My 1980 Datsun 720 diesel dually

[wayno]

Something happened and it posted the same reply twice, so I edited it.

This truck is at daily driver status now, it has not been a daily driver for years.

[wayno]

I put the truck up in the air today and figured out where more oil leaks were, actually it weeps more than leaks, it weeps around that bung that was welded into the oil pan for an oil temp gauge, it's a very slow leak, but to fix it I will have to replace the oil pan, I have never had any luck using a mig welder on these types of leaks while the pan is on the truck full of oil, it just leaks the same or worse.
If I emptied the pan and torched it till it burned off the oil inside I might be able to epoxy it, but in the end the oil pan needs to be replaced to fix it for sure.


I put the 620 mobile home leafs I have on this today, I forgot to take a photo of it before it got dark.
It went on without too many surprises, I think the bolt in the leafs was a half inch farther back but I put them on anyway, I only drove it around 10 blocks(5 away and 5 back), it felt normal but need to drive it farther to tell if there is a difference, it is lower and I have no drop blocks on it.
I tried taking a photo just now but there are too many water droplets floating around in the air.

[wayno]

I forgot about the starting/charging issue I have been having for years without knowing what the issue was, well it turned out to be the fusible link plug, but the reason it would not start was not because of the lack of power to the injection pump controller, it was because of the lack of power to the exciter wire going to the alternator that makes it charge, that damned DPC Module is wired into everything, once the engine was running the fusible link plug wire causing me all the grief was sparking away, and has likely been sparking away for years to melt this hole in the side of the plug.



The DPC Module is wired into everything, lots of things can stop it from moving the injection pump control arm to the run position, no oil pressure, not charging are two of them(found out the charging one a couple days ago, wish I had known it a few years ago), so now I need another fusible link assembly, until I find one at least I know what the problem is now.

[Laecaon]

Next time you do an oil change. Drain the oil. Jack up that side with the plug. Thoroughly clean the area, and try a bit of JB weld on it.

[wayno]

I thought about that Jacob, but today I scrounged around and found everything I needed to do a oil pan swap, I drained all that almost new oil into a bucket, dropped the idler arm, removed the cross member below the oil pan which was not easy to get out or put back in, then I removed the oil pan.
Has anyone ever noticed how much better Nissan gaskets are compared to the gaskets from auto parts stores, the auto parts stores oil pan gaskets are either cork or this rubber type material, while the Nissan gaskets are a firm pressed type fiber board material which fits perfectly, every hole is where it is supposed to be without any stretching which the Nissan gasket would not stretch anyway.
It's all back together and I drove it around a little while, I cleaned the oil catch pan before leaving for my drive, there are no oil drips yet, but I can see the dip stick is leaking where it connects to the tube sticking out of the block, it's like a PVC pipe connection where the male part is sticking up, I would have likely designed it the other way, but dirt will have a harder time getting in the way it is and how much oil actually goes up the tube, enough to leak I would venture to say.
I looked at trying to remove the oil dip stick and trying to fix the leak, it is so tight in there between the block and injection pump that I would likely have to remove the injection pump to get to the small bolt, now if the dipstick housing has a slide in metal mount I might be able to remove it, but if that bolt has to go thru a hole there is no chance at all, I bet one could spend days trying to start that little bolt, to even try I would have to remove the injection hard lines, so I will look at it more tomorrow to see if it dripped on the ground and go from there.
I tried to get photos of it but none of them showed the bolt, too much shit in the way.

[wayno]

So I have a spare engine in the back room, I took some photos of that one.
The area it is leaking.



And the bolt holding the dip stick in position, you can barely see the bolt head just under the glow plug, I cannot see it good enough to tell if the dip stick slides down into position or if it has a hole and the bolt has to be completely removed, it would be stupid to have a hole, at least that is what I am thinking.



There is a lot of shit in the way to even try.

[wayno]

I had the strangest thing happen this morning, I started up my truck and let it warm up so I could pay what appeared to be my final notice to pay my water bill with no prior notice before shutting the water off.
I drove the truck to the bank to get money, then to the water bureau/place, my water bill was up to date and all I owed was a late fee, they took the late fee off without me saying anything other than I never got a late notice before this final notice, I gave them more money and now I am likely good till June, anyway I left the building and a guy that used to own a 620 talked about my truck with me for likely 15+ minutes, he went inside and I started my engine and it had a knock for the lack of a better word, it was a knock but it sounded hollow, not like a rod going bad, I have plenty of oil pressure also as I looked at that right away, so it is knocking away but getting softer and softer as time goes by until it is almost gone, so I got in the truck and drove home watching all my gauges, I changed my clothes(got into work clothes), then I pulled the valve cover to check the valve lash, they might have been slightly loose but not enough to make the noise I was hearing, and I was not going to fine tune them until I knew what the issue was, I took the radiator cap off and the water level looked normal as I thought that maybe I had lost a head gasket and the noise was from water getting into one cylinder, and the noise went away as the cylinder cleared itself.
So I started the engine and it was knocking away as loud as it has ever been, so I got a ratchet extension from the tool box and started trying to find the knock with no success, I shut it down.
Next I raised the truck up off the ground, when I got under the truck I noticed a few things, a couple drips on the oil catch thing on the ground, I looked and seen that there were several oil pan bolt heads that had oil on them, the pan area around the bolts was dry on all of them, so I checked them and they were all loose around 1/4 to 1/2 turn, I went around twice, I only tighten them as tight as I can twist my wrist using a speed handle which is not that tight, I would rather keep tightening them a little every day than to over tighten them and have to replace the gasket.
Truck in the air.



