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***STICKY*** - Timing Belt & Transmission Rebuild Thread (2005 NSX 6MT)

As for the 2nd gear and synchro same thought applies; the synchro has to seat into the gear.



Then install gears 3 to 6. I had to make a long tool out of PVC to help push the gears on. It didn’t take too much effort.

First up was to put something soft under the press because lesson learned…..



Countershaft now ready for the nerve racking part.

The service manual says that after 6th gear is installed to squish the entire gear set down using 2600 kg of force. I’m really happy the press I borrowed has a gauge on it.

My first issue was 6th gear outer diameter protrudes past the shaft area. I didn’t want to put 2600 kgs of force onto the outer ring of the gear. I used the c-clip out of the intermediate shaft and an old washer I had laying around to make a spacer. It worked perfect.




Ends up being a perfect gap:
Then grab all the spacers you need and start squishing:

I gave it an extra pump after I took the picture to bring it up to 2.6k kgs.

After that is done press in the needle and ball bearings and then ready for the end nut.

I used the 2 wood method as the manual states but found it didn’t work very well. I read that a few people were able to hold the shaft by hand and have a buddy torque the bolt but I don’t believe that for a second. Either your friend is a gorilla or your torque wrench is broken!!! 83 ft-lbs is more than the wheel torque. I had to clamp the living piss out of the shaft but even then it spun on me. What worked for me was when the diff gear dug into the wood and held itself; only then was I able to do the 83 ft-lbs then back to 0 then back to 83 ft-lbs. But once that was done the countershaft is now good to go.



Next up is the mainshaft.

New parts. All 4 synchros ($$$), both new shift hubs, and all new bearings.



The very first bearing for 3rd gear is again some cobbled together piece. It was new out of the bag. Out of the 7-8 bearings I bought only 2 were like this so something definitely isn’t right here from Honda. Not worth the effort to return.

The new one is on the left and is much thinner but again, if the rollers are the same size not too big a deal. It’s the soldered together that gets me.


3rd gear and that synchro go on with no effort:


The service manual specifically states to press the shift hub on without lube…but then lube up the shift ring when putting it on.


Original on the right and new one on the left. This is 3rd and 4th gear so doesn’t look too bad.

Shift hub getting pressed on:

Can see the outer ring taking its bath before being put on:
Then it’s the same nerve racking part where you squish everything to 2000 kgs (not 2600 kgs this time). I assume the lesser force is because there are 4 synchros????


None of my sockets would fit however the diff carrier bearing inner race worked perfectly:


Said 2k kgs. I don’t know how this could be accomplished without a gauge. The press went “hard” for a pump or 2 and only after 3 or 4 more pumps did the gauge start to move. After that between 500-2000 kgs was a mere ¾ to 1 full pump. There is no way you can “eyeball” this.

After that throw 6th gear and the outer bearing on and main shaft is done.

Current state of affairs. Next up is the tranny case halves and the dreaded main shaft shim.
Nice work! If I have to open my transmission for a 3rd time I'll buy a press, the pressure gauge is pretty cool. I'm amazed you were able to get the countershaft bolt torqued just by clamping the smooth bottom part of the countershaft. The 5spd torque spec is 112lbft so I clamped the teeth part between two pieces of 2x4s and even that took a lot of cranking down on the vice to keep it from moving on me.

In the past, I've just used a hammer to tap the shaft parts back together. I wonder if the 6spd has tighter interference fit between components?
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[MENTION=33247]MotorMouth93[/MENTION] : I found exactly what you found that the clamping force wasn't enough on the smooth part. My wood was angled a little bit so it only held 83 ft-lbs when the pinion gear teeth dug into the wood; otherwise it was a no go. It looks like they updated the specs for the 6 speeds as I see 113 Nm (aka 83 ft-lbs). Maybe they had their units wrong originally.

When I measured the OD of my shaft back over Christmas all of my readings were slightly above the standard values in the service manual. So I suspect that is what caused me to have to use the press for some of those gears. The pressing effort was minimal I would say and the PVC wasn't strained at all.

Next up was the mainshaft. I bought an aftermarket tool to check the mainshaft thrust clearance but it’s very similar to the OEM tool as per the diagrams.


Throw the main shaft bearing in (without the spring washer) and then check the clearance. Mine came in at 0.152 mm.



Then do something similar to other side of the shaft. I had to get creative with supporting the case. Once the shaft was in there-there was enough weight to keep it somewhat stable.


My reading ended up being very thick (2.5 mm). So way way above any thickness of a shim. I stacked many shims together but then also found a washer that was similar in size and both “measurements” came back the same at 2.5 mm ish.



Now time to do some maths (my favourite). From my measurements I ended up needing a shim between 1.582 mm and 1.652 mm. So since I bought a million of them I ended up going with 0.84 and 0.78 to give me smack dab in the middle @ 1.62 mm.




Once the shim thickness is known press in the clutch side bearing. On my shaft the writing on the bearing was facing the gears (not the clutch) so I installed it the same way. I doubt it makes a difference though.



I bought a new spring washer.

Drop the shaft in

Then bolt the million bolts back together. I followed the direction and torqued them all in stages, in the correct order up to 33 ft-lbs.

