shadejo

Clutch fork failure

112 posts in this topic

Thanks!BTW, where are you sourcing these spares? You are getting trade pricing at Mister Auto? Because their price for a complete clutch kit, releaser and "slave" is quite a bit more than £500.

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I'm working on a repair part for this problem, possibly much better than the acorn nut. I'm wondering about the diameter of the hole in the housing it must pass through for assembly, Tolsen said it's 1/2 inch back on page one. I would like a little more so my new piece can have a shoulder to stabilize it on the flat surface of the fork outside of the dimple. Can the housing hole be slightly enlarged, up to 5/8 inch or so? That is, can this be done in place, or is clearance too tight to get room for a drill? The design is such that the swivel action takes place within the repair part, it sits stable on the fork with a sealed grease cavity and pivot clearance for the rod.Also, my actuator is at the limit of it's adjustment slots, probably due to wear. I'm thinking I will add about 1/4 inch of length to the rod, that gives me a nice thick piece for strength. Does that sound about right? Thinking that this repair part will only ever be used on cars that have high mileage to begin with so no need to have it fit an unworn assembly. This should give ample adjustment for the foreseeable future life of the clutch assembly, if I ever have to replace the clutch pack it will start over with a new fork and actuator as well.Pictures and design notes/dimensions to be posted after testing.

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Hole diameter is about 17 mm. 1/2" is size of my new ball, the one made out of bronze at end of actuator rod that is, see picture below.

It cam't matter much whether actuator rod touches side of hole as long as that part of the rod cannot get caught in hole. That was why I tapered mine in way of transition from bronze to original steel rod:

Posted Image

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Alex,When I did mine I measured the Actuator rod at 4.106" in length.After I had brazed on my brass machining the new length was 4,323" an increase of 217 thou. The slotted adjustment was enough to allow for this increase.

post-894-1379880580_thumb.jpg

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About four months ago I did the acorn nut repair to the Clutch Actuator to fix the Clutch Fork punch-thru problem.I typically drive about 5000 km per month, so thats about 20,000 km ago.Today I experienced a few bad shifts followed by the 3 bars of death.I pulled the clutch actuator and sure enough the clutch fork is badly worn with a much bigger hole.So the result is that the acorn nut repair is only temporary, the tranny will have to be dropped and a new fork installed.Time to pull one of my spare smart cars out of storage, until I have the time to fix this one.Canmanpost-9481-1380144352_thumb.jpgpost-9481-1380144394_thumb.jpg

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Yikes yup its certainly just a temporary band aid solution to the problem. Thinking out loud if your fork is good and not punched through would it make sense to do the acorn nut mod to increase the surface area to reduce and create even wear? This is just me thinking out loud so set me straight if I'm off course.Just curious, and preventative maintenance is always a good practice.

Edited by dmoonen

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I just installed my own repair part to this all-too-common problem. I think this one is a keeper, but it requires a lathe or some skill with other tools to make it. I apologize, no photos were taken. Please take some and add to this thread for posterity if anyone tries this.

Start with a brass pipe fitting in 3/8" male pipe size and a much smaller other end. This is what I had on hand in 3/8 by 1/4 barb, without a lathe choose something like it so you have the hole already there to almost the right size and depth and a barb to hold it by, with a lathe use a pipe plug as you can drill on centre properly, or start from scratch with bar stock. You want as small a through-hole as possible, best none.

Both methods: Drill out the ID to 1/2" down to .250 bottom thick bottom, round the bottom as best you can. I have ball nose bits so it's easy, you can grind the end of the drill to get a nice socket shape as well.

With a lathe: Chuck on the hex, do the socket with a 1/2" ball nose and turn off enough threads to be able to chuck it square the other direction. Flip it, turn the outside down to about .650-.675 and put a 45 degree chamfer on the closed end, if possible leave a small land in place, perhaps .025". A concave radius that roughly matches the fork dimple would be ideal. It doesn't have to be too precisely fitted, it kind of really wants to sit properly. I cut the length down at Eddies shop to about 0.400", it was too long as made. I didn't foresee that it must be short enough to not contact the housing in the actuator retracted position. It can be pretty wide and still pass though the access hole on installation, but will interfere when in place if it's too long. This will make sense when you're looking at the fork through the hole in the hosing.

