Has anyone tried running the LS1/T56 combo with an s15 diff and ring gear. From what I understand the rear end gearing of the S15 is taller because of the 6 speed they come with. Also how much benefit would you see from something like this. I'd imagine that it would be great for highway MPG and such and when tracking a car I'd assume that it would require you to shift alot less.

The T56 already has a stupendously high .5:1 2nd overdrive (6th if you don't know what I'm talking about), so it doesn't really matter what final drive you get it'll be revving quite low cruising down the highway.

but for those that drag race, wouldn't a taller rear gear mean fewer shifts in the 1320? I'm not merely concerned with just 6th gear, i'm looking into all possible benifits/downfalls of that set up.

These are the gear ratio's for the S15 6 speed and final drive

gear ratios 3.626:1, 2.200:1, 1.541:1, 1.213:1, 1.000:1, 0.767:1, final drive 3.692:1

These are the gear reatios for an ls1/t56 powered corvette

Gear Ratio1st gear 2.97:12nd gear 2.07:13rd gear 1.43:14th gear 1.00:15th gear 0.84:16th gear 0.56:1final drive 3.42:1.(note these may not be exactly correct as i've found various ratios for the t56 online, but none were vastly different from this)

So I found some calculators

This is what you would have w/ an s15 rear end gearset and t56 transmission

1st gear

6500 RPM 43.03 MPH6000 RPM 39.72 MPH5500 RPM 36.41 MPH5000 RPM 33.10 MPH4500 RPM 29.79 MPH4000 RPM 26.48 MPH3500 RPM 23.17 MPH3000 RPM 19.86 MPH2500 RPM 16.55 MPH2000 RPM 13.24 MPH1500 RPM 9.93 MPH1000 RPM 6.62 MPH

2nd Gear

6500 RPM 61.74 MPH6000 RPM 56.99 MPH5500 RPM 52.24 MPH5000 RPM 47.49 MPH4500 RPM 42.74 MPH4000 RPM 37.99 MPH3500 RPM 33.24 MPH3000 RPM 28.49 MPH2500 RPM 23.75 MPH

3rd Gear

6500 RPM 89.37 MPH6000 RPM 82.50 MPH5500 RPM 75.62 MPH5000 RPM 68.75 MPH4500 RPM 61.87 MPH4000 RPM 55.00 MPH3500 RPM 48.12 MPH3000 RPM 41.25 MPH2500 RPM 34.37 MPH

4th Gear

6500 RPM 127.80 MPH6000 RPM 117.97 MPH5500 RPM 108.14 MPH5000 RPM 98.31 MPH4500 RPM 88.48 MPH4000 RPM 78.65 MPH3500 RPM 68.82 MPH3000 RPM 58.98 MPH2500 RPM 49.15 MPH

5th Gear

6500 RPM 152.14 MPH6000 RPM 140.44 MPH5500 RPM 128.74 MPH5000 RPM 117.03 MPH4500 RPM 105.33 MPH4000 RPM 93.63 MPH3500 RPM 81.92 MPH3000 RPM 70.22 MPH2500 RPM 58.52 MPH

6th Gear

6500 RPM 228.21 MPH6000 RPM 210.66 MPH5500 RPM 193.10 MPH5000 RPM 175.55 MPH4500 RPM 157.99 MPH4000 RPM 140.44 MPH3500 RPM 122.88 MPH3000 RPM 105.33 MPH2500 RPM 87.77 MPH

Now I would imagine that in addition to being beneficial on a drag strip, a gear ratio like this would also be helpful on a road course.

Furthermore I don't see the LS1 or any of the LSx series motors having any trouble propelling our cars with such a tall final drive ratio due to the lighter weight of the 240 and the gobs of torque the LSx series engines have.

What size axles are on the s15 diff, if you are building motor are using FII would be more concerned about snapping the axles. I got a 327 turbocharged motor. only driven a few times as the build is not quite done. it moves like hell with a tko500 1st 3.27, 2nd 1.97,3rd 1.34,4th 1.00 ,5th .68 I got the q45 diff 3.54 with the 31 spline axles. some guy is running this diff and axles with a reported 1200hp with a supra motor drag racing.

your set up should be fine I personally wanted the shorter first gearto go with the taller diff ratio to help get moving.

but like you said the gobs of torque should make that almost irrelevant.

