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HowTo: Replace M/T Input Shaft Bearing [Dissasemble SR20 Manual Transmission]

42K views 26 replies 18 participants last post by  Germ20 
#1 · (Edited)
:NOTE: This HowTo is not finished but I am posting it so that I can save it!

Hey girls and guys, this is a HowTo for dissasembling and reassembling an SR20 Manual Transmission in order to replace the Input Shaft Bearing, Output Shaft Bearing, and Throwout Bearing. This will be from start to finish, from jacking the car up, to dropping the transmission, to test driving your car afterwards. This is my first how to so be easy on me!

Symptoms of Bad Bearings:

The reason for replacing the input, output and throwout bearings is to eliminate some noises that are coming from the transmission due to worn out bearings. Worn out bearings can cause the transmission to not function properly making it more difficult on the motor and your leg.

Bad Throwout Bearing- A bad throwout bearing will start in the form of a whirrrrring noise when you push the clutch in. The noise should go away when you release the clutch. The reason for the noise is when you engage the clutch, you are putting pressure on the bearing which is putting pressure onto the pressure plate and due to the play in the bearing will make the whiirrrrrring noise. In worst cases, you may not be able to engage the clutch.

Bad Input/Output Shaft Bearings- Bad input and output shaft bearings will show their symptoms just the opposite. You should hear a Whirrrrring noise when the clutch is not engaged and the car is in neutral. Given that your throwout bearings is good, the sound will stop once you push the clutch in. Typically you can hear this whirrring while in gear although alot quieter. It will get proggresivly worse over time. There may be other symptoms but I'm keeing it simple.

UPDATED: August 5, 2009

So far I have gotten to the point with the transmission dissasmbled waiting on my bearings to arrive! I am also at a stop due to not getting a Puller(will get these today). Dissasembly will be the easy and by easy I mean easierrrr part.

Tools:

Tools list will be updated after I am done. Here's a basic list.

  • Metric Sockets
    -10mm
    -12mm
    -14mm
    -17mm
    -19mm
    -21mm
  • 36mm Axle Socket
  • Combination Wrenches
    -12mm
    -14mm
    -17mm
    -21mm
  • Ratchets
    -1/4"
    -3/8"
    -1/2"
  • Extensions
    -3/8"
    -1/2"
  • Impact Wrench
  • Impact Sockets
  • Puller
  • Prybar
  • Hammer/Mallet
  • Flathead Screwdrivers
  • Jackstands
  • Jacks(2 Preferably)
  • 1/2" Breaker Bar
  • Pliers
  • Wire
  • Oil Pan
  • New Bearings
  • Transmission Oil MT90
*You should have a variety of Regular and Deep Sockets to make it easier*

Procedure:

1. Drive your car into where you're going to be working. I would suggest somehere like a garage or carport incase it rains or something cause this may take a while. I removed my battery, and intake to make things easier. I suggest you do the same.




2. Jack up the car from the crossmember. In my case that meant driving onto wood blocks and removing my bumper. Make sure to put wheels chocks on both side of one of the rear tires. You can also leave your E-Brake on. Put the car on jackstands and remove the jack.





3. Remove your front wheels. I'm using a 19mm impact socket with my impact gun.



4. Now you will be removing your brake calipers which involves 2 17mm bolts. First take off your brake line clip. I always hang my calipers with wire to keep them out of the way. Remove your rotors.






5. Now remove the 36mm axle nut. Take the cotterpin off first. I used my Impact which make things so easy.






6. Now we need to drop the knuckle in order to remove the axles. Use a flathead screwdriver to pry off the car and use a 17mm Wrench or ratchet depending on what you have to loosen it. You will also want to remove the abs sensor bracket to give it more play(10mm socket). If the knuckle doesnt slide off easy, turn the castle nut upside down and thread it back on. Now hit it with your hammer or mallet. Once it starts to slide down, take the nut off and it should come down easy.




