86 4x4 720 Project

[datzenmike]

The 4x4 came with 215/75R15s that are 27.7" tall. So close to 3" of difference Making your 4.11 differential seem like a 3.72. Speedometer is 50 when doing 55 or 10% out.

 

I had a Z24 in my 3,400 pound 620 with 10.5 X 31 and a 4.11.... it was terrible. You had to use 4th on every little hill and not at all if running into the wind.

[datzenmike]

5 minutes ago, powderfinger said:

I also noticed when I changed the drivers side wheel bearing that when I put the caliper back on the inside brake pad was dragging on the rotor quite a bit causing a lot of resistance to turning the wheel. I know the lines have air in them because I have to pump the brakes at least once before they feel normal so that is something else that could be causing a major impact to acceleration.

 

If you can spin by hand then not that excessive. If you need both hands on the tire, maybe. Air in the lines won't cause the pad to rub abnormally. Make sure the caliper is free to slide on the two pins. Perhaps some brake grease. Often I have just slipped a screwdriver in and pried the pad and the piston back into the caliper slightly to 'break it loose'. Sometimes they just stick from dirt or maybe rust. Be sure to pump the brakes several times to return the piston/pad snug against the rotor before driving.

 

Bleed those brakes. Eventually you will have to panic stop and not have time to double pump. Too late then.

 

 

[powderfinger]

1 hour ago, datzenmike said:

The 4x4 came with 215/75R15s that are 27.7" tall. So close to 3" of difference Making your 4.11 differential seem like a 3.72. Speedometer is 50 when doing 55 or 10% out.

 

I had a Z24 in my 3,400 pound 620 with 10.5 X 31 and a 4.11.... it was terrible. You had to use 4th on every little hill and not at all if running into the wind.

Man 215/75/15s will look mighty small on this truck but it's seems clear these 30.5s are way too big. I will definitely clean the calipers up this weekend and make sure the pads are moving fine, added to my list of other things to do before putting the truck on the road. Hopefully I'll have the transmission swapped out this weekend.

[datzenmike]

With some work you can keep the same height and just go wider. Stock is 8.50" wide. A 245/65R15 is same but 9.5" wide course you loose the extra 1.5" of ground clearance.

 

You can also swap the front and rear differentials to the earlier 4.375 from the '80-'82 720 and kep the taller tires..

[powderfinger]

That's good to know that the earlier diffs are lower ratio. I'll keep my eye out, sometimes you see people selling whole trucks for little or nothing just to get them out of their yard. I am going to have to buy tires anyway because I don't want to run these loud ass mud tires all year. I'll do some digging to figure out what to get. Walmart has a great deal on some Goodyear Wranglers all terrains in 235/75/15 but that's the smallest they have, $80 each. Drop down to 215/75 or 225/75 and they don't even have any knock off chinese tires that cheap in an all terrain. Just nervous that the 5% higher ratio from the 215/75/15s will annoy me.

 

[datzenmike]

Going back to the stock set up will be more like a 10% increase in gearing. This will improve acceleration at all speeds and lower the crawl speed.

[powderfinger]

34 minutes ago, datzenmike said:

Going back to the stock set up will be more like a 10% increase in gearing. This will improve acceleration at all speeds and lower the crawl speed.

Yes, I meant the 235/75s would be around 5% higher than the 215/75s.

[datzenmike]

Got ya. Thought you meant the 30.5" ones.

[Charlie69]

Just a heads up I have had seperation problems with Good Year Wranglers in the past and when taken in for waranty I am told no waranty because tir failed do to low pressure.  My tire pressures were good.  $ out of 4 tires failed within 3 months of buying them.  I buy Toyo tires and have not had any problems.  I used to run BFGoodrich All-Terain TAs on my 4x4 great tire in my opinion.

