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Grinding gears with clutch fully engaged.


vinylman33

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Hey guys I am totally new to this forum and a I just purchased an 85 Nissan 720 2WD. I am noticing that was the clutch pedal fully engaged I am grinding going from first or 2nd to 3rd and at stops trying to go back in to first gear. I just bought this truck yesterday and got the carburetor adjusted this morning and after I get this resolved I should be good to go. Thank you so much for all of your help in guidance.

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If the clutch pedal is in the up position the clutch is said to be engaged. If the pedal is down on the floor it is said to be disengaged.

 

 

I'm going to assume you mean the clutch is disengaged. Yes there should be no moving connection between the engine and the transmission. This is a hydraulic clutch so a failure in it will result in the clutch being fully or partly engaged when it should not be.

 

Find the clutch master cylinder. It's under the hood in front of the driver and to the right of the brake master cylinder as you look in from the front. Check that there is fluid in it. If not fill with hydraulic clutch fluid or DOT3 brake fluid. This may bring back the function. If it does not, air may have been pumped in a trapped and it will need to be bled to remove it.

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Bleeding it is not hard, there is a little thingy down there you turn (I recommend a set of HF hard line wrenches), but it almost requires two people.

 

 

 

Stick your cellphone under there on the cross member and take a video of the slave moving in and out to see if it is pumping the fork and "working" air will keep it from pushing the fork all the way in and separating the transmission from the engine.

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ok so today I bled the lines and also installed a new slave cylinder, bled them again, and again...  still have grinding with the clutch disengaged... should I try replacing the clutch master cylinder? or what about the slave cylinder? One more question where can I get shifter bushings? no one seem to have them and or can't get them??? thanks again.

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When I was having the same problem with my 510, I replaced the slave cylinder first without curing the grinding. Then I put in a new clutch master cylinder and it has been fine ever since. The cylinders are fairly inexpensive (even for someone as cheap as me) and once both are replaced you have the peace of mind knowing they shouldn't cause you any trouble for awhile.

 

But as captain 720 said, it is worth watching the movement of the clutch fork at the slave cylinder. I believe it needs to have about 3/4" of travel but someone else may have a more accurate figure for a late 720.

 

Len

 

 

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@captin720 Yes the fork thing moved and had good travel. Power shifting seemed to be fine. I will replace the master tomorrow and see what happens. @LenRobertson thanks for the info as well!!! Side note how do I post pics on here??? Id luv to show you my first truck project!

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If no air trapped, the slave has to follow what the master does. If master is working properly then the slave has no option but to also work properly... unless leaking or the flex line has a bulge in it.

 

Slave push rod travel should be just over one inch. If the slave is moving this much the problem is in the pressure plate. Broken/bent diaphragm finger, damaged bent disc, bad pilot bushing. Possibly the release bearing, but you would most likely hear or feel something.

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hey guys, got the hydraulic lines working and got all the air out of them, still having a grinding issue, however, I managed to drive it down to a reputable transmission shop and determined that the pilot shaft is stuck? (still learning terminology). Anyway instead of replacing just one part  I figured while I got things apart......I would just purchase a whole clutch kit and a start fresh with new everything. I hope to start this project in the next couple of days. So far I have replaced the Battery, Alternator, Starter, Clutch master cylinder, Clutch slave cylinder, and Full tuneup. I also have a new carburetor on the way.  Not complaining one bit I got this truck for a project truck and it has not disappointed yet been having lots of fun learning how to wrench!!! It's going to be a sweet little truck when I'm all done with it!

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hey guys, got the hydraulic lines working and got all the air out of them, still having a grinding issue, however, I managed to drive it down to a reputable transmission shop and determined that the pilot shaft is stuck? (still learning terminology). Anyway instead of replacing just one part I figured while I got things apart......I would just purchase a whole clutch kit and a start fresh with new everything. I hope to start this project in the next couple of days. So far I have replaced the Battery, Alternator, Starter, Clutch master cylinder, Clutch slave cylinder, and Full tuneup. I also have a new carburetor on the way. Not complaining one bit I got this truck for a project truck and it has not disappointed yet been having lots of fun learning how to wrench!!! It's going to be a sweet little truck when I'm all done with it!

That's the attitude!

 

But you made one error, it is a Datsun you will never be completely "done". As soon as you are done things get really boring.

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Get a Factory Service Manual for your 720, year specific. A chilton or Hayes is ok but a FSM is best.

To replace the clutch, the engine and tranny should to come out from the front. You can take the tranny out the bottom but it's a lot more work.

Search the Ratsun forums for other's experiences.

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ok todays update:
clutch was actually ok-ish, tranny = toast. Now I'm on the hunt. other than the OEM replacement are their any other nissan trannys that just bolt on and are compatible? I thought I read about a 240SX or a sentra?? Im thing of making a trip to the junkyards in  tacoma (3 hr drive) tomorrow..... also while Im at it, any motor/tanny upgrades you might recommend? thanks again. 

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Upgrade to the c trans from a hardbody. Much stronger than the b version. Bolts up just need to shorten your driveshaft and make a small adapter from steel plate on the trans mount. Oh and a little trimming on the shifter hole.

what year?

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I am running a 1988 from an early hardbody it had a naps z. A ka tranny should work fine but as I have learned from my ka swap there is about a 5 degree difference in the bellhousings. Not a major issue the trans just sits at that slight angle. It would angle 5 degrees towards the driver. Find a hardbody with a naps z and it will sit like it is supposed to.

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