Transmission Grinds

[sepulveda87]

Hello everyone,

Ive done some research for this problem i am having and cant really find anything but here is what i am dealing with. Bought a t2t4 tranny from hmotorsonline (thanks steve for the hook up!) works awesome! I had the motor rebuilt about 3 years ago with a stage 4 act clutch and bisi 8lb flywheel. Ive noticed that in high RPM it grinds and locks me out but if i do normal shifting speed its fine. But i noticed as well that it is hard to put it in first gear from neutral. In order for me to get it in first gear i have to put it in second gear and then first. What could this be? I was thinking it can be the cables since they are old and most likely worn out. ive adjusted the cables at the shifter and i still have play (more than normal) so i am hoping this is it. i looked at the throw out bearing on the tranny before i put it in and it was good. Could it be that maybe the clutch isnt fully disengaging? How can i adjust the clutch pedal to make sure the clutch is fully disengaging?

I was thinking of buying a new slave and master clutch cylinder and the hybrid racing no cut box with the H/F bracket and RSX shift cables and cable bushings at the tranny since this is my weekend racer.

OEM accord cables brand new go for no less than $350 so i might as well get the race-spec ones from hybrid and the rest of the setup.

Any idea and opinions would be greatly appreciated!

[johnl]

But i noticed as well that it is hard to put it in first gear from neutral. In order for me to get it in first gear i have to put it in second gear and then first. What could this be? I was thinking it can be the cables since they are old and most likely worn out. ive adjusted the cables at the shifter and i still have play (more than normal) so i am hoping this is it.

Unlikely to be the cables. If you have more play at the lever than should be normal then have a look at the rubber bushes at the gearbox end of the cables.

Could it be that maybe the clutch isnt fully disengaging? How can i adjust the clutch pedal to make sure the clutch is fully disengaging?

Could be. If so then it's either air in the hydraulics (bleed the system), or too much free play at the pedal (adjust free play to spec, about 3mm at the pedal pad).

Other things that come to mind are marginal synchromesh cones, or the wrong oil in the gearbox. Some oils (usually 'synthetic') are too 'slippery' to allow the synchromesh to work properly.

I was thinking of buying a new slave and master clutch cylinder and the hybrid racing no cut box with the H/F bracket and RSX shift cables and cable bushings at the tranny since this is my weekend racer.

What is a "no cut box"?

OEM accord cables brand new go for no less than $350 so i might as well get the race-spec ones from hybrid and the rest of the setup.

'Race-spec' shifter cables, I thought I'd heard everything...

The only improvement I can think of that might be made to the cables would be to replace the rubber bushes (at the gearbox end) with spherical rod ends. I've actually done something somewhat similar to this, but using greased brass discs pressed into the eyes where the bushes would normally be. It's a long while since I looked, but from vague memory there might also be a rubber bush at the lever end of one of the cables (if there is then that too could be changed for a rod end, and I may have done the brass disc thing here on my car too). Eliminating the rubber does make for a better feel to the shift action.

[Tishock]

Grinding

I too believe the synchro/sleeve cones maybe worn (see pic). Maybe not completely worn out but the tranny may just be showing its age. That would explain the grinding at high RPMs.




Shifter play

Like johnl said check your shift cable bushings and the shifter plate bushings


Clutch engagement

Also besides checking the hydraulics, try this quick clutch diagnostic tip:

Raise the car, so that both front wheels are off the ground. Now start the car in neutral. The wheels will spin on their own, but very very slowly. If they're spinning quickly, then the issue is your clutch and not the hydraulics.

[johnl]

Raise the car, so that both front wheels are off the ground. Now start the car in neutral. The wheels will spin on their own, but very very slowly. If they're spinning quickly, then the issue is your clutch and not the hydraulics.

This won't test whether or not the clutch is disengaging fully, because the test as outlined isn't activating the clutch disengagement. In neutral with the clutch engaged (pedal up) the wheels may still rotate because of fluid drag within the gearbox. With the pedal depressed any wheel rotation should stop because the first motion shaft should become rotationally isolated from the crankshaft, if not then it suggests the clutch isn't fully disengaging.

