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Today at Atelier Kaz - ex-Honda R&D, F1, Indy/CART engineer

CL Hyd System 01

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6 Comments
by
Kaz-kzukNA1
, 15-11-2011 at 10:24 PM (2690 Views)




The owner commented that from time to time, he was having difficulty on selecting gears on downshift only.
He didn’t feel any issues for selecting 1st or Reverse gear from standstill and no issues with upshift.

I suggested the owner that it is very unlikely to be Clutch (CL) Hydraulic (Hyd) System related but the owner wanted to replace it any way as there was a sign of leakage at the Slave Cyl and start from there.

I test drove this NSX several times over the past few years and every time I noticed that the gear shift was somewhat notchy regardless of the GBox temperature or even after replacing the MTF.


May be the word ‘notchy’ is not correct.

It’s more like ‘heavy’ just before selecting the gear and not exactly the same but similar to the feeling when you have installed a brand new shift cable.
You will be amazed how heavy it feels and even regret for a long time until it start feeling smooth after replacing this long pair of cables….
This NSX is at very low mileage and not used regularly so that won’t help….


Any way, before touching anything, wanted to confirm the owner’s comment so took the car on the road.

First thing I noticed was the extra play at the CL pedal resulting in bit too high initial height.
By now, everyone knows that our NSX has quite high CL bite point at the pedal and thus, fairly high initial CL pedal height compared to other sports cars.

It is quite common among the NSX owners in Japan to replace the CL pedal to Type-R spec together with the damperless joint on the CL Hyd system for this particular reason.



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Once it's done, the initial height of the CL pedal will be lowerd and it will be almost at the same height as the Brake pedal like this.




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On this NSX, while the pushrod on the master cyl was not touched (and normally, you should not), it looked like someone removed the CL pedal switch and didn’t put it back to the original position.
There was a little extra play at the beginning of the pedal stroke.

Will be checking the CL pedal height any way after replacing the master cyl.



During the short test driving session, never experienced the downshift issue but once again, I felt moving the shift lever was notchy/heavy.
Neither sudden pop out of the gear nor vibration through the shift lever while applying on/off throttle in 1st and 2nd gears so snap ring seemed to be fine.

Normally, I don’t open or remove the shift cable while replacing the CL Slave Cyl and CL Hose but may need to do so just to see how the cables and the shift linkage are moving inside that white plastic cover.

More to follow.

Kaz
Categories
Clutch Master/Slave Cyl

Comments

  1. paulc's Avatar
    Kaz how easy/difficult is it to change the snap ring.

    Regards

    Paul
  2. Kaz-kzukNA1's Avatar
    The snap ring is on the countershaft bearing recess and it is sitting on the shoulder of the transmission case so obviously, it's a GBox off job.
    If you want to just check it, you can do so by removing the sealing cap with square recess on it at the side of transmission case.

    I’m presuming that you are asking this with the ‘snap ring failure’ issue on very early model NSX in mind.

    If that is the case, then replacing the snap ring won’t fix the issue because there is nothing wrong with it.

    Because it was informed from Honda as ‘Broken Snap Ring’, several people misunderstood the genuine cause of the issue and thought that there was a problem with the snap ring itself.

    The damage to the snap ring was actually caused by the machining issue on the transmission case and thus, you must replace the case.

    Unless you are replacing the Gbox as an assy, replacing the transmission case and re-using the shafts, etc will force you to measure and select the correct thickness of thrust shim so not a quick job unless you already have variety of shims in stock.

    Then, probably the most time consuming process would be putting back the transmission case in place especially with 5MT box.

    Aligning all these shafts to the correct recess on the case side with just two hands…. Not impossible but I won’t do it without the helping hand on 5MT box...
    6MT box is much easier.


     So, as I don’t know the background of your question, I’m not sure whether I answered your question or not but hope you can get some idea from above.

    Kaz
  3. paulc's Avatar
    Kaz thats brilliant many thanks, I have a JDM 1994 model though Sudesh suspects it might be a 1991 model and it has started to jump out of first and second gear, not all the time it seems to depend on how you put the gear stick in, not very technical I know. Once again many thanks for your advice.

    Paul
  4. NSXGB's Avatar
    Paul. If your gearbox number is within this range: J4A4-1003542 through J4A4-1005978, it is within the known snap ring failure. Might be worth checking to hopefully cancel this off your list.

    Info courtesy of NSXPRIME.
  5. Kaz-kzukNA1's Avatar
    JDM doesn’t use J4A4 series Gbox. Different gear ratio.

    Just to be clear.
    The snap ring on any Gbox with similar design may fail for a certain reason.
    I saw it failed on another Honda (I think it was the GBox from Civic) but it’s just so rare.

    Therefore, even your NSX is out of the above ‘snap ring GBox’ range, it could fail but very-very rare and not like the common failure of Main relay.
    On the other hand, even if the GBox is in that range, not all of them will fail.

    Quote Originally Posted by paulc
    ........ I have a JDM 1994 model though Sudesh suspects it might be a 1991 model ...........
    If your NSX is JDM, that's easy for me to tell the model spec. If you open the bonnet and look at the metal plate in front of the radiator, you will see the Japanese character as ' 車台番号 '. This is your JDM Spec VIN.
    You will see lots of numeric digits (i.e. xxx below) after the ' NA1- ' marking and first three digits will tell you the model spec.

    NA1-100xxx Sep/90 ---
    NA1-110xxx Nov/92 (NSX-R) & May/93 (NSX) ---
    NA1-120xxx Feb/94 ---

    Therefore, if you don't see NA1-120 on your metal plate, it's not the 94 spec.

    Quote Originally Posted by paulc
    ...... it has started to jump out of first and second gear, not all the time it seems to depend on how you put the gear stick in, not very technical I know. Once again many thanks for your advice.

    Paul
    Bit worrying comment there....
    Popping out of 1st and 2nd gears is one of the most common phenomena with snap ring failure on our NSX.

    Unlike ordinary cars, our NSX uses helical gears on all of the main and counter gears including the reverse.
    Added to this unique design, the 1st and 2nd main gears are directly cut on the main shaft and thus, the shift folk for 1st and 2nd is on the counter side.
    Therefore, if the snap ring is already damaged, it could push the folk out of the position resulting in this common phenomenon.

    As NSXGB mentioned, it is best to investigate your snap ring.

    It’s easy to check and you can do it without taking the Gbox off the car.

    Kaz
  6. NSXGB's Avatar
    Apologies for the assumption. Great info.