Sticky gearchange

[Lotus Roy]

Hi,

Six months into NSX ownership I am really enjoying Honda motoring, with one proviso.

I have a curious issue with the gearchange. Normally it is a delight, but if I have been cruising in 4th or 5th for a few minutes the gearlever goes sticky and needs a jolt to get it to move. If you then change gear again after a few seconds the change is fine (even into and out of 4th or 5th).

Does anyone recognise this problem or have any ideas on how to cure it?

I was wondering if the clutch is dragging but can't explain why this only affects the change if one hasn't changed gear for a while.
I have read somewhere that the clutch plates need 'setting up' in some way. Could this be the problem?

Hoping for help. :(

Roy

[Pride]

What year, model and mileage is yours Roy???

[lotusolly]

When was your gearbox oil last changed? Surprising how much difference that can make and an easy start point.

Olly

[marknsx]

are you sure its not your Lotus:D

[mutley]

First off I would go for a gear oil change ( I'm getting mine done soon too). I have a similar problem. My gear change is fine when cold, but not good when hot.

Cheers
Jim

[Nick Graves]

Yup - that synchro sticking thing is normally a sign of bad oil.

Crunching in VTEC is as a result of them using engine oil instead of MTF...

[Lotus Roy]

Thanks Guys,

There seems to be a consensus building here. I bought the car from Graham at Plans Performance Motorsport and it had a full service then in July 2015. That included a gearbox oilchange with Honda MTF oil added. We have even tried adding a gearbox oil additive in September, thinking it might be lubrication-linked but nothing changed. I am quite prepared to try another oilchange if it is thought to be valuable. What do you think? the car has done about 2000 miles in my hands.

It is a 1991 model with about 85,000 miles on the clock, was an import from Japan last year and we have reason to believe that it had not had much recent use in Japan before it came over.

My Elan has the sweetest gearchange I know MarkNSX! Not super-light in the Japanese way but very positive and 'mechanical'. But I have to admit the Honda has a better heater!!

Thanks everyone for your help. Any further opinions would be welcome.

Roy

[paulc]

Good luck, an change will not harm it.

Trust me the gear change on my Lotus Esprit is not light and sweet!! I would say it is very mechanical though!!

[Kaz-kzukNA1]

Hi, Roy.
So, your NSX is JDM 91 5MT.

Q1: Any known modifications on the engine as well as inside the gbox such as different spec flywheel, DF, etc?

From your OP, it was not clear whether this issue happens just once or multiple times during your journey.
Q2: After this issue happened, can you repeat the same issue again and consistently?
Q3: If not, when does it happen again? For example, after parking the car for several hours or overnight.

Q4: Does the issue always happen for the first time when you stayed in the 4th or the 5th for a few minutes or randomly happen whenever you stayed in the 4th or the 5th for a few minutes?


For your reference, unlike other cars, the gears inside the NSX gbox is not submerged in the MTF.

NSX gbox relies on the gbox oil pump for the gear lubrication and the oil pump is driven by the final driven gear that is on the DF body.
So, unless you rotate the wheel, the oil pump won’t be rotated and thus, not feeding the MTF to each gears.

The oil pressure generated at the oil pump will go through the oil passage built inside the 5th-Reverse shift shaft, Main shaft, Counter shaft, CL case before splashing the oil to the gears, bearings, DF, drive shaft spline, etc.

This is the reason why it is so important to use soft (bit exaggerated but water like viscosity even at very cold temperature) viscosity MTF but one can hold very strong oil film even at high temperature.

Because of this oil pump mechanism and the narrow oil passage, if your issue is related to the MTF, you will notice big difference in shift feeling before/after the MTF warmed up and when you start driving for the first time after parked the car overnight.


From what you wrote so far, I don’t think your issue is related to the MTF.
In fact, you will notice the issue in other gears and not just getting out of specific gear position.


The best way to test this is to start the engine and start moving the car after 1min (for the summer) or a few minutes (for cold winter) at very slow speed (like below 15mph).
The key is not to warm up the gbox (MTF). By the way, unless you live in sub-zero climate, no need to fully warm up the engine before start driving the NSX.
Focus on the feeling when you select 2nd gear. Try selecting 2nd gear multiple times and remember the feeling.

Now go out for 10 – 15 min normal cruising session.
Your MTF is now warmed up and softened so repeat the above slow speed test.

