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Throwout Bearing - Type "A" and Type "B" Trannys and Problems


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My 1972 240z has a 1971 L24 and a type "A" transmission. One of the previous owners appears to have completed an automatic to manual transmission swap at some point in its life.

I am in the process of replacing the type "A" transmission with a 260z 4-speed. I wanted to keep the 4-speed but liked the gear ratios of the 260z transmission. The 260z transmission came with the clutch fork and throwout bearing.

I dropped the type "A" transmission yesterday and pulled the fork and bearing off. For starters, I am glad I am doing the swap. The bearing is on its last legs (you can spin the bearing freely - no lubricant whatsoever) as is the transmission (the input shaft is hard to turn compared to the 260z 4-speed and you can hear some grinding inside the case). The drain plug had a fair amount of metal shavings around the magnet.

Now comes the interesting part. I compared the throwout bearing from the type "A" and 260z transmissions. From everything I have read, the bearing collar for a 1971 setup (pressure plate) is the smallest of them all and should be lower than the 260z collar when placed side by side. However, this throwout collar is nearly a finger width taller than the 260z collar. This leads me to believe that the collar is for a type "B" transmission which is the tallest of all the collars.

This observation lead me to the conclusion that I may have a 1972 pressure plate. However, this does not make any sense as the engine and transmission are from a 1971 car. Prior to dropping, the transmission shifted fine, with only the occassional grind going into reverse, going into first at a stop, and going into second. Let me stress occassional.

So I ask, what would be the symptoms of an inappropriately matched bearing collar and pressure plate? In this case, if a 1972 collar was used with a 1971 pressure plate: ?? - No idea.

Now, if the collar were a 1971 collar and a 1972 pressure plate, I can see that the clutch would not completely disengage and I should get grinding all the time.

I could replace the entire setup, but I am pulling the engine next year and I am just doing this to get the car back on the road while I build-up my new engine.

Is there any way to identify the pressure plate?

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If the clutch operated correctly before the teardown, I'd be strongly inclined to continue to use the collar that I knew worked with the clutch cover that you now have. Trying to second guess it when you already have a combo that works sounds like a potential problem to me.

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I was involved with a discussion about this subject last march:


From what I can tell of that discussion the throw-out bearing collar selection is based more on the clutch pressure plate than the transmission.

My 71 had a later series B 4-speed when I bought it and it had the longer (series A) throw-out collar. There are links in that thread to other discussions on this subject.

Because I installed the Centerforce brand clutch I eventually bought the throw-out bearing collar recommended for that clutch. If you are keeping the existing clutch it may be that you need to keep that collar.

I don't know for sure, but I suspect that if you put too long of a collar in you will never be able to get the clutch to fully engage, and too short of a collar will prevent disengagement.

(Real helpful huh... next I should give a dissertation on pencils or something else that is obvious.)

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By the way, on the subject of series B transmissions.

To install the series B transmission in a series A car you will have to cut the floor to allow the shifter to reach 1st and 3rd. On my car the center console was also broken out at the front to allow the shift lever to reach.

I was never able to get the inner shift boot mounted to my satisfaction. With the floor cutout, the opening is too big for the series A inner shift boot. The later shift boots appear to be held in place with either bolts or screws, but I resisted that idea because the brake and fuel lines are directly under the passenger side of the shift boot mounting location. (passenger side for left drive = right side of car Dang Yankee that I am)

After all the trouble that I had bending those lines (by hand) I was not about to take the risk that I would drill through one of them.

I eventually gave up and used clear storage tape to hold it down while I installed the center console. I am still not happy with the result.

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