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Getting a 1980 4x4 back on the road


Paulz

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Hi again, I posted a couple of times before about the neglected 720 ranch truck given me by my neighbor.  I have it home and running now, the plan is to see if it will pass a California smog test, if so I will register it and fix it up for road use.  If not I'll use it off road at my property.  Hoping you guys can help me address some issues:

 

1. This thing must have a dozen vacuum driven fuel/emissions related gizmos. It was pulling under 15 inches of  vacuum until I removed the air cleaner and plugged off everything but the ignition advance, now it's around 18 and idles nice.  I'll have to start reconnecting things and figure out where the leaks are.

 

2.  Carb looks new, In fact it appears as if the head has been redone.  The secondary butterfly was stuck, got that free and can feel it kick in.  There is still a mid range stumble that comes and goes but other than that it seems to be OK.

 

3  Checked all the fluids last night.  The transfer case is low, couldn't even get my finger down to see what is uses, 90w?

 

4.  As I mentioned before, there is a skip/clunk when descending or turning in 4WD with hubs locked.  I have noticed with it on a lift that the left front hub locks when the knob is turned about half way.  The right on the other hand doesn't lock until the knob is turned almost all the way clockwise, like maybe if it turned further it would lock in further.  Maybe there is an adjustment for that?  Not a big deal at the moment.  I have purchased a 1980 year specific Nissan factory service manual, they don't even mention a 4x4 model. 

 

Thanks for any help.  It's a fun little truck I hope to get some good use out of.  And it's funny, people really like seeing it,  I have some photos, do I have to upload to photobucket first?

 

 

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The only help I can offer is Do Not Use Photobucket.

 

Try Imgur or Flickr.  They seem to work well for this forum.

 

 

 

 

 

Sorry, not a 720 guy. Someone is sure to come along here soon.

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Sounds like a fun truck.

 

The locking hubs are probably just dirty with old sticky grease. If you don't engage them all the way, you will definitely get the noise you describe. Be careful using 4wd until you identify or fix the problem,a s if it is a stuck hub, and only engages part way, you can explode the splined ring inside the hub.

 

You should be able to disassemble the hub and clean it out. Then test it for operation before you apply a thin layer of new grease and reinstall it on the truck.

 

Gear oil for the t-case? Just about any gear oil will do. I'm pretty sure these things will run on bacon grease if that's all you can get your hands on. It is a divorced case, right? I like to use Redline MT-90 in the transmissions, but the t-case should be ok with 75-90 gear oil.

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Thanks guys.  Here is a photo via Imgur.  It's the L20 engine, divorced t-case so I'll go with the 90w.  The trans (4 speed) might need some fluid, hard to tell my finger hits the shift fork right away.  It's hard to shift when cold, maybe some Redline would help that.

 

Oh, the previous owner put an electric fuel pump on it, the mechanical is still there on the block disconnected.  Are the mechanical pumps failure prone?

Ny9HCpy.jpg

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My opinion I have never used mech pump but Electric pumps are just a lot more reliable and they are a slap-n-go and wont cause problems unless you have the problem like me and they keep going out( i went through 5 so far -.- settled for the carter 4070 pump and so far so good!!)

 

Mechanical pumps are kinda bad because of where its located by the carb so it has to pull/push fuel from the tank with vacuum i believe and its just a no go. its also a pain in the ass to make sure that its sync'd along with the carb its just a hassle i think.. If you really wanted to you could reconnect it as a secondary pump or whatever to double down on your fuel flow but its most likely not needed as the electric pumps are sufficient as carbs on the 720s dont really need that much. 

 

as for vacuum leaks I printed out diagrams of the lines and just tracked every single one down and removed/capped or whatever(32/36 weber on z24) I bet you can find a forum on the l20 motor and people have been through that process.

 

A good trans fillup is probably all you need for the shifting issue.

 

That truck looks straight and could be a lot of fun in that area to mud or hillclimb etc. too bad it isnt King cab though.. hate the single cab life :P

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For now stick with GL4 80w90 in the t case and transmission. GL5 in the differential. Synthetic will likely begin to seep past the upper seal where the primary driveshaft enters. They tend to dry or wear out from being so high up. Mine began leaking at all three as soon as I added synthetic and had to replace them.

 

All previous L series engines, 13 years of them in 8 models including 6 cylinders, used the mechanical fuel pump in them and they have proven reliable and problem free. I've never had or seen a bad pump only pictures of after market ones. They can easily be rebuilt, but people just buy an electric one.

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Mike, what was that brand of trans fluid you liked to use? You posted a pic of the bottle once.

