Clutch Disengagement issue 11" clutch

[Speed_Racer 61]

I've recently completed an auto to muncie 4 speed trans conversion on my 61 Bisc with all restored factory linkage/fork. New 168 tooth flywheel, and a 552 cast iron bellhousing.

I installed an 11" LUK clutch kit but the issue I'm having is that the total release bearing travel is not enough to fully disengage the clutch disc, even with the clutch free play eliminated/release bearing right up against fingers of the clutch with the pedal up. It grinds in reverse, hard to grab any gear, and the car wants to move with even the slightest movement of the clutch off the floor. The angle of the fork is correct and there's doesn't appear to be any slop in the linkage, so I'm thinking that this clutch must just need more distance to disengage than the stock linkage is designed to provide.

I'd rather not lengthen the 'arm' on the zbar to get more throw either.

Can anyone recommend a specific 11" clutch for a 10 spline Muncie that they've had luck with working with the stock linkage which at least allows for some free play adjustment?

 

[Phil Reed]

I'd like to see a picture of your clutch fork.

 

[Speed_Racer 61]

Come to think of it, I can't be entirely certain that the fork is a restored original. It came with the bellhousing and I was told by a few sources that it's the correct one for a 61. It's 10.5" long, tip to tip.

The remainder of the linkage is from Paul on this site and is all nicely restored originals inc. zbar, rods/pins etc...

 

[MRHP]

Can you get any pictures of the installed linkage from different angles? From the top, and bottom.

 

[Phil Reed]

That is a 55-60 clutch fork. You will need 61-63 fork. That will put your pivot point about 1/2 inch forward. Paul will have one.

 

[Speed_Racer 61]

Okay...a few things... I just went back out to look at everything again after my maiden test drive. A couple of things I noticed;

1) The rear portion of the [plastic] fork groove on the release bearing is broken. PLASTIC CRAP! Not sure why LUK makes plastic pieces on their release bearings.

2) I now noticed play in the upper clutch rod to Z bar linkage. There's an anti rattle spring that Paul included but I couldn't really see how it attached to the Z bar portion so I left it out and before the test drive, everything seemed tight. Here's a vid to the play in the linkage:

From underneath, this appears to be equal to about 1/16" to 1/8" of bearing travel, so that's not helping.

Linkage pics

Chris

 

[MRHP]

Number one, you have way too much slop in the upper linkage. It also appears your upper z bar ear is much too far forward. It is over center so the travel is diminished. I believe the over center issue would be remedied with the correct throw out arm Phil has recommended.

 

[Speed_Racer 61]

That is a 55-60 clutch fork. You will need 61-63 fork. That will put your pivot point about 1/2 inch forward. Paul will have one.

Okay I may have to try that. I'm going to see if taking up the play in the upper clutch rod helps.

 

[63impalass409]

Is the clutch disc itself installed the correct way? Very easy to put it in backwards.

 

[Speed_Racer 61]

Number one, you have way too much slop in the upper linkage.

Is there supposed to be slop there and then it's just tightened up by the retaining spring (not in pic)? Or is it supposed to be a fairly snug fit there?

 

[Speed_Racer 61]

Is the clutch disc itself installed the correct way? Very easy to put it in backwards.

Yes I was sure I installed it correctly with the 'flywheel side' label facing the flywheel... but nothing would surprise me with this swap!

 

[Phil Reed]

It looks like you have the correct 61 clutch fork push rod. Get the correct clutch fork.

 

[MRHP]

No slop in the upper joint. By what Phil has explained, the correct fork arm would move the linkage in the correct direction you need it to go.

 

[DonSSDD]

The geometry is off, caused by the wrong clutch fork like Phil said and/or the wrong bell housing pivot bolt/mount for the clutch fork.

While you have it apart, check this too. Your clutch fork when mounted should be fairly "square" to the lower clutch rod, where they meet. It is angled forward now.

Phil or someone will know the correct length for the clutch fork pivot bolt, I think that over the years there may be 2 or 3 of these in different lengths that screw inside the BH.

I think your z bar at the firewall clutch rod connection should be straight up at rest or very close to it. Is your clutch rod, z bar, and lower rod a matching set from a 61?

Once you get this right, you won't have to mess with it again for a long time. You must be young like Phil and I and still able to drive a manual tranny?

 

[pvs409]

I did not read this until today..
After reading all the comments and the pictures.
I have done this a number of times on my 62's, a 63 and at least one 61 Chevy.
I did supply the 1961 linkage.