If you notice significant change in selecting 2nd gear, you may have MTF related issue or using too high viscosity MTF when it's cold.
If using Honda MTF-3, you won’t feel this.
From what you wrote so far, I don't think you will notice big difference on selecting the 2nd gear before/after the MTF warmed up and thus, your issue is not MTF related.

4th and 5th use separated shift fork so selector cable needs to move differently and you seemed to be fine in selecting the gear so for now, I’ll leave the selector and shift cables adjustment.

You seemed to be fine with other gears so I’ll leave the CL Hyd system (CL master/slave/hose). If you have problem disengaging the CL, you will have problem selecting the gear because you can’t reduce the input torque and speed.

For twin disc plates CL on the 5MT and NSX-R/S 6MT, you will need to ‘initialise’ the mid plate guide. If this was not done, you will have big time selecting any gears so this is not related to your issue.


It all depends on the answers to my questions above but if it only happens at exiting the 4th and 5th gears, it sounded like the sleeve over the hub is not sliding out smoothly from 4th and 5th gears
so you may need to open the gbox and inspect each components.
Hope not.....


Kaz

[Lotus Roy]

Hi, Roy.
So, your NSX is JDM 91 5MT.

Q1: Any known modifications on the engine as well as inside the gbox such as different spec flywheel, DF, etc?

From your OP, it was not clear whether this issue happens just once or multiple times during your journey.
Q2: After this issue happened, can you repeat the same issue again and consistently?
Q3: If not, when does it happen again? For example, after parking the car for several hours or overnight.

Q4: Does the issue always happen for the first time when you stayed in the 4th or the 5th for a few minutes or randomly happen whenever you stayed in the 4th or the 5th for a few minutes?


For your reference, unlike other cars, the gears inside the NSX gbox is not submerged in the MTF.

NSX gbox relies on the gbox oil pump for the gear lubrication and the oil pump is driven by the final driven gear that is on the DF body.
So, unless you rotate the wheel, the oil pump won’t be rotated and thus, not feeding the MTF to each gears.

The oil pressure generated at the oil pump will go through the oil passage built inside the 5th-Reverse shift shaft, Main shaft, Counter shaft, CL case before splashing the oil to the gears, bearings, DF, drive shaft spline, etc.

This is the reason why it is so important to use soft (bit exaggerated but water like viscosity even at very cold temperature) viscosity MTF but one can hold very strong oil film even at high temperature.

Because of this oil pump mechanism and the narrow oil passage, if your issue is related to the MTF, you will notice big difference in shift feeling before/after the MTF warmed up and when you start driving for the first time after parked the car overnight.


From what you wrote so far, I don’t think your issue is related to the MTF.
In fact, you will notice the issue in other gears and not just getting out of specific gear position.


The best way to test this is to start the engine and start moving the car after 1min (for the summer) or a few minutes (for cold winter) at very slow speed (like below 15mph).
The key is not to warm up the gbox (MTF). By the way, unless you live in sub-zero climate, no need to fully warm up the engine before start driving the NSX.
Focus on the feeling when you select 2nd gear. Try selecting 2nd gear multiple times and remember the feeling.

Now go out for 10 – 15 min normal cruising session.
Your MTF is now warmed up and softened so repeat the above slow speed test.

If you notice significant change in selecting 2nd gear, you may have MTF related issue or using too high viscosity MTF when it's cold.
If using Honda MTF-3, you won’t feel this.
From what you wrote so far, I don't think you will notice big difference on selecting the 2nd gear before/after the MTF warmed up and thus, your issue is not MTF related.

4th and 5th use separated shift fork so selector cable needs to move differently and you seemed to be fine in selecting the gear so for now, I’ll leave the selector and shift cables adjustment.

You seemed to be fine with other gears so I’ll leave the CL Hyd system (CL master/slave/hose). If you have problem disengaging the CL, you will have problem selecting the gear because you can’t reduce the input torque and speed.

For twin disc plates CL on the 5MT and NSX-R/S 6MT, you will need to ‘initialise’ the mid plate guide. If this was not done, you will have big time selecting any gears so this is not related to your issue.


It all depends on the answers to my questions above but if it only happens at exiting the 4th and 5th gears, it sounded like the sleeve over the hub is not sliding out smoothly from 4th and 5th gears
so you may need to open the gbox and inspect each components.
Hope not.....