Without lathe: Same with the internals, for the outside hold the barb in a drill and shape by hand against a grinder. Finish by checking the fit in the fork and housing hole before cutting the barb off.

Both methods: Buy two of the fittings you choose for a starting point, you probably won't be satisfied with your first attempt unless you're Tolsen.

Ensure the rod fits nicely into the socket and has enough pivot to allow the new part to stay stable to the fork, check the fit into the car being sure not to drop it inside. Grease up the socket, put a good bead of your choice of two-part epoxy on the end that contacts the fork and install. Ensure it it is angled fairly flat to the fork so the rod has full pivot. Since the fork is angled one way in the actuator retracted position, it goes past 90 degrees and about the same the other way with actuator extended. So if you can see that the rod is almost but not fully pivoted in the correct way when you install it, you know you have full travel available. Overload the actuator adjustment to hold it firmly against the fork, double check the angle is good, let the epoxy set and then correctly adjust everything. Mine is in without epoxy and with the new socket held on the rod with an short piece of silicon rubber tube, it seems stable but I think epoxy would be better. Just let it stay in place as part of the fork if you have to remove the actuator later, while mine is part of the rod. Because the fork surface is so rough and also wider than the new smooth greased surface there should be a strong tendency to stay in place and let the new pivot do the moving. Maybe it's better without epoxy? I'll let you know in 100K km!

Because I used the silicone rubber tubing, it acts as an excellent seal. An O-ring that is snug on the rod, and about an inch of tube that is snug on the both the O-ring and the new brass bushing cup. If you epoxy yours, figure out something to shield it a bit to extend lube intervals, even a chunk of foam slipped one the rod would help. Lube with B-services or less, especially with the silicone tube. If packed up well with grease in the cup, it'll be good for years.

All the pivoting action now takes place between the rod and the new brass piece. The rusted pitted lousy now-with-a-hole bearing surface of the fork won't be part of the problem anymore.

I'm not going to make any for others for money, don't ask. My time is too precious for that. I possibly might for some sort of barter though... Try your offer. Edit: That may change if there is demand.. How about $75 with Canadian shipping included for a nice kit? I need about 10 before I'll sacrifice a fishing/hiking/camping/beermaking/etc day. Sign-up below, gauge demand.

I feel this is an excellent long term viable solution as long as the clutch itself hasn't been damaged by the mis-adjustment that happened as the wear developed. The actuator rod must also be in fair shape. I do fully release this idea and rough guide to anyone who want to make up a batch for sale. I'll even give more suggestions and help refine your design if anyone wants to tackle this. I'll appreciate the one I get if it's better than the one I prototyped, but that's all I want.

Update: I have changed my mind, the epoxy mount is preferred. If the actuator adjustment is perfect with no slack whatsoever, non-epoxyed will work, but if it ever goes loose at all the new part will slightly move against the fork with bumps etc and not be as stable as I want it. I still very much like the concept, this will work. Look for a new one with photos to show up.

Edited by Alex
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Sign-up for above kit. Complete, with silicone sleeving, no epoxy supplied but needed for installation. I'm thinking epoxy and the silicone sleeving as a seal is the way to go. The actuator can be removed for servicing leaving the silicone sleeve in place on the bushing cup. The existing rod must be in sorta reasonable shape, I'll leave enough extra adjustment that you can reshape even a really fubar-ed rod and still be ok. Just get the end rounded and well polished smooth, it'll be fine.1. 2.etc

Edited by Alex

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Sign-up for above kit. Complete, with silicone sleeving, no epoxy supplied but needed for installation. I'm thinking epoxy and the silicone sleeving as a seal is the way to go. The actuator can be removed for servicing leaving the silicone sleeve in place on the bushing cup. The existing rod must be in sorta reasonable shape, I'll leave enough extra adjustment that you can reshape even a really fubar-ed rod and still be ok. Just get the end rounded and well polished smooth, it'll be fine.1. David_182.etc

Edited by Alex
Matched quoted text to edits made.