Someone will have to be sitting in the car with the clutch pedal depressed with first gear selected. If the clutch is releasing completely then the wheels should stop rotating when the pedal is depressed.

But even so, the 'released' driven plate may scuff lightly on the pressure plate and / or flywheel and cause a very small amount of torque to be transferred into the gearbox, the wheels may still try to rotate (in gear due to being in gear, or in neutral due to fluid drag, though fluid drag may not be strong enough to rotate the wheels). In gear, if the rotation is easy to stop manually then the clutch is releasing well enough, but if it's more difficult then it may not be.

Note that stopping one wheel from rotating may cause the other wheel to rotate at twice the speed in the opposite direction (due to the action of the differential), so have someone try to prevent rotation at one wheel while you try to stop rotation at the other wheel.

[sepulveda87]

Unlikely to be the cables. If you have more play at the lever than should be normal then have a look at the rubber bushes at the gearbox end of the cables.



Could be. If so then it's either air in the hydraulics (bleed the system), or too much free play at the pedal (adjust free play to spec, about 3mm at the pedal pad). Ive bleed several times no air lol ive tried to do the adjustment as well but idk maybe its the clutch because its a stage four?you barely let the clutch go and you are OFF! lol

Other things that come to mind are marginal synchromesh cones, or the wrong oil in the gearbox. Some oils (usually 'synthetic') are too 'slippery' to allow the synchromesh to work properly.



What is a "no cut box"?

http://www.hybrid-racing.com/store/h...t-shifter.html



'Race-spec' shifter cables, I thought I'd heard everything...

http://www.hybrid-racing.com/store/h...e-version.html

The only improvement I can think of that might be made to the cables would be to replace the rubber bushes (at the gearbox end) with spherical rod ends. I've actually done something somewhat similar to this, but using greased brass discs pressed into the eyes where the bushes would normally be. It's a long while since I looked, but from vague memory there might also be a rubber bush at the lever end of one of the cables (if there is then that too could be changed for a rod end, and I may have done the brass disc thing here on my car too). Eliminating the rubber does make for a better feel to the shift action.

yeah hybrid racing has good stuff but its kinda expensive lol

[sepulveda87]

im thinking too just take off the stage 4 and go with the OEM clutch that came with the tranny from hmotors and leaving the light flywheel on there

[johnl]

http://www.hybrid-racing.com/store/hybrid-racing-k-swap-bolt-in-short-shifter.html

Oh, a short shifter. Never hard the term 'no cut box' before...

The damaged (badly modified?) shifter pictured on the linked site looks nothing like the stock shifter mechanism in my car...? There is no big white plastic box for starters.

I've modified my shifter by welding a flange to the back of the shift lever, and drilling a hole in the flange for the cable attachment that is significantly higher than the stock hole. This shortens fore / aft shift motion. There are actually several holes in the flange, the correct (compromise of desired and possible) hole location was found by some trial and error...

For shortening side to side motion I've cut and welded an extension into the vertical lever that controls the plane in which the lever is going to shift (i.e. 1st and 2nd, or 3rd and 4th, or 5th and reverse).

Both of these mods work very well, but the former one does create cable clearance problems (to the underside of the odds and sods tray in the centre console) requiring some lateral thinking to resolve (difficult to describe).

Further shortening of the shift action can be achieved by shortening the levers at the selector lever box on top of the gearbox. I've cut and shut my levers here so they are approximately half the original length. The lever box on top of the gearbox needs to be removed and the levers taken out to perform this modification.

While you're in there, there are two hairpinish shaped springs inside the lever box that spring load the shifter mechanism into the 3rd / 4th plane, if you remove one of these springs then the spring loading becomes less. This isn't a significant issue with the stock amount of lateral shift lever throw, but can be when this action is substantially reduced, i.e. the spring loading into the 3rd / 4th plane will become a lot stronger if the second spring is left in situ (because with the shortened lateral lever throw you have less leverage over the springs).

