I have had this for almost five years. Man at work said they make trucks like this now. No place to check the fluid. I have not found a check hole. I would like to change the fluid. I am experiencing a shudder from the rear, and slow speeds while turning. Have read some old posts on the shuddering. I have not seen grease fittings either. Am I blind? Are they there?

 

Driver side, look at the pinion and then up and toward the rear of the differential slightly. You will see a threaded plug. It takes a 3/8" driver (just use an extension on the end of your ratchet) IIRC.... or maybe it's 1/2".... you'll see it. Fill to the bottom of this hole when the truck is level. 75 W 140 full synthetic gear oil with a bottle of Ford friction modifier if you have a LS rear. MAKE SURE you can get this fill plug out BEFORE you crack the seal on the rear cover to drain it. Might have to use an impact on it. Takes several quarts of fluid.

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If you have the shudder, when turning out onto road with rear wheels turning at different rate, sounds like you do indeed have the limited slip diff. I had the same problem on my 06' XLT 2wd. When I changed my fluid I used two bottles of the friction modifier at the suggestion of one of the post i read. I also did figure eights in parking lot after the job on test drive. The shudder improved but did not go away completly for several weeks. It's been several years now and no more shudder. Good Luck

Shawn 06' XLT 2wd 165K miles and going strong

 

I believe I found the plug. Looks pretty bad. My 3/8" set inside easily, trouble
is it spins out. Plug is rusty. Who had this truck the first five years, and what
services they did, who knows. What do you pros use to break something loose,
PB Blaster, hot tranny fluid???? Or do I save what oil religion I have and let the
pros break this plug and I have to buy new parts from dealer? Thanks.

 

The limited slip rear clutches will get chatter in them when the special additives wear out. This is not an emergency but drain it and change it ASAP. You might be able to use a big 'Easy-Out' in the plug.
Here's a 'last ditch' trick; take it to a welder and have him weld a 1"- long section of a 3/8" hex key into the plug. Apply PB Blaster penetrant around the edge of the plug when you get home with it. The heat will also probably help you break it loose and you can replace it or just keep using it - but whatever you do, use a little anti-seize compound on the threads when you put it back - not enough to get into the housing. There may be some sludge in the bottom of the housing after the old oil drains out. you can scrape this out with a piece of stiff paper or thin cardboard.

 

My compressor is not powerful enough to run the impact. I will try to use the business' s behind my house this week to see if that will break it. Three day weekend coming so I'd like to get these loose. I did soak it with ON.

 

Hey, I got the plug loose. Glad I bought that gun. Do they suggest using a gasket, or is there one for sale? Or, use Permatex. My manual gives diff amounts
depending on size. I was planning I my on buying 3 quarts. Is that enough? $15
per quart of the Purple. Also, rinse down inside with brake cleaner? Thanks for
all the help.

 

It has a friction modifier in it. Is it overkill then to use them Ford friction modifier I bought as well?

 

No. You want to use it.

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Hell no! Don't put any solvents in that rear! Drive it and get it warm. Stop on a level place and remove the rear cover. When all the oil is gone, use something like a jar scraper (get them at the Dollar Store) to get any sludge at the bottom. Put the cover back with a good RTV gasket maker, then install the specified amount of fresh gear lube.

 

Got it done. Drove to warm it up. Really black when I drained the old out. Wiped out the old from the bottom with a lint free cloth. Didn't take as much fluid as I had planned on but it's always better to have more. Thanks for all the advice.

 

I'm curious - if the plug hole was stripped out, how did the impact wrench help you?