Clutch / Gearbox Issue - Advice please

[vf2ss]

Yesterday I accelerated WOT in 1st to 2nd (both to redline), then in 3rd eased up, put it in neutral and coasted about 1000-1500ft to the light (did not downshift). At this point there was nothing abnormal, no grinding (neither heard nor felt), no mis-shifts, and nothing seemed out of the ordinary.

Once at the light, however, I realized it did not want to go into 1st. Was able to get it into 2nd and just babied it home a mile from that intersection. It seemed to drive normal making way through residential without ever completely stopping until home and clutch pedal weight/effort all seem normal. Back in the garage w/clutch depressed it does not want to go into 1st or R but can get it into 2nd and 3rd but requires some effort (did not try 4 or 5). When the car is off, and whether the clutch is depressed or not, the gears go from 1 to 5 very easily but will not go into R (have not driven since).

Eager to hear Primer's thoughts on this... any help appreciated!

Relevant History: '92 with 62k on it. At 52k I ordered an SOS built 5-spd JDM short-gear trans w/NSX-R final drive and new SOS Sport 275 clutch+flywheel all installed at local Acura dealership. Also had clutch master+slave cylinders, lines, o-rings, hoses, reservoir all replaced at 58k (@same place). It is naturally aspirated w/following mods (if that's a factor): I/H/E, Prospeed RDX Inj+CAI, chipped & tuned, ATI super damper (produces 258HP@201lb-ft SAE adjust@5100ft elevation) thanks

 

[docjohn]

I popped a clutch plate spring on a powergrip clutch and had issues like yours....

 

[Old Guy]

Listen to the Doc!

Given the symptoms, I would check for a dragging clutch

 

[nigel]

Clutch problem

What year ? 5 or 6 speed ? XMSN snap ring range ? Drain the XMSN. Inspect the fluid, magnet, and look for metallic bits. Smell fluid for burnt clutch. If nothing obvious , FLUSH, with new, proper fluid and re-fill. Report back.

Cheers

 

[Old Guy]

What year ? 5 or 6 speed ? XMSN snap ring range ?
Cheers

I assumed that the

SOS built 5-spd JDM short-gear trans

would have addressed any snap ring issues.

 

[Jerry@Mobile]

Check your clutch master and slave for fluid loss and or leaks. Hope that's all it is. Jerry

 

[vf2ss]

Thanks for all the feedback.

Yes, I failed to mention that one of the first things I did was check for leaks out of the firewall in the footwell as well as fluid levels in the reservoir and everything seems all good. After reading around some, it seems that a popped clutch plate spring and/or dragging clutch matches some of the symptoms...saw what happened to MexiRicer's as well. Will keep everyone posted.

 

[vf2ss]

Hey everyone, just a followup the issue is still not resolved.

So far, the NSX tech@dealership and Chris@SOS do not see a smoking gun.

Here's what's been done/uncovered and crossed off the list so far after disassembly:

• Lots of heat checking on flywheel and pressure plate (excessive for 10k)
• Master cylinder was replaced and adjusted and the problem persisted
• Master/slave hydraulics confirmed working properly
• Bearing not getting caught up in snout of trans
• Disk is sliding on properly lubricated trans shaft
• Clutch plate springs intact
• Compressed width of disc (using soft aluminum jaws) - 8.51mm

A question SOS had was does the problem go away when you turn off the engine? The tech said w/engine off and stepping on the clutch it would only go into 2nd, 3rd, & 4th with normal effort and 1st, 5th and R were much more difficult. After spending some time on it either pushing (on 1st or 5th) or pulling (on R) it would eventually move right on in and then it would operate with normal effort similar to 2,3 & 4 and without needing to depress the clutch pedal.

I also met up with a few local Primers and they thought: try a new fork, new throwout bearing, new pilot bushing, and/or do damper delete. Everyone so far seems to agree that the overarching issue here is the clutch is not releasing all the way when pressing the clutch pedal down. Still waiting to hear back more from Chris.