Kaz

Hi Kaz,
I will try to answer your questions in order as best as I can.

Q1. I do not know of any modifications to the car (except it has an aftermarket exhaust) but we don't have any details of the car's former life in Japan.

The issue happens throughout a journey, each time the car has cruised in 4th or 5th for a few minutes. You can change out of 5th with the stickyness and immediately change out of 4th without stickyness . Indeed you can change back into 5th and if you then change down again fairly promptly (can't be more precise) the change is fine. In and out of 4th is fine in traffic (where 5th would be inappropriate) when the change is being used frequently, but again, cruising in 4th for a few minutes renders the change sticky when first used again. This is so whether the car is fully warmed up or not (in fact I am tempted to say it is more pronounced with the car warm). I hope that gives a clear picture of the problem.

Q2 It is consistent IF the gearchange is not used regularly. But if the gears are being shifted constantly it is not consistent.

Q3 Parking up or when during the day you are using the car seems to make no difference

Q4 Under the cruising conditions described it does always happen. It happens throughout any drive if the car is left in 4th or 5th for some time. If you keep changing gear it doesn't happen. The change is slightly stiffer into any gear when the car is cold, but that stiffness goes away in the change generally quite quickly as the 'box warms up.
The service notification does say that Honda MTF3 was used last July and I have no reason to doubt this (and this problem has not changed over the past few months since I have had the car).
I have tried your "2nd gear selection" test cold and warm and there is not much difference in the 'weight' of the change cold to warm.

I wondered if the clutch might be dragging but like you I thought that would inhibit the release of all gears not just 4th and 5th. But is that something I should have checked before diving into the gearbox?

Though we have already added a gear oil additive, might it be worth trying one of these PTFE or Moly coating additives or is that not wise? Is the gearbox oil separate from the diff. oil? Several of these coating additives are not recommended for some diffs.

Thanks for your detailed answer . I hope I have answered your queries adequately.

Roy

[goldnsx]

An additional MTF change won't help you out as all of the oil gets changed during a proper oil change. And before you dump a serious amount of money into opening the gearbox you might check the hydraulics as it smells pretty strong from your description (1 mile against the wind if you like :)) that they are about to fail. Have they been changed in the past? Try this: after driving a long time in 5th apply the clutch several times fully before you shift into 4th. If it's smooth then -> 99% hydraulic (master or slave, change both then). I'm looking forward to your results you find. :)

You've replied when I wrote. :) From your added info it smells even more about hydraulics. Yes, the clutch is dragging when it gets sticky but due to low pressure in the clutch hydraulics. For some reason your hydraulics go 'low' when you didn't use it for some minutes which points at a faulty system. Maybe just a little bit of air or low on fluid or a faulty master or slave rubber gasket inside.

Adding that oil additives are a waste of money as the MTF3 contains all ingrediments the tranny and differential need to be happy.

[Kaz-kzukNA1]

There is no need to add such oil additive for the gbox or for the engine.
If something like that has huge benefit, production car manufactures would have done it from the R&D stage.

Each NSX gears are hand assembled and even bench tested before placing the assy inside the gbox and any necessary adjustments were done by the engineer with their own hands so as long as each parts were not damaged, everything should be smooth.

Not sure whether you have ever seen how the gear shifting mechanism works on the synchro based gbox but all gears on the main/counter shafts are always engaged (in contact each others) but freely spinning (except the 1st, 2nd and reverse gears on the Main shaft. They are directly machined on the Main shaft) when in neutral position and the shifting operation is done through the combination of synchro hub, sleeve and blocking ring.
On our NSX, not only all of the forward gears are using helical design with the synchro mechanism but also the reverse gear is using the helical with synchro mechanism as well.
With high stress treated helical gears, there is not much point in using oil additive.
For the engine, you never know the effect of such chemical on the titanium rod.

Back to the shifting operation.
When you are getting out of the gear back to neutral before selecting another gear, the gear/sleeve/hub/blocking ring are spinning at the same speed and if you reduce the input torque by disengaging the CL, the sleeve should smoothly move over the hub/blocking ring to get neutral.
In fact, the gear ratio in 4th is 1.033 so the input and output rpm are almost the same so better condition any way.

