Engine Oil Change and P0420?

There are scheduled maintenance intervals in the owner's manual, but I'll tell you how I would maintain it. I would definitely service the transmission but pay attention to what is in the pan when you lower it. Any sparkly things or pieces of metal are not good and mean that the trans is on it's last leg. Also service the diff. And pull a spark plug to see how it looks, if it's worn quite a bit replace them, but the intake has to come off so you may as well replace the gaskets while your there! Also have a look at the interior fuse box and make sure that there are no wires inserted to any of the fuses! I had to replace the entire dash wire harness and repair some other things because the employee of a certain pest control company decided to jam a wire into one of the fuses and power something that pulled way too many amps! The result was an inferno that nearly burned the whole truck down, just an FYI. Also clean the throttle body real good and give the mass airflow sensor a cleaning. If the power steering unit were to go out it would need to be programmed.

It would probably take me 3 weeks / 3 pan drops to completely replace the transmission fluid, I think I might find a shop with a machine to get all of the fluid out + replace the filter. Or is that a bad idea? The rear end requires a special additive I think.

Luckily a tune up was just done on this truck, the third or fourth one it has had during its service.

Also it has a P0420 code showing up 3 times in the memory. Guess I should go ahead and replace the cat on the passenger side so that engine light doesn't drive me crazy. I prefer bolt-on applications for exhaust work, would I need to remove both cats anyway or is there a way to split them?

The only way to do only one cat is to cut it out and weld in a new one because it's a Y-pipe set up. Using the flush machine is a pain on these trucks because of the low flow until the thermostatic valve opens and fluid gets moving, usually have someone in the vehicle holding the revs up to 1500 or so just to get things moving. It's hard to believe that they didn't do the trans service but either way it would be a good idea to do it manually without the flush machine then do it a few more times like you said just to get things clean slowly and not jar and chunks out.

Looking at the parts online, looks like bank 2 cat slides into bank 1 cat, with hank 1 having more of a Y shape. Looks like I'd either have to take both down and disconnect from each other off vehicle or just replace both at the same time.

Do you recommend pulling off the diff plate and giving the gears a good soak with carb/brake cleaner? What's a good additive for these limited slip gears?

Motorcraft SAE 75W-140 Rear Synthetic Axle Lubricant with motorcraft friction modifier. And yes to the brakeclean to clean up.

It's getting closer to doing this maintenance checkup. So I have a few things to clarify:

The transmission oil is Mercon LV right?
I will order 3 trans filters to do a slow cleaning of the trans.
Part # FT-138 comes up when searching about the trans filter. It says "Pump Inlet Filter". Is this actually serviceable? Or should I not worry about it?

The rear end takes 5.5 pints of 75w-140, with the XL-3 modifier. Right? Use all of the modifier?

If I can jump in here. I would do a tune up and brake system flash as well as the oil services. here is the transmission fluid specs:

Fluid Types
Automatic Transmission Fluid

Ford Part Name

- Motorcraft MERCON LV ATF

Ford Part Number

- XT-10-QLV

Ford Specification

- MERCON LV

NOTE: Automatic transmissions that require MERCON LV should only use MERCON LV fluid. Use of any fluid other then the recommended fluid may cause transmission damage.
Capacities
Automatic Transaxle

6R80 .................... 13.1 quarts (12.4 liters)

Here are guides to help you with the services needed:

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

and

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

Differential service video.

https://youtu.be/ygti8zvpg4M

Transmission service video

https://youtu.be/NUOBl4bqtss

Here are the differential fluid specs as well:

DIFFERENTIAL FLUID

Front

Ford Part Name

- Motorcraft SAE 80W-90 Premium Rear Axle Lubricant

Ford Part Number

- XY-80W90-QL

Ford Specification

- WSP-M2C197-A

Rear

Ford Part Name

- Motorcraft SAE 75W-140 Rear Synthetic Axle Lubricant

Ford Part Number

- XY-75W140-QL

Ford Specification

- WSL-M2C192-A
Capacities
Axle Fluid Capacity

Front Axle .................... 3.5 Pints ( 1.8 L )

Rear Axle 8.8/9.75 .................... 5.5 Pints ( 2.6 L )

Note: Fill to 1/4 inch to 9/16 inch ( 6 mm to 14 mm ) below of fill hole.

Please let us know if you need anything else to get the problem fixed.

Well just got the truck today and it's not leaking a drop of anything. However the engine codes are p0420 and p0455. Need to know which cat to replace and where this evap leak may be.

Also the driver seat belt receptacle will not latch. The little black tab inside gets stuck and stays down when pushed down and won't latch with the belt. Have to use a screwdriver to spring the tab up and make the button work, but putting the belt in only causes it to stick once again. I've tried shop air, wd-40, brake cleaner.

If I can jump in here. You have a large leak in the EVAP system so I suspect it is the fuel cap or purge valve but I attached the test that you need to run through.

As for the P0420 code, that is bank 1. More than likely it is the converter but I attached the other possible causes.

Unfortunately the latch will need to be replaced. There could be ways to fix this specific issue but I have never had any luck trying to repair them.

And bank 1 is the passenger side on this?

Correct. Bank 1 is the one with cylinder 1 on it. In this case it is passenger side.

Wondering what this looseness is back here. I can lift the rear end up. Maybe leaf springs?

We have to keep each post to the same question or topic. Others won't find the questions or answers on different topics under a heading that doesn't match the issue.

Lower the vehicle and put the weight on the suspension and see if it is still loose and then post that info with the video on a new post. However, if it doesn't do it when the weight is on the suspension then it is normal.

https://www.2carpros.com/questions/new

It does do it with weight on it.

My original title was "potential services to extend longevity", however when Ken replied it changed the topic to an oil change

Oh. Understood. They will actually narrow down each thread to a topic just for this reason. If you try to open a thread that is so general it basically does the same thing. Think about it from another persons perspective that they are looking for this suspension issue and would have to scan through an entire thread named "potential services to extend longevity" in the hopes that this suspension issue is in there. Rather then seeing a thread named, Loose leaf spring or whatever, matching their vehicle description, they would go right to it.

The point of this website is to offer a free service to not only assist you but all who visit with the same issue. If we can assist you with this issue and others can find it, then they are helped immediately.

Let's get a new post started and we will figure out what that is.

https://www.2carpros.com/questions/new

Back on topic about the trans service: the fluid is a little dark, but still has the red tint and doesn't smell burnt. Also I didn't find the ford dipstick plug from the factory, so I assume it's been serviced before. Does this look normal?

The magnet looks good. That is normal wear and tear.

Roy

That amount of metal is absolutely normal. The fluid is dark which is just a sign of it wearing which is what it is supposed to do. Go ahead and replace the fluid and filter since you have the pan off and you should be good to go. I would not worry about flushing the unit to get all the fluid out. If it is not burnt then it is fine to just drain and fill it. Clearly you can clean that magnet off but again, that is nothing to worry about.

I drained just under/right at 6 quarts from it. Can I add it all at once or do I need to add 4 and start it?