• Speed racer I bet you have somewhere around 3 to 4 inches of free play in your clutch pedal under the dash(too much)- there should be no movement in the pin at the top of the Z bar when you have the right free play ......... Do you know how you check this ? The clutch pedal is depressed until you feel resistance from it hitting the throughout bearing that hits the clutch forks -Proper free play should only be 3/4 " to 1 inch on the pedal when you depress it.
• Or also check for clutch release with the transmission in gear with someone pushing the clutch to the floor -turn the driveshaft...
• You can and should lengthen your lower threaded arm to reduce your free play -assuming the rod will not hit the exhaust manifolds or pipes when you lengthen it. What is your free play if you adjust the treaded rod "out as far as it will go" ?....In fact run it out as far as you can and test the car..... Try this first and make sure it does not work before you have to check what I have noted below on my 409s.
• I installed a full 1961 Chevy clutch linkage set on a 61 Impala 409 car and it had all the original linkage that I remember and how we installed it. That car is in California now and I can get pictures of it since my pictures did not come out. That car had two lower parts to the lower linkage -a rod and a 90 degree bracket to the Z bar and the threaded rod. I did not like this lower linkage set -too loose and to many connections.
• On my two 409s I had to have a longer lower rod(over 11 inches long) and in one case I had to reverse the rod to have the threaded end at the clutch fork to clear my stock 409 big tube cast iron exhaust manifolds. Thats why you have a longer adjustable threaded rod on your set as compared to the 2 stock pieces

• The Z bar he has is 100 % original 1961 to match the upper rod through the firewall
• The upper clutch rod through the firewall is 100 % original to fit his 61 under dash clutch linkage and pull back spring on the clutch support bracket under his dash.
• The lower rod he has is threaded for adjustment (like all 61's) and had a flat pin that sits on top of the clutch fork. I do not remember how long the lower threaded rod is that he has.
• I have found at least 2 different types of lower 1961 push rod linkage while installing linkage in 4 - 409 - 1961, 1962 and 1963 Chevy's. One set of 61 lower linkage rods and brackets I think is not a good setup (it has 3 different pieces..)
• On my 409's the lower clutch push rod has to be threaded "to get the clutch pedal free play right" and it has to be at least 11 inches long with a sliding swivel with 2 tightening nuts(or the rod and pin that Speed racer has). The rod needs to be 3/8 by 24 threads and have 3/8 by 24 nuts for the swivel when buying a new repro lower rod.
• The clutch fork does not have to be changed....... In fact if he changes to a 62-63 clutch fork the push type rod with a pin end and a pin for the clutch fork --- for those years has a lower push rod that is "not long enough"(its just over 9 inches)".
• I just had this exact problem(that Speed Racer has) on my 62 Impala SS 409 Convertible with a stock 552 cast bell housing and a 62-63 clutch fork. It does have a Richmond 5 speed transmission with a short throughout bearing. I had way to much free play -the clutch would not disengage--- (the factory original push rod with a pin and pin in the top of my 62-63 clutch fork was too short) and I had to buy a 12 inch long threaded rod(from Show Cars) and modify a original pin in the top of the clutch fork. The reason I did it this way is the 62-63 clutch fork does not have a slot in it to install a long 11" to 12" long threaded rod and a pin through the clutch fork hole.
• I actually purchased every lower rod for 1961 to 1963 -- 283, 327 and 409 cars "that Show Cars had" that I did not have - to try to solve my problem with my 62 SS 409 convertible. I would have had to remove my 5 speed transmission and change to the clutch fork like Speed Racers 1961 set. "I did not want to remove my transmission.................."
• My 2nd 409 car ----a 1962 SS 409 Hardtop has all the correct 62 to 63 clutch linkage (Z bar, upper rod with a pull back spring to the firewall). I have the 1955 to 196o clutch fork in this 62 SS 409 Hardtop -- This 409 has a Muncie 4 speed, a 11 inch flywheel and clutch and a scattershield. It has a 11 1/2 long threaded rod for the lower arm with a pin in to hold the arm in the slot on the 1955 to 1960 clutch fork that has a slot in it. With this set up I got the proper free play.
• The 61/62-63 409 style clutch fork that everyone is suggesting does not have a slot for a lower rod. It is about 1 " closer to the the Z bar "as has been noted on this posting" but in my opinion that is not enough to get the right free play when you adjust the linkage(as I stated above all 61's had lower threaded rods --62 and 63 did not have a threaded lower push rod).
• Why the original "shorter" lower rod and pin to the clutch fork for the threaded rod does not work on both my 409s and on speed racer's 1961 ( his might with more adjustment as I noted above ?) .., I am still not sure..... I do know that what I suggest above with 11 inch lower rod and swivel and nuts DOES WORK ..... perhaps its the short throughout bearing vs a tall throwout bearing or just slightly different clutch release forks is part of the problem.
• Finally the lower rod and pin that Speed Racer has -- I looked everywhere to find the flat pin that mounts the rod(that I sold him --to avoid pulling my transmission) to hold the 11 inch threaded rod in the clutch fork and they are not available (I found the GM part number - but I could not find a used or NOS part) - I made one from a repro 62/63 pin that was flat on one side conical on the other side.
• I personally like the threaded rod and pin and 55-60 Clutch fork much better than the rod and pin on top of the clutch fork even though its not correct to get better clutch adjustment and also because you can use a rod that fits into the 55-60 "clutch fork slot" pushes on the center of the clutch fork vs the top of the clutch fork.....Both methods work I have them now on both of my 409s
• Here is the lower push rod and pin on my 62 SS 409 Hardtop that I used - but the one I have is even longer than this one...http://www.ebay.com/itm/1955-1956-1...sh-Rod-Kit-Belair-Sedan-/253165597797?vxp=mtr

