clutch adjustment

[lucian03]

done a 4-speed conversion on 1978 malibu. have to take all free play out of pedal to get transmission to shift smooth. any ideas on what the problem is? used 4-spd conversion kit from dixie monte carlo, hay-85-100 street clutch kit from summit racing. 1985 corvette bellhousing with correct clutch fork ball location bellhousing suppose to be correct for this application, 1978 clutch fork.

 

[Rt Jam]

Sounds like not enough travel in the linkage. Pedal to the floor is not disengaging pressure plate enough.

Are the levers correct? Is your set up supposed to have free play?
Even when setting up freeplay. The less, the better. If it calls for 1". It can be 1/8" with no problems. As long as it's not zero. Although many modern cars are preloaded.

 

[buick7332]

done a 4-speed conversion on 1978 malibu. have to take all free play out of pedal to get transmission to shift smooth. any ideas on what the problem is?

Do you have a Gbody clutch fork and bell housing?

 

[bracketchev1221]

I would question the length of parts for proper travel. Fork ball height, throw out bearing length, proper linkage etc.

 

[Bonnewagon]

All of the above. What trans? What clutch? What linkage? What bell housing? We need a complete list all of the parts that were used. A stock set up uses an inch of clutch pedal free play and full disengagement long before the pedal hits the floor. Even with totally stock parts there can be problems so be specific.

 

[gnvair]

My best advice is to make sure the holes in the clutch pedal and z bar are not worn and elongated. Also that the pushrod ends that fit into these holes are not worn.
The reason is the linkages on those cars are very sensitive and require as little free play as possible in order to get enough travel to fully release the clutch. When you have wear at those locations you will basically have to make up for it via removing all of the free play. This is very hard on the thrust flange of the crankshaft. This has been my personal experience on several factory 4 speed Malibus.

 

[Bonnewagon]

I have found that even with all new equipment there can be issues. The pressure plate design can be one of the biggest factors. Compare my 1981 Malibu wagon that had a Chevy V-6 and a Saginaw three speed manual trans. It was designed for Grandma to be able to operate it. It had a flat finger diaphragm pressure plate. Free play was 1". The clutch pedal took the entire travel, almost to the floor, to fully disengage the clutch. BUT, I could do that with my right hand. EZPZ. Almost no pedal pressure required. The flat finger PP and the linkage geometry combined to make it effortless to push the clutch pedal down, but it used all the travel, almost to the floor. Now compare that to the Pontiac 400 I had in that same Malibu, same Z-bar, pedals, and linkage. I used a RAM Borg & Beck pressure plate. It was very hard on my leg, and took a huge effort to push the pedal down. But the clutch was fully disengaged after about two inches of pedal travel, after the throwout bearing touched the PP fingers. Pushing the pedal down more only made it harder to do, and was pointless. Great for fast shifting, sucked in stop-and-go traffic. Different geometry, different purposes. Finally, when I last had my Saginaw four speed out of the Bonnewagon for maintenance, the only thing I changed was a new clutch disc. I kept the same stock bent finger diaphragm PP. The same Malibu linkage then acted like it was all wrong, just like the OP's problem. No free play, full disengagement happened down at the floor. I played with the clutch fork pivot ball, pushrods, nothing helped. I even stepped up to the Speed Direct ball end push rod kit. It was better than the stock stuff, but did not solve the problem. This did. I changed the linkage geometry by relocating the upper push rod hole slightly lower on the upper Z-bar arm. That caused the lower rod to travel farther with less travel of the upper rod. It solved everything. I feel no difference in pedal effort. But I have 1" free play, and full disengagement about halfway through the pedal travel, nowhere near the floor. It is better than it was before I did the work. ...........................................................................................................

 

[stew86MCSS396]

I kinda was waiting for a response from the OP with which parts he's using in his conversion before I added my $.02.

Screen handle MCSS396 with a 4-speed Muncie. I initially noticed a similar issue with the clutch pedal fully depressed, it was difficult to shift it into any gear. Adjusting the linkage until I get full clutch disengagement but on the other spectrum, no pedal free play and I'm sure the TOB was loaded up against the pressure plate at all times. Before finding a solution I lived with shut the engine off, shove it into reverse, start engine, reverse vehicle, shut engine off, pop it into 1st, start engine...as long as the vehicle was moving I was able to shift through all the forward gears which I made sure upon coming to a stop down shift into 1st or else go through the stop/start engine routine. This was probably harsh on the synchros but this was before Internet forums and knowing what the viable solution would be.

Anyhoo call it luck or a mystic power that lead me to a junkyard looking for a factory gbody jack. In the trunk of that regal there lay a Popular Hot Rodding magazine that I folded it, stuck it in my back pocket and grabbed all the pieces I needed for the OE jack. Later that evening when I was getting some quality reading time in 💩 lo and behold there was a clutch geometry article in that magazine.

Trying to keep this long story short, per the article from memory...
OE flywheel thickness are .960" measured from crank face to clutch contact surface and aftermarket ones whether they are lighter or heavy can vary in thickness.
The top of the pivot ball to a factory bellhousing mating surface should measure 4.75".

If you view the z-bar as a fulcrum and for simplicity sake let's say it's 2:1 ratio. With that said, any deviation from the above measurements would actually be doubled.

In my case, the Lakewood scattershield measured 4.85" and the block plate added another ~.120" which put BH depth at 4.970" (.220" too deep). Lakewood does make an adjustable pivot ball but it only adjusts an additional .100". I can't remember who probably Mcleod sold me a pivot ball that I could adjust to gain the .220" that I needed and that fixed my shifting issues.

 

[Bonnewagon]

I had to use an adjustable pivot ball once. I needed to re-locate the clutch fork in the bell housing window. For some reason the fork was too close to the rear of the window. It did not have enough room to travel for full clutch dis-engagement without hitting the rear of the window. The pivot ball allowed me to move it forward so that the entire travel occurred within the confines of the window, as it should. Remember that even though the clutch pedal is moving a great distance, because of the geometry, the action at the flywheel is minute. If you have re-surfaced the flywheel several times, that can be enough to cause problems. Back when our cars were new, GM used two types of diaphragm pressure plates. The flat finger and the bent finger plates were used, with the tall and short throwout bearings accordingly. There used to be three pivot balls, short, tall, and in-between. Normally these parts could be interchanged to solve various problems. Plus, parts from different models could be substituted in the same way. Once you start using aftermarket parts, problems occur that need things like adjustable pivot balls, different TOBs, etc, to solve.

 

[lucian03]

All of the above. What trans? What clutch? What linkage? What bell housing? We need a complete list all of the parts that were used. A stock set up uses an inch of clutch pedal free play and full disengagement long before the pedal hits the floor. Even with totally stock parts there can be problems so be specific.

used 4-speed conversion from dixie monte carlo, hay-85-100 street clutch kit from summit racing, 1985 corvette bellhousing with correct clutch fork location , with clutch fork 14066235 g.m.