1980 720 2WD (AZJones' Build Thread)

[arizonajones]

OK! So I've changed this old thread into a build thread. Now you can see my progress from Datsun-Noob to No-So-Noob.... I'll dump in some new pictures today

[arizonajones]

Couple more pics on the day I brought her home:

 

[arizonajones]

I've mentioned this in another thread, but here's a thing:  

Within a couple weeks of owning her, I double-clutched a shift and the clutch slave cylinder push rod popped out, allowing the seal to blow and the clutch fork to fall off. So... disconnected the  tranny (which I guess I needed to do anyway cause the TO bearing had been squeeling pretty loud.)

I discovered that the reason the pushrod had the slack to pop out was that the previous owner had rebuilt the clutch and put on the wrong sized collar. 

The one on the left is the one that was in, the right side one is the new proper one:

[wayno]

No, that likely is not correct, I was over there and looked at that, it wasn't that far off, you put that collar in there, and you will likely have an issue even getting the tranny to mate to the engine, as the clutch will be pressed in all the time and the truck will not move.

That tall one looks like an L16 collar made for a 200mm flywheel, there is one size between them collars you have in the photo in your post that could possibly be for the 225mm flywheel, your short one looks like a 240mm.

Here is the difference between a 240mm(left) and a 225mm(right) collar, your tall one is to tall, and it looks cheap, but that would be my opinion on the cheap.

 

I wonder if the angle of your photo might be deceiving, can you get another photo at the same angle of my photo?

In your photo the one on the right, the tang looks totally above the other one, that would be to high for a 225mm cover/flywheel.

[arizonajones]

I wish I had another photo, but that's the only one I have. I basically just ordered the one for a 225mm clutch off of RockAuto. With the short one that was in there before, we had to replace the original pushrod with a really long bolt(without bolt head) so that the slave cylinder had enough travel to fully engage the clutch. With the taller collar, there's a more normal gap between the fork and the slave cylinder. I still have the original, though...

[wayno]

Have you already installed the transmission?

Like I said, that photo could have been deceiving at that angle, to me it looks like a half inch or more difference, that is a giant difference at the slave end of the arm.

[Charlie69]

Just wondering are all clutch slave cylinder push rods on the 720 non adjustable?

[wayno]

There is no adjustment, it's a predetermined length.

Just wondering are all clutch slave cylinder push rods on the 720 non adjustable?

[wayno]

I am thinking that there is a way to check this issue before ever installing the transmission, I have looked over a few photos I have taken, and am coming to the conclusion that if one sets the clutch cover on a flat surface, and then sets the collar with the bearing mounted on it on top of the diaphragm that it should always be a predetermined measurement, 4 1/4 inches.

OK, I believe that the left cover/collar is 240mm, and the right cover/collar is 225mm, yet when one puts a straight edge across the top of them sitting on a flat surface, they are level, the reason for this is that there is a predetermined amount of space inside the front case for the flywheel, clutch cover, disc, and throwout bearing collar/bearing, this predetermined amount of room never changes, you can see that when I measure it this way, it is 4 /14 inches.

When I measure them individually it also comes out to 4 1/4 inches.

240mm

225mm

So I suspect that when a 200mm clutch cover/collar are set on each other, they will also measure out at 4 1/4 inches also, but to know this for sure I would have to gather all 3 of these sizes together and measure them.

I do realize that this way of measuring them is not perfect, but if they all are measured the same way, it should be very close.

If we all used this method when putting together unknown clutch cover/collar combinations, it might avoid a lot of headaches.

[84720FourWheel]

My T/O bearing looks like wayno's. Yours seems rather long.

[arizonajones]

Wow. Wayno, that is awesome information! Thanks for posting that. :thumbup:

As far as my transmission goes, that TO bearing pic is kind of old (I am playing a lot of catch-up on getting info into this build thread) so I've had it in for about a year now. It's not given me troubles that I can tell, but it is a cheap generic clutch kit that's installed right now, so whenever I get a chance to upgrade I'm going to refer back to your pictures. I'll post the info of what is currently installed and compare it to whatever I put in next.

 

For now, I'm going to put in some more images of projects from the last year - some upholstery and some small painting projects...

[wayno]

So are you saying you have that tall one in there, or the short one?

[arizonajones]

So are you saying you have that tall one in there, or the short one?

I've had the tall one in for about a year.

[wayno]

So the photo you posted was deceiving then, as it should not have worked at all with an L16 collar in there, and this is not an assumption, as others have done this and had to remove the transmission to fix it as it would not work with any rod length. 

[arizonajones]

So the photo you posted was deceiving then, as it should not have worked at all with an L16 collar in there, and this is not an assumption, as others have done this and had to remove the transmission to fix it as it would not work with any rod length. 

Yeah, it was a low-resolution cell phone camera, so it could have looked different than reality. I'll put it on my to-do list to measure the old collar though and post it up when I get a chance. 

