Hot Rods Clutch pressure plate issues

I'm wrestling with a pressure plate clutch pack issue. This is mounted in front of a Saginaw 4 speed which is behind a 250 inline six, all inside a '48 chevy truck.
I've changed my linkage and Z bar set up a few times now and I'm still getting the same symptom. Its a progressively hard pedal for about 3" of pedal travel and then it feels like it bumps over a hump and it gets easy for the last 2" of travel. The return of the pedal has a lot of pressure that finally bumps over again and returns to original pedal position.
I can only describe it as oil-canning. It feels like the pressure plate fingers reach a point to where it goes past its leverage, and "pops" past that point and the rear wheel can then be rotated. When releasing the pedal, it "pops" back against my left foot and then returns to the original position.
I even slid a long breaker bar over the clutch fork to work the pressure plate directly, byp***ing the linkage. It still has this oil-canning effect and it feels like it takes more effort to move the clutch fork than it should.
The clutch pack I ordered was a 10" LUK 1104003 that came with a throw out bearing and a pilot bushing. I also ordered a LUK 88131 flywheel. Both were rated as stock replacements. I'm using a stock clutch fork and stock aluminum bellhousing.
Does anyone know why I'm getting such a hard pedal with the oil-can effect?
Thanks for any input!

 

Borg&Beck, Long, or Diaphram?

 

Sounds to me like the ratio is wrong. I ***ume you used the original pedals, so linkage would be similar, but home made. The pedal travel seems like its going too far, and a different hole in the arm to shorten up the distance it travels.

 

I see it's a diaphragm style and ***ume you're using the New disc and matching T.H. bearing that all came as a kit. That said we know that the disc loads the P.P. to a certain point due to its Thickness. The fingers of the P.P. now move inboard to proper loaded position. It's a to center and over center fulcrum style movement. My question is are you sure you have the correct thickness disc. Have you actually driven your Truck so that your sure the disc is fully releasing enough to shift the Trans. I also ***ume the aluminum bellhousing your using has the Ball style pivot for the Fork to mount on.

 

Since it's a diaphram style clutch, maybe some mix up between whether you need a high-cone or low cone diaphragm. What style was the old pressure plate, ***uming you had one? Maybe look at the length of the throwout bearing as well. Is the T.O. properly seated in the end of the clutch fork?

 

Make sure when you installed the throwout bearing in the fork that you have all of the fork in the groove, do not use the sheetmetal clip on the fork to clip the throwout bearing into place

 

Does your housing have a removable inspection cover on the bottom so you can watch the clutch operate? I would remove the clutch and put it in a hydraulic press......flywheel and everything. Then use the hyd press to make the clutch operate. If there is a problem, you should be able to see it. Might need an extra input shaft and the front bearing retainer to keep it aligned while pressing it.

 

If you changed to hanging pedals does your ***embly have an over center spring that helps push the clutch. try removing the push rod and push the pedal when about 1/2 way down does it snap to the floor? https://www.ebay.com/itm/155052961816?hash=item2419e07018:g:u2cAAOSwxehiuJmF

 

Its possible you solved your problem yourself. Have some one look while depressing the clutch ,is the firewall flexing or something shifting

 

It might be a dumb question but, is the clutch installed properly?

 

Define stock fork and bell housing. Stock to 48 I don't think so since it's aluminum.
Here's an issue I had once using bell housing F lets say onto vehicle that normally uses bell housing A. The issue was fork end out side of bell housing was to low as compared to where it should and caused major bidding to happen with the throw out bearing to bearing retainer sleeve. Think steel ring sliding down a pipe and suddenly stopping.

 

Look for unusual wear patterns on the pressure plate fingers and where they contact the face of the throwout bearing. Hard to describe in words so maybe post some pics if something looks su****ious. Also check for wear, roughness or rust where the T.O. bearing slides on the transmission's front bearing retainer.

