SR trans gears any different from KA? (lots of text)

Sketchy564

Sketchy564

Driver
Im wanting to swap my transmission since my synchro's are going, and grinding all the time unless i feel it into gear. Im thinking about picking up a KA trans and rebuilding it when i go to automotive school so ill have fresh synchros and smooth gear engagement with no grinds. Sounds like a good idea, but i cant stand the high RPM in 5th gear cruising. I also feel like 1st gear is pointless unless im stopped, and the rest of the gears are too short. I could also do SR trans instead, which would have lower miles and i wouldnt have to rebuild it, and possibly have taller gears. Im trying to figure out if the gears on both transmissions are any different.


From what ive always read online, the gears are exactly the same, except the KA tranny has a tiny bit of a taller 5th gear for economy (which still sucks balls). However, real life experiences prove this wrong.

I currently have an SR20 with a KA transmission. I cruise at 65mph in 5th gear at a little over 3k. My friends that have SR's with the SR transmission can cruise at 65mph doing about 2.7k. They can do about 75mph at 3k, which for me is over 3.5k. Keep in mind we all had the 4.08 final drive from the diff.

Two weeks ago i swapped a j30 vlsd with the 3.9 final drive which should have made me cruise a little closer to what they cruise at, but i still cruise at a MUCH higher RPM than them. Put it this way, my 5th gear is closer to their 4th than it is to their 5th.
My 3rd gear tops at around 70ish, while their 3rd is around 93 mph. My top of 4th gear is 100...
They can also reach a little over 60mph in 2nd gear. I have to shift into 3rd and go a little before i hit 60.


If you go on google and try to look this up, you will find mixed info, but almost everywhere will say that the 5th gear on the KA tranny is taller, and all the other gears are exactly the same. I find this hard to believe given the above info about my friends cruising RPMs

Heres a quote from one forum

KA is a bit taller IIRC. You should be turning less RPMs with 5th gear given the same speed. Since 5th is an OD gear anyways, you don't really lose anything.
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The KA and the SR MTs are basically identical. The only difference in the gear ratios is OD; the SR is 0.838, the KA is 0.759.
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Heres a quote from another forum
5th gear ratio in SR20DET 5 speeds is 0.760.
5th gear in all CA18 5 speeds is 0.838
5th gear in SR20DE 5 speed is apparently 0.838 (I can't personally confirm this one though, never pulled an SR20DE box apart)
6th gear ratio in S15 is 0.76
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This one basically says that the N/A SR tranny is like the KA tranny, but the sr20det tranny is taller (which seems to be true)
OK, Changing transmissions in cars with different power levels is a good way to knock off 1/4mi times. For you guys that wanna go fast. But know this, the transmission with more torque in it will decrease your gas mileage, since you will be at a higher RPM in the taller gears.

below statement is just an example:
here's the scenario:
Nissan has the SR20DE and DET.
Now, so the DE can Hang with the DET, it has gearing that will allow it to keep up with the more powerful engine. Gears are the great equalizer for power variances.

So now, say you throw the DE tranny in the DET, you will drop seconds on your 1/4 mile time. but your gas mileage drops since your Revs will be higher in the higher gears. but hey, you'll get where you're going quicker! This is basically one of the formula that car makers go by. change a couple of teeth in the transmission instead of giving the car more power, and it can hang with the more powerful variants/cars.
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This a picture from FR sport comparing the gear ratios of a KA/SR 5spd transmission vs a Z32 trans. Which states that 5th gear on BOTH SR and KA would be 0.759
XcessiveManufacturing__03.jpg



For those who dont understand gear ratios, simply put: the higher the number, the shorter the gear, the lower the number, the taller the gear.

