The Stovebolt Site Forums The Shop Area Engine Shop Clutch? Tranny? Linkage?

Have a GMC 1/2 ton with a 261 in it. Replaced the clutch complete. Rebuilt the tranny. Was adjusting the shift linkage for the 3 on the tree today. Managed to get the neutral gate on the shift box working smoothly. Can get it into all gears with the engine off and clutch depressed to the floor. Have about 1/2 to 3/4 inch pedal freeplay before the clutch arm starts to move. Pulled the bellhousing pan and looked at the release bearing. Can rotate it with my finger with just a small scratching sound against the PP springs. Moves back and forth just about 1/8 inch away from the PP. Checked that the clutch disc is separating from the PP when the clutch is depressed. Moves about 1/32 to 1/16 inch off the flywheel when the pedal is fully depressed. Problem is that the tranny gears grind when trying to move into any speed and I can't get any of them to engage. Is the disc far enough away from the PP at that distance? This is driving me nuts as I've finished the rebuild but can't go anywhere!!

49 geezer,

Excellent troubleshooting. You sure have been down this road before it appears. My only thought would be that with the clutch pedal completely depressed the wiggle room between flywheel and pressure place should be much much more than 1/32 to 1/16 of an inch. This is provided this is what you meant, or that I read it correctly.

Even with a hanging clutch, your three speed should be fully synchronized, even into first shouldn't it...why the grinding.

I wonder if the shift forks (side cover) are aligned correctly inside the transmission. The thing should attempt to go into gear without grinding if all is proper inside the transmission.

Stuart

Stuart;
A bit more information. The tranny has an unsynchro first. I also agree that the disc should be moving further away from the plate when the pedal is fully depressed. Here's what else I've checked. Put the tranny in third gear, depressed the clutch and started the truck. Immediately the speedo went to 20 mph with the pedal down. Let out the pedal, same speed. Pushed the pedal in and out several times and no speed change. Also put the tranny in neutral and used a board in the cab to depress the clutch pedal fully. Should have been able to rotate the disc right? Can't do it. So obviously, the clutch is the culprit. Now, the clutch is an 11" 6 bolt unit with raised springs on the plate. I got it from Carter along with the disc and throwout bearing. In looking at some of the other vendors, some show two different bearings where Carter shows only one. The two are differentiated by being for "flat diaphragm plate and raised diaphgram plate". I'm wondering if I've gotten the wrong throwout bearing. If I increase the pedal free play just an 1/8 inch to get the bearing from not touching the splines, then that will make the distance that the pedal has to travel to fully depress the splines even further and negate any release of the disc from the plate. Are there indeed two different bearings and is one longer than the other?

49 geezer,

I'm calling on my memory banks, but I'm pretty darn sure there was a long and a short throwout bearing. Chevrolet usually used the pressure plate with the multitude of flat fingers and the short throwout bearing. Not sure, but I thought the other type, with the three arms, was referred to the Borg & Beck type and it might have taken the long throwout bearing.

You are very hot on the trail of a solution, and when someone pops into this thread that has been down this road recently, the answer will be revealed. Anything more from me will be speculation and confuse the issue...as usually happens. Good luck.

Stuart

The problem could also be a tight fit in the pilot bushing, (if it a bushing and not a bearing), or the clutch disk installed backward. Some disks have hub springs that stick out further on one side and will hit the flywheel it not installed correctly.

There are 2 types of diaphram clutches. One has the fingers inside the pressure assem. & the other the fingers stick out to the edge, commonly called a beehive clutch. The first one uses a t.o. bgr with a coller called a long T.O. brg. the beehive uses a short brg. with the brg. next to the groove. If you have the right match adjust the clutch to a point where there is almost no freeplay. Then put it in high gear with the engine off & start it up. If it will start slip the clutch a little to wear down the high spots. If it doesn,t start working you are going to have to pull it back out. If it does you can go back & put a little more free play in the linkage. Did you get a reman clutch or a new matched set?