Then start setting up the gauge


….and of course….reading is way way off. Spec is 0.006 to 0.008 inches. I came in at 0.011 inches. The maths have failed me (not like a do that for a living….FFS..I blame the formula �� ).

I will comment on one thing that is mentioned in the service manual. They state that do not turn the shaft tool more than 60 degrees after the dial gauge stops moving. I found this strange as why would any reasonable person keep cranking the bolt when it’s already tight. After I had the dial gauge up I now know what they mean. The speculate that the spring washer DOES NOT FULLY COMPRESS. In the photo below my reading “settled out” to 0.011. I gave the tool bolt another little turn and the dial gauge went to 0.012-0.013 briefly and then re-settled down to 0.011. Meaning the spring washer is compressing and then forcing a certain amount of pressure back onto the mainshaft. So what they say in the manual to not go more than 60 degrees means based on the reading of the dial gauge. This makes sense to me in my very very little and limited experience. Why would they put a spring washer in there if all it was meant to do was flatten to a shim basically. I believe it’s the spring washer that absorbs some of the shock in the system as the dynamic forces are always greater in magnitude than static forces.

Someone please correct me if I’m wrong in my thoughts above!!!


…so I unbolted the million bolts, re-did the maths and now came up that I need either 1.02 + 0.69 = 1.71 mm or 1.02 + 0.72 = 1.74 mm shim. I opted for the smaller one as that’s in the middle of what I would need.


Bolt everything together and re-jig the whole thing. Take the measurement and………reading is still off (of course). It’s better but I still came in at 0.0085. I younger me would probably call it good but nope…fussy me didn’t accept.


So this time I abandoned the maths. I put exactly what Honda had in there originally. 1.02 and 0.75 to give me 1.77. Set it all up again and bingo…bang on the money now at 0.0065. Sometimes it’s better not to use your brain and try to question what Honda had.


That adjustment took way longer than I care to admit but at least it’s done.

The thrust clearance was fairly linear this time around.
Now onto the diff preload. This time I learned from my mistakes and checked what Honda had in there to begin with.

Some new parts:



I used the old inner race to press in the new one. If you look closely the bearing cage sticks up higher than the inner race so you can’t push from the outside.



For the outer races I heat gun’d the area for a little while and they popped in with little fuss. Just the lightest of taps with the hammer.



Same thing for the tranny case side:




Then drop the diff into the casing. Make sure to use plenty of lube both in the front and in the back of the rollers.

There was uncertainty on which method of checking the preload the various techniques gave. The actual tool, the “bolt” method, and the rubber plug method. I made 3 passes, in both directions, with each of the tools and every one of them gave me between 23-25 inch-lbs (not ft-lbs) of torque; the spec is 17 to 26 inch-lbs. So use whichever method you have access to! The one concerning thing on my diff was right at the start of the pull it was very lumpy/jumpy until I started putting consistent torque on the tool. This shouldn’t happen if the rollers are all squished evenly I’m thinking. That’s about the only thing that has me worried thus far.



Long story short I’m happy that the shim that was already in there ended up working. Big waste of money on all the spare shims I bought but that’s okey. I can post them for sale and eventually sell them when some money shifts their 6 speed tranny in a decade or 2.
Next up was the shift fork. For the 5 of you that have been following along my earlier 3rd/4th shift fork gave readings that were out of spec. So I gambled on a new one even though it was way more expensive than it should have been (more than freaking 2nd gear on its own). I’m happy I got it though. In the picture below the old one is on the right and the new one on the left. It almost looks like my original is missing a piece out of it. Only thing I can think of is factory defect since how does that even happen…resting your hand on the shifter while driving would wear out the shift sleeve but not the fork.



New one is bang on for measurement


I bought new spring clips and spring washers. Happy I did as the original spring washer looked flatter than the new one.

What a pain these little barrel springs were.


Offset the gap. I don’t know how you would get them in there without marking the edges.

After that lube up any slide-y bits and onto the next.

I like how the new seals come pre-greased now.




I read some recent stories that people had issues with their throwout bearings. I didn’t want to chance anything so ended up buying a new bearing guide. Probably a waste of money.




Put the passenger side axle seal in. Use the old one to hammer down on instead of the new one.


Then moved onto the countershaft clutch side bearing.



This bearing has a lot of denotations on it for some reason.

This one took way more hammering than I expected. I positioned the oil ports in the same location as the original. Thankfully I had a picture earlier in this thread that helped me �� .


Pull back and check every so often to make sure it’s going on straight.


After that put the retainer on and stake the bolts



Select lever up next. This is the one that goes left to right between the driver and passenger.


New seal

Next up was the oil pump and magnet. I bought a new oil pump arrangement mainly because I had pieces of magnet in my old one. I’m sure it was fine but this was surprisingly low cost so I didn’t want to mess around.





I can also now confirm that the OEM magnets for the 6 speeds only have 1 magnet! I even bought 2 just to make sure it wasn’t a random weird one. So I figured since I already had 2 might as well build a super magnet with both elements. They’re not glued in or anything they’re just held in by their own magnet force.




The clutch case side is now completely finished.
Onto the transmission case. Same thing again with the shift lever (this one moves forwards and backwards selecting the gears).



It passes from the left into the hole with the liner in it.


Coming in from the top in the picture below

New outer seal