Engine Oil Change and P0420?

All at once is good. It is only the pan that drained.

Roy

You can add it all because it is just going to fill the pan but I always do just what you stated when doing the pan and filter. Add 4 quarts, start the truck, add one more then as it gets warm, start checking it and topping it off.

I added 5 and it's at the top of the stick. Cold. Should I start it and add? Or just add it anyway?

Keep in mind these sticks are the little ones bolted on. And there's an A and B sections.

Start it and let in run until it reaches normal operating temperature. Then top it off.

Roy

Specifically when the transmission temperature gauge is in the middle?

Correct.

Well, it's taking forever for the transmission to get up to temperature. Should the fluid level be in the A or B area?

Here it is from the manual. Figured it may be easier to see it as well.

Just make sure you do your final check when its to operating temperature.

Well the temperature gauge is close to the middle, but not exact. I'm at 7 quarts adding and I'm at the top of section A. This is weird considering I measured 6.

It is never 1 for 1 meaning you put in just what came out. If someone did this before and didn't follow the process I attached before then they under filled it. Stick to the process and it will take whatever it takes.

Well, after I wrote that it started reading in the middle of B. It's running by the way. Should I leave it alone? I hear this type expands.

Correct. It expands when hot.

I would leave it alone.

You are good.

Roy

Nope. Stick to what it says. The fluid doesn't "expand" but it does thin when it gets hot which is why it is critical to do this check with the engine running and up to temperature. But you can't be wrong at this point if you want to leave it.

Just saw Roy’s answer. Either way. You will be fine. You are only talking a half quart or less at this point so if you are checking at operating temp, top it off. If it is not completely to operating temp then just stop.

Well, I drove it and it shifts pretty smooth. Not too different than before the service, which should be a good thing.

Good work. That is a good thing. If it shifted fine before then no different then before is the goal. Come back to 2CarPros whenever you need something. We are here to help. Thanks

For that rear differential the manual said to use RTV on the gasket, I thought Felpro gaskets require no RTV.

Correct. You use one or the other. Ford doesn't have the gaskets. They have you use RTV and not a gasket. I know Fel Pro offers them so if you use that, just make sure you get it lined up. If you want to use a small dab of RTV just to hold it in place that is fine. Otherwise just put two bolts through the cover, then put the gasket on those two bolts and start them with your fingers in the differential. Then put all bolts finger tight before tightening any of them.

How about this differential? It's a bit bubbly. I just drove it 15 miles before removing the cover. The fluid was a dark gray with yellow tint with light behind it. Kinda sludgy too. But no movement of the pinion.