^(removing abs bracket)



7. Drain the Transmission Fluid. You need a 1/2" racket and an oil pan. It will come out quicly so beware. Make sure to do this before you remove your axles so that you don't get tranny fluid all over your floor!




8. Next is removing the axles which on the passenger side means removing the 3 12mm bolts on the axle bracket(?). The passenger side should just slide out once those bolts are removed. The driver side is a little different. It doesnt have any brackets but you need a prybar. Pry the axle off with a quick jolt so that it comes out easy. Once the axles are out, you are in business....






9. Now I started prepping the transmission to get lowered which included removing the starter, unplugging all harnesses/sensors and disconnecting shifter linkage.




9A.^Remove the Starter, 2 14mm bolts. Let it hang there till you're under the car.



9B.^Remove the sensors off the transmission, there are 3.



9C.^Remove the clutch slave cylinder. 2 12 or 14mm bolts, I forget. Just move it out of the way.

9D. Remove the Shifter linkage, there are 2 12mm bolts(If I remember correctly) Remove both stabilizer(?) and linkage. If you have gotten this far, you know were they are.

10. Now I didn't get too many pictures of the next steps and its somewhat involved. Start with jacking up the tranny, just a little. Don't lift the whole car...



10A.^Jacking up tranny. Thats Norm. he's asian:asian:, you may need one for small areas YOU wouldn't usually be able to get to.



10B.^That's me. We put a block of wood with a car jack on top to jack up the motor, not the best way but it works. You need to have both the tranny and the motor supported because you will be removing the motor mounts and cross member.

10C. Now remove the cross member completely, trust me it's easier that way. Remove the Tranny mount, again trust me on this one.

10D. Now you can unbolt the 14mm tranny bolts, there are about 6 of them? Not sure but you'll see them. After this, I dropped my downpipe so that I didn't bend it when I dropped the motor/tranny. You may or may not need to do this. I might be forgetting something but just make sure that the tranny is free to move and that the motor can move down as well.





11. Now you can wiggle out the tranny. Slowly move both the Motor and the transmission down using the jacks. You may need to SLIGHTLY pry it just to get it loose. It should come out relatively easily. Be carefull not to just drop the tranny and not the motor because the Input shaft is in the motor still so you don't want to break anything! The tranny is not too heavy so you can help carry it down so that it doesnt fall. Here are some miscellaneous pictures.









^And that's my tranny! She is dirt as hell which shouldn't be but oh well. Muchacha Sucia!:naughty:



^That's my pressure plate. It's only 3 months old...how cute.


11. Now here's the hard part. haha no not hard but very involved and you must be organized because we are taking apart the tranny. I HIGHLY RECOMMEND HAVING THE FSM HANDY.



^thats my tranny, she's not very pretty.





^that's Norm again, neither is he. haha jk. As you can see, he's removing the 12mm transmission casing bolts. There are about 10 of them. Of coarse we were referring to the FSM so we knew to remove the case cover before the transmission casing, but we decided to do it backwards; which is the next step.

12. Now you have to remove the case cover.



Remove the mainshaft bearing snap-ring. We didn't have the right tool, but we made due with what we had. I recommend have the snap-ring pliers. After you take off the snap ring, you can remove the transmission case. Make sure to remove it at an angle so that you clear the 5th shift fork.





^Transmission case removed. ready to remove gear stacks!

12. Next remove the 'fork shaft' and the 'reverse idler gear spacer'.





^the reverse idler gear is the one that kinda crooked it the picture. there's a spacer on top of it.

13. Now remove the 'shift forks'. first remove the 5th shift fork which is the on on the top, next remove the 3rd & 4th shift fork, then remove the 1st & 2nd shift fork.
*Be careful when removing the 3/4 and 5 forks because they have 2 'shifter caps' that act like bearings on the control bracket. These are small but have big job*





^removing the 5th shifter fork.



