J30 or Q45 pumpkin

[JesusFreakDrifter]

Hey i was looking through the threads and see people talking a lot about welded diffs, which looks like a good idea for drifting, which i plan on doin. But there have been a couple of people going with J30 diffs or Q45 or 300zx, whats the advantage of having one of those diffs?

[drift freaq]

Q45 differential will not work in our cars, if You had searched you would have found that out without me telling you. You would have also found out you can use the 300zx NA differential.

[Dousan_PG]

read this all and never speakanother word

http://www.ka24development.com/vlsd.html

[drift freaq]

Originally Posted by Dousan_PG

read this all and never speakanother word

http://www.ka24development.com/vlsd.html

that was a good link aaron, I was not aware that with extra parts you could make the Q45 work. In the past its pretty much been a well it won't bolt in and there are some differences thing. Apparently he found a work around.

[punkz]

Originally Posted by Dousan_PG

read this all and never speakanother word

http://www.ka24development.com/vlsd.html

Thank you for posting that. That helps me out with a bunch of questions I was having

[DarkRaptor42]

Ive got a question on this subject if someone could answer it for me that would be awesome. If i have a z32 na dif and open it up, can i take the gearset off of my open diff and use the lsd in the open diff? The z32 diff I have access to is missing the output flanges. If I can just take out the center and make it work with the open setup that would be awesome. Thanks ahead of time.

[SoSideways]

Originally Posted by DarkRaptor42

Ive got a question on this subject if someone could answer it for me that would be awesome. If i have a z32 na dif and open it up, can i take the gearset off of my open diff and use the lsd in the open diff? The z32 diff I have access to is missing the output flanges. If I can just take out the center and make it work with the open setup that would be awesome. Thanks ahead of time.

Please use logic.

And logic says yes.

[DarkRaptor42]

san q very much

[R33GTS-T]

i have a different question but its related to the J30 diff...

I have an RB25 swapped into my s13 and i'm running a J30 diff. Now i am well aware that the RB is not meant for economy gas mileage but that doesn't mean that I want the engine to be at 3000RPMs in 5th gear and i'm only going 70mph.

I put down 280whp and ~250wtq at .85 bar (stock turbo). If I were to swap in a diff with a lower final drive would it completely destroy any low RPM acceleration that I have?? I road race and autox the car and can't afford to lose all of my low end grunt but at the same time I can't be topping out my gearing half way down the straight at VIR or Summit Point either.

Thanx in advance

- Daniel

[drift freaq]

Originally Posted by R33GTS-T

i have a different question but its related to the J30 diff...

I have an RB25 swapped into my s13 and i'm running a J30 diff. Now i am well aware that the RB is not meant for economy gas mileage but that doesn't mean that I want the engine to be at 3000RPMs in 5th gear and i'm only going 70mph.

I put down 280whp and ~250wtq at .85 bar (stock turbo). If I were to swap in a diff with a lower final drive would it completely destroy any low RPM acceleration that I have?? I road race and autox the car and can't afford to lose all of my low end grunt but at the same time I can't be topping out my gearing half way down the straight at VIR or Summit Point either.

Thanx in advance

- Daniel

Daniel you will lose some low end acceleration going with a lower final drive i.e. 3:70 or 3:54. Though given the amount of torque your engine has you still should have decend acceleration. I Have to go back and check but I am pretty sure there were Skyline models that came with 3:70 ratio stock. The Z32TT came with that ratio for the very reason of it being a high horsepower turbo engine. Essentially, with a lower final drive on a turbo engine, you will stay in boost longer on every gear because you won't run through your gears as quickly. So it could make your car faster.

[R33GTS-T]

Originally Posted by drift freaq

Daniel you will lose some low end acceleration going with a lower final drive i.e. 3:70 or 3:54. Though given the amount of torque your engine has you still should have decend acceleration. I Have to go back and check but I am pretty sure there were Skyline models that came with 3:70 ratio stock. The Z32TT came with that ratio for the very reason of it being a high horsepower turbo engine. Essentially, with a lower final drive on a turbo engine, you will stay in boost longer on every gear because you won't run through your gears as quickly. So it could make your car faster.

thank you for the great reply back

so if i were to run the Z32TT diff i would have a 3.70 final drive correct? Right now I definitely run through the gears rather quickly and when driving on the street when I'm doing 45ish mph i'm in the high 2000RPM range and then shift into 5th....not really ideal for street travel ya know

As for the autox, the car definitely hauls and I have yet to encounter an autox course where I'm out of my powerband. I haven't had a chance yet to go on any road courses but hope to be able to track the car in the coming month.

