KA transmission v/s SR transmission (gear ratios)

[SketchyRollin564]

So my transmission kinda sucks. It grinds 3rd all the time, and gives me a hard time going into gear if i dont shift slow and smooth at high rpm. I make it work without grinds (most of the time), but its a pain in the a**, granted its a 19+ year old transmission. Its a KA transmission mated to an SR bellhousing, on an SR20 of course. From what i know, they are the exact same thing, except the 5th gear is taller on a KA for "economy" purpose.

I think this is s*** lol. Ive looked online and cant find the information i want. Ive read too much mixed things, where i feel like its mostly people just talking out their a** that dont know much, so i might as well get more of those s*** facts from here, and hopefully some people who actually know what theyre saying

so i have a two questions to ask, seeing as im looking into changing my transmission when i swap my engine again, and i want to pick the right one for my preferences

1.) is one stronger than the other? From what ive heard the SR trannys are stronger. Not like im going to be putting down 600whp, but it would be nice to have one that can handle more abuse, as far as banging through gears, clutch kicking with a strong clutch, etc.

2.) Is there any other difference in the gear ratios besides 5th gear? Ive heard that the KA has a longer 5th gear and the rest are the same, but then ive also heard that the SR has a different final drive, i dont remember if its longer or shorter though. Would imagine shorter if the 5th gear is shorter, but if it has more power then it would make sense to be longer. Also not that it counts since its not real life, but in forza 3 with an s13, you can hit 60 in 2nd gear before redline... you cant do that in real life lol, thats another thing that makes me think the gearing might be taller with an SR transmission

this ones a big one for me, because the short gears are cool and all, but it gets annoying as fawk having to shift from 1st to 2nd at 10mph when im just cruising, and it gets REALLY annoying having to cruise on the highway doing 65 mph at 3200rpm. And if i want to go 75mph with traffic, im basically riding 4k the whole time... not the best for gas, and it cant be that great for the engine either... plus its just annoying hearing it


so... anyone who knows there stuff, or who has had both transmissions, what do you think about the two in comparison to eachother?

thanks in advance

[OutToWinPAHC]

Gear Ratios
KA24(D)E & SR20DET (S13/S14):
1st- 3.321
2nd- 1.902
3rd- 1.308
4th- 1.000
5th- 0.759

CA18DET (S13)
1st- 3.321
2nd- 1.902
3rd- 1.308
4th- 1.000
5th- 0.838

SR20DET (S15)
1st- 3.626
2nd- 2.20
3rd- 1.541
4th- 1.213
5th- 1.000
6th- 0.767

[Hijacker]

To answer the question a bit more in depth.

1) I wouldn't call either transmission stronger than the other. They're very similar, so unless Nissan went to the length to use stronger materials in one gearbox, but not the other, there should be no strength differences. In real world applications, I've seen both gearboxes handle a lot of stress.

2) The 5th gear is the primary difference between the KA and SR transmissions. I did some research on the final drive ratios and came across this link. It's the only comprehensive list of final drive ratios for r200 differentials that I found. There's a pair of pictures hosted a bit down the page that lists different gear ratios and what chassis they relate to. I think most of the confusion about final drive ratios comes from people using the EU service manuals. Most euro models utilize different final drive ratios for whatever standards and practices work for those countries. The USDM, however, uses a 4.083 final drive just like the JDM models.

As for the RPM differences at highway speeds, it should be teensy. There is a .007 difference between the 5th gears for an SR and a KA (0.752 SR/0.759 KA). That should relate to maybe a hundred or so RPM difference on the motor at similar speeds.

So in short to answer your question, you'll be fine using a KA gearbox on your SR. If you're SUPER worried about it, you can have a shop rebuild the transmission. Hell, you could have them rebuild the SR transmission with a KA rebuild kit. Just tell them not to worry about rebuilding 5th gear since it's different.

[AZ89two4Tsx]

^ Yeah, he pretty much summed it up perfectly.

If you want a better highway cruising RPM, you're going to have to switch to something like a J30 diff.