If shifting regularly improves the situation at the 4th and 5th gears, it seems to be teeth alignment issue due damage or excessive wear on some of the parts.
You will get far better idea by watching some of the videos on the web (you can find lots of nice ones on Youtube) than reading these text.
So, if you are having problem sliding the sleeve out of the specific gear especially the 4th and 5th, your issue is more likely to be internal parts issues specific to these gears.

If the CL is not disengaging properly due to CL Hyd sys, sticky release bearing, dislocated torsion spring, etc, I would imagine you will have issues on other gears or even shifting into 4th and 5th gears and not just getting out of these two gears.

Kaz

[goldnsx]

It could be the hub of 4th/5th but then why does it happen only after a long time in on of those gears? I don't think it's related to the internal shifting mechanism. It's related to time somehow and clutch hydraulics react more to this. I'm interested in his findings.

A little bit OT:
One thing that worries me most is that Honda canceled the 5th gear (23461-PR8-000) and other transmisson parts from the parts catalog (unavailable). I've seen 5th gears with damaged teeths from people shifting from 2nd WOT to 5th.

[Kaz-kzukNA1]

I hope I’m wrong because if the issue can be fixed without opening the gbox, that will save the time and cost.
CL Hyd sys can be checked fairly easily.
Unlike the brake reservoir fluid level that drops as the brake pad/disc wore, the CL fluid level won’t change even after other parts wearing and can be bled very easily on non-LEV model.

If CL master is already leaking, just replace CL master/slave/hose as a set.

As Roy's NSX came from Japan, being as early model (91), with its mileage (85K miles), issue on 4th and 5th, etc, I have some ideas on how it was driven in Japan and probably similar issues that required overhaul of several gboxes after having problem on the 2nd, 4th and 5th.
Honda even modified a certain parts for the issue at the 5th position.

The driving environment in Japan is quite different compared to Europe.

Very low average speed but lots of steep and twisty roads (50% of the land is covered by the mountain), lots of traffic jam in the city area, heavy acceleration/deceleration, etc.
I used to replace my CL every 30K miles on my NSX while in Japan.
After moving to UK, I can go over 100K miles with the same driving style on the same CL.


Much better shift feeling than several years ago. Still bit difficult to get out of 4th and 5th gears but no issues in selecting any gears.
I wrote this comment a while ago on UK based NSX when the owner told me that he was having problem on the 4th and 5th gears.
It was well before Roy posted his issue here and it’s a different NSX.

This NSX had its MTF replaced several years ago when the drive shafts were refurbished but as expected, the shift feeling didn’t change (test driving was done in cruising mode).
The CL master/slave/hose were replaced as a set later as the master was already leaking but again no changes in the shift feeling (test driving was done in cruising mode).
The shifter/selector cables were checked as the Eng/Gbox came out for the Eng Refresh.

When I wrote above comment, the test driving was done as part of the health check service and thus, it was quite different from the cruising mode test driving session.
With test driving for the Health Check, I have to shift regularly and very short cruising in 4th or 5th gears before I have to shift again.


The key factor here is the 4th gear and this is the reason why I don’t think it’s CL or CL Hyd sys related.
The same reason why the shift feeling won't change even after replacing MTF or the CL master/slave/hose on other NSX with similar issues on 4th.

As mentioned in my previous post, the gear ratio for JDM 4th gear is 1.033.
This means that the input/output rpm are almost exactly the same.
Therefore, as long as you release the TH pedal to reduce the input torque, you can get out of 4th gear even without touching the CL pedal with very little effort.
I can do this with my JDM NSX as I have no issues in 4th position.
With Roy's NSX, I think he will struggle to get out of 4th gear after cruising some time.

There is a specific condition (wear/damage on the specific area of the multiple parts) on the certain parts that can cause this stickiness if cruising for some time yet it won’t happen if shifting regularly.
Addition to this condition, for the 5th, there is another parts that may cause the stickiness or issue selecting/getting out the 5th gear and Honda modified this specific parts for this.

I hope I’m wrong.....

Kaz

[Kaz-kzukNA1]

.......................
A little bit OT:
One thing that worries me most is that Honda canceled the 5th gear (23461-PR8-000) and other transmisson parts from the parts catalog (unavailable). I've seen 5th gears with damaged teeths from people shifting from 2nd WOT to 5th.
While many 5MT parts are no longer available in Europe and US, they are still available in Japan.
At least that was the case until late last year because I bought many 5MT parts on several occasions including the 5th gears, 5th hub/sleeve set, etc that are all shown as ‘discontinued’ in Europe and US parts system.
I even bought some of the 5th gear parts, bearings, synchro, etc for another owner last summer.