It's important to pay attention to the angle at which the levers need to be welded back together, because shortening the levers changes the angle at which the cables attach to the levers. Some tweaking of the bracket that holds the ends of the cable sheaths may also be required to avoid cable / sheath friction where the cables exit the sheaths.

With short shifting mods at both ends of the cables I can now use a substantially extended shift lever, that places the shift knob much closer to the steering wheel (about 100mm away from the steering wheel rim). The position of the shift knob is also changed by careful bending of the lever, plus the stock adjustment available at the cables, to help position the knob where I want it to be. I now don't have to reeeaaach for the gear lever, I just let go of the wheel and drop my hand a short distance onto the lever.

Because the shift action has been very substantially reduced, even with the longer shift lever the shift action is much shorter than stock (and very 'snicky', satisfyingly 'mechanical'). The fore / aft throw at the lever knob is about 80mm give or take. The lateral throw would be about 30mm at the lever knob (from one plane to the next plane). If I were using the stock lever length then the throws would be substantially less than this.

http://www.hybrid-racing.com/store/hybrid-racing-replacement-shift-cables-for-rsx-and-swap-vehicles-race-version.html

Those cables do look worthwhile, if pricey. As I mentioned earlier, I've removed all the rubber bushes from my cables, replaced with metal to metal connections. The rubber does cause a significant amount of 'rubberiness' in the shift action (surprise...), getting rid of it definitely does improve shifting feel (contributes to the 'satisfyingly mechanical' feel). Whatever is used to replace the rubber, you need to allow for some degree of lateral misalignment in the metal bushes where the lever rods pass though.

[deevergote]

Honestly, if the stock setup isn't working properly, modifying it isn't likely to fix it, or do anything good at all for that matter.

johnl touched on pretty much every applicable point already, but I wanted to bring it back to that, since the focus has since shifted to the short shifter mods.

The transmission may be worn. After 20 years or so, the synchronizers can wear out. Especially if the previous owner wasn't good about replacing the fluid regularly. Most people I know, even car enthusiasts, often don't understand the importance of fresh transmission fluid!
What fluid are you using? I've had the best luck with GM Synchromesh (now branded as AC Delco Synchromesh, I believe), while others prefer Honda MTF. Anything else, even the factory recommended motor oil listed in the user manual (for our cars, at least... not sure about the later model performance units) doesn't seem to work as well.
If you're using anything but one of those fluids, change it out.

There should be no need to adjust the pedal itself. If there's a problem with engagement, it's likely due to your system still having a bit of air in it. My own clutch isn't quite right after changing my master and slave. I'm not driving the car at the moment, but once it's back on the road I'll be taking it straight to Honda. I've frustrated myself enough trying to get it right! I know it's a blow to the ego for any enthusiast, but taking it to a pro that does such things day in and day out might be the easiest solution. Especially if an improperly engaging clutch is potentially causing additional harm to your expensive transmission!

From my experience, short shifters only create a "notchy" feel, and tend to wear out the synchros even faster. Then again, all I ever did was move the shift cable mounting points by various methods (adapters, welded a new mounting point on the shift lever...)
johnl, your approach intrigues me. I've never seen such extensive modifications done to shorten the shift! I'm curious to see if what you've done would eliminate the issues I've experienced.
If you ever feel so inclined, a DIY with pictures showing exactly what you've done would be a HUGE contribution to this community! We're in the process of refreshing the DIY section, so we're definitely looking for new and interesting DIY threads!

[Raf99]

Op, I'm curious to know if a quick double clutch at high rpms results in the same problem as non-double clutching.

thanks

[johnl]

Most people I know, even car enthusiasts, often don't understand the importance of fresh transmission fluid!

I change mine at 100,000km intervals.

What fluid are you using? I've had the best luck with GM Synchromesh (now branded as AC Delco Synchromesh, I believe), while others prefer Honda MTF. Anything else, even the factory recommended motor oil listed in the user manual (for our cars, at least... not sure about the later model performance units) doesn't seem to work as well.
If you're using anything but one of those fluids, change it out.

I've used a Motul synthetic oil formulated for use with synchromesh (as opposed to their oils that are intended for 'crash' gearboxes and don't work with synchromesh). It was great for a 'slicker' shift feel, but, it was too slippery for the synchromesh in the Honda gearbox (may be fine in others).