^3rd & 4th shifter fork.



^this is one of two shifter caps. remember don't loose these.

14. Now remove the control bracket and 1st&2nd shifter fork. The bracket is held on by 3 10mm bolts.



15. Once all the forks are removed and the control bracket is removed, you can unbolt the input shaft retainer bracket. There are 3 12mm bolts(it's the triangle shaped bracket). I don't have good pics of removing it but you'll find it.


16. After the bracket is loose, you can remove the input shaft and bearing retainer, mainshaft and the reverse idler gear. I found it easier to remove the two gear stacks at the same time since they are kinda meshed together. Make sure to draw them out straight so you don't damage the oil drain on the clutch housing. With the two gear stacks removed, the reverse idler gear will slide right out.




^both main and input gear stacks. In this picture, the input shaft is on the right and the mainshaft is on the left. On the very left is the Final drive where the lsd(given you have lsd) is located. we won't be messing with any of this.

When you pull out the input shaft, the 'input shaft bearing' which is what we are replacing is on the bottom. It has a spacer and a snap ring on the spline side.



^Input shaft bearing removing the spacer and the snap ring.


17. NOW you are really set, to replace the bearing you will either need a puller or you can do what i did go to your local winchester and have them pull out the old one and put in the new one. If you buy a puller, you need to make sure that it is long enough to reach the bearing, you will need at least a 4" puller. I don't have pictures of them pulling it and putting the new one but you'l figure it out.





^The new bearing! nice and clean. you can see how freely the new one moves and how little play it has. Now it's time to put everything back together. I will say, this was the hardest part by-far. I ended up only replacing the input shaft bearing and not the output or mainshaft bearing. My mainshaft bearing was in good condition but it was mosty because I couldn't find parts store that carried the mainshaft bearing.
 
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#7 ·
Update! Finished the car yesterday and everything is good so far. Almost done with the write-up, just need to finish reassembly. This was a hell of a crazy project!
 
#9 ·
^thanks juan! im proud of myself right now, just took the car for another test drive and got worried because I started hearing a similar noise but I topped off the fluid and drove it and it feels really good. No noises! I will update as time goes on. thanks gnet!
 
#14 ·
wow looks like an enormous puzzle good job on the tranny


mods can we get a sticky???
 
#17 ·
You guys rock, awesome !
 
#23 ·
Ok so back on topic. I have currently took apart the transmission to change the input shaft bearing and change seal. I'm doing it on my 01 which has an LSD. you have to pull out an extra 2 snap rings a 6 mil bolt to get to the reverse idler and open the side case to remove the reverse idler gear before spliting the case.

also there are 3 rods for the shift forks and about 6 , 2piece retaining pins that hold everthing together and a few more snap rings.(not fun) ok so now i'm at the input shaft seal and bearing. by the looks of my bearing it is completely shot. so after i pull out the seal i notice a hole thats pretty clean/like its suppose to be there about 3mm diameter that leads to where the throw out bearing sits. I don't know what to do? is the housing shot or what guys?
 
#24 ·
Ok so everything is back together, pressed in/out new bearing (good thing i had a shop press and the right tools here) and replaced new seal after cleaning up the lip a bit with a dremmel. checked all components of the tranny and everything checked out good, was thinking of doing the main bearing while i'm here but there's no part at any nissan in the country(2weeks for deliver)so ef that, cleaned out the internals with a magnet and rag then put everything back together (wat a b*tch but everything all in). I'm hoping that hole in the case was just a oil tunnel for lubing up the throw out bearing. power washed the whole tranny and where it bolts up with engine(covered starter and throttle body. Now i'm just about to put everything back on. i'm a pray to the G20 gods that this works. ohh and yeah i changed out the input shaft seal that was leaking and changed out the rear main seal. going to throw on my JWT pressure plate and organic clutch disc. machined the flywheel and good to go.

post again later

oh and say a prayer for me guys
 
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