Any other thoughts/ideas?

Fly wheel:

Clutch disc (front/back):

Pressure plate (outside/inside):

Close-up Pressure plate fingers:

Fork (does it look off?):

Throwout bearing:

 

[Old Guy]

Indeed things appear to have gotten hot. Anybody behind the car must have been treated to the aroma of burnt clutch toast.

Without speculating on the original cause of the toasted clutch, in terms of the current problem have the flywheel and pressure plate been checked for flatness? Perhaps warp is a better term than flatness because of the now obvious non flatness due to surface damage.

 

[Big McLargeHuge]

The fork should probably be replaced. You can see big grooves worn into the two ends that touch the release bearing, a new one should be smooth & rounded. I don't think that would contribute to clutch dragging though, presumably the slave piston would travel the same distance with a new vs. worn fork and therefore pulls the release bearing the same amount. Still good to replace though. I don't see how a pilot or release bearing would cause dragging unless they were super busted which yours aren't. I'd definitely get that flywheel and pressure plate measured & reworked thoroughly before reusing them, or consider replacement.

I've read that getting rid of the clutch damper might help, or rather for example, if you install an NSX-R "short-throw" clutch pedal which reduces the total pedal travel (therefore the amount the release bearing pulls on the pressure plate/clutch discs), you need a damperless clutch line to gain back the lost travel. The diaphragm in the stock clutch damper absorbs some of the hydraulic pressure, so you might see if installing a damper delete or a full stainless clutch line straight from master->slave helps properly disengage the clutch.

Hopefully the Acura dealer adjusted your clutch pedal free-play after they installed everything, and re-checked it again after the 100 mile break-in (which I doubt happened). Science of Speed's included manual with the Sport 275 was explicit about checking and re-checking it after the install. Something in me says it was installer or manufacturer error. Where are the alignment markings for the flywheel & pressure plate? They were big obvious orange lines when I installed mine but I don't see any on your kit. Were the flywheel & pressure plate bolts tightened in the proper sequence and to the proper torque?

FWIW, I also just installed the 275 along with short gears & the 4.23, and also have the NSX-R short clutch pedal and damperless clutch line and everything works so far but only ~1500 miles in.

 

[vf2ss]

The fork should probably be replaced. You can see big grooves worn into the two ends that touch the release bearing, a new one should be smooth & rounded. I don't think that would contribute to clutch dragging though, presumably the slave piston would travel the same distance with a new vs. worn fork and therefore pulls the release bearing the same amount. Still good to replace though. I don't see how a pilot or release bearing would cause dragging unless they were super busted which yours aren't. I'd definitely get that flywheel and pressure plate measured & reworked thoroughly before reusing them, or consider replacement.

Thanks for pointing that out... did not know that the ends of the fork should be smooth and rounded and although it's likely not the culprit, will be getting a new one and noted on the rest of your comment.

I've read that getting rid of the clutch damper might help, or rather for example, if you install an NSX-R "short-throw" clutch pedal which reduces the total pedal travel (therefore the amount the release bearing pulls on the pressure plate/clutch discs), you need a damperless clutch line to gain back the lost travel. The diaphragm in the stock clutch damper absorbs some of the hydraulic pressure, so you might see if installing a damper delete or a full stainless clutch line straight from master->slave helps properly disengage the clutch.

I didn't know the NSX-R short throw clutch pedal is compatible with LHD...it fit? I see your point if installed you'll need to for sure install a damper delete or full stainless clutch line from master/slave. The NSX-R has a proprietary damperless clutch joint but it's my understanding that it is not compatible with LHD, is that what you encountered?

Where are the alignment markings for the flywheel & pressure plate? They were big obvious orange lines when I installed mine but I don't see any on your kit.

Would you happen to have a pic of this by chance?

FWIW, I also just installed the 275 along with short gears & the 4.23, and also have the NSX-R short clutch pedal and damperless clutch line and everything works so far but only ~1500 miles in.

Great setup and a blast to drive I bet!