The problem occurred when trying to select first gear at rest, it was easy with a cold gearbox, but with some heat it became quite difficult. The synchro action baulked the shift and it wouldn't go into gear unless second gear synchro was engaged before quickly shifting into first (and sometimes this didn't work easily). It would have been easier with no synchromesh at all.

Anyway, changing to Honda MTF cured the problem.

From my experience, short shifters only create a "notchy" feel, and tend to wear out the synchros even faster. Then again, all I ever did was move the shift cable mounting points by various methods (adapters, welded a new mounting point on the shift lever...)

It's unavoidable that lessening the throw will create a 'notchier' shift feel, because the leverage at the lever is less. Any 'notch' that occurs within the box will be more evident and easily felt. If you like a buttery shift action then a short shifter is not for you (same goes for removing the rubber from the cable linkage). I like the notchiness. A short shifter will also increase the stiffness of the shift action, which some people may not like. My shift action is significantly stiffer than stock, but I got used to it very quickly, and it's not hugely stiffer

The stiffness helps you feel the synchromesh readiness to allow the shift without stressing the cones. If the resistance is too high (i.e. it doesn't just 'slot in') then you should be able to feel this more easily with a short throw shift action.

My wife doesn't like it, but then she doesn't like the light flywheel, or the stiffer springs and dampers, or the stiffer rear ARB, or the stiffer suspension bushes, or the increased caster angle, or the stiffer engine mounts, or the stiffer clutch, or what I've done to the seat, but she does like her very nice Saab 95 (so it's not my problem...).

As to wearing out synchros, this is operator error. You need to become attuned to the new shift action, and never force a shift. It's all in the timing, and developing a feel for what the gearbox is doing (and a shorter / stiffer shift action tends to allow more feel in the shift for what is happening inside the box).

I could mount an argument that a 'numb' long throw action (i.e. stock) is more likely to cause synchromesh wear because the 'vaguer' nature of the shift action and the greater degree of leverage (that you have with a long throw) tends to mean that more force may be exerted on the gearbox internals as you change gear, and if the synchromesh is having to work hard because the rpms don't really match up well enough this will wear the cones. I'm wondering whether your experience with short throw shifters and subsequent worn synchromesh is more coincidental than causative?

Perhaps more damage could occur if the driver fails to adapt to the changed shift action, i.e. not becoming more sensitive to the action and feel, and being too 'ham-fisted' with the now more sensitive shorter throw action. This could result in shifts being forced if the driver is still trying to move the lever as fast every time as they may have with the stock shift action.

Just because it may be possible to move the lever a shorter distance and faster out of and into a gear doesn't mean that the lever should always be shifted that way. Feel for what is happening inside the box is important, as is getting the timing right. If the timing correct then the shift can be very fast (especially with a lightweight flywheel), but if it's wrong then it should never be forced. That it takes more time to move the lever with a longer throw may help mask some degree of 'ham-fistedness', that may be more problematic with a shorter shift action?

johnl, your approach intrigues me. I've never seen such extensive modifications done to shorten the shift! I'm curious to see if what you've done would eliminate the issues I've experienced.
If you ever feel so inclined, a DIY with pictures showing exactly what you've done would be a HUGE contribution to this community! We're in the process of refreshing the DIY section, so we're definitely looking for new and interesting DIY threads!

Hmm. I could do a wordy DIY (I'm good at 'wordy', some might say verbose...), but photos of all the mods as they are performed won't happen. I may be able to show what has been done, but I'm a total novice at posting photos. If I can find time I'll see what I can do with photos, but don't expect too much.

Yes, I have gone to a deal of trouble to improve the shift action (in the eye of the beholder as that may be...). Primarily I wanted to relocate the lever knob so I wasn't having to stretch to it every time I shifted gear (more of an issue since I had earlier moved the steering wheel a lot closer to the driver, and further from the wheel). A longer lever increases the shift throw, so I needed to shorten the shift so it wasn't way too much movement. Modifying the shifter mechanism at the lever end resulted in a more or less stock throw with the longer lever, but I wanted more (less...?). One day it occurred to me that there was more than one way to skin the cat...

