04lariattexas

Is this my fill plug on my rear differential cover? It's a threaded plug that has a square hole in it like to stick a socket wrench in it. Also is it ok to add fluid in it even though it's not the same? For example I'm not sure what's already in there and I think I'm low cause I've been hearing the humming noise when I sometimes step on the gas. I want to use royal purple gear oil.

08limited2148

Yes, it's located on the driver's side and you can use a 3/8 drive to remove it. The fluid type is syn. 75/140 with limited slip (check the tag on the back casing. It should have an "L" in the description). If it does then it requires limited slip additive with the fluid. I don't know if Royal Purple will cover that application. Read the bottle or go to their website, it should say.

Mod (Ret.)

You're best and safest bet would be to drain and re-fill the rear end. How many miles are on the rear end? Has it had service yet?

I'm not a fan of "topping off" a rear end in hope that it will quiet down. If it's low, theres a reason; it is leaking somewhere, and that needs to be addressed. That could be the reason for the noise you're hearing. Get it checked by a qualified expert.

Will most likely save you a ton of money down the road.

04lariattexas

The truck has 78k on it now. I've only had it for about two months. It is my daily driver to work. I'm not sure when the last time it was changed or serviced. I did a visual inspection underneath the entire truck yesterday and couldn't spot any drips or wet spots anywhere but I know that doesn't mean much. I'm trying to avoid taking the cover off because I don't want to screw up and have a leak later on cause I didn't put the cover on good. Can I just use a sunction gun and get all possible fuid out and then fill back up with new stuff?

04lariattexas

I forgot to ask how many quarts of fluid will it take. Am I gonna need to add a friction modifier additive as well?

driver444

Usually a gallon covers it, with some left over. You only need friction modifier if you have a limited slip differential. Open differentials don't need it.

attaboybob

put it on level ground, unscrew it, and dip your finger in the diff hole. see if you feel fluid...if so..your good. touch and smell the fluid, it should be a good oily consistancy and not be burnt or watery.
if you decide to change the gasket, be sure to clean out the area real well with brake fluid....gears and all.
when you refill, do not over fill. the fluid is meant to keep the gears lubed and cool. too much fluid counter-acts that process.

BOB

04lariattexas

How hard should it be to turn? Mine seems hard as hell. I don't want to screw anything up. Just go for it? Talking about the fill plug by the way

Cold

it will be tight you dont want it coming out driving down the road

Mod (Ret.)

You're due for a rear end fluid change with your mileage. An average cost for having this done properly (they open the cover, clean, inspect, re-seal the cover and add new fresh fluid) is about 70 bucks. Then your good to go for another 75K.

Be honest with yourself in this type of service/repair. If you've no done it before, don't know what to look for during the inspection process, or are concerned with any noise you are experiencing, take it to a shop and have it done.