 

[Big McLargeHuge]

My car is RHD so that's how I was able to use the NSX-R clutch pedal, sorry for not specifying that first. I'm not aware of a short factory pedal that fits a LHD car but have seen some FB posts where people modified or drilled their pedal to get a different leverage point on the master cyl pushrod and achieve a similar result.

SoS also has a damper delete offering, I bought the kit with my clutch but only ended up using the slave cylinder adapter (O-ring nipple X 1/8" FNPT, slave hose is 3AN) since I installed a long SS braided hose from master to slave and had no need for the damper delete block or slave hose. I'm not sure if the kit without their adapter is useful to anyone since I heard they don't sell it separately.

I don't think the NSX-R damperless joint would be handed, the factory damper mounting block should be in the same place in both LHD/RHD cars so I assume you could use the NSX-R joint if you wanted, but might as well just go with SoS. I don't miss the clutch damper in the slightest.

Here's a pic of the alignment marks on top. Your pressure plate looks like it has an orange splotch on the lower left so the paint mark might've been hit with solvent cleaner during install.


Personally I'd get the PP/flywheel checked or replaced, install a damperless joint or hose, and check the pedal free-play at least before driving again. Without something obvious to fix it'd suck to put everything back together and have the same problem.

The shifting behavior you described sounds odd. With the engine off, you should be able to shift into all gears with the clutch either in or out, though with the clutch in (disengaged) it should be slightly easier the first time since the synchros aren't working against the resistance of the input shaft to rotate when engaged to the engine/flywheel. Once you've engaged all the gears sitting still, it will be extremely easy to engage any of them again since the synchros & gear teeth are already lined up perfectly.

The same also applies if the engine is running and you're standing still, with the clutch in it should be easy to engage all gears and even more so if they've already been engaged with the clutch still in. As soon as you let the clutch out in neutral, the input shaft spins again and misaligns the synchros & gears so the shift effort resets. Of course, if the clutch is dragging, it will never be easy to engage gears, but some might be easier than others (1st offers the most resistance to an idling engine so presumably would be harder to engage with a dragging clutch).

So why are 1st/5th/R so hard to engage at first but then become normal even with the engine off? I would check the adjustment of the shift cables, if they're too short or long then it will be difficult to engage the gear properly. 1/5 are the same direction on the shift lever on the bottom of the trans, so if that cable is the wrong length it might be a contributing factor.

An easy test would be to disconnect the cables from the bottom of the trans and shift the gears directly by hand, with the trans in the normal horizontal position is should be fairly easy. If you notice the same difficult behavior in 1/5/R then, that to me would point to something internal to the transmission, there are no other factors at play. Same idea as above, once a gear is engaged, disengaged, and engaged again, the effort should noticeably decrease if the input shaft was not moved. 1/5/R also have their own separate shift forks so unlikely to be related to a bent fork, though 5th is known to be a weak link.

 

[vf2ss]

...have the flywheel and pressure plate been checked for flatness? Perhaps warp is a better term than flatness because of the now obvious non flatness due to surface damage.

Not yet but working on it, thanks

My car is RHD so that's how I was able to use the NSX-R clutch pedal, sorry for not specifying that first. I'm not aware of a short factory pedal that fits a LHD car but have seen some FB posts where people modified or drilled their pedal to get a different leverage point on the master cyl pushrod and achieve a similar result.

SoS also has a damper delete offering, I bought the kit with my clutch but only ended up using the slave cylinder adapter (O-ring nipple X 1/8" FNPT, slave hose is 3AN) since I installed a long SS braided hose from master to slave and had no need for the damper delete block or slave hose. I'm not sure if the kit without their adapter is useful to anyone since I heard they don't sell it separately.

I don't think the NSX-R damperless joint would be handed, the factory damper mounting block should be in the same place in both LHD/RHD cars so I assume you could use the NSX-R joint if you wanted, but might as well just go with SoS. I don't miss the clutch damper in the slightest.

