Rebuilding the SR20 trans

[s14unimog]

Before anyone suggests getting another transmission, know that I am aware of all of those options. Think of this inquiry as me simply wanting to conduct an experiment to push on with a "newly rebuilt " SR20 factory 5-speed.

On with the questions...

Does anyone on here have any experience with sourcing bearings or syncros outside of Nissan? I know where I can get a bearing a syncro kit for the KA's transmission, but of course they can't really comment on it's compatibility with the SR's. My thought, considering that you can swap trans halves between the two, is that they share the same bearing sizes. However, I hear the gearing is a little different between the two, so I am hesitant to think the syncros will be the same too.

[1988montecarloss]

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pretty sure my trans just shit the bed and sr or even ka trans dont exactly grow on trees up in maine so i might just rebuild it

[JSimpson]

Isn't the gearing the same between the SR, CA, KA and RB20? Pretty sure the gears and input/output shafts and forks are identical.

[KAT-PWR]

I've been under the impression the only difference is the bellhousings
Nissan has always had that "parts bin" mentality. So it seems it would have been smart for them to use the same trans with different bells between JDM/USDM models instead of designing a whole new trans.

[Agamemnon]

KA = SR internals.
All KA transmissions had a 0.759 5th gear while SR20DE came 0.838 5th gear. All 5speed SR20DET transmissions came 0.759 5th gear.
KA rebuild kit fits SR transmissions.

[JSimpson]

KA = SR internals.
All KA transmissions had a 0.759 5th gear while SR20DE came 0.838 5th gear. All 5speed SR20DET transmissions came 0.759 5th gear.
KA rebuild kit fits SR transmissions.

Thought so, thanks!

[huaiqiane]

it would have been smart for them to use the same trans with different bells between JDM/USDM models instead of designing a whole new trans.http://goo.gl/NQIZBB

[jr_ss]

S14 SR trans has the .838 gear Agamemnon.

[Agamemnon]

Non turbo SR's came with the .838

[Kingtal0n]

SO one could pick up the haynes manual for a nissan 240sx and use it to build a sr20det manual transmission? Fantastic!

I feel like the rear gear in our cars should be closer to 3.73 than 4.08 for a 350rwhp sr20det.

I really love the S15 rear gear but its just a bit out of reach for the 5-speed, I know it would lunch my clutch.

And if it wasn't for the cir-clip issue I would have been rocking the 6-speed a long time ago.

[KiLLeR2001]

I'm showing same part number for 5th gear on 10/94+ S14 KA transmissions as the S13/S14 SR20DET.

[s14unimog]

KA rebuild kit fits SR transmissions.

Have you actually done a rebuild on an SR transmission? I have a group down here called Southern Gear Company that sells aftermarket rebuild kits for transmissions and they have a kit for the KA that runs ~$190 for bearings and syncros. The guy at their shop was asking me for the casting numbers on the case to confirm compatibility on the SR's but I haven't gotten him that information yet.

[jr_ss]

Non turbo SR's came with the .838

So did S14 DET's.

[s14unimog]

well the good news here is that I highly doubt anyone needs to replace their 5th gear. So this is really a moot argument. What ever the ratio is, it more than likely that the syncronizer hub is the same size.

Either way, with the 4.08 and stock SR box you can pull around 155-160mph if you have enough space and/or HP.

hZCG83HZBek

[cotbu]

Either way, with the 4.08 and stock SR box you can pull around 155-160mph if you have enough space and/or HP.
This is true, i think there's another limiter for the s13sr ecu for 255km/hr though. Or it just feels like you're pulling an open parachute.

[omgRWDgoodness!]

well the good news here is that I highly doubt anyone needs to replace their 5th gear. So this is really a moot argument. What ever the ratio is, it more than likely that the syncronizer hub is the same size.
Actually, I do. It developed a grind after I installed a new clutch/flywheel & Nismo slave cylinder and drove it for a few weeks without realizing that I needed to adjust the clutch pushrod. :-/

[s14unimog]

Actually, I do. It developed a grind after I installed a new clutch/flywheel & Nismo slave cylinder and drove it for a few weeks without realizing that I needed to adjust the clutch pushrod. :-/

In a synchronized transmission you are not meshing gears while shifting, but rather engaging the hub via the synchronizer assembly. If you feel a grind while trying to enter a gear, that's the synchro sleeve attempting to cross over onto the the respective gear hub, but the synchro's friction surface to too worn (or the input shaft still has load on it) and it cannot slow it enough to allow the engagement - hence the grind you feel/hear. the physical helical gears of 1st through 5th run meshed the entire time. It's whether or not the hub on the main shaft is live or not.

Reverse is the only gear set that you actually mesh together. It also does not have a syncro assembly connected to it.

[Agamemnon]

So did S14 DET's.
I stand corrected. You're right.

My source was incorrect.

http://tech.240sxone.com/500/gear-ratios-and-drivetrain-info/
https://en.wikibooks.org/wiki/Nissan_240SX_Performance_Modification/Transmission