[johnl]

Op, I'm curious to know if a quick double clutch at high rpms results in the same problem as non-double clutching.

thanks

With modern synchromesh gearboxes 'double de-clutching' is never necessary (unless the synchromesh isn't working).

There is some confusion 'out there' as to what 'double de-clutching' actually is. It is;

1) Clutch pedal pushed to disengage the clutch, and the lever moved to neutral.

2) The driver then briefly releases the clutch pedal ('up') to momentarily re-engage the clutch while the gearbox is in neutral.

3) The throttle pedal is now 'blipped' to bring the engine rpm up so that the rotating speeds of the dog teeth are near enough that the teeth will engage without clashing.

4) Re-depressing the clutch as the lower gear is cleanly selected.

5) Releasing the clutch pedal.

This series of actions strongly changes the rotating speeds inside the gearbox (when the box is in neutral, i.e. #3) to bring the dog teeth into near enough rpm match that clashing of the teeth doesn't occur, and that when the clutch is finally released the rpm of the engine in that gear will match the speed at which the road wheels are rotating, which prevents chassis lurch and torque 'spikes' at the wheels (as the wheels either force the engine rpm higher or lower).

However, with synchromesh the cones are able to do this quite well without the need to re-engage the clutch (i.e. the 'double clutch' bit, step #2, isn't required).

With good synchromesh all that's needed is to 'rev match' on down-shifts, i.e. to 'blip' the throttle pedal as the gearbox enters neutral and before slotting into the lower gear, and letting the synchromesh cones do the work inside the box. This may or may not require a momentary pause as the lever arrives in the neutral plane, depending on the gearbox (gap between ratios and strength of synchro action), the rapidity at which the rpm rise with the 'blip', and operator skill.

I see some people 'blipping' the throttle on upshifts, which is just silly.

The rpm is irrelevant, i.e. when downshifting it doesn't matter what the rpm is before changing the gear, or after, you can do this at low or high rpm. It's a useful technique to make quick and clean shifts that don't cause a spike in torque at the wheels when the clutch is released, so it results in a smoother shift that is less likely to result in loss of driven wheel traction or chassis 'lurch' as the clutch is re-engaged.

[Raf99]

I wasn't looking for an explanation of what double clutching was.

Op?

[johnl]

I wasn't looking for an explanation of what double clutching was.

Sorry, misunderstood the nature of the question. I read it as a general question, not as one looking for further info from the OP.

I'm not sure of relevance, since the problem doesn't seem specifically associated with high rpm shifting.

[Raf99]

Double clutching at high rpms (with no throttle blip) eliminates other factors. But no need to write a long novel reply, I know the implications and just curious if the Op tried it.

[deevergote]

My experience with the notchy shifting was that it occurred regardless of how fast I attempted to shift. Even when shifting slowly and carefully, the added resistance in the shifter made it hard to differentiate between 2nd and 4th when shifting out of 3rd. Normally, the 2nd gear downshift would require a bit more force, and the 4th gear upshift would slide naturally into place. With the short shift modifications (I've tried numerous types), both gears felt similar. After nearly blowing my engine while racing and shifting ham-fistedly into 2nd instead of 4th, I put it back to stock! Once the cables were back in the stock position, the shifts felt natural again.
It's not "notchy" in that it feels like it's clicking into gear. The "notchiness" I refer to is the added difficulty getting into any gear. I'm wondering if further modification as you specified, john, would eliminate the bad parts, and leave the good.

It's also possible that my transmission is already damaged. I had an axle replaced at a Chrysler dealership (before I was confident enough to do it myself.) and the mechanic put standard gear oil in my transmission. The extremely thick type that smells like eggs and crap. Until it was warm, grinding occurred. Once warm, it shifted fine. I was young, of course, and unaware that the wrong type of oil was in my transmission... so I continued to drive it like that for quite a while. By the time I learned what was in there, the damage was done. 3rd and 5th will grind if I'm not careful.