Here's a pic of the alignment marks on top. Your pressure plate looks like it has an orange splotch on the lower left so the paint mark might've been hit with solvent cleaner during install.

Personally I'd get the PP/flywheel checked or replaced, install a damperless joint or hose, and check the pedal free-play at least before driving again. Without something obvious to fix it'd suck to put everything back together and have the same problem.

The shifting behavior you described sounds odd. With the engine off, you should be able to shift into all gears with the clutch either in or out, though with the clutch in (disengaged) it should be slightly easier the first time since the synchros aren't working against the resistance of the input shaft to rotate when engaged to the engine/flywheel. Once you've engaged all the gears sitting still, it will be extremely easy to engage any of them again since the synchros & gear teeth are already lined up perfectly.

The same also applies if the engine is running and you're standing still, with the clutch in it should be easy to engage all gears and even more so if they've already been engaged with the clutch still in. As soon as you let the clutch out in neutral, the input shaft spins again and misaligns the synchros & gears so the shift effort resets. Of course, if the clutch is dragging, it will never be easy to engage gears, but some might be easier than others (1st offers the most resistance to an idling engine so presumably would be harder to engage with a dragging clutch).

So why are 1st/5th/R so hard to engage at first but then become normal even with the engine off? I would check the adjustment of the shift cables, if they're too short or long then it will be difficult to engage the gear properly. 1/5 are the same direction on the shift lever on the bottom of the trans, so if that cable is the wrong length it might be a contributing factor.

An easy test would be to disconnect the cables from the bottom of the trans and shift the gears directly by hand, with the trans in the normal horizontal position is should be fairly easy. If you notice the same difficult behavior in 1/5/R then, that to me would point to something internal to the transmission, there are no other factors at play. Same idea as above, once a gear is engaged, disengaged, and engaged again, the effort should noticeably decrease if the input shaft was not moved. 1/5/R also have their own separate shift forks so unlikely to be related to a bent fork, though 5th is known to be a weak link.

Thank you for this info...very helpful!

P.S. Now that you mentioned it I do see remnants of the orange splotch on the pressure plate and corresponding alignment peg on flywheel.

 

[13th]

Hi everyone!
I had a pleasure to drive my NSX for 10 mins after buying it)) and...had almost the same issue after 2grs to redline. Then smelled clutch. The difference is I cannot engage ANY gear while car is running +:

1. noticed if I start i.e. with the 1st or 2nd gear engaged and release brakes without even releasing clutch pedal the car goes. feels like I have automatic transmission which I dont))
2. while starting and riding this way I can shift gears (more or less), easier up than down. if I stop - I have to turn car off and repeat 1st step.
3. Pulling is good, doesn't fell like smth is wrong with clutch disc.
4. Clutch fluid is leveled.

p.s.: 1997 NSX, 6speed, SOS supercharged, oem clutch, SOS Short shifter.
p.p.s.: my NSX is the only one in my country so help would be really appreciated!

 

[Old Guy]

I am 'smelling' a clutch that is not releasing.

You say clutch fluid is leveled. I am not sure what that really means. What is important is that the clutch fluid level has not changed. Inspect inside the car in the footwell. If the MC develops an external leak it most commonly leaks into the interior around the hole for the clutch pedal push rod.

I don't know how air would get into the clutch system; but, as a first step you might want to try bleeding the clutch hydraulics to make sure that there is no air in the system which is causing a non release problem. It is probably not your problem; but, it is one of the easier things to rule out first. Everything else cost more and is harder to do.

Its a hassle; but, as a first step you can jack up the back of the car and get under there to inspect where the slave cylinder engages with the clutch fork (you will have to pull back the rubber boot that covers the fork - slave interface). Honda does not provide a spec for acceptable slave travel. You will have to have someone depress the clutch pedal while you watch the slave cylinder and then you make a judgement as to whether the travel is sufficient because the factory service manual does not provide a specification for slave travel. If the travel is minimal you may have a clutch hydraulic failure. The MC can fail with out losing fluid. The seals on the MC piston can fail allowing fluid to escape back into the reservoir with a failure to generate hydraulic pressure.

