shadejo

Clutch fork failure

112 posts in this topic

OK, I thought I knew all the common failure points (and it seems like the two Smarts I have on the road have expeienced most of them.....)Last night, wife phoned from the grocery store to say the car would not switch out of neutral. Sounded like a clutch actuator problem so I towed the car home and took a look this am. Actuator is fine, but the pushrod from the actuator to the clutch release fork had pushed right through the release fork ! In other words, the actuator rod moves in and out but is never going to release the clutch....Spoke with local dealer who noted they had seen "one or two" of these which always makes me a little suspicious. The car that failed has only 69k on it, so I consider this a very early failure.Needess to say this is a "remove the powertrain, split the transmission off the engine" . Didn't like the numbers the dealer mentioned for labour, so guess how I'll be spending my weekend !I'd like t hear from anyone else who has seen this to get a sense of how widespread the problem is.ThanksJohn

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I've never heard a fork break before. Perhaps yours had a manufacturing defect like a notch in a higher stress area initiation a fatigue crack.Removing transmission only takes a couple of hours. I recommend dropping powerpack subframe a wee bit to improve access. Get rear end up on axle stands as high as they will go. Lift front axle sufficiently so axle stands get a uniform support in way of contact with support/ jacking points on chassis. Remember to slacken off rear axle bolts before you jack up rear end.

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I've heard of this. Lack of lubrication on actuator rod end wears a hole right through fork. A tiny shot of a thick lubricant down the rod prevents this. Be sparing, use an extension tube, be sure it is on the outside of the rod (relative to clutch), oil/grease contamination of the clutch is a bad thing.Better yet, when the clutch is being adjusted insist they remove the actuator and apply a dab of "black grease" to the end of the rod. Black grease being the thick molybdenum disulfide grease, very good for fretting-type wear prevention.

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A thought: Before getting right into pulling the tranny, pull actuator off. It's possible the hole in the fork is actually very small and the ball on the rod is worn right off. A new actuator rod installed with proper lubricant may serve for a few years. No idea if the rod is available as a separate part though. Perhaps an appeal for a dead actuator may bear fruit? A hard nylon shell over the actuator rod tip would be nice, if you can find/fabricate such a thing and the slots are long enough to get proper adjustment with the extra length.

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Posted (edited) · Report post

A thought: Before getting right into pulling the tranny, pull actuator off. It's possible the hole in the fork is actually very small and the ball on the rod is worn right off. A new actuator rod installed with proper lubricant may serve for a few years. No idea if the rod is available as a separate part though. Perhaps an appeal for a dead actuator may bear fruit? A hard nylon shell over the actuator rod tip would be nice, if you can find/fabricate such a thing and the slots are long enough to get proper adjustment with the extra length.

Actuator is already off. This is how I found the problem - I was shocked that the actuator rod was "stuck" into the casing and knew it had a ball end on it so something was not right. Tugging at the rod carefully with vice grips to remove it and a look inside confirmed the rod had gone right through the fork !I agree wholeheartedly with the need to lubricate and will be adding this to the planned maintenance. I am quite convinced from what I saw that this is simply wear over time, not a manufacturing defect per se. No sign of any metal fatigue, just a "punch through" failure when the metal got too thin.tolsen - I was under the impression that transmission separation from engine required complete powerpack removal (also the view of the dealer when I had a discussion this am and quoted 6+ hours) Can you confirm that this is feasible and time effective without? I presume if I put car up high as you suggest, remove axle shafts and ground wire, and remove back engine mounts I can pivot the power unit down a fair way for access. Is this similar to what you are suggesting ? If so, I guess I should then be able to separate transmission from engine without completing the removal of the engine from the car? This wouldbe good news as I was figuring I would need to disconnet all the coolant hoses, wiring at the front of the engine and would bepleased if that is unnecessary. Edited by shadejo

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That is a weird failure: I had done over 160,000 km on my green smart before I first lubricated the actuator. It does make sense to me that the ball end needs some lubrication. A heavily city driven car would probably explain a very "early" failure.

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Posted (edited) · Report post

What if you made up a mushroom shaped metal piece to push into the new hole? The head of the mushroom would stop it from falling through the hole and the pressure of the rod as well as the proper adhesive would stop it from falling out. You could machine a spherical depression in the head to accept the push rod. This could be machined from hard self lubricating bronze or any other more appropriate material...Just a possibility.

Edited by gordo.bernard

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So everybody will be greasing their balls from now on?I wonder whether excessive dust is part of the problem. Less dust in the UK due to constant rain so less silica dust that can wear out the socket in the fork. Fork itself is a plate pressing and the socket is therefore not particularly thick, probably no more than 3 mm thick.Yes, you can remove gear box on its own. Intercooler has to be removed first and lowering power pack sub frame a wee bit gives you sufficient access room. Some find it even easier if you also remove EGR valve.Removing the whole power pack and subframe is not a DIY option if your Smart has aircon.

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I was chatting with the shop foreman at MB a while back, he told me this is fairly common. The actual fault is the clutch disk sticking on the splines of the input shaft on the tranny. If the disk sticks, it may not fully release, which will keep tension on the end of the rod at the release fork and will wear a hole through it. Can cause lots of other weird problems like a slipping clutch or a clutch that releases very harshly.

