1981 720-D 4X4

[BlackCasio]

Hello all,

 

I got my 720 a few months ago, and its been treating me great, but in the past few days it's gotten very shakey. It's most noticeable when I push the clutch in and just coast in neutral and at lower speeds in general. I was told it might be the brake rotors being out of round, but that happened to my last car and this is more of a bumpy ride feeling. The ball joints and struts look a bit worn, but would either of those make it shake that much?

I also noticed a clanking sound coming from under the truck while it shakes. Mechanically the truck runs great, I'm just stumped on what this problem could be.

 

Thanks

[datzenmike]

Brake rotors are more noticeable when applied and slowing to a stop. Felt through the brake peddle as a thumping.

 

Damaged wheel or tire:

Raise each wheel and spin by hand while watching the tread for wobble, lumps or high spots. I've had tires that the tread was separating. They had a lump as large as the palm of my hand. The car would wiggle as I slowed to a stop... not as noticeable at speed.

 

Driveshaft:

More noticeable as a faster vibration than tires or rotor. Like loud hum. Caused by worn U joint allowing the driveshaft to run off center and be unbalanced. Balance weight may have fallen off. Check for clean spot where it was. Rear slip shaft spline may be worn.

 

Lost wheel balance weight or out of balance tire:

Vibration that can increase or decrease at certain speeds. Look at the rims for a clean space where a weight may have fallen off.

 

Loose transmission or transfer case mounts

Inspect by looking at rubber mounts.

[BlackCasio]

Well from what you said and what I've found asking around, it sounds like my U joints are bad. I checked the tires, got them balanced, and checked all of my mounts and everything checks out besides the rear U joints. There is a bit of play in it when moved by hand, and I've noticed the vibrating is most noticeable when I'm coasting in neutral at a low speed (15mph and lower).

Does anyone have an idea of how much it would cost to get them replaced in a shop? I don't have access to a shop and I live in apartments that don't let you work on cars in the parking lot, or I'd do it myself. Also, would it be best to replace both the front and rear U joints? The front has never given me a problem and I've used 4X4 a fair amount.

Thanks

[datzenmike]

Do it indoors with a screwdriver and a large hammer. Two 12mm wrenches to remove. It's easy... look in the HOW To section I did a write up probably several pages in.

[Snoopy76]

if it were me, and money were no object, i would replace all six. yes, six. at least my 81 4x4 kc has six. two between the trans and transfer, and two in each driveshaft, front and rear. they are $7.00-$16.00 each at oreillys, and less at rockauto.com do you have someone in your area that could help you replace them?? it's a pretty simple job, and only takes a few hours to replace all of them. if you take your truck to a shop, you're probably looking at 2-3 hours of shop time, and depending on where you go that could run you anywhere from $60-$100 per hour. plus the shop's markup on parts, which generally runs 15-25%. so you're looking at somewhere above $120 to do a simple repair. if it were me, i'd look for a friend with a house that i could work on my ride at. i'm not sure where you are at in oregon, but if you lived nearby, i'd be willing to help

[datzenmike]

How To:

 

http://community.ratsun.net/topic/2329-u-joint-replacement/

[BlackCasio]

Awesome, thanks for the link and How To. I would accept the help, but I'm up in Portland and it looks like your Central Oregon. 
I inspected the front joints and they looked fine and don't have any play, so I think I'll do just the back and between the trans and transfer for now since I don't use the 4X4 a lot. 

And since I'm discussing problems with my truck, what could be the cause of a delay when I hit the gas pedal? It idles around 1100rpm and dips down sometimes but not like its going to die, and if I hit the gas pedal when its way down it takes a second or misfires. At normal 1100rpm idle it doesn't do it. Also, I can hear the carb open and suck air, it just takes a second for the rest of the engine to respond. Any ideas? 

[datzenmike]

Take the top off the air filter when warmed up. Is the choke plate full open or slightly closed? If partly closed this would explain the fast idle. Your gas mileage is likely poor also.

 

 

While you have it off. With engine OFF look down inside and pump the gas ... You should see a strong squirt of fuel into the primary barrel. If not, your accelerator pump is not working and this is the cause of the sudden nose dive when you hit the gas hard from an idle.

[BlackCasio]

Got the U joints done and throttle problem fixed (it was indeed the accelerator pump) and now she's running much better. BUT, a few days ago I loaded up the bed with big container plants so it was pretty weighted down, and now the back rides lower than the front. I wasn't told that it has a lift when I bought it, but I'm pretty sure it did, and now the back seems to be back to stock height. Any ideas of what could have happened?

[BlackCasio]

Also, thanks again for the how-to on the U joints, your technique worked flawlessly!

