a 3.70 lsd in the car now and like it a lot. You said you wanted your turbo to spool up even quicker, but I was taught you want the turbo to be able to spool up longer. To get all the benefits from it, Not Quicker for a street car with a stock turbo. That's also if the turbo is stock. Quote Link to comment Share on other sites More sharing options...
X64v Posted April 15, 2009 Share Posted April 15, 2009 FWIW I run the stock 3.364:1 R180 behind my 81-83 ZX N/A 5 speed mated to my L28et (7.3:1 SCR) at 12psi, and love it. I have no problem with torque for driving around town, and I love being at 2500rpms at 70mph on the freeway, still under 3k at 80mph. On boost I still have plenty of power for passing even in 5th gear. Quote Link to comment Share on other sites More sharing options...
mikesz Posted April 15, 2009 Author Share Posted April 15, 2009 check out this site. http://www.geocities.com/z_design_studio/ early 5spd gears: 3.321, 2.077, 1.308, 1, 0.864 later 5spd gears: 3.062, 1.858, 1.308, 1, 0.745 turbo T5 gears: 3.500, 2.144, 1.375, 1, 0.78 max speed with 215/60/15 tires and 6,000 rpm early 5 spd w/ 3.54= 38, 61, 97, 127, 147 later 5 spd w/ 3.90= 38, 62, 88, 115, 155 turbo T5 with 3.54 = 36, 59, 92, 127, 163 later 5 spd w/3.54 = 41, 68, 97, 127, 170 Wow, Good info.My zx was converted from an auto to manual.I have the R180 with the 3.54 gears.I didn't know this for the life of me.Should i just stick with what the R180?I do have the auto turbo ecu installed.Maybe that explains the rpm's. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted April 15, 2009 Share Posted April 15, 2009 Remember that these cars were designed when the speed limit was 55mph. So.......it's very easy to run the car above the revs at which the ecu decides to start ignoring sensors. This is a huge problem for 280zx turbo drivers because stock gearing puts the engine in the aforementioned state while cruising around 70 or 75mph......not sure what rpms this happens in the N/A version. This kills mileage. Quote Link to comment Share on other sites More sharing options...
woldson Posted April 16, 2009 Share Posted April 16, 2009 I wish I had one. That makes sense, never thought of that even though now it seems obvious:)! That engine has plenty of power to cruise at a lower rpm. Quote Link to comment Share on other sites More sharing options...
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