Clutch fork throw

[Zed Head]

I found an old video about broken noses.  You're not the first, by far, to get stuck in a weird transmission problem hole.

Edited July 14, 2020 by Zed Head

[EuroDat]

Zed Head has a point. I also have another question. When you fitted the transmission to the engine, did the bell housing mate up the the engine or did you pull it in with the bolts?

You should be able to push it all the way without any mechanical assistance. That could indicate the collar is jamming on the tube and pushing on the pressure plate. I would not think it could result in so much fork travel without disengaging the clutch. That doesn't seem to be the case when you tested it with the drive shaft.

[zKars]

About the only issue I have with what has been discussed and suggested, is that the magic 92mm measurement must be made with the pressure plate bolted down to the flywheel with the disk in place. Those finger tips move downward a lot when you bolt the pressure plate down.  

Now that said, I've been able to make a very short collar work just fine with a clutch fork that has the hole and adjustable length push rod. Just had to make the push rod longer and adjust it out. No monkeying with the ball stud length. So the 92 mm rule applies best for the fixed length rods and forks with no holes, but there is fair bit of error either way that would still work. 

Pedal clutch rod length works into this too. And is your slave rod the "right" length?

 

Edited July 14, 2020 by zKars

[Zed Head]

No offense zKars, there's a lot in this thread.  But his problem, summarized, is that he has the longest collar he can find and still does not have room behind the fork to get enough fork throw before the fork hits the back of the hole.  A longer rod won't help (that sounds wrong somehow...). 

This is his starting point.

[rcv]

2 hours ago, EuroDat said:

I took some measurements of my spare transmission to give you something to go on

This is great, thank you - I'll take measurements on my transmission as soon as I can get into the garage and post a comparison to your picture.

 

1 hour ago, Zed Head said:

I went back and watched your video and when you move the fork I don't see the bearing/sleeve moving

It's a little hard to see in the video, but the collar/bearing are definitely moving when I move the fork.  When I'm flicking the fork forwards you can kind of hear the sound of the bearing "slapping" against the springs.  I shined a flashlight in there and watched it move, so I'm pretty confident the bearing/sleeve aren't bound up. There is the little circular retaining "clip" that goes around the collar anyway that holds the fork tines to the collar ears.  This keeps the two pretty well coupled so it would be difficult to pivot the fork without moving the collar, right?

 

1 hour ago, Zed Head said:

Most old transmissions have a groove worn on the nose.

My nose looks pretty clean, and I didn't notice any grooves worn in it. I'll take some pictures when I grab those measurements to compare to @EuroDat's. 

 

1 hour ago, EuroDat said:

When you fitted the transmission to the engine, did the bell housing mate up the the engine or did you pull it in with the bolts?

I'll admit that I struggled getting the transmission on the first time and tried gently coercing it together by tightening the bolts.  I got nervous as the bolts tightened though, so I took the whole thing back off and have since gotten good at slipping the splines in without any mechanical advantage.  I don't think I caused any damage the first time - I've been able to take the transmission on and off a few times since without any issue, and I didn't notice any cracking/bending/etc of the nose.  I'll inspect thoroughly though and see if anything looks rough.

 

1 hour ago, Zed Head said:

You're not the first, by far, to get stuck in a weird transmission problem hole

Honestly that's a relief to hear. I'm beginning to feel like I'm losing my marbles with this, so it's comforting to know I'm not the first ?

 

[EuroDat]

29 minutes ago, rcv said:

Honestly that's a relief to hear. I'm beginning to feel like I'm losing my marbles with this, so it's comforting to know I'm not the first ?

Don't worry. You are not the first and certainly not the last. If you play with your datsun long enough you, you will be here again asking questions. Most of us have been through it.

If you can identify any reason for the problem, then I would try the washers behind the pivot ball. Like Kars said, you have an adjustable push rod and if needed you can make a longer one easy enough.

Your biggest concern is binding on the back of the bellhousing when you disengage the clutch. Maybe check the collar next time you have the transmission of the engine. Make sure it doesn't come too far off the tube and jam.

[cgsheen1]

After reading (most of - well,, part of) this thread, I'm really glad that I've hoarded a bunch of collars. I'm no good at measuring the whole clutch package so I just stick the transmission up temporarily get the slave on and check the throw. If the slave push rod is jammed tight, too long. If I can push the fork and rod back into the slave,  too short. If there's only a slight amount of push back into the slave (about 1/4" or less), it's just right.

[rcv]

1 minute ago, cgsheen1 said:

I'm really glad that I've hoarded a bunch of collars

Any chance I could convince you to take pictures of all of the unique collar types with calipers between the ears and the bearing mating surface? I’m planning on writing a Pulitzer Prize winning novella on my saga and it would be nice to have some good pictures to go along. 

[cgsheen1]

(He thinks I have calipers...) I'll see what I can do - though I thought all the different length collars have already been documented.

[rcv]

Heh a ruler will do just fine.  This has been documented in several places, but never with all of the collars at once, and never with the relevant measurement. My diagram [here] is basically what I'm looking for, but with real measurements instead of computer magic and ideally with bearings attached.  It's not critical, just something nice to add to the archives if you're bored on a weekend.

Edited July 16, 2020 by rcv

[Captain Obvious]

Man... Every time I open this thread, I'm hoping and expecting the "Eureka!! I found it!!"

The suspense is killing me!!  

[rcv]

You and me both!  It's hard for me to get in the garage on weeknights, but I'm hoping to find some light at the end of this transmission tunnel this weekend.