 

I don't have problems with leaking after filling with MT-90 Redline. The main reason I use it is because of cold weather shifting. After years of customer complaints of hard cold shifting, I did a day's worth of research and found that the Redline was the probable fix. I have now been using it exclusively in Toyota and Datsun manual transmissions for about 6 years and have not had any customer complaints since.

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Thanks for the replies.  Yeah a king cab would be nice, but for a freebie I can't complain.  It is tight, especially for my fat old ass. Are these the original seats? If I do get it registered for road use I may have to change them.

 

I was going to hook up the mechanical pump that's still on there to a jar of fuel and run the engine but the input spigot is broken off.  I've had a couple of cheap electric pumps go bad (probably ethanol) but this one appears to be hanging in there.  

 

The transfer case was the only thing low on fluid and the outside is black (as opposed to light brown dirt everywhere else) so it probably does leak.  I'll top it up and see what happens.

 

So the slow shifting trans when cold is common then.  Not too bad for me right now but I do change fluid I'll take your advice.

 

About it for now, can't work on it for a couple days.  I did order a new tailgate handle, old one broken. That was cheap.  Had to drill out the rusted screws on the tailgate panel.  

SrNq5Kl.jpg

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if your dash and door panels are blue those are most likely stock seats.. there were 3 color options i believe.. Blue Tan and Black. 

EDIT: I noticed your center console is black.. yea i think those seats arnt original.. Its a common thing to swap them out at least those ones look clean

Yea i would just remove that old mech pump and clean up the lines and make the engine bay look less cluttered :)

 

Thats unimaginable for me to think that someone would just give a truck away especially in california.. then my friend comes by and his new ride is one that someone just gave to them like I need that kind of luck lol. I guess I am i bought a 81 720 xlt for $250 and a 99 ram 1500 for $250 and they were both pretty much running trucks just had massive dmv issues which is a shame. now I have to part out a 91k total mile ram.. but at least the money is going towards my main focus... my 85

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Thats unimaginable for me to think that someone would just give a truck away especially in california..

 

Smog, man.... SMOG!!!  It's a battle every 2 years... and they get more creative in failing you.  They WANT the old cars and trucks GONE.

 

I have to do mine again and question if fixing the engine is even worth the battle, (Head gasket at 164K) or store the truck until I can move out of this damn state and take it with me.

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Smog, man.... SMOG!!!  It's a battle every 2 years... and they get more creative in failing you.  They WANT the old cars and trucks GONE.

 

I have to do mine again and question if fixing the engine is even worth the battle, (Head gasket at 164K) or store the truck until I can move out of this damn state and take it with me.

I feel you i got until aug of 2019 to figure something out so I got time.

California is a a cruel place to the automotive industry.

 

About my friend getting the truck for free no surprise its got smog issues... 90s f150. Good thing cops apparently don't check that where I live (seems like every car i go by still have 2017 tags) 

 

I would replace that HG and try to get an address in madera (no smog there idk why California is broken....) which is what im looking to do as I have family up there. or double cat /stock air filter mod and pray that i pass visual. if that fails I would store it and high tail tf outta here the second I see an opportunity.

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Mike, what was that brand of trans fluid you liked to use? You posted a pic of the bottle once.

 

I don't have problems with leaking after filling with MT-90 Redline. The main reason I use it is because of cold weather shifting. After years of customer complaints of hard cold shifting, I did a day's worth of research and found that the Redline was the probable fix. I have now been using it exclusively in Toyota and Datsun manual transmissions for about 6 years and have not had any customer complaints since.

 

I only mention it because it isn't cheap for the synthetic to have it leak out and make a mess. You can drain or refill with 89w90 and it usually stops. (at least my old L20B engine did)  The replacement seals were about $25 each times 3. It would be cheaper to just run regular GL4.

 

The oil I use in my transmission is General Motors DELCO Synchromesh Transmission (friction modified)

 

OmMdGQu.jpg

The GM dealer was a dick and kept asking for what GM car I wanted it for. Kept giving him the part number and assuring him I knew what I wanted. When pressed I finally told him it was for my '76 Datsun and he got all pissed off looking. Then they were out of it. Lordco had if for $3 cheaper anyway. Pretty sure it has to say 'friction modified' on it. It is absolutely GL-4 safe to use.

 

There is another that says Synchromesh Transmission fluid with a different number # 89021808  but does not say synthetic blend nor does it say 'friction modified' on it. This may simply be a Canadian container labeling. Go with the top picture.

