oakleyp2

I have an 85 300zx that turns around 2700rpm running some where around 80mph.
i just bought a 90 300zx na 2+2 and it turns 3500rpm to run 80mph.

i would have thought the 90 model 5 speed would turn less rpm than the 85 model automatic. did someone make a change to the 90 model that i dont know about or is this about right?

emo236

Don't quote me since I don't own an NA, but that should be about right. NA's have shorter gears for quicker acceleration (since they don't have turbo power ) .

oakleyp2

appreciate it EMO... just thought it was odd.

Boosted Z

the twin turbo and n/a have same gear ratio the twin turbo on the other hand has stronger internal parts in the tt trans

emo236

I don't belive that to be true at all. People swap out the TT rear end with an NA rear end. You do know that the gears are in the diffy, right? Someone with more knowledge on gear ratios of Z's tune in...I'm not that qualified in this area.

ZLover4Life

wow. That was just dumb, sorry. We're talking about final drive, not the transmission.

The NA rear end is a 4.083, the TT rear end is 3.692

3.692 = 4.083 = FALSE

emo236

Thanks...anyone running with an NA rear end or have installed a set of leader gears?

oakleyp2

Sounds like i need to swap the center section out with one from a TT, is it possible to swap the center section of the rear end?

oakleyp2

would it be worth swapping my current throttle bodies with ones from a 240sx?????

emo236

why do you want to? Performance will suffer quite a bit I imagine. You can just replace the gears inside the diffy, but it wouldn't be a good idea. Most people do it the other way around (NA rear on a TT)

oakleyp2

i drive on the interstate quite a bit. i just wanted to make it turn less rpm for cruising. i'm all new to this import stuff. dont get me wrong i like the z very much. i just grew up on chevy's. my last toy was a 65 chevy II. I could do anything on that car but these Z's are jsut a little different.

do you have any suggestions on the 240sx throttle bodies?

emo236

I believe that usually 240sx's use Z32 throttle boddies as an upgrade for them,not the other way around. Your engine was made to run at that RPM for that speed, it won't hurt it. If you're worried about gas, it won't help that too much either. I would just stick with your NA rear end. Check out the stage charts stickied at the top of this forum for what your mod sequence should be.

oakleyp2

yeah your right, gas prices suck anyway. appreciate the advice and info.

Boosted Z

well i was talking bout the trans not the diff you dont got to be smart a$$ it doesnt state in the begining if its the diff ratio or trans

emo236

The title of the thread is gear ratios. You obviously didn't know where the gears even are....they're in the diffy not the trans. You don't have to be hurt about it, you posted when you didn't know what you were talking about.....we've all done it, not big deal....just don't try to make it a big deal.

entropy31

thats typically a z31 mod, not a z32 mod. the 240sx TB is 60mm, but i am not sure od the diameter of the z32 TBs. even if the 240sx TB is slightly bigger, i doubt you will net any gain untill you reach extremely high HP.

oakleyp2

I put mu cold air intake in lastnight and it seemed to smooth the engine out some and a little more responsive. think i'm going to leave it as is for now. I have a z31 also and had seen something before aoubt the TB swap from a 240, was unsure if it applied to the z32.

you know, if i could find someone close that had a TT and wanted to exchange rear ends i would do it. that just erks me about the rpms that car turns to run 80. i spent several years in Germany and that car to me is a autobahn car not a qtr miles car.

Thanks to everyone for the comments.

CanyonCarver

Uhhhhh, fwiw, the subject was gear ratios, and trannies have gear ratios too. The TT and n/a have the same primary drive ratios. SEE HERE :-)

oakleyp2

i think i'm problaby concerned about the Final Drive Ratio. i appologize to everyone if i have confused anyone based on thread topic.

emo236

you're right CC, didn't think about that. It was obvious to me that he was talking about final drive though. But good call CC.

CanyonCarver

This was why I clarified the tranny ratios.

Boosted Z

so i was right fromt the start that they have the same ratio. i wish people would chat and not fight id love to talk about my build but no one ever posts on my new build page i got pictures an no one cares

ZLover4Life

:::sigh:::

No one ever said you were wrong about the TT and NA having the same transmission gear ratios. I said your response was dumb because...

and

Being right about something that is absolutely irrelevant to the discussion doesn't justify your response.

That'd be like Rizz asking if the 1985 struts were the same as the 1990 TT struts and I responded by saying "the 90TT struts are 2 way adjustable while the 90NA struts aren't" which does not answer the question at all.

So, let me answer the question in the thread that died over a year ago for a reason.

The reason the 90 turns more RPM at the same speed is because the FINAL DRIVE ratio of the 90 is 4.083:1 while the FINAL DRIVE ratio of the 85 is 3.7:1 (or 3.54:1 if Turbo). A smaller REAR END (a.k.a. final drive, nothing to do with the transmission) means that it will turn less RPMs at a given speed.

If you had given THIS reason instead of saying "the NA and TT have the same transmission gearing," which is irrelevant because we're talking differences between 1985 and 1990 and not NA and TT, I wouldn't have ridiculed you.

b300z

it didnt help that you came here and automatically gave yourself a bad rep with your poor posting skills and hydropower theories.
a big help would be to clean up your posts. use punctuation, understandable sentences, and lists instead of throwing everything into a big paragraph sentence. also, post more pictures of your z(engine and all) and use a photo uploader to post your pics on the forum.

and also, dont bring back dead threads

ZLover4Life

You left out irrelevant responses.