[powderfinger]

I am thinking about swapping the motor from my 2wd into my 4wd so I can start daily driving the 4wd. Plus the transmission has to come out of the 4wd anyway. The 4wd motor runs decent-ish but has a nasty rattle to it. If I swap them, I can get the 2wd back together later. My question is, the 4wd has the Z24i in it, is there anything that will cause me problems putting my standard Z24 in a truck that has the "electro injection" engine in it?

 

I would swap all the ignition components over with the motor out of the 2wd and it has a Weber carb on it so I think all I will need is one wire for that if I remember correctly. I know that the wiring is different for the Z24i but would there be any issue with ECU? Any other potential issues? 

 

Still not 100% sure I will do this yet but it seems like the quickest way to reliably get this truck on the road. I'll try to get a video posted sometime this week so everyone can hear the engine in the 4wd and give your diagnosis.

 

 

[datzenmike]

 

 

1/  I think easier to keep it Z24i when swapping in the 2wd engine and keeping it carburetored. It's all there and working. Just swap the Z24i intake on. The oil pump has to be dropped on the 2wd engine and the drive spindle and the CAS (crank angle sensor) swapped in, all the wiring and coils are there and waiting. This can easily be done with both engines out. No wiring to change or modify.

 

2/ If you were to try running the 2wd engine as a carburetor engine in the 4x4 the in tank high pressure electric pump would need to be disabled and the 2wd electric pump fitted on and wired up somehow. You would have to power the 2wd distributor some how from the ignition as the CAS is not wired the same. The Z24i coils are connected to power transistors and are fires by the EFI computer. I don't know if they will work with the 2wd distributor but you can always swap the 2wd coils in. Either way the coils will need to be wired to the 2wd distributor. Carburetor throttle cable is most likely different also. 

 

    

[powderfinger]

Thanks Mike, sounds like I'll probably be sticking with the Z24i. I was hoping to just swap the other motor and keep it as is. It runs great with the Weber carb and I like the simplicity of the setup. All the emissions stuff has been taken off the engine in the 2wd as well. That's neither a good nor a bad thing but I will have to decide weather to swap all of that over from the Z24i engine in the 4x4. I am guessing some of it may be necessary for that setup?

Edited August 30, 2021 by powderfinger

[datzenmike]

I don't think so. None of the emissions are required for EFI operation and all the EFI (other than the O² ) sensor(s) are on the throttle body and it's all on the intake which is being swapped on anyway.

 

One other thing that would have to be swapped but wasn't mentioned is the oil pan and pick up tube. The 4x4 is different.

[powderfinger]

Got the transmission changed out this weekend, got everything back together, and put some tires on it. I got these wheels off of another 4x4 720 that I have, I almost used the factory 720 ST wheel but I am glad I went with these I think they look awesome. The other truck also has a brush guard on it that I plan to clean up and put on this truck. They are getting harder and harder to find, now I just need to find a roll bar that's made for these trucks.

 

The truck still isn't running great, pretty sure I will end up pulling the motor sooner rather than later. The previous owner had the timing advanced past the 20deg mark. I got that straightened out but it still isn't running the best. It idles fine and once I get it up over 3000 RPMs it does ok but in between it really struggles. Even at idle I can press the gas to get it to rev up to 2000RPM and if I hold the gas there the truck will stumble and idle back down to 1000RPM before slowly climbing back to 2000RPM..strange.

 

 

[datzenmike]

If idles then has to be the carburetor.

 

Next time it drops to 1,000 while driving it, as quickly and safely as you can get the clutch in and the ignition off. Let the engine stop and safely roll to a stop on side of road. What you are trying to do is capture exactly how the carburetor is when this happens. Turning the ignition off ASAP will prevent the electric fuel pump filling the fuel bowl while stopping. So, lift the air filter out of the way and look at the round sight glass on the front of the carburetor. Is the gas level at the white dot on the glass???? It may be fine or it might be empty. It would be good to know. If fine we move onto the next thing.

[powderfinger]

I haven't had it drop back to 1000RPM while driving yet but it will do it fairly consistently when sitting still. That being said I haven't driven it that much yet because I still haven't changed the front and rear diff fluid or the t-case fluid. I wasn't able to get the fill plug out of the t-case because the converter was in the way to get anything to it. Will probably just end up cutting the converter off because the bolts are rusted and rounded.