 

The oil is quite thin like warm 10w30, and golden almost orange, and clear. I think I've had it for 3 years now and notice no changes even to just below freezing. It used to grind into second (slightly) on the first few cold shifts even in the summer and down shifts mostly just could not be forced in unless well slowed down. Now like silk, up and down, and it actually shifts faster with the same old effort. I have to admit it was well worth the $37 for two liters. You should be able to get it for around $10-12 US a Qt.

 

 

Having said all this I doubt Ford, Chrysler, Toyota and all the others that have their own transmission oils actually have their own blend. It's likely made in one place and different dyes used to color them and different labels used. 

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About 25 years ago, I was on a road trip in my brother's MGB. We stopped in a small auto parts store in Iron River WI to get some tune up parts. I told him be wanted NGK B6ES spark plugs and he asked what the application was. I said never mind. He pressed, so I said MG. He said do you mean GM?

 

Just give me the fucking parts dickhead!

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if your dash and door panels are blue those are most likely stock seats.. there were 3 color options i believe.. Blue Tan and Black. 

EDIT: I noticed your center console is black.. yea i think those seats arnt original.. Its a common thing to swap them out at least those ones look clean

Yea i would just remove that old mech pump and clean up the lines and make the engine bay look less cluttered :)

 

Yeah the door panels and dash are black.  I think it'd be easy to find seats that give another inch or two of leg room.  Ideally I'd like a bench.

 

 

Smog, man.... SMOG!!!  It's a battle every 2 years... and they get more creative in failing you.  They WANT the old cars and trucks GONE.

 

I have to do mine again and question if fixing the engine is even worth the battle, (Head gasket at 164K) or store the truck until I can move out of this damn state and take it with me.

 

An airline pilot friend of mine was based in Phoenix and kept an '80s Mustang there.  Every time his registration came up for a smog test he would check the box that said the vehicle was out of state and get his new tags, did this for at least 6 years.  Now he's based in San Fran, the car is here with engine check light on, he still checks that box, just got his tags.  Tempting...how would they know?  Wouldn't work on a transfer though I doubt.

 

 

I don't recommend synthetic. I always get leaks.

 

Paulz I like the L motor EZ to work on.

 

Mechanical fuel pumps are fine. Try to find the stock ones if possible. Key is a low pressure pump under 4 pounds so it don't fuck up the carb.

 

I think the 7204x4 are hard to turn on the steering. Is there power steering?

 

I'm going to put a fuel pressure gauge on it now and see what the electric pump is putting out.  It has a mid range flat spot, might as well eliminate fuel pressure.  I see mechanical pumps on the auction site, pretty cheap.  

 

Yeah 720 4*4s can be hard to turn when power steering breaks, i know all of them have it. The 80 might weird though because its always weird. Z motors are not that hard to work on, and the manifolds are on opposite sides.

 

No power steering on this one, only belts are alternator, water pump and smog pump.  1980 was an odd ball year I'm told, factory manual doesn't even mention 4WD.  And it is hard to steer.  

 

I only mention it because it isn't cheap for the synthetic to have it leak out and make a mess. You can drain or refill with 89w90 and it usually stops. (at least my old L20B engine did)  The replacement seals were about $25 each times 3. It would be cheaper to just run regular GL4.

 

The oil I use in my transmission is General Motors DELCO Synchromesh Transmission (friction modified)

 

OmMdGQu.jpg

The GM dealer was a dick and kept asking for what GM car I wanted it for. Kept giving him the part number and assuring him I knew what I wanted. When pressed I finally told him it was for my '76 Datsun and he got all pissed off looking. Then they were out of it. Lordco had if for $3 cheaper anyway. Pretty sure it has to say 'friction modified' on it. It is absolutely GL-4 safe to use.

 

There is another that says Synchromesh Transmission fluid with a different number # 89021808  but does not say synthetic blend nor does it say 'friction modified' on it. This may simply be a Canadian container labeling. Go with the top picture.

 

The oil is quite thin like warm 10w30, and golden almost orange, and clear. I think I've had it for 3 years now and notice no changes even to just below freezing. It used to grind into second (slightly) on the first few cold shifts even in the summer and down shifts mostly just could not be forced in unless well slowed down. Now like silk, up and down, and it actually shifts faster with the same old effort. I have to admit it was well worth the $37 for two liters. You should be able to get it for around $10-12 US a Qt.

 

 

Having said all this I doubt Ford, Chrysler, Toyota and all the others that have their own transmission oils actually have their own blend. It's likely made in one place and different dyes used to color them and different labels used. 

 

Gonna top up the T case today with GL4 and buy the GM stuff for the trans.  How much do I need for the 4 speed?

 

 

Thanks for all the advice guys!  

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