[datzenmike]

Got the U joints done and throttle problem fixed (it was indeed the accelerator pump) and now she's running much better. BUT, a few days ago I loaded up the bed with big container plants so it was pretty weighted down, and now the back rides lower than the front. I wasn't told that it has a lift when I bought it, but I'm pretty sure it did, and now the back seems to be back to stock height. Any ideas of what could have happened?

 

Only way the height can change is if you broke the springs or if it had air shocks that are now blown.

 

 

Never heard of a 720-D. what's the D for?

[BlackCasio]

Springs look pretty flat... I don't think it has air shocks though, not to my knowledge at least. Thanks

I actually don't know what the D stands for, I haven't been able to find any info on it. Its a 4x4 longbed single cab and it's got a really complex front end that the owner said was stock, although I haven't seen any other Datsun's with it. 

How do you post pictures? I tried from my Gmail but it won't let me use that extension. I've got some pictures so you can see the "D" model. 

[datzenmike]

http://community.ratsun.net/topic/691-how-to-post-pictures-and-keep-online-photo-albums/

 

Never heard of it from Nissan. But there were conversion companies like for the Bushmaster and campers.

[BlackCasio]

Here's the truck. I'll take some more pictures once it stops raining, but you can kind of see the extravagance of the front end. 


And here's the owners manual that states "720-D"
 

[datzenmike]

Very near the end when the Datsun name was reverting back to Nissan. This was announced around Sept '81 and transitioned through the next three years. Never heard of the D is all. Well until now. I pulled an old owner's manual out and... there it was.

 

'82 280zx-D

'81 S110-D (200sx)

'81 and '82 720-D

 

 

Anyone have any '83, '84 '85 Owners Manuals? Do they have the D on them too????

[BlackCasio]

Hah! That actually makes me feel better, I couldn't find anything on a "720-D".... 

[BlackCasio]

Ok sorry for the delay, its been pretty crappy weather and I've been busy with the holidays. 
 

Here's a few pictures of the truck. The front end is what I'm most curious about because I haven't seen any other's with the same thing. I was told by a friend that it looks similar to an off road package he had on an old Jeep Cherokee, but I'm new to this so I'm clueless. 

Front end pictures:

And here's a few more for kicks:

New U-Joints!

 

 

 

Only seen a few with these gauges

[datzenmike]

This looks normal. There was a huge metal skid pan on the early 720s. Yours is missing but it bolted up to all those holes above the tension rod and the side tow hooks..

 

 

[BlackCasio]

Do you know of anywhere I could find one? Or is it even worth having on? 

[datzenmike]

From a wrecking yard truck? Not needed for most uses. Nissan dropped it on later models.

 

[BlackCasio]

Seems like making a custom one would be cheaper and easier than finding one. 

Does anyone know of a place where I can get a new exhaust system with a catalytic converter within ~50 miles of Portland, OR? Or a cheap place online?

 

Also, would Rancho RS5000 shocks bolt up to an 81 4x4? 

[datzenmike]

If you don't have regular emission tests you could just replace the pipe all the way back to the muffler. Any muffler shop can do this, or buy the pre made pipe and just add a straight piece of pipe where the cat was.

 

 

 

Also, would Rancho RS5000 shocks bolt up to an 81 4x4? 

 

 

That's like saying will Goodyear tires fit my 720. I'm sure if you specify that you have an '81 Nissan truck they can find the right size for you.

[Snoopy76]

rockauto.com had some Rancho shocks listed for our trucks a while back, and for a pretty decent price too I might add.  And as for the exhaust, I'm pretty sure your truck should be smog exempt in the PDX area, as mine is here in S OR due to its age.  However, if you take your truck to a muffler shop to have all of the exhaust replaced and the catalitics are in place, then they have to replace them too.  The proper procedure for getting a muffler shop to delete the cats is you have to do it first.  this is easily done with a sawzall, and a straight piece of pipe from an auto supply store, and either a couple clamps or screws.  Cut out the old cats, hopefully already have measured the pipe and have the appropriate size ready to slide into place, and either clamp or use self tapping sheet metal screws to hold it while you drive to the exhaust shop... 

 

http://www.nissanpartszone.com/  may have the pipe from the manifold to the cats, and rock auto had the piece from the muffler to the back

[BlackCasio]

new problems are coming up more and more...

as of last night, my truck won't idle and I can't figure out what the problem is. if the auto choke is on it stays on, and if you have your foot on the gas it stays on, but as soon as you let off it runs down really low rpm's then dies. I can't drive it as is because it dies between shifts when downshifting. I was thinking fuel pump, but wouldn't that affect any rpm's? any advice is appreciated! 

other problems are e-brake not working (not a huge problem), and clutch master cylinder leaking, but a new one is on its way.

[BlackCasio]

tried making it run rich and it still dies when choke is off. the more it warms up the rougher the idle gets, when first started with choke on it doesn't misfire or have any hesitation in the gas pedal, but when warm constant misfires and gas pedal is almost unresponsive.