The other clutch release test is a simple push test With the transmission in neutral, parking brake off and ignition off push the car forward. This will give you a sense of what the normal resistance to movement feels like (or if there is some other problem if it doesn't move). Next, with the transmission shifted into 5th or 6th, parking brake off and the ignition off, use a pedal jack or have someone in the car depress the clutch pedal to the floor. Now try and push the car forward. If the car moves forward relatively easily like it does in neutral then the clutch is releasing. If the car can't be pushed forward or is really hard to push forward and you can hear that the engine is turning the clutch is not releasing.

If the clutch is not releasing, the first check is the hydraulics and clutch slave cylinder movement. If the hydraulics are fine, then its a deep dive into the clutch itself. If you got the clutch hot enough that you could smell it you may have distorted the clutch disc sufficiently to prevent it from getting a clean release.

 

[docjohn]

now we can be liking all the techno helpers ....

 

[13th]

I am 'smelling' a clutch that is not releasing.

You say clutch fluid is leveled. I am not sure what that really means. What is important is that the clutch fluid level has not changed. Inspect inside the car in the footwell. If the MC develops an external leak it most commonly leaks into the interior around the hole for the clutch pedal push rod.

I don't know how air would get into the clutch system; but, as a first step you might want to try bleeding the clutch hydraulics to make sure that there is no air in the system which is causing a non release problem. It is probably not your problem; but, it is one of the easier things to rule out first. Everything else cost more and is harder to do.

Its a hassle; but, as a first step you can jack up the back of the car and get under there to inspect where the slave cylinder engages with the clutch fork (you will have to pull back the rubber boot that covers the fork - slave interface). Honda does not provide a spec for acceptable slave travel. You will have to have someone depress the clutch pedal while you watch the slave cylinder and then you make a judgement as to whether the travel is sufficient because the factory service manual does not provide a specification for slave travel. If the travel is minimal you may have a clutch hydraulic failure. The MC can fail with out losing fluid. The seals on the MC piston can fail allowing fluid to escape back into the reservoir with a failure to generate hydraulic pressure.

The other clutch release test is a simple push test With the transmission in neutral, parking brake off and ignition off push the car forward. This will give you a sense of what the normal resistance to movement feels like (or if there is some other problem if it doesn't move). Next, with the transmission shifted into 5th or 6th, parking brake off and the ignition off, use a pedal jack or have someone in the car depress the clutch pedal to the floor. Now try and push the car forward. If the car moves forward relatively easily like it does in neutral then the clutch is releasing. If the car can't be pushed forward or is really hard to push forward and you can hear that the engine is turning the clutch is not releasing.

If the clutch is not releasing, the first check is the hydraulics and clutch slave cylinder movement. If the hydraulics are fine, then its a deep dive into the clutch itself. If you got the clutch hot enough that you could smell it you may have distorted the clutch disc sufficiently to prevent it from getting a clean release.

Thank you!
"leveled" I mean it is "MAX" mark, sorry English isn't my native language)

I'll try it all and be back

an update:
first, smth green in in clutch tank, for sure all to be cleaned and changed

second, as you said I started from footwell and found a leakage I think.

third, touched it) its more "water" than "oil"


What to do next? is there a thread?
Thanks!

 

[Old Guy]

That green - brown stuff in the bottom of the clutch reservoir is normal. It forms after about 2 years when the clutch fluid is exposed to air, particularly if the humidity levels are high.

Hard to diagnose the shiny stuff on the back of the rubber boot at the clutch pedal. It would be fairly common to pack the inside of the rubber boot with some grease so that the rod slides through the boot fairly easily / with no noise. Brake fluid is much thinner in viscosity than oil. What is on the tip of your finger almost looks like the grease which has been diluted by brake fluid suggesting a leak from the back of the master cylinder.