After I finished that I started looking around, I had not put the 2 bolts on the bottom holes of the transmission that held the bottom of the plate, so I pulled on the plate with my finger and let it go, it sorta sounded like the noise so I found some bolts and did that, otherwise everything looked fine, so I got that extension and thru it under the truck and started the engine again, it was knocking away as loud as ever, I got under the truck and started checking things, I grabbed the clutch arm and forced the arm away from the clutch cover about an 1/8th inch, it's not the throw out bearing, I grabbed the extension and started listening to everything, it sounded like the oil pan was the loudest, nothing was dented on the sump part of the oil pan, the oil pan looked fine all the way around, there is this sort of flat/curved spot on the front half of the oil pan(sump is in the rear), I touched it and could feel the rod knocking on the oil pan, I put my hand flat on the pan and pressed up and it knocked harder, I let off and the hollow knocking sound continued, now I am under there looking/listening to this and wondering if a rod could be coming loose just after I changed out the oil pan, what are the odds of this happening, I pressed on it again and knock, knock, knock, I looked at it and wondered why it had not knocked yesterday or this morning when I started it, I didn't bottom out on anything, I don't remember having a loud noise when something hits the bottom of the truck, so what I did was get a hammer and I started tapping away on the curved sides of the oil pan on both sides and the noise went away, it's like something hit the middle center of the oil pan and pushed it up into the rods, the oil pan looks fine, it doesn't look like anything hit the front of that sump to force the oil pan up into the rods, it doesn't look like it was on a engine that was sat on the ground either, not to the point where it pushed the oil pan up, and it seems like it would have made noise yesterday/this morning when I started the engine if that was the case.



I am going to keep listening and see if it starts again or a rod noise starts, I just went out and started it again and it is still making a slight noise, but now when I put my palm/hand on the oil pan in that area the noise goes away, is like there is something in the oil pan rattling away inside and my hand pushing against it deadens it, before I tapped on the sides the noise got worse when I pushed up on the oil pan with my hand.
The OEM gasket was thinner than the gasket I removed, but the oil pan that was on it was way ugly compared to this one, I wonder if heating the engine up this morning and the gasket being on all night, I wonder if the oil pan could have settled up, it did not get worse after I tightened all the oil pan bolts after lifting it and then starting it again.

Does anyone think it didn't like having all the dirt on one side of the engine washed off and that pissed it off, the other side don't leak oil and the alternator is on that side and it would be just my luck to get water in it and have it die/go bad like it did on my 521 work truck when I cleaned the alternator area on that truck.

[DRIVEN]

Dunno

[wayno]

I remember when I parked in the bank parking lot I had the front tension rod mounts scrape on the curb, it only lightly scraped, but the oil pan is way higher than them also, it didn't make that noise when I started the engine there, only after it sat for 15 minutes did it start making noise at the water utilities place after I talked about it with that guy for a while.

[wayno]

I put a temporary muffler on this as it was just too loud, I didn't have to cut any exhaust piping, I just slid the 2 flex pipes farther onto each other, it is a lot quieter now, it seems to have the same power but I never got out of 3rd gear, I am doing a bid tomorrow so I will drive it then and see if it feels different on the freeway.

[wayno]

It goes down the freeway just fine, but now it has this rumble in 3rd and 4th gears while picking up speed, it sounds terrible, when I got home I isolated the exhaust system from touching any metal as I thought that was the issue, nope, it's a terrible rumble, like the whole truck is a drum.
I never noticed this before the muffler install, and nothing on that exhaust is touching frame or cab, it's all isolated with rubber like a professional would use.
Can a muffler cause a rumble like like say a piece of the inner fender touching the frame/suspension/steering gear?
The whole cab vibrates when it does this.
I checked and fixed anything that was touching anything else, I fixed couple brake lines, my throttle cable mount was touching the exhaust, my power steering piping touching the inner fender, some of my rubber turbo piping was touching the hood and brake booster, I made a different setup that was smaller that touched nothing without any improvement, this whole thing reminds me of rear gears going bad, but this happened when the muffler was installed, it's so bad I am considering removing the muffler and going back to straight pipe again.

I also looked into the oil dipstick tube/housing, I found on in my diesel parts bin/tub, it has a hole not a notch in it, to get that part out I will have to remove the injection pump, I actually tried to loosen that bolt holding it on the block with no luck at all, it is on there.

I just got to thinking, a rod was hitting the oil pan, can a rod starting to loosen only vibrate in 3rd or 4th gears?

[DRIVEN]

I would think those are unrelated.

