gear ratios in SR tanny?

[kentuckyslider]

I need the ratios for the SR so I can decide on tire size and R&P gearing for my drag s13. My S13 came with a 94 J30 vlsd but I don't know the ratio. I think it is a 3.86 and I know it is higher than the stock 4.08. How do I know what R&P I have? If I want to go with a 4.30-4.60 R&P what is the most inexpensive route to take?

[Tulsa_S-13]

Maybe this will help

All Nissan differentials should have a stamp on the ring gear identifying the ratio.

The J30 differential is 3.916:1

The stock 240sx final drive is 4.083636:1

Since you're making your car strictly for drag racing than I'm guessing you'll want a shorter gear ratio than your current J30 differential.

Luckily as an S-chassis' owner you have several cheap VLSD options to go with. The 180sx, HCR32 [GTS-T Skyline], J30, 300zx, Xterra front differential.

I'm assuming you're looking for a gearing shorter than the stock 4.08:1 FD. In this case, the HCR32 VLSD has a ratio of 4.36:1. I recently purchased one from JHOT Imports for $150! Talk about cheap! Of course, the output flanges differ from the stock 6-bolt flanges. So when needing the 5-bolt flanged axles you can source out a set from the '92-'94 J30.

You'll likely find several 5-bolt 180sx VLSDs floating around for sale. Only the 89-90 CA18DET equipped 180sx's had the 4.36:1 final drive, the other years have a final drive of I believe 4.11:1.

If you're wanting something REALLY short you can use the internals of the front differential from a 2001ish Xterra SE, which have a ratio of somewhere near 4.80:1. You'd have to ask NICO member Codyace more about this setup, as I am not too familiar with it.

Be sure to check out KA24DEvelopment's writeup for more information:

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

[inkslingers13]

Maybe this will help

All Nissan differentials should have a stamp on the ring gear identifying the ratio.

The J30 differential is 3.916:1

The stock 240sx final drive is 4.083636:1

Since you're making your car strictly for drag racing than I'm guessing you'll want a shorter gear ratio than your current J30 differential.

Luckily as an S-chassis' owner you have several cheap VLSD options to go with. The 180sx, HCR32 [GTS-T Skyline], J30, 300zx, Xterra front differential.

I'm assuming you're looking for a gearing shorter than the stock 4.08:1 FD. In this case, the HCR32 VLSD has a ratio of 4.36:1. I recently purchased one from JHOT Imports for $150! Talk about cheap! Of course, the output flanges differ from the stock 6-bolt flanges. So when needing the 5-bolt flanged axles you can source out a set from the '92-'94 J30.

You'll likely find several 5-bolt 180sx VLSDs floating around for sale. Only the 89-90 CA18DET equipped 180sx's had the 4.36:1 final drive, the other years have a final drive of I believe 4.11:1.

If you're wanting something REALLY short you can use the internals of the front differential from a 2001ish Xterra SE, which have a ratio of somewhere near 4.80:1. You'd have to ask NICO member Codyace more about this setup, as I am not too familiar with it.

Be sure to check out KA24DEvelopment's writeup for more information:

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

very nice! how hard is it to swap the xterra front diff? is it just the guts?

[DrifterProdigy85]

Xterra had 4.636 or 4.90. I cant remember what was in what model years though.

SR Gear Ratios1st - 3.3212nd - 1.9023rd - 1.3084th - 1.05th - .759

[Emperor_Tha]

I got the j30 diff 3.916 with 215/45/17 and it just feels like second gear is too long. When redline 1st to 2nd it drops to 4k. Making the car feel slugish. However I think first is too short, its just mash the pedal and then shift fast. 3rd and 4th gear feels pretty strong even at a 3k roll

[supreamS14]

On my road trip I was running from 3.5k-4k rpm. Is there any way to get my rpm's lower on the highway for more gas mileage/ less wear? Im running s13 sr about 250whp, s13 5 speed, stock base model 96 rear end(nismo lsd) and 235/45/17's. I dont know much about gear ratios and I figured people who see this post by kentuckyslider might know. This made me want a 6 speed.

[codyace]

Xterra had 4.636 or 4.90. I cant remember what was in what model years though.

SR Gear Ratios1st - 3.3212nd - 1.9023rd - 1.3084th - 1.05th - .759

I used a 2001 SE Xterra for my parts. Got most info from a thread on F/A

[Kalypso]

bump for a useful thread

I have the j30 diff but I have yet to drive and get the feel for it.

