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Technical Clutch Dragging...

Discussion in 'The Hokey Ass Message Board' started by alteredpilot, Jun 4, 2023.

  1. Got a car here with a 350 and a saginaw 3 speed. When we got the car the pedal was really hard and had a late release. Thought maybe it was just a heavy duty clutch and did't pay it any mind. Well, the clutch went out so here we are....

    So far we have put in 3 different clutch sets with two different diaphragm styles. It has the correct flywheel, pilot bearing, throwout bearing and clutch fork, all new. We've tested it with a stock pivot and an adjustable pivot. The clutch linkage is all fresh and correct. Not binding.

    After we put the first clutch in, the pedal effort was like it should be but it wouldn't go into gear. Pulled the driveshaft and with the clutch pedal down tried to rotate the ouput shaft with a pair of channel locks and could feel a lot of drag. Pulled the tranny out and it spins free otherwise. Swapped out the cultch set and same thing. So we went to the clutch specialty shop and had him give us the stuff he knew to be correct for this set up. He said he bench tested it and that it was working correct. Put it in. Same thing.

    Took the clutch set out and set it up in the press with a dial indicator and the pressure plate is releasing as it should. Checked the clutch fork travel and there is sufficient travel to release the clutch. Stuck another input shaft in the pilot bearing and its smooth with no drag or bind. Tried a couple of adjustments to the pivot and still lots of drag.

    So, if every component appears to be functioning correctly, the only assumption we can come up with is the the clutch disk is binding on the input shaft. Maybe something to do with bellhousing alignment?? We did notice the first few times we pulled the trans out that we literally had to pry it out of the bellhousing, and trying to get it back in was a real bear. We cleaned up the bore in the bellhousing a little and it goes in and out a lot better, but the clutch is still binding.

    What say you. i'm going to go look on the innernets and see what's out there but I figgered I'd see if any of you had any input.

    Thanks in advance.
  2. inthweedz
    Joined: Mar 29, 2011
    Posts: 546


    Is the input shaft bottoming out in the rear of the crankshaft, or outer edge of the spigot bearing??
  3. spanners
    Joined: Feb 24, 2009
    Posts: 1,903


    Sounds like it to me.
  4. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 709

    Kevin Ardinger

    Dumb question, but the disc isn’t in backwards is it?

  5. BJR
    Joined: Mar 11, 2005
    Posts: 9,082


    "Stuck another input shaft in the pilot bearing and its smooth with no drag or bind."
    I am assuming it is a bushing not a bearing. If it is a bearing forget what you are about to read.
    Did you mic the input shaft of the transmission you are using to see if it's bigger than the one you used to test fit the pilot bushing?
    ClayMart and SS327 like this.
  6. SS327
    Joined: Sep 11, 2017
    Posts: 1,931


    Have you used a dial indicator to make sure the bellhousing and block don’t have any runout? Sounds like they may be off center.
    Budget36, RMR&C and Truckdoctor Andy like this.
  7. Look for a transfer of bronze onto the end of the input shaft.
    SS327 likes this.
  8. With the trans on the bench or the floor, can you shift it easily between all gears? Then try installing the trans without the pressure plate or disk installed. If the clutch gear drops into the pilot bushing properly and the flange on the bearing retainer seats fully into the the opening on the bellhousing, that should eliminate any alignment issues. While you're at it install the release fork and check its travel for any suspicious behavior.

    Exactly which style of pressure plate and T.O. bearing are you using? Is the clutch hydraulically, mechanically or cable actuated?
    bobss396 likes this.
  9. Pictures would really help on this diagnosis .
    Pics of the bell,,,the assembly,,,,and the linkage .
    We already know you are using mechanical linkage from your first post .

    427 sleeper likes this.
  10. nobby
    Joined: Jan 8, 2006
    Posts: 1,100


    is it a truck three speed
    on a car bell housing that has had the factory register enlarged by hand filing
    bobss396 likes this.
  11. Mike Lawless
    Joined: Sep 20, 2021
    Posts: 424

    Mike Lawless

    I'm just guessing, but sure sounds like the trans pilot hole is not concentric with the crank.
    You would use a dial indicator on the end of the crank with the plunger on the pilot hole, and record the runout over 360° of crank rotation.
    The commonly accepted tolerance is .005"
    And for example, when I indicated my own bellhousing with the crank, and these were the same components that were in the truck, I got a runout measurement of .022". I'm certain that would have caused similar issues, but maybe not as bad.
    And your comment about hand filing that pilot hole....Yep.
    Budget36 likes this.
  12. wheeltramp brian
    Joined: Jun 11, 2010
    Posts: 2,177

    wheeltramp brian

    I had put a LaSalle trans behind a olds motor and it acted the exact same way it turned out the input shaft was bottoming out in the crank. I cut off about a 16th of an inch with a cut-off wheel and all was smooth
    2Blue2 likes this.
  13. Phil Brown
    Joined: Jun 24, 2022
    Posts: 26

    Phil Brown

    Stick the trans back in without the pressure plate and disk, see if it turns free. If not you probably have an alignment issue
    bobss396 likes this.
  14. Torana68
    Joined: Jan 28, 2008
    Posts: 1,397

    from Australia

    If the gear box isn’t supported until you have bolted it in you can bend the clutch plates centre , check the plate for run out.
  15. So as it turns out my dad has a Browell bellhousing alignment tool. It's go/no-go tool that has a tolerance of .0025". It's a go, so I know the bore in the bell housing is concentric to the crank. Stabbed the trans with no clutch and its still dragging so I think all I'm left with is a binding pilot bushing. Now to figure out if its the bushing or the input shaft that's outta whack.
    Desoto291Hemi likes this.
  16. Moriarity
    Joined: Apr 11, 2001
    Posts: 28,761

    Staff Member

    What kind of car is it?
  17. jaracer
    Joined: Oct 4, 2008
    Posts: 2,183


    Does the engine crankshaft have a lot of play from a worn thrust bearing?
    bobss396 likes this.
  18. Swapped out the pilot bushing. Big improvement. Gonna put it back together and see how it goes.
    Budget36 and loudbang like this.
  19. How bad did the old one look?

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