Did you try the push the car test to see if the clutch is releasing? If you have confirmed that the clutch is not releasing, given what looks like leakage at the back to the master cylinder I would be inclined to try replacement of the master cylinder to see if that fixes the problem.

 

[MJK]

That clutch master is on borrowed time, at best. I change the slave and the Flexi line at the same time, which I just did for the second time since new last weekend. Parts and prices from my 9/1/22 Amayama order are below - used on a USDM 1994.

Honda 46970-SL0-A02 - HOSE, CLUTCH	1	32.84
Honda 46930-SL0-003 - CYLINDER ASSY., SLAVE	1	56.98
Honda 46920-SL0-A01 - CYLINDER ASSY., CLUTCH MASTER	1	74.92

YMMV but I'd start there. You have to be a bit of a contortionist (or take the seat out), but is an afternoon DIY project. There are plenty of good DIY guides on this. Here is one. Some tricks I think are worth repeating are:

1 - fishing the pin back into the pedal/master pushrod union. I use dental floss tied through a hole in the pin to pull it through.
2 - installing the slave is a PITA if you don't compress it and use the plastic cap to keep it compressed while installing. Install first and THEN pop the cap and attach the line. Doing it the other way around is a wrestling match you will not enjoy.
3 - I'd have a couple liters of fluid to flush through to make sure you get ALL the air out. DO NOT let the reservoir go dry. On my car, that means 7 pumps and then refill. A speedbleeder makes it a 1 man job.

 

[Honcho]

Agree. If the clutch master is in that bad shape, the slave isn't far behind. You should replace both.

 

[vf2ss]

Yes, definitely consider doing both as mentioned. Fwiw going back to my post 2yrs ago, the general consensus ended up being the fork (as Big McLargeHuge pointed out regarding the groves). But in not wanting to chance any more downtime I opted to get a new oem clutch w/new fork instead of keeping the Sport 275. Since then everything's been perfect! This reminds me, if anyone wants a great deal on a used Sport 275 w/only 10k on it (measured 8.51mm in a compressed vice using soft aluminum jaws) just let me know ... I'll be posting in FS one day soon.

In reading Honcho's Type S thread I do wish I would have gone with a Fidanza lt wt flywheel w/oem clutch but oh well. Another observation having switched back is getting into reverse is now way easier compared to the Sport 275 and the subtle gear lash whirring in the R&P / in the differential gears that LarryB has mentioned on here in the past with my short gears + R final drive is so much quieter if not gone w/oem clutch.

 

[13th]

Thanks guys!

So I've tried to move the car on neutral and then on 5th gear. It moves, but I would say with +25% effort than in neutral.
Ordered parts a week ago...but it seems that order was cancelled. Will try again.

 

[giu3000]

hey everyone, how are you. I hope you guys have solved it because I am in a drama with it.

I did replace a clutch in a honda nsx that arrived at the shop towed without a clutch (the pedal was on the floor).

All the components have been replaced ( flywheel, pressure plates, clutch disc, bearing, slave and master cylinders), and the hydraulic system has been flushed and also bleeds properly however, the car does not disengage the clutch and I can not put reverse or 5 gear.

Already disassembly the box 3 times and I can not find the problem, Does anyone has a pass for it?

 

[esqu1re]

hey everyone, how are you. I hope you guys have solved it because I am in a drama with it.

I did replace a clutch in a honda nsx that arrived at the shop towed without a clutch (the pedal was on the floor).

All the components have been replaced ( flywheel, pressure plates, clutch disc, bearing, slave and master cylinders), and the hydraulic system has been flushed and also bleeds properly however, the car does not disengage the clutch and I can not put reverse or 5 gear.

Already disassembly the box 3 times and I can not find the problem, Does anyone has a pass for it?

I believe the OP said he replaced the fork and clutch with a stock one and it solved his problem.

 

[giu3000]

I believe the OP said he replaced the fork and clutch with a stock one and it solved his problem.

with more re search on the forum, I read about initialization of the clutch but so far, I can not more get access to the manual where explain this procedure