 

This is a common issue in first gen FE Ford and post 61 bellhousings. The clock placement coming out of the bellhousing of the latter fork changed just a little and don't work for Beans when used in 59 and earlier cars. It causes the fork pushrod travel downhill causing a twist action in the Fork. There's n ow a bind in the throw out bearings travel.

 

It sounds like my 59 corvette when the clutch isn't adjusted properly. When the spring just flips over out of control. JMO

 

OK, lets break down what I mean then. That bellhousing OP has may not (?) be working well in a 48 truck. OP's 3rd sentence states "I've changed my linkage and Z bar set up a few times now". Now everything is way way away from just a 48 truck with stock linkage and later engine and trans that all ready had clutch pedal issues. Heck!, it could be the ball stud isn't of proper length ???

Just giving options to "look" at is all.

 

True, true. Just because you make a connecting link between part A and part C don't mean things are going to work together properly.

 

In going back and reading the opening statement again it sounds like Fulcrum to lever issue. I doubt there is 2 locations for the Fulcrum or Ball in your case but there may be a shorter ball or provisions to screw it in further to aid in initial movement taking less pressure and smother movement. You may be using a tall T.H.B. where a short one would do a better job.

 

^^^^^ Reading again my self "Z bar"?
@The_Monster have you changed things around from this sytle set up of the era of your truck?


Better look at all the parts

 

Keep in mind that if the PP was a Long or Borg and Beck type and is changed to a diaphragm type you may need to replace the fork and/or the throw-out bearing. Might also require a different ball stud as well to get the proper leverage. Saw this problem on a Chevy truck, 4X4 4sp, 250. Parts catalog and tech line both said a diaphragm type would replace a Long or B&B. Not true. Went together fine but the pedal effort was so high you would have had to be a 400lb weightlifter to drive it. Disengagement was also questionable.

 

Leverage length and travel ratio are critical. One minor change can create major issues. I think this is what you're dealing with. Were I you I'd go back to the stock truck pieces for pedal and rods. Then go to the stock truck bellhousing and find the Fork freelength and pivot point and try to duplicate that as close as possible.

 

Thanks for everyones replies!
Now to answer some folks questions:

Seb Fontana-I'm not quite sure what you're asking(?) Not familiar with borg&beck

Rusty Valley-Im not using the original pedal ***embly. When I purchased it, It originally was a '53 GMC that had been in a T-bone wreck. The frame was bent. I swapped it for a straight short bed frame from a '48. The original '53 ***le was lost. However, the '48 ***le was good. I cut the wing windows out of the doors, fabbed new window runners, installed full gl*** and call it a '48.
The frame came with no pedals. I purchased a hanging brake pedal set up designed for '47-'54 trucks. It comes with a beefy firewall support and it bolts into the dash on both sides of the steering column mount (No after market hanging pedal ***emblies for these trucks offer a clutch pedal)
So, I purchased the same thickness steel, traced out my brake pedal and cut it out with my plasma.
It has 5" of pedal movement from resting to floorboard, same as the brake.
The 250 inline six had a thread on the block, back close to the bellhousing mount surface. A threaded ball goes there. The Z bar slides over that and the other end of the Z bar has an original Chevy II mount bracket that I bolted to the frame. The linkage from the clutch pedal to the Z bar AND from the Z bar to the clutch fork is 3/8 hiem joints with S.S. all-thread.
I have changed the location of where the linkage bolts to the clutch pedal, changed the length and position of the arms on the Z bar three times. I even cut out a bunch of cardboard clutch pedals and Z bar layouts, used pivot points and connected them with bailing wire to try out a ton of different leverage points.
However, I dont think its a linkage problem. I byp***ed the linkage all together. I slid a long 5' piece of exhaust pipe over the clutch fork and pulled it back, simulating the movement of a depressed clutch, and it has the same symptoms. Very hard to pull (at least harder than I think it should be) and then POP, it oil-cans. When it releases, it almost chucks the pipe out of my hands!