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[That makes a lot of sense Chris. Sounds like I better take a good look in there while I have everything apart.Gordo, I considered the repair you describe but was concerned that keeping the piece in place would be a gamble, better to change it out entirely.I have the engine lowered at the moment and am about to ttry and separate the tranny from it in situ. If I don't like the progress I will revert to dropping the whole assembly as I have done on a couple of other cars. Incidently, I have dropped te powertrain on aircon cars by removing the airco compressor and tieing it up out of the way (lines intact) and then removing the engine.OK back to work for me, hoping to get it removed tonight.Thanks to all !John

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Am I reading this correctly that, although we shoot spray lube into the actuator box, the OTHER end of the actuator rod needs lubrication too?

And where do I stick the straw? Now be polite you! :P

Bil :senile:

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[Certainly looks as if some lube there is a good idea Bil. I have had the tranny out tonight, and changed the fork but the old one had a hole cleanly worn through it from the actuator rod. I checked the input shaft splines and clutch plate splines and they actually seemed to be quite clean. Nevertheless, I wiped everything down with solvent and then dried it all, put a small amount of lube on the fork pivot point and began reassembly. I intend to put a small bit of moly grease on the end of the actuator rod when I complete reassembly tomorrow and on the weekend. If I was doing one in place I would use a bit of spray lithium grease pointed at the end of the actuator rod.John

Edited by smart142

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[Thanks, John.How concerned should I be that I might spray too much - or in the wrong direction - and get it on the plates or bits that shouldn't have lube on them?

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Can't remember where but saw one that had a fatigue failure as well - cracked across one of the arms on the wishbone - got to remember these suckers have to exhert a lot of force frequently (i.e. each shift - has to overcome the clutch springs) so they will wear and they will crack (bell arms on the old cars used to be the same - either bending or breaking or the bushing holes wearing).Keep grease and oil out of the clutch housing unless you can really get control of where it is going - just spraying in there with an aerosol will result in a toasty slipply clutch.Cheers,Cameron

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With an extension tube on a can of spray grease work the tube down the rod, parallel and on the outside relative to the clutch assy. About two inches in (someone will soon correct me if I'm off) is the fork. One short squirt, being sure the tube is straight and parallel.Much better is to remove the actuator and apply a dab of black moly grease, but that has to be done in conjunction with a mechanical then computer adjustment, unless you feel confident about getting the actuator back in the precise position it was.Do NOT just randomly spray in the general vicinity! Precision or nothing.There are also heavy industrial chain/gear/wire rope lubes very suitable for this application, that's what I used.

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MB's part system shows a grease to be applied to fork and possibly to spline or bush bearing at end of splined input shaft.

Posted Image

Item 16 is:

Q0001893V000000000 GREASE GEARSHAFT

Q0012959V000000000 1 SIZE GREASE GEARSHAFT

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I know Honda makes a specific grease for the splines of the clutch. It is "Ultra High Temp Urea Grease" and use only a very thin coating of it so you don't get a buildup with the clutch dust. It works extremely well. Makes a clutch move like hot butter.I use this stuff on the tip of the actuator rod. Pull out the actuator and put a small dab on the tip of the rod, then reinstall the actuator.

Edited by MightyMouseTech

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Interesting. Last time I did an adjustment, I cleaned the actuator out with almost half a can of brake/electrical cleaner, then took a wire wheel to the rod which was 100% coated with fairly thick oxidation. When it was spotless, I loaded the housing with HHS2000 and put a drop on the end of the rod, without knowing how beneficial that turns out to be. Next service I'll repeat, but with a thick moly or urea lube.

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For the curious, the broken fork. 5 minutes to change - after the transmission is out that is.....!

post-7726-1308322064_thumb.jpg

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What work is possible using this method ( lowering the subframe and removing the transmission from the engine)?i.e. Is a complete clutch plate replacement possible as well as removing the flywheel for machining?CANMAN

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[Looks possible to do anything that would necessitate flywheel removal.Note that I did not even lower the subframe - I simply raised the car, placed it on ramps, supported engine and transmission from below (floor jacks), released rear suspension x piece and muffler, removed axle shafts and released left and right mounts. Several wire connectors and tie wraps need to be cut of course andthen the entire powertrain assembly can be carefully lowered (front mount still in place) and allows reasonably clear access to things once the intercooler and EGR are removed.Transmisson separation was a bit tricky as removing it changes the balance of the assembly. I had one assistant and a 3rd floor jack involved at that point and to put the transmission back in place. Sorry, I didn't take pictures as for most of last night I was by myself and was filthy from the usual oil residue that gets on things ! Still need to reassemble intercooler and EGR and raise everything back into place. Not all that difficult to do but getting at all the engine to trans bolts (9 in total) requires some bending and crawling underneath !Thanks to tolsen for the suggested approach which I modified slightly...John

Edited by smart142

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What's all this talk about balls? Mine only has a ball on the end that's inside the actuator housing. The end that goes inside the clutch housing is just a rod. ????

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[Rod end is rounded like a circular segment of a ball. Have just inspected mine. Rust and grit erodes the socket in fork such that rod may punch through. I believe best preventative maintenance is spraying sticky grease (chainsaw bar oil perhaps or chain grease) on rod end and socket in fork. Grease needs be applied fairly frequently to be effective. In my humble opinion there is no risk of contaminating clutch friction plate unless you really go totally OTT with the grease.Greasing spline seems to be impossible without splitting gearbox from engine. With clutch actuator removed one can operate clutch by hand and easily feel whether spline is getting dry.

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Posted Image

Fork socket for actuator rod in my 2002 Cabrio Cdi. Socket is worn to at least 50% of plate thickness.

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My actuator rod did that too. Not as bad, but the rod itself was worn almost to a point on the end and it was at least an inch shorter. Duck parted out his fubarred actuator and sent me the pin. I now have a spare unit, ready to be used when needed.

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