So my rear diff has become increasingly noisy. So i check the fluid level and when i stuck my pinky finger in about half way the only fluid i could feel was the fluid that was on the side wall of the differential. Im no pro, so my question is, when i check the fluid should i be able to stick my pinky finger in and feel more like a "pond" of fluid as opposed to having to scrap the side of the differential to feel fluid? My gut tells me that im really low.

 

Hi.

From yer owner's guide, fer the 8.8 and 9.75 rear diffs:


"Service refill capacity is determined by filling the axle to 1/4-9/16 inch
(6-14 mm) below the bottom of the filler hole with the vehicle on a level
surface"

If it's low and noisey, drain it and change the fluid. For a traction-Lok, add 4 oz of XL-3 FM.

[I]"Add 4 oz. (118 ml) of Additive Friction Modifier XL–3 or equivalent
meeting Ford specification EST-M2C118–A, for complete fill of 8.8 inch
and 9.75 inch Traction-Lok axles."


Note that XL-3 is hydrophyllic - attracts and retains moisture. Hence a 30K / 3 year drain/refill interval is highly recommended to eliminate the risk of corrosion. Diffs are not sealed - they have vents.

good luck

MGD

 

Great info! Guess I should of included the fact that I have a Truetrac, also I stuck my pinky in as far as I could. And couldn't feel anything

 

True that is is not sealed and has a vent, but where did the fluid go? Sounds like a leak somewhere to me

 

You shouldn't be able to stick your finger in anymore than an inch and not feel anything.

 

Finally got a video of the rear diff. Hopefully someone with more knowledge than me will chime. I don't think it sounds normal though.

 

Hi.

How do you know i'ts not the rear disc pads dragging or the internal emergency brake mechanism/shoes that is either dragging or has loose parts inside? lol

ASAP, I'd be checking the rear diff by popping off the cover, as you KNOW it's low on fluid, and if it isn't already toast, it will be if you keep running it low.

good luck

MGD

 

Good point. I might have to remove it to eliminate that possibility.

 

Got my rotors off and it seems that a lot of the noise was coming from the parking brake shoe. Though there is still some noise. Does this sound like an incorrect backlash or something different?

 

fill it up til fluid runs out of the hole. it will blow out what it doesnt want.