Pist-n-broke-Yes, everything came as a kit. I ordered it from Napa and told them I was working on a '72 Nova with a 250 inline and a Saginaw 4 speed.
Good question, I dont know if I have the correct thickness of disc, but it was the napa computers suggestion.
I have not driven the truck yet. However, I lifted one rear tire off the ground with a stand, and put it into first. With my brothers help, I would depress the clutch as he would try to rotate the tire. Once the pressure plate "popped" he could then rotate it, but not before that.
And yes, the aluminum bell housing is the ball style that the clutch fork clips into.

ClayMart-I was unaware there were high cone or low cone pressure plates to choose from. Humm, maybe I have a high cone. That would explain the hard clutch pedal?
Unfortunately, I dont have an original pressure plate or clutch pack to compare it to.
I'll look to see if the T.O. is properly seated. I know I paid close attention when ***embling it, but it may have moved?

57chevymadman-Correct! I read that in the service manuals I have and paid close attention to that, however, it could of moved just before bolting it all up. I'll check on that

Ekimneirbo-Yes, it does have the inspection cover area. I dont have a cover on it right now and thats a fantastic idea, DUH! I'll have my brother work the clutch while I peek to see anything.
I have a large hydro press. Thats also a great idea to take it all out and look at everything operate on the press.

Sunbeam-thanks for suppying the ebay picture. No, my pedal ***embly came from Speedway Part # 91047538. A spring ***ist sounds like a nice idea though, hummm

Garyf-The pedal ***embly I purchased was well engineered to eliminate firewall flex, so thankfully thats not the problem

NoelC-Thats not a dumb question! And at this point, who knows!? It sounds like I may be pulling this motor/trans again, so I guess time will tell

Johnny Gee-Good question, its not a stock fork and bell from a '48. I just let everyone know what this drivetrain was in to give a visual really. I feel like this drivetrain could be in any stripped down frame and I would be having the same issues.

Claymart-It hasnt run with this transmission. The motor runs like a dream but I havent ran it with this trans yet. Not until I get this sorted

Pist-n-broke-Maybe the clutch fork I have isnt the correct one for this bellhousing. I never gave it much thought. Ive only seen ones like I have in all my chevy repair books. But maybe they were different somehow??

jimvette59-how did you get it back into adjustment?

jimmy six-I dont think theres clearance before the oil can, because the tire wont rotate until it oil cans. The clutch fork moves 2" total. I thought, if it will release before it oil cans, I'll adjust the clutch arm or Z bar linkage to make it only push the clutch fork 1".

Johnny Gee-Are there different clutch fork ball lengths??? If so, I had no idea! man, theres way too many variables going into this now! haha

Pist-n-broke-T.H.B. whats that?? So thre ARE different legths of balls? There is only one ball location in my bellhousing. I have about 4 bellhousings of the same era. They all only have one ball location

Jonny Gee-Ive moved SOOOOO far away from the original set up! hahaha! BUT, even still, with the exhaust pipe on the clutch fork, it still oil cans. So I dont think its my pedal, linkage set up.

Brandol-VERY INTERESTING!! It sounds like this may be my problem?? How do I check if I have one or the other? This may be what Seb Fontana was refering to? I gave my part info earlier. Can you tell if those are one or the other?

Pist-n-broke-Ive looked at the orignal illustrations of what the 47-54 truck clutch pedals and linkage looked like. My application wont work with that set up. Also, The pipe on the clutch fork gives the same oil can, so I dont think its the linkage.


Ive sourced a cable company that makes custom cables for all applications. I may go to a clutch cable for this set up and forget the linkage set up.
Thanks to everyone for all your suggestions and ideas! I'll update this thread as I learn more.

 

Personally I’ve had no luck with LUC clutch kits, first one I got the clutch and pressure plate were too small, throw out bearing was correct, back to the parts place, wrong clutch in correct box so they sent it back. Second one comes in, disc and pp are correct but the throw out bearing is nfg, greased and in a sealed bag but rough as department store *** wipe. Took that **** back and went to another parts store and got parts from another source.