Thanks! From what I've been able to see, there is a TO bearing that is 1 7/8" long (high) and another that is 1 1/4" long (high). I have the plate that has many fingers (not flat but raised somewhat outside the PP collar) and not the three finger type. The TO bearing that is installed is the 1 7/8" bearing. The TO bearing shaft is riding well on the bearing but just not depressing the fingers enough to give me full release. Now, if the bearing should be a 1 1/4" unit, it seems like that would be counterproductive in that the ability of the TO shaft would be 5/8" less "tall" and I wouldn't get any depression at all on the fingers unless....by using the shorter TO bearing, I can adjust the clutch linkage in a way that would allow the bearing to get closer?? Right now, the clutch linkage is adjusted approximately in the middle of the clutch arm. I can adjust it either way approximately an inch or so. The assembly I got from Carter's installed beautifully and my machinist who rebuilt the engine balanced the PP and never said that there might be a problem. Still think it has something to do with the TO bearing but really don't want to pull everything out if there is another solution. Stuart may be right in the fact that the short bearing may be correct for the Chevy clutch and I've installed the wrong one.

49 geezer,

What you say makes sense. If your clutch arm is adjusted mid-point on the threaded adjustment, your pedal free play is proper and your TO bearing can be released enough to spin freely, then it should seem all is correct.

The difference between a long and short TO bearing would show itself in where the clutch arm was adjusted. Both might work, but the incorrect one for the pressure plate would put the adjustment at the extreme end of the range.

Did any arm or piece of linkage get changed to reduce the pivot point or change the advantage/travel when the pedal is depressed. How about thick carpets!

It seems unlikely that a Bolt supplier could send the wrong item as they deal with these rigs all day long. It's something obvious I'll bet.

Stuart

The manuals will have you adjust the clutch for pedal free play but I understand that the proper way is to pull the inspection cover and adjust for lutch disk to pressure plate to flywheel gap with pedal pressed. I think bottom line is that you just want some free play at the top of the pedal to keep the throwout bearing from being constantly driven when pedal is not pressed.

From your description you have the wrong TO brg. The one with the fingers extended to the edge of the clutch takes the short brg.

Please describe what you mean by "fingers extended to the edge of the clutch".

I think you best described it as "raised somewhat outside the pp coller". The other style has the fingers almost straight across in the center of the pp.

Hey wrenchbender,here's a picture of my 1951 preassure plate.It is the original application for the truck.Maybe this will help explain !! my 1951 chevy preassure plate

This is a borg and beck heavy duty truck application,will make your leg hurt !!
borg and beck preassure plate

Thanks Tim. That is the original type with the flat fingers. It uses the long T.O. brg. The newer type has the fingers curved up out of the cover. The newer type came out about early-mid 70,s & is in most replacements. It uses the short TO brg. That,s the best I can explain it.
Tim, Are you comeing to the Woodlands swap meet in April? Con & I have a booth but I don,t know the #,s yet. I will post them when I get them. Come by & say hy.

10-4 wrenchbender! (BTW, I was explaining some of the people responding to this post and my wife thought your name handle was very funny). I have the fingers that rise out of the PP collar and not flat like Tim shows. Therefore, I'm going to get the shorter TO bearing, yank the stinking tranny and longbed extension next weekend and get the darn thing in. Hope it's right 'cause something is certainly wrong. It was interesting that Carter sold me the entire clutch assembly and they only list the long TO bearing and no short one and as fitting from early '40's to the 70's. It's a pisser!

OK...got the entire thing apart. Looking at the clutch disc. One side of the disc has an extended hub at the center and the other side is basically flat. Doesn't the entended hub face towards the front of the engine (flywheel?) and the flatter side towards the rear (tranny)?

Nope, usually the extended hub tucks inside the pressure plate housing. The flat side goes to the flywheel. There usually isn't enough room for the hub and spring plate to tuck inside the flywheel recess. You can confirm this by holding the clutch plate against the flywheel.