Also just for reference, heres the final drive ratios of the different differentials
240sx = 4.083636
NA z32 = 4.083636
J30 = 3.91666
180SX = 4.36:1 (this for CA18 equipped cars, not positive about SR20)



I made this thread to find the info out for myself, from people who have actually had experience with both transmissions, as opposed to just repeating what they've read on the internet. That being said, has anyone actually had both transmissions and would be able to confirm that the gears are different or the same? Also if you could answer a few questions

-Which transmission do you have (s13 sr, s14 sr, sr20de, sr20det, ka, etc.)
-what RPM do you cruise 65mph at in 5th?
-Can you reach 60mph in 2nd gear?
-What speed does top of 3rd gear put you at?
-Is the SR tranny any stronger than the KA tranny? (ive heard some say stronger, some say weaker)

thanks
 
Never had KA tranny. I have sr 6 speed that needs rebuilding and am going to KA, so im very interested as well.

-in 6th I cruise at about 2k
-I dont think I can reach 60 in 2nd but who knows, my speedo doesnt work
-again, no speedo, but i woud say pretty ffast.
-as for strength, i dont see how they would be any different. I know the 6 speed is more prone to drivetrain shock due to the dual mass flywheel.
 
takechan said:
Never had KA tranny. I have sr 6 speed that needs rebuilding and am going to KA, so im very interested as well.

-in 6th I cruise at about 2k
-I dont think I can reach 60 in 2nd but who knows, my speedo doesnt work
-again, no speedo, but i woud say pretty ffast.
-as for strength, i dont see how they would be any different. I know the 6 speed is more prone to drivetrain shock due to the dual mass flywheel.
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well the 6spd is different as far as ratios, heres a graph
autech20gear20ratio.jpg


anyways, this link might help you out a bit
http://www.nissansilvia.com/forums/index.php?showtopic=508981&st=0
 
idk what youre talking about cause I didnt read any.

A ka, SR, rb20 are so close to being the same, you WILL NOT notice a difference. Like, at all.
 
Just drove on 95...

-ka trans with truck/frontier internals
-2800rpm at 65mph--3200rpm at 75mph (5th gear)
-I got up to 55mph in 2nd
-3rd gear is the same as mph on the gauge so like up to 88-90mph or so safely
-Ive always heard mixed results, my shit is pretty strong tho. Im def going to go boost on it.

But yea like he^ said. Youll barely notice a difference.
 
Bearcat said:
idk what youre talking about cause I didnt read any.

A ka, SR, rb20 are so close to being the same, you WILL NOT notice a difference. Like, at all.
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Not sure about that, if you read some of my post (its long, i know), the difference in speeds at the same RPM and gears is pretty different from my KA tranny and my friends SR trannies

they can cruise 65mph at 2.7k, while i do 65mph a little over 3k. They hit 62ish in second gear, while i have to shift into 3rd and go a little to hit 60. Its enough of a difference that i noticed it.

Also my friend has an RB20 with im guessing an RB20 trans, and when i race him, we are right next to eachother til about 130, however you can clearly hear us shifting at completley different times, and you can hear how much tighter my gears are and how much longer his gears stretch. Ill be well into 5th while hes getting ready to go from 4th to 5th.

s.m.d.g.f.t.w. said:
Just drove on 95...

-ka trans with truck/frontier internals
-2800rpm at 65mph--3200rpm at 75mph (5th gear)
-I got up to 55mph in 2nd
-3rd gear is the same as mph on the gauge so like up to 88-90mph or so safely
-Ive always heard mixed results, my shit is pretty strong tho. Im def going to go boost on it.

But yea like he^ said. Youll barely notice a difference.
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Seems like nice gear ratios, a lot different from mine. I would love to be able to do 65mph in 5th under 3k.

Also, by "3rd gear is same as mph on gauge", you mean the needles move exactly the same on both tach and speedo in 3rd gear right? I remember my s14 was like this and i always thought it was cool. However, with my s13 its not like that. My needle in 4th gear moves closer to my speedo than my 3rd...
 