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My clutch has now been replaced, failure point was actually the main clutch spring. After removal and careful inspection of the old fork wear proved minimal. So the bottom line is that a regularly lubed fork will last the life of a clutch, and the blame is on MB for not listing this as a critical lube point with a B service.

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A quick and dirty way to get the job done without taking the trans out is remove the clutch actuator push rod from the actuator, weld a nut onto the actuator push rod (yes this does render it useless to do the job right), put the small end of the rod into a drill and smooth off the points of the nut with a bench grinder (spin the drill the opposite direction as the rotation of the bench grinder and this will round it off nicely), lube it up with grease and reinstall it. Since the new push rod is bigger than the hole clutch works again. Not ideal but does the trick for cheap.Troy

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Don't know if it is the Clutch fork, but 3 bars while running, can't get in gear, can't move the car with is power.... I feel the actuator try to engage when I put it in gear.Call Towing and now in my garage.Code P0702.Grrr..

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My clutch packed it in at 228K, due to spring deterioration not plate wear, and the fork was in fine shape. Due to the amount of city and busy local highway driving I do there were an awful lot of shifts on it, so I guess the life is acceptable.The bottom line here is that a fork will easily last the life of a clutch with regular lubing, but not when run dry. MB, shame on you for not including this with the B service! At a minimum annually.

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Here's a picture of my fork, it's not the best picture but you can just make out the crack forming from the 11 o'clock to the 3 o'clock position.

post-6231-0-91513400-1413426081_thumb.jpg

I'm not sure whether to attach a 1/2" brass nub/acorn nut onto the end of the actuator rod, as some have had it fail regardless or just go whole hog & have the fork replaced by a professional

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Mine is also in a bad state and will be coming out today. My big plan is to butter up socket with 316 stainless steel by TIG welding. Then shape the weld buttered socket with a ball grinder. Will be interesting to learn how socket at other end looks like too.

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I have a small hobby type brazing/welding torch & was thinking of brazing the crack in situ then nutting the actuator rod but that is just a pipe dream, much better off to do it your way I think.

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Those without welding skills can of course buy a brand new fork. Price £ 19.63 less 20% VAT when exporting to Canada, hence £ 16.36 plus freight, Canadian handling fees and taxes. This is the complete fork assembly complete with guide tube and release bearing.

http://www.wanapart.co.uk/other/clutches-other-3189-000-245-sachs.html

My preference is for repair. The weld does not need to look good. Grease up bearing, guide tube and inner pivot at same time.

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I wonder why this thread does on show up on list of latest discussions?

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Latest discussions is really just a list of new topics. This one was started in 2011, so not recent. It does show up in the recently added posts section though.

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I understand now. Must be showing my age. Became 60 on 9 October. Those over 60 enjoy UK wide free bus travel here. Dundee for me weekly bingo night. Aberdeen for cheap ale. The only problem is the return bus ride that according to some can be rather painful unless I bring my porta potti.

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I decided to "nut" my actuator rod. The most difficult part of the job was sourcing a 3/8" brass acorn nut, unless you want to order a bag of 50 from Fastenall with a 2 day wait & a $10 shipping fee.....finally found one at a sailing marine supply shop for $1.40!

Many thanks to Smart_guy (Troy) of Wilson Automotive in Williamsburg Ont. for warning me of the crack, he even mentioned the nut trick! He is well worth the drive to his shop.Thanks for the freebie Troy!

Edited by strawboss
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I think I have a solution for this problem that can be done in-situ that will last the life of the vehicle. 

 

As many of you know, I've been working quite a bit on transmission & clutch actuation related items on this car lately and I didn't want to invest the time in an external clutch actuator until I solved this ball socket wear problem. 

 

I'll post pics of the new design shortly. I have a high precision CNC lathe here so I can whip these up like hotcakes.

 

- Quick question, and this is important to my design: Is Anyone's actuator anywhere near the limit of travel in the bolt slots AWAY from the bellhousing? Both of mine here are near the middle. Middle or closer is perfect, further and I need to know. I would think MB can hold close enough tolerances that everyone is in the same ball park. I assume as it needs to be adjusted over time it keeps getting closer to the bell housing right? Please let me know if you know!

 

Dave

Edited by DesignerDave
Added question about actuator adjustment position

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