[DrifterProdigy85]

I got the j30 diff 3.916 with 215/45/17 and it just feels like second gear is too long. When redline 1st to 2nd it drops to 4k. Making the car feel slugish. However I think first is too short, its just mash the pedal and then shift fast. 3rd and 4th gear feels pretty strong even at a 3k roll

The J30 having a lower R&P makes the gears longer in the sense of Speed. The 1st to 2nd shift dropping to 4krpm is gonna happen regardless because that has to do with the Transmission Gearing. If you would lengthen 1st gear, you could get more Speed from it which would then make for being at higher RPM when shifting into 2nd. The OS Giken kit is setup this way.

[Emperor_Tha]

The J30 having a lower R&P makes the gears longer in the sense of Speed. The 1st to 2nd shift dropping to 4krpm is gonna happen regardless because that has to do with the Transmission Gearing. If you would lengthen 1st gear, you could get more Speed from it which would then make for being at higher RPM when shifting into 2nd. The OS Giken kit is setup this way.

if only it is safe to rev to 7500~7800 all the time in first then shift to second and be at roughly 4.5k . I think the powerband a lot smoother from gear to gear.

I got s13 blktop stock head with Ras

[DrifterProdigy85]

With the OS Giken Kit you will be around 5krpm when redlining 1st to 7500rpm and shifting to 2nd. Going from 2nd at redline to 3rd would leave you around 5500rpm. And up around 6krpm shifting from 3rd at redline to 4th gear.

[kentuckyslider]

Drifterprodigy, I am going down to 24.5" tires with my 3.91 J30 R&P and that should help some at the drag strip but not enough. I run 265/35/18's on the street and autocross and it just leaves 2nd gear way to tall. I am going to wait until I get my cams and intake in and retune with and without water/methanol injection and see what my TQ curve looks like and where I peak HP at before I decide what to change my R&P to.

If you or Codyace could provide a link to the Xterra 4.60 swap I would appreciate it. I think that is were I will go. ThanxThe 4.36 jdm 180sx might also be a possibility? I know the 4.90 Xterra is out without 28" drag tires!

[kentuckyslider]

Maybe this will help

All Nissan differentials should have a stamp on the ring gear identifying the ratio.

The J30 differential is 3.916:1

The stock 240sx final drive is 4.083636:1

Since you're making your car strictly for drag racing than I'm guessing you'll want a shorter gear ratio than your current J30 differential.

Luckily as an S-chassis' owner you have several cheap VLSD options to go with. The 180sx, HCR32 [GTS-T Skyline], J30, 300zx, Xterra front differential.

I'm assuming you're looking for a gearing shorter than the stock 4.08:1 FD. In this case, the HCR32 VLSD has a ratio of 4.36:1. I recently purchased one from JHOT Imports for $150! Talk about cheap! Of course, the output flanges differ from the stock 6-bolt flanges. So when needing the 5-bolt flanged axles you can source out a set from the '92-'94 J30.

You'll likely find several 5-bolt 180sx VLSDs floating around for sale. Only the 89-90 CA18DET equipped 180sx's had the 4.36:1 final drive, the other years have a final drive of I believe 4.11:1.

If you're wanting something REALLY short you can use the internals of the front differential from a 2001ish Xterra SE, which have a ratio of somewhere near 4.80:1. You'd have to ask NICO member Codyace more about this setup, as I am not too familiar with it.

Be sure to check out KA24DEvelopment's writeup for more information:

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

So to get the 4.36 R&P I need the diff out of a R32 GTS-T with the RB20, or a 89-90 180sx that had the CA18 in it? I found JHOT on ebay and will contact them this week. They also have very cheap prices on s13 silvia front end conversions. Thanx for the hookup. I shouldn't need the axels since I already have a 94 J30 setup?

[Tulsa_S-13]

So to get the 4.36 R&P I need the diff out of a R32 GTS-T with the RB20, or a 89-90 180sx that had the CA18 in it? I found JHOT on ebay and will contact them this week. They also have very cheap prices on s13 silvia front end conversions. Thanx for the hookup. I shouldn't need the axels since I already have a 94 J30 setup?

Correct.

Axles from the 94 J30 will work fine, I actually just got back from picking up a set of 94 J30 axles from OKC.