Paul

 

[Phil Reed]

A 61 must have the "override spring" installed under the dash on the clutch pedal also.

 

[Speed_Racer 61]

Thanks everyone for chiming in. As usual, Paul's very detailed approach is much appreciated.

A 61 must have the "override spring" installed under the dash on the clutch pedal also.

Yes, I have that spring, but my return is a little weak and has a hard time returning through the free play area. I may add a '62 style return spring to the linkage.

The Zbar lever angle is exactly how it looks in the manual, and is also determined by the upper clutch rod length, and as Paul says, both are from a 61 so I can't see how the lever is sitting too far forward. Maybe it was the camera perspective. It looks in-person to be pointing at 11 o'clock. Also, from a geometry perspective it seems to be not bad. At about 1/2 clutch pedal travel the fork centre line is perpendicular to the engine, so seems pretty squared up. Also, at rest, the outer fork end is in front of the ball stud, so both of those should mean that I'm at least getting a symmetrical 'swing' pattern at the fork throughout the pedal travel. It could be adjusted a few degrees here or there to be perfect but does that really change the overall 'throw'?

Paul: the lower rod and attaching mechanisms seem fine from a length perspective. I have lots of adjustment through the threaded swivel on the forward end. I can adjust it all the way back so there's 3/8" of space between the release bearing and clutch fingers (about 3-4 inches of pedal free play) AND, I can also adjust it right up tight so the release bearing is right on the clutch fingers (no free play) at the start of the pedal travel.

However, when I adjust it for no (or little) free play, I made an interesting discovery.... this clutch fork hits the floor/toeboard seam!! So it's preventing about 1/8" of release bearing travel.

When I adjust it for lots of free play, the outer part of the fork sits more forward of course, and at full travel doesn't quite hit the seam. Even then though, my total release bearing travel is about .500" which once I adjust a free play gap, still might not be enough 'throw'. This is where that 61-63 might have come in handy. I think the bend in it is more aggressive and it would start more forward, allowing full throw and not hitting the seam.

I'm going to see if I can mod the seam a bit to get full throw with a tight free play adjustment and then measure to see if I have enough pressure plate to clutch disc clearance for 'full' release (apparently about .050" of gap between PP and clutch disc).

....or, I may try an adjustable ball stud, raise the height of it and move the fork forward away from the floor seam....

Oh how I love these open bottom bell housings!

 

[Speed_Racer 61]

It looks like you have the correct 61 clutch fork push rod. Get the correct clutch fork.

Just a quick update on this. I found a proper 61-62 clutch fork, used. It puts the outer part of the arm about an inch forward. That seemed to sort out all of the geometry issues, it drives like a brand new car now. It must have a different pivot ratio as well.

I don't get why the aftermarket suppliers can't get it straight when it comes to application/fittment. I can't find a single supplier that either has this 61-62 fork, or that correctly labels the fork in the pics above as not fitting 61-62.

 

[Don Jacks]

If you';re using a diaphram type pressure plate,the correct flywheel to disc clearance should be .035.The ..050 is meant for the Borg-Beck pressure plate.Excessive clearance on a diaphram pressure plate will cause the clutch pedal to stick to the floor on a high rpm quick or "speed" shift.

 

[mark johnson]

Setting the clutch linkage to the Assembly Manual specifications has worked well for me. I try to adjust it once a summer (when the car's together!) and it's pretty amazing to me that it usually always need the adjustment due to disc wear, etc.