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Sketchy564 said:
Seems like nice gear ratios, a lot different from mine. I would love to be able to do 65mph in 5th under 3k.

Also, by "3rd gear is same as mph on gauge", you mean the needles move exactly the same on both tach and speedo in 3rd gear right? I remember my s14 was like this and i always thought it was cool. However, with my s13 its not like that. My needle in 4th gear moves closer to my speedo than my 3rd...
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^Yea thats exactly what I mean, needles move the same on both gauges. Oh and just for informative purposes I have s13 diff no j30 shit lol. Maybe your cluster is fucked up?
 
s.m.d.g.f.t.w. said:
^Yea thats exactly what I mean, needles move the same on both gauges. Oh and just for informative purposes I have s13 diff no j30 shit lol. Maybe your cluster is fucked up?
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If it makes a difference i have the single cam (5, 15, 25, etc. mph) speedo, but the tachometer is from a twin cam, redlines at 7k. Doubt that matters though

right now my speedos not hooked up. It always was, but when i swaped the motor and went to go plug up the new speedo a few days later, the busted ass clip broke even more. i need to fix it. The speed measurements of after the j30 though, were done by GPS, which should be more accurate than the stock speedometer with 17" wheels

but i can also tell you that in bens old car (white coupe) we could do 3k on the highway and feel like we were doing 75ish and flowing with traffic or passing people. Ryans car was the same way, and his speedo works (sometimes)

In my car, if im doing 3k on the highway, im in the slow lane and EVERYONE is passing me. I do 3k cruising on 441 flowing with traffic sometimes, no lie

im wondering if i have a different transmission than KA or SR... because ben and ryan both had sr20 transmissions, and they for sure had taller gears than i do. And if those online "facts" are true, it should be the other way around
 
if your complaining about a few rpms an wanna save gas just get a bicycle then you wont have any toruble. i think its so pointless on trying to get longer gearing on a 240 with an sr its not even worth going through the trouble.
 
Finkelstein said:
if your complaining about a few rpms an wanna save gas just get a bicycle then you wont have any toruble. i think its so pointless on trying to get longer gearing on a 240 with an sr its not even worth going through the trouble.
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Not really, the cars my daily. Come january, ill be going to school to lake worth and back every day for over a year, which is a good 15 solid minutes on i95 each trip. If i want to do 75mph on the way to school, im going to be doing a little under 4k the whole time. You cant say that burn up a lot more gas than being able to do the same speed at 3k.

The main thing im trying to figure out is if SR and KA gearing are supposed to be the same, but SR a little shorter in 5th, why my rpms are noticeably higher than my friends with SR trannies, in 5th, and every other gear.

And why their transmissions are also taller than i remember my s14 being, which had a stock KA with KA trans

---------- Post added at 03:25 PM ---------- Previous post was at 03:17 PM ----------
benarovi said:
sell ur car and get a moped listen to otis
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lick my asshole
 
i was always told that the sr tranny and ka tranny were the same, just different bell housings
 
on the v8 car i run a z32 n/a tranny. this is the gearing speed graph i made a while back

It is correct in real life ...


speed.jpg
 
Tire size is going to affect it more than anything.

I have personally ran a ka, sr and rb trans on my sr. Its a couple rpm difference at cruising speeds.
 
IThaJokaI said:
Tire size is going to affect it more than anything.

I have personally ran a ka, sr and rb trans on my sr. Its a couple rpm difference at cruising speeds.
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Maybe, but keep in mind we all had 215-225/45/17's, so i doubt that extra 10mm width will effect the height of the tire to any noticable degree

I really cant figure out any reason my ratios are so different from theirs.

Which trans gave you the tallest gears? I just want to be able to do 3k on the highway and flow with traffic. I would also like to be able to hit 60mph in 2nd gear
 
Did you open the diff and check the markings? That would make absolutely no sense, unless your tach is broken.

You might have gotten a vlsd that isnt a j30(3.89)
 
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