 

This is the Z24i with the throttle body injection. I bought a service manual for 86 720 but I guess they decided to put the Z24i in the ST models after they printed the service manual because all it mentions is the standard carbureted engines, at least from what I have found so far. Truck also has some slack in the driveline, you can hear a pop after letting the clutch out sometimes when accelerating. Acts like a bad universal joint but I looked at them all and they seem good. The rear ones look fairly new. Worried it's the rear diff but I'll change u-joints first or just put an driveshaft from another truck on and try it out.

 

I just realized I didn't attach a picture to the previous post like I meant to so here goes. It's is going to look really nice once I get the buffer out and wax it. It has rust bubbles over both rear wheels where mud sat on the inside lip of the wheel well for years and slowly ate away at the metal.

 

Edited September 7, 2021 by powderfinger

[Charlie69]

There is a Z24I 720 supplement manual.

 

 

 

[MaddieCycle]

I had a similar clunk in the driveline for about 1000 miles, then I got some noise in the transmission.  Turned out several bearings were worn.  Had the trans rebuilt and put in a new clutch and the noise is all gone.  

[powderfinger]

Just put a different transmission in it and it is still making the same noise but I guess it could also be the transfer case. Probably going to be trial and error until I figure it out. The noise sounds like its farther back near the rear diff but sometimes these things are hard to pin point.

 

3 hours ago, Charlie69 said:

There is a Z24I 720 supplement manual.

 

 

 

 

I am sure that will be easy to find 🙂 I'll start looking online this evening when I get home.

[banzai510(hainz)]

put on jacks then put in gear and see if you can hear where it comes from

[datzenmike]

Put 4x4 in your profile. Check that the engine, transmission and transfer case mountings are tight. Also that the transmission to engine bolts are tight. (this engine/transmission may have been removed in the past) Costs nothing and may save you changing U joints that it doesn't need. 

 

Yes! Z24i forget the previous post about the fuel level. The Z24i has a coolant temperature sensor (NOT for the gauge) but for the EFI to know just how warmed up the engine is. If faulty it may think it's cold and warming up. Idle may be increased for this.

[powderfinger]

Thanks, I'll look for the temp sensor. I know all the transmission bolts are tight because I just put the transmission in but I did not check the transfer case yet.

[datzenmike]

On the EFI 200sx the sender was near the thermostat beside the gauge sender but it was quickly moved beside the number 1 exhaust spark plug. This gave a much quicker response to actual combustion chamber temperatures. On the Z24i probably on the head

[powderfinger]

I took at look and didn't see a temp sensor but in all honesty I didn't really look that hard yet. I did find a couple of possible issues though. The first is some sort of sensor on the throttle body that has the wires cut. Pic below, not sure what these wires went to, I haven't found two wires anywhere else that are cut. You can see the sensor on the left has two black wires, I believe one has a white or silver stripe and the other a yellow stripe and they have been cut. Highly doubt this is the temp sensor because of the location.

 

 

The other thing I found is a connector with a wire missing. This connect comes right off the battery. I'll have to find a service manual for the Z24i so I can track these down.

 

[datzenmike]

All I have is the '86 'mid year' FSM but it's the last half with the D21 Hardbody. They also had the Z24i but there were some differences.

 

 

On the left is the 'idle up' solenoid valve, the FICD (fast idle control device?) on right. These come into play to speed the engine up at idle when there is an added load from accessories such as air con, power steering or strong electrical load. It stabilizes the idle.

 

 

 

The wires on the right connected to the + battery post are fusible links. (on the Hardbody they are Green and two Browns) Looks like one in the foreground is missing. It goes to connector and has a broken White/Red strip? wire, also cut or burnt. If replaced someone may have wired around the fusible link that is damaged. In left background I see White/Red wire with heat shrink tubing on it.