[callmeweezy724]

i have a 95 j30 diff.. i havent driven it yet im working on my swap now. nice coupe by the way.

[DrifterProdigy85]

Drifterprodigy, I am going down to 24.5" tires with my 3.91 J30 R&P and that should help some at the drag strip but not enough. I run 265/35/18's on the street and autocross and it just leaves 2nd gear way to tall. I am going to wait until I get my cams and intake in and retune with and without water/methanol injection and see what my TQ curve looks like and where I peak HP at before I decide what to change my R&P to.

If you or Codyace could provide a link to the Xterra 4.60 swap I would appreciate it. I think that is were I will go. ThanxThe 4.36 jdm 180sx might also be a possibility? I know the 4.90 Xterra is out without 28" drag tires!

I dont know of any links that show the swap done but you will need the Diff from the Xterra (search the junkyards) and if it were me, id just take it to a shop to have the R&P pulled and installed in your Diff.

[kentuckyslider]

I dont know of any links that show the swap done but you will need the Diff from the Xterra (search the junkyards) and if it were me, id just take it to a shop to have the R&P pulled and installed in your Diff.

What R&P are you running in your car/what tires at the track? I would like to know a little more about your setup. With your MPH you should be running mid to low 11's with the right tire and R&P combination. 4.60 with a 26" tire will be a stretch if I change to a top mount GT3076 with meth and start putting down over 500whp. Wishful thinking, I know, but that is where I want to be when I get done with this car.........10.99@130mph..... surely it can be done?

[DrifterProdigy85]

275/50-15 Tires with 4.363 R&P. I havnt ran on a prepped track yet. My run was on a grudge night with no VHT. Kept spinning off the line.

[kentuckyslider]

Sub 2 sec. 60 ft= sub 12 sec pass. I ran 1.75 60 ft. when I hit the 11.7@117. I have seen these cars run 1.5 60ft with 4.08 R&P and 26x8.5x15 MT wrinkle wall tires. Mt Et street radials are what you need. I drop the clutch at 6500rpm if the track is preped with my 235x60x15 ET street radials.

[kentuckyslider]

275/50-15 Tires with 4.363 R&P. I havnt ran on a prepped track yet. My run was on a grudge night with no VHT. Kept spinning off the line.

With your R&P the 235/60/15 ET street radial is perfect for you. Trust me it is plenty of tire if the track is right. Run them at 18psi, do about a 5 sec. burnout, and launch at 6500-7000rpm and they'll hook.

[DrifterProdigy85]

Im happy with my 275's. Sorry but i dont need tire or gearing advice. My cars setup for when i put my T67 on and able to run 135+mph traps.

[kentuckyslider]

We will compare slips. Are your 275's drag radials?

[DrifterProdigy85]

There BFG Drag Radials. My suspension is too stiff currently and ive only been once on an unprepped track. 2nd pass was a 1.91 60ft, did 12.06 @ 120.5mph. I was slipping the clutch from 5krpm and as soon as boost came on the tires would break loose to redline. Once i put the 50mm overfenders and stock suspension on the rear again, theres no doubt ill be in the 1.7 or so 60ft area. My tires choice is fine, its my suspension setup that needs tweaked now.

[codyace]

Would I be a wiedo for changing out ot stock struts at the track? LOL. I bet it would get a bunch of looks.

Downfall: Who knows where my toe and camber would go with stock crap back on lol.

There BFG Drag Radials. My suspension is too stiff currently and ive only been once on an unprepped track. 2nd pass was a 1.91 60ft, did 12.06 @ 120.5mph. I was slipping the clutch from 5krpm and as soon as boost came on the tires would break loose to redline. Once i put the 50mm overfenders and stock suspension on the rear again, theres no doubt ill be in the 1.7 or so 60ft area. My tires choice is fine, its my suspension setup that needs tweaked now.

[kentuckyslider]

I have Tien S tech springs and Tokico HP struts and my car comes out hard for a s13. I don't think I can do much better than the 1.75 60 ft. with radials. To get down to the 1.5 range you need wrinkle walls, but it will be very hard on your drivetrain at a well preped track. Cody, Tulsa, and Prodigy, thanx for your help with the gearing, I have a 4.36 180sx rear end on the way. With 26" tires and the 4.36 R&P i will hit 102mph in third and 133 in 4th @ 7500rpm. If I ever get enough power to run out of gear I will raise my rev limiter.