[wayno]

I already believe I know what your old collar is, it's for a 240mm clutch cover/disc, while you have a 225mm cover/disc, that is why the longer rod was needed originally, but the thing about the L16 collar(200mm) is that it usually forces the arm so far forward that it hits the transmission case before releasing/disengaging from the clutch cover.

How far away from the slave is the arm?

You have a 1/16th inch of slop in the shorter rod now, correct?

Yeah, it was a low-resolution cell phone camera, so it could have looked different than reality. I'll put it on my to-do list to measure the old collar though and post it up when I get a chance. 

[wayno]

Does yours look like this now, or is it farther forward/backward?

Can you get a photo of yours at this angle?

[datzenmike]

I am thinking that there is a way to check this issue before ever installing the transmission, I have looked over a few photos I have taken, and am coming to the conclusion that if one sets the clutch cover on a flat surface, and then sets the collar with the bearing mounted on it on top of the diaphragm that it should always be a predetermined measurement, 4 1/4 inches.

OK, I believe that the left cover/collar is 240mm, and the right cover/collar is 225mm, yet when one puts a straight edge across the top of them sitting on a flat surface, they are level, the reason for this is that there is a predetermined amount of space inside the front case for the flywheel, clutch cover, disc, and throwout bearing collar/bearing, this predetermined amount of room never changes, you can see that when I measure it this way, it is 4 /14 inches.

When I measure them individually it also comes out to 4 1/4 inches.

240mm

225mm

So I suspect that when a 200mm clutch cover/collar are set on each other, they will also measure out at 4 1/4 inches also, but to know this for sure I would have to gather all 3 of these sizes together and measure them.

I do realize that this way of measuring them is not perfect, but if they all are measured the same way, it should be very close.

If we all used this method when putting together unknown clutch cover/collar combinations, it might avoid a lot of headaches.

 

Wayno, years ago I found a reference to this height and it was about 89.4mm or 3.52". Now this is installed height with the disc and the PP bolted down all the way up to the top of the release collar. Something that can be measured on a vehicle.

 

 

 

Using this chart my '78 FSM 620 225 diaphragm spring to flywheel height is 33 to 35mm.

 

If you select the second from the bottom (225 from 12/'74) A distance of 52.5mm and add them you get 87.5mm. Getting close.

 

Additionally I noticed that the release bearing sits proud of the housing by about 1/16" or 1.6mm so added that's 89.08mm.... bingo!

 

What do you think? Could we say broadly that it's 89mm from the back of the release collar forward to the flywheel surface for proper clutch operation?

 

Can you install your two PPs and remeasure the heights?

[wayno]

As I said Mike, it's not really the right way, but with some more research I would guess that they all would measure out to about 4 1/4 inches, and I am sure there could be some exceptions, like the roadster cover may be made differently.

I am just trying to come up with an easy way of saying to someone over the internet that if they put it on the table, and set the collar on top of the cover diaphragm, that it should come out to this measurement.

To tell the truth, it should be common knowledge what the collar height is for each cover, whatever mm cover/disc it is, but none of us has made the effort, so members here have issues, and we all just say that the collar follows the clutch cover, which is obvious once we make the mistake ourselves once.

I will try to find an L16 cover and collar and figure something out, it gives me a reason to clean up a little around here.

[datzenmike]

Only problem with doing it on the table is you have to remove everything to do so. It would seem that 89 or 90mm is simply measured on the vehicle. (well, unless you already have it off) Then both measurements have merit. Looks like roughly 4.5" or 3.5" if installed. This height regardless of PP and disc width keeps the clutch arm in the center of it's range of motion.

[wayno]

I understand what your talking about Mike, but I am talking about loose parts, that is generally when folks get into trouble, they buy a 5 speed off something and then forget to get the collar or never change out the collar, they just put a new clutch kit on, and slide the 5 speed on and call it good.

I wonder if all collars are made the same except for the height when they are sitting on a table?

 

240mm is 53mm tall with the bearing installed

225mm is 57mm tall with the bearing installed

 

I don't have an L16 collar to measure, but for ease, measuring this way above would be how most would have the part in their hands, with the bearing on the collar like in the photos below.

 

[datzenmike]

I think there are dozens of different diaphragm heights and why there are so many different collar lengths. Look at the charts below.... How is it that a 200mm OH600 and N1600 also fit a 225mm and a 240mm on the bottom chart?

 

200mm

 

225mm and 240mm

 

I probably have over a dozen collars with bearings on them from over the years.

[wayno]

OK, so we are back to the collar follows the clutch cover, and that fixes nothing for the average guy in his driveway with a bunch loose parts.

I just thought there might be an easy way to deal with this for someone that has to go looking for the part they need, it would have been nice to give someone an approximate measurement, but I will bow out of this now.

[arizonajones]

Mike & Wayno - Thanks for posting all of this resource info.

 

Wayno - Here's a shot of the slave cylinder currently. (also there is the 1/16" of play)

[wayno]

It looks right to me.  :thumbup: