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gearbox help


Bambam91

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hi all,

 

ive just attempted a gearbox changeout on my 1985 nissan datsun 720.

 

i bought a reconditioned gearbox from what the guy told me was a 1985 nissan datsun 720.

trouble is when ive gone to drop the motor in.. ive noticed that the starter motor mount is on the opposite side.

 

ive checked the gearboxs for any kind of serial or model number. all i could come up with is the original had "NMCA Z3" casted next to the reverse switch, and the recon gearbox had "H3" casted in the same position.

 

this is the old bellhousing, with the starter motor mount on the correct side.

img1972n.th.jpg

 

this is the recon gearbox bellhousing with the mount on the wrong side.

img1969b.th.jpg

 

any idea what this recon gearbox is out of and if there is anything i can do to make it fit or shall i just start looking again.

 

cheers, Mat

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720 diesel.

 

What you can do is swap the front case from your old one onto this one. The good news is that the diesel and 4x4 5 speeds are identical gearing.

 

i was starting to think that.

 

how easy is that to do for a novice :P

 

http://720world.com/forum/topics/how-to-remove-front-case-from

 

found your how-to though a bit of googling :P might as well give it a shot.. see how i go. any tips?

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Take the diesel one apart and measure the lower front (counter) bearing diameter. If it's smaller you will have to pull it off and put yours on it. Yours, being an '85, will likely be 62mm size. This is easy enough to do with a 3 jaw puller. Pound on with sledge and a block of wood. Pretty straight forward.

 

Be sure to check the magnet on the drain bung. This is supposed to be re-built? The drain will tell you if it isn't if it has chunks on it.

 

Get a good sealer for the case. I hate RTV silicone crap. There is one from PermaTex.... silvery and you let set for 10 min and then assemble. Just use enough not lots. The case halves are precision machined (not at all like a Chevy :lol: ) and the excess will squeaze out inside the transmission.

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Take the diesel one apart and measure the lower front (counter) bearing diameter. If it's smaller you will have to pull it off and put yours on it. Yours, being an '85, will likely be 62mm size. This is easy enough to do with a 3 jaw puller. Pound on with sledge and a block of wood. Pretty straight forward.

 

Be sure to check the magnet on the drain bung. This is supposed to be re-built? The drain will tell you if it isn't if it has chunks on it.

 

no worries, cheers for that

 

ill let you know how i go :)

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the bearing from the old gearbox was the 62mm and the new gearbox was the smaller bearing.

i have a 3 jaw bearing puller but i cant seem to get in behind the bearing due to the gear being so close behind it.

 

any suggestions?

 

the magnet was clan of metal in the inside looks immaculate. so thats a plus

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Grind the puller down?

 

i ended up doing this before i read your reply.. worked a treat :P

 

with the help of your how-to i have successfully swapped the front casing over

 

ive dropped the motor in and bolted everything up.

motor starts and runs fine, but i can't seem to get the clutch to engage. ive tried bleeding the line from the master and slave cylinders. im not really sure where to go from here.

 

is there anything i couldve done wrong or anything you could suggest. im at a loss here haha

 

cheers for all your help so far

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I can't get the clutch to disengage then :P

 

I can start the truck in neutral but when I press the clutch.. I can't put it into gear

 

When the clutch pedal is pressed, the slave cylinder moves, pushing the little rod and pushing the clutch fork. I'm not sure if its pushing the clutch fork far enough for the thrust bearing to disengage the clutch.

 

I'm not sure what to do

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I can't get the clutch to disengage then :P

 

I can start the truck in neutral but when I press the clutch.. I can't put it into gear

 

When the clutch pedal is pressed, the slave cylinder moves, pushing the little rod and pushing the clutch fork. I'm not sure if its pushing the clutch fork far enough for the thrust bearing to disengage the clutch.

 

I'm not sure what to do

 

 

When you get under the truck(truck not running or clutch not pushed in), how loose is the rod between the slave and clutch fork, there should be about a 1/16(1 or 2 mm) of an inch play, or just loose, depending on how you look at it?

If it is really loose then there might be an issue, and you can try making a longer rod but it should have been the same as before unless you put a differant clutch cover or used the wrong throw out bearing collar/sleeve.

What clutch fork/TO bearing collar sleeve did you use?

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The slave pushrod should move 1.18" (or about) measure it and see.

 

ill measure that later on and check

 

When you get under the truck(truck not running or clutch not pushed in), how loose is the rod between the slave and clutch fork, there should be about a 1/16(1 or 2 mm) of an inch play, or just loose, depending on how you look at it?

If it is really loose then there might be an issue, and you can try making a longer rod but it should have been the same as before unless you put a differant clutch cover or used the wrong throw out bearing collar/sleeve.

What clutch fork/TO bearing collar sleeve did you use?

 

if i push the slave cylinder all the way in theres a fair bit of play, but without pushing it in the rod sits hard up against the clutch fork

 

ive used the clutch fork/TO bearing collar sleeve from when i was running the 220mm flywheel. so that may be my problem?

 

Good point Wayno. Only the transmission should have been swapped. The release bearing collar should be the one for the Z24 motor. Clutch arms and slaves should be the same.

 

i had swapped the motor from a z22 to a z24 a few months before the transmission gave way. i didnt change the clutch fork or throw out bearing collar then. should i have done?