[wayno]

It sounds awful and I grit my teeth every time I get to them RPMs in 3rd gear now, once I get thru it it sounds fine again.
I sure hope it is not my rearend, as I only have one set of them gears(3.3 gears), I keep coming back to I only noticed it after putting the muffler on it, I do not recall all that vibration when it was straight out the side under the door or after I piped it out the side behind the rear tire.

[DRIVEN]

Just seems telling that you say it's only in 3rd and 4th gear. Rearend should either be speed consistent or load consistent. Exhaust should be RPM consistent regardless of speed or gearing.

[wayno]

OK, I was laying in bed wishing I could go back to sleep and this thought just came to me, I did several things to this truck over the last couple weeks, I also made very short never getting out of 3rd gear test drives, actually barely getting into 3rd would be more accurate, they were 5 block test drives, my first long drive was to the water bureau to pay a bill, 2 things got my attention on that drive, it was very noisy/loud driving it which I assumed was because I used coat hanger wire to hold the muffler system up, and the knock I had after I started it in the water bureau parking lot.
Well the thought I had was that I put them 620 mobile home leaf springs on the truck which was likely a 3 or more inch drop, what if that is the vibration I have now, maybe the drive line angles are wrong.
I never really thought about this as the only truck/vehicle I have ever lowered was the 520, and that was an extreme drop(6/7 inches), and driveline angles were on my mind on that drop the whole time, this one I never gave it a thought.
So today I am going to shim up the carrier about an inch and take it for a test drive longer than 5 blocks and see what happens.

[wayno]

The pinion angle is the issue, I raised the carrier up 3/4" and it was a little better, I raised it up 1 1/2" and it is even better but not totally gone yet, my issue now is what degree pinion angle wedges do I need, 2 degree, 6 degree, I have never dealt with this before.
I really do not want to raise the carrier up any higher, it's getting close to the cab tunnel so I need to use pinion angle wedges.
I went to Baxters and they had them, but $30.00 for wedges seemed kinda steep, so I came home and checked ebay and it is even worse except for a couple sellers that were selling what looked like black plastic ones.

[DRIVEN]

One of these would really be helpful.
https://m.harborfreight.com/dial-gauge- ... 34214.html
You want the engine and pinion to be on the same plane with about 1.5* - 2* difference (ideally) at the driveline. No more than 3 degrees.

[wayno]

Well unless I raise the truck up and lower the rear axle onto jack stands I will not be able to even see the angles of both drive lines and the rear axle, I have not done this yet as I like to be able to sit upright when I am under the truck, this below is where I am at.
Right now I have a 2 degree wedge on the rear axle with the fat part towards the back which drops the pinion flange down, I have the carrier raised one and a half inches and I am still not there yet, I asked the guy at the parts store his opinion and went with it even though I didn't think he understood what I had done so far, I kept telling him I had raised the carrier and I had shimmed the axle in the back an eighth inch and was 2 degrees enough, he said put the 2 degree shim in and remove the spacers holding the carrier up and I would be good, so I put the shim in and drove it and I was still not there in my opinion, so just to see what would happen I removed one of the spacers and now I was only 3/4s of an inch raised, I drove it and it was worse again, I told that guy more than once that I didn't think he was getting what I was saying and I was right, I put the carrier back up one and one half inches and it is derivable that way, it's not terrible, I think I will go buy a 4 degree wedge tomorrow somewhere else and out that in and see what happens, if that is not enough I can put the other 2 degree wedge in there to make it 6 degrees, I would really like to have the carrier on the cross member where it belongs.
Here is the truck now.

[wayno]

I removed the spacers just to see if that guy at the auto parts store was right, nope.
So I went to another store and bought 4 degree wedges and installed them, all is good now except for one thing, the head of the bolt sticking out the top of the leafs to keep the axle centered on the leafs is not tall enough to go thru the 4 degree wedge and center the axle, what am I supposed to do about that?
I could see a little of that centering pin with the 2 degree wedge, I tightened it down and drove it to make sure the vibration was gone and it is with the carrier mounted on the cross member without spacers, I looked at all the different angles with that carrier raised like that and came to the conclusion I was dealing with three different angles with it raised, that is way too high above my head to figure out 3 different angles and how to fix it, so with the carrier mounted stock I only have to deal with 2 angles, and I suspect that is where I lost the guy at the auto parts store also, way over his head.
The issue with the centering pin being to short is that the axle is leaning forward/down hill, if that axle were to move that direction the "U" bolts would get loose, this could be an issue, I thought about putting a metal tubing over the nub sticking up as the wedges have a huge sized hole in them, so does the axle, but any metal tubing that would go over that pin and go in the wedge and axle holes would not have much shear strength, it would likely have a 1/16th inch or less wall.
I have never seen a 1 inch drop block with a 4 degree wedge built into it, but they likely do exist, but I have no interest in having this truck be any lower, I am just short of having 4 inches of clearance between the axle and the frame now, just short of 3 inches clearance is not on my top ten list.
Has anyone on here ran into this issue before?

[DRIVEN]

Nope. All my lowered dually diesel extra cab long bed 720s have been completely trouble free.