 

THB means Throw Out Bearing. I'm going to agree with you here that your initial problem is something inside the Bellhousing. Until you can do a full swing smoothly with the Fork something is wrong. I believe there are 3 different Forks that you could be using. The difference is the outboard ends pending vehicle they come from. I also believe from the pivot ball detent to actual T,H,B, fork they all are the same. I have been told there is a Truck Bellhousing that's deeper for a larger pressure plate and the screw in ball is different to them. May or may not have anything to do with your problem. Best of luck to ya.

 

On most standard duty diaphragm clutches, the release fingers lay fairly flat. They angle up only slightly toward the center where they contact the T.O. bearing forming a "low cone".

Heavy duty or H.P. diaphragm clutches will have fingers that angle up more prominently and form a more pronounced "high cone". This is also where having the correct height T.O. bearing is critical.

 

I only use Centerforce or Ram clutch kits. Never had a problem with either one and great service. I tried putting a NAPA kit in a OT ford 4x4 once it did not fit. Took it back and got a CenterForce. Worked great!

Your issues kind of remind me of a backwards disc.

 

if you haven't I'd get someone to push the pedal while you watch the clutch linkage move through it's cycle. You may have a rod bending and then popping straight after the z bar breaks over a certain point.

I've run a Cast iron V8 bellhousing with the stock floor pedals for probably 150K and outside of wearing out a few disks never had a problem like that. I never run fancy clutches either as mine are usually mix and match of what is in the stash in the shed or what I got a deal on at the parts house I used to work at.

 

I checked online but can't find an illustration under the part# you gave. Just Google long style, B&B style, and diaphragm style. Click on "images" in the heading across the top of the page and it will display photos. If you saw and recall the PP you put in it will be obvious which one you have. Did you ever have the PP that was originally installed? If they look radically different you need to look further into this to see what PP and throw-out bearing fits your application.
The relationship between the throw-out bearing and PP is critical to proper operation. You not only have to be concerned about the spacing of the throw-out bearing to the clutch, it has to engage the fingers on center and maintain center through the range of travel. The "oil can" feel you are getting could be the bearing sliding laterally across the PP fingers as it goes through its travel.
You might also consider that most 6/8 cyl Chevy motors had the option of an 11" clutch and many of the flywheels are drilled for both patterns. If you have a fork for an 11" clutch that could be the problem. I think the bellhousing is the same for both 10" and 11" and they make up the difference by using a longer fork.
I would hold off on ordering a cable setup as it sounds like your problem could well be the arm/throw-out bearing relationship. You also need to consider @Pist-n- Broke's advice about the linkage. As simple as it looks, there's a whole lot of monkey motion going on down there and it only takes a small deviation to screw up the whole process.

 

The throw out bearing could be the wrong one. Chevy did use 3 different styles. Long and Borg & Beck were mostly used in Fords. I think someone earlier in the thread ***umed you were working on a Ford.

 

Alright Fellas, here's how I see things given what we know. The main issue is clearly inside the Bellhousing. I can't remember if OP stated he had No clutch at all when he started but ordered a total of Clutch package. He has to believe he was shipped what he asked for but without O.E. (original equipment) to compare the new to there's an open door for a mix up. Then again, the person packaging the Kit Package could put any one of four wrong pieces in the box. There again an open door for a F up. Add to that the Fork Movement clearly isn't right and I believe it was stated not sure if it is the one that started life with this bellhousing. This is often the results of stacking pieces in a box together thinking everything is right when it's not the right combination. Unless you know visually that all the pieces are correct to each other you're counting on a minimum wage worker hitting a home run before you even get started. I've had this issue handed to me before and my only way to correct it is to find an all together Polish Blueprint sitting I can take apart and make sure by comparison that the parts in the problem package are in fact right to each other. I don't know how else to sort things like this out.

 

In post #25 @ClayMart touched on the different Belleville springs used in diaphragm pp’s, the flat finger and the bent finger. A Chevy six would use a flat finger pp and I think those use a throw out that has a spherical face. Is your t/o flat or does it have a radius?