Z BAR (bell crank/cross shaft)rebuild

[bake74]

     So my Z BAR in my 74 k10 (manual clutch) needed to be rebuilt.  My clutch made a pop sound while driving it and besides the Z BAR being in terrible shape I found out that I am missing the 2 springs that are down by the Z BAR.
     I have not been able to locate them anywhere.  In the 74 service manual at the top of page 602 is the 2 springs I am talking about.  So if anybody can find out where I can buy these 2 springs I would be eternally grateful.

     So my Z BAR that came out of my truck.


     The new rebuild kit I bought(only found 2 places that sell them, year one and 4 speed conversions) the screwdriver on the left represents the frame rail and the right screwdriver represents the engine block.  (If you notice my old one I took apart does not have the teflon bushing on the right side of the Z BAR).



     This is the end for the L shaped clip that is the frame rail side.


     This if the engine side that has no clip and only 1 teflon bushing that goes in before the ball stud.  The ball stud itself had a rubber concaved washer on it when I got it, you can see it in the pics.


     Here is the assembled Z BAR with the felt washers that are suppose to keep any metal to metal from happening.  Though I am not to sure how long they are going to last.  Also you will see that the grease zert they sent me in the new kit is not going to fit, I will have to get another or use the old one if I can clean it.


     I have come to believe that when you bolt everything in and fill the Z BAR with grease, the pressure of the grease is what keeps the teflon bushings against the ball studs and keeps the grease from coming out.  When I was putting it together I could push the teflon bushing all the way into the Z BAR, so there is no groove or slot to stop the teflon bushings from moving in.  Therefor I conclude that the pressure of it being filled with grease is what keeps them in place.

[bd]

Bake, the frame rail (outer) side of the bellcrank should have a snap-ring OR internal shoulder that the inner bearing seats against.  Grease will not hold the plastic bushings in position.  Since the outer pivot ball is stationary within the bellcrank, both of its plastic bushings are mechanically "fixed" in position to cage the ball.

The engine (inner) side of the bellcrank is supported by a "floating" pivot ball that has to move axially to allow for engine movement.  I believe the inner pivot ball either doesn't use a plastic bushing, or it uses a bushing that is "caged" onto the pivot ball, between the ball and the stud.  Again, grease will not hold the bushing in place,

The felts are merely dust seals.  The springs are not special and can be procured locally from a hardware supplier.  Unless Auveco makes them, use the diagram in the manual to approximate replacement springs.

[bake74]

     bd, I cleaned that thing extremely well and looked even with my glasses, There is no evidence whatsoever inside the Z BAR on the frame rail that could have held the nylon bushing against it.  I was through in the inspection because I could not believe it.  Granted I have not looked at a new one, but this one was as smooth as could be inside on both sides, no wear marks.
    All 3 nylon bushing that came in the kit are exactly the same, no difference.  The engine side had a rubber bushing already installed on the outside of the ball stud, so the kit said the nylon bushing went in the inside.

[bd]

IIRC - the cranks I've rebuilt had an interior shoulder.  For grease to hold the bushings in place, there would have to be continuous pressure inboard of the bushings.  If any grease escaped the tube, the bushings would walk and the bellcrank would move end-to-end and drag against the supports.  Something has to cage the bushings that cup the outer ball to keep the bellcrank laterally stationary.

[bake74]

     That is what puzzled me when I looked at it today, I guess I need to order a new z bar and deal with it.  I haven't greased it yet because it struck me as weird.

[bake74]

     Ok, so I got this back in my truck and am finally happy with it.  The engine side nylon bushing kept sitting about 1 1/2" in and not resting on the ball stud. (you have to push the whole Z-Bar that much toward the engine so that the threaded part of the frame rail ball stud which is held in place by a C ring can clear the frame rail).
     So after talking it over with BD, I took his advice and shopped around for a light compression spring that was the same diameter as the nylon bushing, cut it down to size and installed.  This way after pushing the Z-Bar against the engine and back toward the frame rail the spring will keep the nylon bushing against the ball stud where it is suppose to be.
     I have to say that it feels better than brand new.

[Greybeard]

I never knew that these things were even rebuildable. Yes, I really do seem to live under a rock. When I had to fabricate the entire linkage, add the pedal and create the body lift drop linkage to get the SM465 to work in a purely automatic frame I was just happy it all worked and never thought to ask about a rebuild kit at Napa. The bellcrank I got from the salvage yard was in poor shape and is the same today I guess. It works smooth but doesn't give the feel I would like. But I think that is just matter of adding at least one stronger spring either on the linkage or at the fork.   

[bake74]

I never knew that these things were even rebuildable. Yes, I really do seem to live under a rock. When I had to fabricate the entire linkage, add the pedal and create the body lift drop linkage to get the SM465 to work in a purely automatic frame I was just happy it all worked and never thought to ask about a rebuild kit at Napa. The bellcrank I got from the salvage yard was in poor shape and is the same today I guess. It works smooth but doesn't give the feel I would like. But I think that is just matter of adding at least one stronger spring either on the linkage or at the fork.   

     They do sell rebuild kits, see above, and there is a ton of difference in mine now.

[Engineer]

Good thread.

I have had a zillion 4sp trucks apart and don't remember the spring. It does make sense. There has to be something to load the bushings, and allow for engine torque.

[bake74]

Good thread.

I have had a zillion 4sp trucks apart and don't remember the spring. It does make sense. There has to be something to load the bushings, and allow for engine torque.

      The spring does not come in the kits, bd and I went back and forth a few times trying to figure out how that bushing was suppose to stay in place. 
      I finally decided to find a light spring that would work to keep it in place, put it on and off about 3 times checking the tension and where the spring/bushing combo sat.  I think it is a vast improvement over just the rebuild kit.

[Captkaos]

All the ones I have ever pulled apart (of course they were OLD) never had springs in them.

[bd]

All the ones I have ever pulled apart (of course they were OLD) never had springs in them.

Correct!  I suggested adding the spring as an experiment.

[LDO]

Sorry, I know this is an old thread but any info on the spring?  I'm rebuilding mine and would like to give it a shot.

thanks,
LDO

[Don5]

Are you guys talking about the clutch fork return spring located from the frame to the clutch fork? Mine broke the other day and I started looking for one. I tried the hardware store, Autozone, O'reilly's and couldn't even find one. I bought the kit from Advance but I didn't think it would hold up. I finally went to the GMC dealer. The dealer informed me that there were 2 left in the entire dealership computer. I bought the one that was in Texas. By the time I got it, it cost me about $20 including shipping. The other one was located in Arizona. I saw the same one on Ebay right after I bought mine. I think the guy was making $5 more than I paid by the time shipping was added. 

[Greybeard]

i don't know this for fact however I believe that the spring is simply a spring meaning it can be picked up at any hardware store that has a good selection of springs. On the other hand, any spring with the same diameter wire and coils can be fabricated to work. Just use as little heat as possible, if any, when bending them. They won't look good, but they work.