EazyBreazy wrote:but for those that drag race, wouldn't a taller rear gear mean fewer shifts in the 1320? I'm not merely concerned with just 6th gear, i'm looking into all possible benifits/downfalls of that set up.

These are the gear ratio's for the S15 6 speed and final drive

gear ratios 3.626:1, 2.200:1, 1.541:1, 1.213:1, 1.000:1, 0.767:1, final drive 3.692:1

These are the gear reatios for an ls1/t56 powered corvette

Remember though that Corvette transmissions are not readily swappable into the S chassis and have different ratios than the F-body T56s (except for 4th, which is still 1:1. Only the GTO T56 has an F-body case w/ Corvette internals.

Just curious,are the cases different size and what about the viper t56?

cnichols wrote:
Remember though that Corvette transmissions are not readily swappable into the S chassis and have different ratios than the F-body T56s (except for 4th, which is still 1:1. Only the GTO T56 has an F-body case w/ Corvette internals.

MOST corvettes didnt get the GTO ratios, they were the same as the F body, 2.66 first gear as opposed to the 2.97 first. The good 2.97 trans are the M12's, which were Z06, gto, ctsv, regular corvettes got the 2.66 transmissions.

OP: The newer Q45 R200 will get you the 3.69 ratio, and should at a much lower cost, will also get beefier output stubs from the carrier.The earlier Q45's have a 3.53 ? ratio, which is what i'll be using for now with my GTO trans, though I may step to the newer 3.69 later.

Z28ricer wrote:
MOST corvettes didnt get the GTO ratios, they were the same as the F body, 2.66 first gear as opposed to the 2.97 first. The good 2.97 trans are the M12's, which were Z06, gto, ctsv, regular corvettes got the 2.66 transmissions.

Good to know...did all Corvettes have the same final drive? If so, I just figured it made sense for them all to have the same tranny ratios as well. Learn something new everyday.

Z28ricer wrote:OP: The newer Q45 R200 will get you the 3.69 ratio, and should at a much lower cost, will also get beefier output stubs from the carrier.The earlier Q45's have a 3.53 ? ratio, which is what i'll be using for now with my GTO trans, though I may step to the newer 3.69 later.

Are you certain that the newer Y33 Q45 (97-01) has the beefier output shafts? They are not the same evenly spaced 6 bolt pattern that came on the G50 (early Q45), but an evenly spaced 5 bolt pattern like the S13 and J30 5 bolt axles. This is something I've never seen anyone talk about w/ any certainty and I haven't had time to take it out of my Y33 to check.

I'm more interested in finding a rear end that will not break than I am worried about the final drive.

Any idea what HP level these Nissan diffs will support?S13/S14/Z32 ViscousS15 helicalQ45?

I got the q45 diff 3.54 with the 31 spline axles. some guy is running this diff and axles with a reported 1200hp with a supra motor drag racing

so far I hit 4th gear fast (shifting at 4000rpm because the motor is not broken in ) with 6psi but on a fully built 327 , though not properly tuned yet.


Modified by 450SX! at 8:06 AM 4/1/2009

450SX! wrote:I got the q45 diff 3.54 with the 31 spline axles. some guy is running this diff and axles with a reported 1200hp with a supra motor drag racing

That's exactly the info I was looking for! Thanks!

Eikon wrote:I'm more interested in finding a rear end that will not break than I am worried about the final drive.

Any idea what HP level these Nissan diffs will support?S13/S14/Z32 ViscousS15 helicalQ45?

Don't worry about the diffs, worry about the axles.

cnichols wrote:
Don't worry about the diffs, worry about the axles.

im making ~450tq and the r200 diff is still holding. but im on my 2nd set of axles

cnichols wrote:
Good to know...did all Corvettes have the same final drive? If so, I just figured it made sense for them all to have the same tranny ratios as well. Learn something new everyday.

Are you certain that the newer Y33 Q45 (97-01) has the beefier output shafts? They are not the same evenly spaced 6 bolt pattern that came on the G50 (early Q45), but an evenly spaced 5 bolt pattern like the S13 and J30 5 bolt axles. This is something I've never seen anyone talk about w/ any certainty and I haven't had time to take it out of my Y33 to check.

Not sure on the rear ratio, just found out the hard way that they were avail with the 2.66 gearing.

Never really looked into the Y33 outputs, figured they would be the same as the earlier ones, I guess if they did swap over then if/when I decide to go with the 3.69 ratio, i'll just swap the gears onto the earlier carrier.