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You said,

 

if i push the slave cylinder all the way in theres a fair bit of play, but without pushing it in the rod sits hard up against the clutch fork

 

ive used the clutch fork/TO bearing collar sleeve from when i was running the 220mm flywheel. so that may be my problem?

 

I don't understand what you mean in the first sentence, the clutch slave should be all the way in(bottomed out) when the clutch pedal is not being pressed, then when you press the clutch pedal in it will move the fork far enough to disengage the clutch, so if you crawl under the truck and force the slave in, does it stay in? How much play does the rod have? Enough to let it almost fall out?

What flywheel clutch cover do you have?

Did you use the same throwout bearing/collar/fork that was used before, or did you use the throwout bearing/collar/fork that was on the diesel transmission?

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The clutch slave creeps out until the rod is hard up against the clutch fork. If I push the clutch slave until bottomed out.. There's about 10-15mm play between the rod and the fork. If I force the slave in I can remove the rod. So enough play to do that.

 

I bought a new 240mm clutch and pressure plate with cover and new t/o bearing.. Didn't think I'd need to change the collar as well though.

 

I used the same t/o bearing collar and clutch fork as I used with the 220mm flywheel and clutch. I didn't get those with the diesel.

 

 

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The clutch slave creeps out until the rod is hard up against the clutch fork. If I push the clutch slave until bottomed out.. There's about 10-15mm play between the rod and the fork. If I force the slave in I can remove the rod. So enough play to do that.

 

I bought a new 240mm clutch and pressure plate with cover and new t/o bearing.. Didn't think I'd need to change the collar as well though.

 

I used the same t/o bearing collar and clutch fork as I used with the 220mm flywheel and clutch. I didn't get those with the diesel.

 

Datzenmike would know better than me if the collar is wrong, as I don't know a lot about that stuff other than the sleeve/collar follow the clutch cover, if you were using a 220mm flywheel/clutch cover, and you changed to a 240mm flywheel/clutch cover and used the same throwout bearing/collar for the 220mm cover, there might be an issue, lets let Datzenmike chime in.

 

You might also be able to make a longer rod, but I am also unsure about this, but I would try it, there should not be enough play to pull the rod out, unless you force the fork itself backwards, the slave should be basicly bottomed out when the clutch pedal is not bring pushed, if it creeps out, then the sleeve is wrong, or the rod isn't long enough.

You should not be able to remove the rod, unless you force the fork out of the way with a pry bar(as if you were pressing in the clutch).

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Datzenmike would know better than me if the collar is wrong, as I don't know a lot about that stuff other than the sleeve/collar follow the clutch cover, if you were using a 220mm flywheel/clutch cover, and you changed to a 240mm flywheel/clutch cover and used the same throwout bearing/collar for the 220mm cover, there might be an issue, lets let Datzenmike chime in.

 

You might also be able to make a longer rod, but I am also unsure about this, but I would try it, there should not be enough play to pull the rod out, unless you force the fork itself backwards, the slave should be basicly bottomed out when the clutch pedal is not bring pushed, if it creeps out, then the sleeve is wrong, or the rod isn't long enough.

You should not be able to remove the rod, unless you force the fork out of the way with a pry bar(as if you were pressing in the clutch).

 

I might try making a longer rod.. See if that helps.. If not ill start looking for a new collar

 

Thanks for your input :)

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You need to use the collar that was on the motor you have. It's matched to what ever clutch you have and has to stay with it.

 

If one came with the diesel 5 speed do not use it.

 

 

It sounds like he changed his flywheel/disc/clutch cover from a 220mm to a 240mm and used the 220mm collar with the 240mm clutch cover setup, and I don't know myself if the collars are differant.

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Good luck to you, I hope it is not a collar/sleeve issue, as that will require removing the transmission.

 

haha i hope not too.. ive already had this engine/transmission in and out 2 or 3 times in the past week haha

 

You need to use the collar that was on the motor you have. It's matched to what ever clutch you have and has to stay with it.

 

If one came with the diesel 5 speed do not use it.

 

the diesel box didnt come with a clutch fork or throwout bearing collar

 

It sounds like he changed his flywheel/disc/clutch cover from a 220mm to a 240mm and used the 220mm collar with the 240mm clutch cover setup, and I don't know myself if the collars are differant.

 

correct wayno

 

ill give you the story from the start

 

bought the 1985 nissan datsun 720 with z22 motor, 220mm clutch flywheel assembly and 5 speed gearbox to suit.

 

water pump shit itself and blew the head gasket between the cylinders, which in turn cracked the block

 

bought a z24 engine from a nissan pathfinder and swapped everything from the original z22 over onto it (sump, 220mm flywheel/clutch assembly, 5 speed box etc).

 

ran flawlessly for a few months and then the gearbox gave way.

 

swapped the flywheel out with a 240mm one and new clutch disc/pressure plate assembly to suit the 240mm flywheel.

 

bought a gearbox from a 1985 nissan datsun 720 diesel. swapped the front casing and counter bearing over from the original gearbox. also used the clutch fork, throw out bearing collar from the original gearbox, replaced the throw out bearing with an identical new one. used the original clutch slave cylinder and rod from the original gearbox.

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