Differential fluid questions

[ponyboy0123]

Coming up on 50k miles on my 18 and was looking to do some preventative maintenance including changing the dif fluid, I just have a few questions since I keep seeing different answers online, I’ll keep it simple

1. 75w85 or 75w90?
2. How many quarts? I’ve seen 1.6qt being thrown around
3. Do I need to add an additive?
4. Is any reputable brand okay?
5. Since this will be my first time attempting myself, anything else I should know?

I’ve got the standard 3.15 gear dif for reference.

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[Johnny Rockit]

It can't hurt to go by Ford spec fluid. That is all I got. When theree are many answers, I tend to follow the manufacturer's recommendation.

 

[TopJimmyCooks]

https://www.opmustang.com/store/p2/...FORD_MUSTANG_REAR_AXLE_LUBE_CHANGE_KIT.html#/

OP includes instructions with the order. Same for trans fluid. Easy.

 

[ice445]

I used redline 75w85, but you aren't going to be any worse off using a 75W90. You do need some kind of limited slip additive, either added after the fact, or as part of the fluid you choose. The correct fill level is 9mm below the fill plug (I used a zip tie where I measured 9mm from the end then bent it 90 degrees). Buying two quarts will get you there.

If this is your first time, make sure the vehicle is supported on a lift or 4 stands and completely level. Remove the fill plug first to make sure it can be done. Any fluid transfer pump can be used.

 

[Jerryinpa]

Coming up on 50k miles on my 18 and was looking to do some preventative maintenance including changing the dif fluid, I just have a few questions since I keep seeing different answers online, I’ll keep it simple

1. 75w85 or 75w90?
2. How many quarts? I’ve seen 1.6qt being thrown around
3. Do I need to add an additive?
4. Is any reputable brand okay?
5. Since this will be my first time attempting myself, anything else I should know?

I’ve got the standard 3.15 gear dif for reference.

Hi,
I looked up the diff gear oil for my new 2022 and it calls out 75w85 full synthetic motorcraft. XY75W85QL $31 a quart on Amazon. Mine is a 3.55 LS.
I heard many times, gear oil is gear oil...
But in warranty i would use oem fluids.
50000 isnt enough miles to change it, but i tend to change fluids early also!
thabks, Jerry
Thanks,Jerry

 

[NKNEFA6]

I went with the Royal Purple 75 90, which includes the additives that Ford recommends. I have had no issues with this while using B&G in the mt82.

 

[KingKona]

https://www.opmustang.com/store/p7/...mission_and_Rear_Axle_Fluid_(In_Stock).html#/

 

[GTP]

If you aren't tracking your car, I'd just change it at the recommended interval. Which is 150k mile, IIRC.

DD is not hard on the gear oil. Low temps and low gear-on-gear pressures.

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