I guess what my biggest question is if i were to switch out to a 3.70 or 3.54 final drive where will it shift my powerband? Will i lose tractability on an autox course or will it just haul a little less?

- Daniel

[orion::S14]

^^^ Z32TT diff is NOT an otion for you...it's an R230, too big for your chassis.

A numerically lower diff would slow your acceleration, but increase top speed. You'll have MORE traction at lower RPM.

Basically, it's less TQ multiplication...think of riding a bike...try to start in the big gear up front and smallest in back...that's a Q45 diff. Slow to start, but will get you going very fast eventually.

Now do the same...but use the middle gear up front and (edit!) biggest in back ("granny gear")...that's the 180SX 4.36:1 diff...supper fast accel, but you're spinning your legs so fast by ~12mph that you can't go faster!

See what I mean?

- Brian

[R33GTS-T]

from your weblink Brian it states that the J30 diff has a 3.92 final while the z32na diff has a 4.08 final drive then wouldn't the z32 diff actually give me slightly shorter gearing when compared to the j30???

[orion::S14]

Yes..stock is 4.083:1, J30 is 4% higher gearing (numerically lower).

It's hardly noticeable, but I like to try and stick with the 4.083 or higher...unless you need to do +150mph.

- Brian

[SoSideways]

Originally Posted by R33GTS-T

from your weblink Brian it states that the J30 diff has a 3.92 final while the z32na diff has a 4.08 final drive then wouldn't the z32 diff actually give me slightly shorter gearing when compared to the j30???

Yes, 3.92 final drive will give you slightly taller gear ratios than the 4.08, but the difference isn't really noticable.

I had the stock open diff from the S13 with the 4.08, would do about 3500rpm at 80mph.

Then I switched to the J30 diff with the 3.92 final drive and now I'm at around 3300rpm doing 80mph.

Not that much difference.

However, now that I've put 17s with 225/45/17 tires on, at 80mph I'm more closer to like 3100rpm. Will be going with 235/40/17s next, so that should bring the rpms right back up to around 3200-3300rpm @ 80mph.

[R33GTS-T]

hmmm.....so i'm pretty much screwed in terms of getting a taller final drive into the car right??

I'm going to be running either 245/45/17s or 255/40/17s in the rear

here's another thing though, i'm running an RB25DET and tranny (of course) so my gear ratios are going to vary when compared to an SR20 tranny b/c of differrent ratios in the tranny yes?

[drift freaq]

Originally Posted by R33GTS-T

hmmm.....so i'm pretty much screwed in terms of getting a taller final drive into the car right??

I'm going to be running either 245/45/17s or 255/40/17s in the rear

here's another thing though, i'm running an RB25DET and tranny (of course) so my gear ratios are going to vary when compared to an SR20 tranny b/c of differrent ratios in the tranny yes?

You can get seperate rings and pinions. if I did not state it earlier, which I think i might have, some skyline's came with 3.70 gears in a R200 diff. Most of the guys that are answering your questions are not running RB25's, they are running SR's or KA Turbo's. There is a torque difference between a 4 and 6 cylinder engines. I am currently running 4.08's in my RB car and I do like it.Though.. ya at 70 mph on the freeway, I could easily have another gear or be lower in my rev band, not because I am over revving, but because of the sheer torque of my engine.
I would say shoot for 3.70, or 3.92 aka J30, or research the different Skyline diffs. Which are actually all R200 cases and will bolt in our cars. GTS diffs were VLSD's , R32 GTR and R33 GTR were clutchpack and R34 GTR was helical.

[R33GTS-T]

Originally Posted by drift freaq

You can get seperate rings and pinions. if I did not state it earlier, which I think i might have, some skyline's came with 3.70 gears in a R200 diff. Most of the guys that are answering your questions are not running RB25's, they are running SR's or KA Turbo's. There is a torque difference between a 4 and 6 cylinder engines. I am currently running 4.08's in my RB car and I do like it.Though.. ya at 70 mph on the freeway, I could easily have another gear or be lower in my rev band, not because I am over revving, but because of the sheer torque of my engine.
I would say shoot for 3.70, or 3.92 aka J30, or research the different Skyline diffs. Which are actually all R200 cases and will bolt in our cars. GTS diffs were VLSD's , R32 GTR and R33 GTR were clutchpack and R34 GTR was helical.

great thank you very much....i'll hope onto the Skyline Forums i'm on and start researching diffs from those guys

[KAZILLA]

Save yourself the trouble, and get a real LSD. I did, KAAZ!!

[R33GTS-T]

i'm not looking for a better locking diff right now...i'm looking for a lower final drive