Interesting. Both my GMC and Chevrolet shop manuals clearly show a cutaway of the clutch assembly with the raised or elongated hub of the disc facing towards the flywheel. I went down to my truck and placed the disc up against the flywheel. There is definitely room for the hub to fit totally within the recess in the center of the flywheel.

My bet is that the books are correct. Mine went in the other direction because the hub was touching the pilot bushing. Mine is probably backwards, but it has worked flawlessly for many years. Take a real close look to make sure nothing is rubbing. Also, make sure the clutch disk slides freely on the input shaft of the transmission. If it is snug at all, it may not be backing off the flyweel when the clutch is disengaged.

It,s usually marked on the disc. (Flywheel side). The extended part goes to the pressure plate.

Interesting again. The disc I've got is marked with flywheel side on the side that is flat in the center hub. The other side, with the extended hub is not marked at all. Originally, I installed the flat side towards the flywheel based upon the imprinted markings stating "flywheel side". However, from my earlier posts on this subject, I could not adjust the free play enough to release the disc from the PP. Tranny was grinding in all gears. I'm thinking that the elongated hub needs to be towards the flywheel (it'll fit nicely) and that's what will solve the problem. The shop diagrams all show the elongated hub facing towards the flywheel. My original parts were exactly what I have now as replacement parts. Nothing else has changed except the position of the disc. So, I have a 50/50 opinion on which way it should face.

I've seen this problem come from not driving the pilot bushing in far enough. Loosen all the tranny bolts and install a flat washer on each bolt between the tranny and the bell. Then see if the no release problem is still there.

Hey Geezer....please check your email!

Dave

Still not sure what to do here. The picture below shows the disc with the "flywheel side" clearly marked. However, this is on the flat side of the hub. Any possibility that the rebuilder of the disc did this one backwards? Just fishing here.....

Also, this is an 11" clutch, 6 bolt on my 261 but is mated to my original 3 speed tranny that I rebuilt. Do I need a different clutch assembly period? I always thought that you matched the PP and disc to the flywheel.


http://good-times.webshots.com/photo/2089747560010188466PAAWEf

Yes you match the clutch size to the flywheel. I like the smaller ones with the old trans. It,s easier on the syncros but doesn,t make much difference.

Problem solved! Went to NAPA with the 11" disc part number I got off their website. They ordered it for me and when I got it, the elongated part of the hub was on the side clearly marked "Flywheel side". Put the disc in with the pressure plate I got from Jim Carter, used the long throwout bearing and perfect! Restabbed the tranny (with some difficulty because I must have gotten the alignment to the crank bushing off by 1/8") and readjusted the linkage. Works great and disc moves freely with the pedal depressed. Now, onto reinstalling the two u-joints and balls again. Posted some pics of the clutch issue in a new album.

http://community.webshots.com/user/geezer

Refilled the tranny today and injected grease into the rear u-joint fitting to replace what I lost when I took the drive train apart. Checked everything over and started the old Geezer up. No TO bushing whine, all quiet from the tranny. Slipped it into 1st, 2nd and 3rd gears. Smooth through the neutral gate of the shift housing and the rear wheels did what they were supposed to do. Checked reverse...all good. Clutch behaving like it should and tranny was quiet (truck is still on jackstands). Now, onto final tuning and dual 2bbl carb adjustment. Still idling too fast but that may be my initial timing. Getting closer to getting this sucker back on the road. Been a longgggggg rebuild.

Hi you sure have a lot of good feedback on your
question. So I'll add my 2-cents by saying it soiunds as if the clutch is in backwards, I did that once on a 42 Dodge power-wagon. Good luck.

This is scary! I have been working on my T5 swap for months... had it in and out of my '52 a dozen times and never thought that the clutch disc might be in the wrong way. I am using RCF-4190 which is a 9 1/8" 14 spline disc. Anyone know if the flat side goes toward the pressure plate or the flywheel? I have always installed it with the flat side to the flywheel.

Just did some grinding on it last night for more clutch travel and almost have it back in... if that doesn't fix it I suppose I will tear it down again and flip the clutch disc.