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New 720 owner. Sooo Many questions.


720_Daniel

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I just bought a 1982 720 KC 4X4. I've always loved how these trucks looked and wanted a project. Now I've got one. 

350k miles and all the problems I've been reading about on the Ratsun forum too. 

Rust in the floor, carb running rich, seats beat to hell, valves rattle, and the most troubling is the rough shifting. 

 

My goal is to do an electric conversion. But in the meantime, I need to get it running smoothly enough to pass smog. The previous owner pulled all the EPA-required emission tubes off, so I'll need to start there. I don't really want to make the engine pristine, but It will take a good while to plan and prep before I'm ready to do my EV conversion, which I may never even end up doing. Regardless, I'll need to clean up the transmission issues first because I plan on using the existing drivetrain. 

 

So, on to my first critical question. 

I really feel like the clutch isn't fully disengaged when pressed in. It's resistant to go into first at idle. It grinds going into reverse. It downshifts roughly. If I'm on a slight downhill (rolling forwards) with the truck in reverse and the clutch pushed in, it won't roll. If I then shift to neutral, it rolls. 

It looks like the previous owner recently replaced the master cylinder(bright, shiny plastic), so I bled it and made sure that the adjustment was wound out as far as possible, but it didn't help. 

 

I wonder if I didn't bleed it right. I put a hose on the bleeder valve and the hose into a jar that caught the old fluid. Then I pumped it through to make a continuous fluid line (the hose end was covered and couldn't pull air back in. I pumped at least 2 volumes of fluid through the line. I then tightened it up and topped it off.  The clutch didn't seem any stiffer. 

The pedal movement before pushing the master cylinder rod is out of spec. It's almost an inch. 

 

Any suggestions would be welcome. 

 

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If going to electric why wast time fixing it to tear it all out?????

 

 

 

Push on pedal with thumb. It should only move a few mm or 1/16" till there is resistance. Look up under the dash where the push rod from the master cylinder joins the foot pedal. The end is threaded with a clevis yoke and a clevis pin through the pedal. There is a locking nut that needs to be loosened, pull the cotter pin out of the clevis pin and disengage the pedal from it. Turn the clevis yoke out, install the clevis pin and test the clearance is 1/16". Keep adjusting till you get this. Do NOT forget to tighten the lock nut and put the cotter pin in the clevis pin when done.

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I'm not 100% sure I can handle an electric conversion. I want to do it, but I'm worried I'll be out of my depth. So, I figure I should at least have a cool working truck and improve what I can in the meantime. 

 

I did extend the yoke out as far as it would go. I think the clutch safety button is busted off (and bypassed), so the pedal comes up higher than it should. This exaggerates the play in it. I'll adjust the stop next time I get into it. And then, the clevis pin has a little play in the hole. The only thing I can think is that my hydraulic fluid isn't stiff enough, I didn't bleed it well, the slave cylinder is bad, or there are deeper transmission issues. 

 

And for the record, Datzen Mike, I appreciate your reply and all of your helpful answers throughout this forum. My grandfather was a Datsun maniac, and always had a few in repair rotation in the front yard. So, I'm quite nostalgic about this little truck already. Electric or ICE, I'm happy. 

 

I found some floor panels on ebay that look like they fit. Do you know if the floor panels can just be unbolted and replaced? That would be fantastic. 

https://www.ebay.com/itm/154657557031?fits=Year%3A1982|Model%3A720|Make%3ADatsun&hash=item24024f0a27:g:Qw0AAOSwWDlgxGKE

Thanks .

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Have someone work the clutch for you while you get under and measure how far the slave push rod moves. It should be 1.18"... give or take. If you have an inch of travel that should be enough. If you do, then the clutch itself may be damaged and not releasing.

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I've had a clutch disc spring fall out into the pressure plate and jam in it before. And a warped clutch disc. Both will rub against the flywheel or the pressure plate or both. Because the clutch does not properly release the synchro rings (which are basically little clutches) not only have to match gear speeds they also have to try to speed up or slow down all the spinning weight of the engine and flywheel.

 

Clutch in and slow shift into reverse producing a constant 'grinding of gears' is definite proof that the clutch is not fully disengaged for what ever reason.

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You said it looks like the master cylinder has been replaced. From my experience with the aftermarket replacements, it seems that the rod that attaches to the pedal, is to short. I wish I had an original to compare. The adjustment on mine is at the very end of that rod and that’s with a new clutch in it. That rod needs to be about 3/4” longer to be able to adjust it the way Mike mentioned. 

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Here is mine...Works perfect.Got it from Auto Zone,lifetime warranty...Been using this  type since 94.Clutch and pressure plate was replaced in 2009 when I got my Jasper engine.That was 92,000 miles ago.I have a lifetime Auto Zone clutch slave cylinder too,so if that or the clutch master cylinder goes out I remove both and take back and get new one's for free.

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Edited by Thomas Perkins
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I deleted my clutch damper with a double female connection.  Mine is an '85 2wd.  There is also a bleeder nipple on the damper.  Just a heads-up, not something that would necessarily be a problem.  But, I was afraid that it was too old to be any good for keeping things clean at the seal at the slave.

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No change in the clutch feel without the damper.  And who knows how necessary it is to bleed the line at the bleeder screw at the damper?  But, it isn't like I was shifting to make the back tires chirp going into second gear, before the damper delete.  I probably don't accelerate the 720 in traffic to actually need a damper, but, I could imagine how the leaf springs are better off with a bit less axle wrap, especially when the bed is loaded kinda heavy.

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The damper just softens the clutch feel for the driver. Works equally well with or without and why I asked to see if you experienced the same. Has no effect on the clutch grip or action.  

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