I better check the latest status as I would like to build fresh 5MT or 6MT using new parts with different final and DF plus C32B engine but using non-DBW TH one day if I can’t get hold of specific NSX from Japan.

Kaz

[goldnsx]

Interesting. What about differences in availability of other parts discontinued in the US/Europe?

[Lotus Roy]

An additional MTF change won't help you out as all of the oil gets changed during a proper oil change. And before you dump a serious amount of money into opening the gearbox you might check the hydraulics as it smells pretty strong from your description (1 mile against the wind if you like :)) that they are about to fail. Have they been changed in the past? Try this: after driving a long time in 5th apply the clutch several times fully before you shift into 4th. If it's smooth then -> 99% hydraulic (master or slave, change both then). I'm looking forward to your results you find. :)

You've replied when I wrote. :) From your added info it smells even more about hydraulics. Yes, the clutch is dragging when it gets sticky but due to low pressure in the clutch hydraulics. For some reason your hydraulics go 'low' when you didn't use it for some minutes which points at a faulty system. Maybe just a little bit of air or low on fluid or a faulty master or slave rubber gasket inside.

Adding that oil additives are a waste of money as the MTF3 contains all ingrediments the tranny and differential need to be happy.

Hi Everyone,

I have now had a chance to try a few things to try to sort out my sticky gearchange.

I have tried 'pumping' the clutch pedal when faced with a recalcitrant change and lo and behold, it moves well! It is an awkward thing to do so I am not certain it cures all the problem, but it definitely makes a difference.

Also I have tried cruising for a few minutes in 3rd gear and the change becomes sticky out of third, so it is related to how long since the clutch was last used rather than what gear you are in. I reckon it must be clutch hydraulics so I guess the next step is to bleed the clutch. There is no sign of any leakage anywhere and the resevoir is full.

Does this make sense to everyone?

Thanks for the help.

I will keep you all posted.

Roy

[goldnsx]

Makes perfect sense. It looks like you've found the problem and - as expected or happy enough - it seems not to be related to gearbox internals.

Bleeding the hydraulics can help if there's air in the system which should not be the case. But my guess is that you have a bad internal gasket. If your clutch hydraulics are more than 15 years old I'd throw them out (before you finally get stranded or ruin the gearbox internals in the end).

Happy motoring!

[Lotus Roy]

Makes perfect sense. It looks like you've found the problem and - as expected or happy enough - it seems not to be related to gearbox internals.

Bleeding the hydraulics can help if there's air in the system which should not be the case. But my guess is that you have a bad internal gasket. If your clutch hydraulics are more than 15 years old I'd throw them out (before you finally get stranded or ruin the gearbox internals in the end).

Happy motoring!

Hi GoldNSX,

Which end do you suspect the gasket problem? Slave or master cylinder?

I think a bleed is worth a try first, don't you.

Roy

[goldnsx]

You can give it a try but honestly I don't believe it won't be any better. Only if the last bleeding procedure was faulty...but then you would problems all the time.
It can be one of them or both, hard to tell. Regarding the (relativ low) price of the parts and the risk to be left stranded somewhere out in the desert it's not worth the hassle. In aeronautics you always change both because the newer one will wear out the older one even faster (harder fluid impuls dynamics).

Good luck!

[Nick Graves]

I recently (had) put a new M/C rod seals and slave (might as well do it!) because my clutch had developed an inconsistent feel; sometimes the pedal had stiction, sometimes it seemed light, sometimes I clearly couldn't bloody drive properly. Slight weep from M/C was the clue.

It's fixed it and I've stopped doing learner starts/crunching gears.

[Kaz-kzukNA1]

Hope you can fix the issue by replacing the CL Hyd Sys.
As mentioned earlier, I know another UK based NSX with similar issue on 4th and 5th gear, even after replacing the MTF and Hyd Sys for other reasons so interested in your findings.

And probably goldnsx already knows this from my post on NSX Prime but the 5MT 5th gear parts are still available in Japan but not sure why they were discontinued in US and Europe.....

Kaz