Hi, I just changed the oil in my rear differential, I have the 9.5. I added the bottle of Ford friction modifier to my oil and added 3 qts of fluid. The manual says the capacity is about 2.75qts but nothing ever came back out the fill hole.

I am wondering if I should add some more oil until it does come level with the fill hole, or just leave it alone since it has what the manual says it can hold in it?

Thanks

 

Add more till it's about 1/4 inch from spilling out the fill hole. If you add too much and it starts to spill, just let it sit and drip, when it stops put the plug back in.

 

What's the service interval of changing this anyway, 150k miles I'm guessing???

 

I run my LS to 100k, but if you tow a boat and launch it off the trailer, do it every 30k. Ford says lifetime, but that's BS.

 

OK will pop some more in there then. I just didn't want to overfill it since I am already over what it says it can hold.

I have 160,000km on mine and I am doing to hopefully resolve some noise on low speed cornering.

 

Noise and chattering from the back end? That should take care of it.

 

Yep that was the noise. I opened the plug tonight and the oil was running out. I'm thinking the temperature change from when I installed it to once it heated from driving expanded it. I'll check it again in a few days and make sure it's still full.

So far no noises, but I want to do more driving first before signing off on the repair

 

I would say that regarding towing a boat, it would depend on if you have to submerge the rear axle to launch. I don't. I still didn't change mine until about 100-110K.

 

Usually 100-150k is good for the gear oil. It's synthetic on the newer trucks too.

If you have a non-ls diff, then it's fine for a long time. When you have them limited slips in the play, I wouldn't go much beyond 100k, especially if you tow.

 

If the viscosity gets off the norm, the traction lock will let you know when it needs changing.

 

Well I have driven it for the week now and I would say all my noises are gone. So for me, changing the fluid was the answer.

Now onto my next issue, rough idle in gear. That goes away if I turn the AC on.

 

Regardless of the next on the list issue, good job on fixing this one on your own. You saved money and you know it got done correctly.

 

Well it's done, but if it was done correctly is still in the air