Differential oil change and leaks

[tcp71]

I did an early change of the gear oil in my 2016 F150's rear differential. It is a 9.75" electric locking unit. In 2015 the specified fluid went from 75w140 (still specified for the F250 and f350) to Motorcraft® SAE 75W-85 Premium Synthetic Hypoid Gear Lubricant XY-75W85-QL. Having a bunch of 75w140 on hand from my 2009 truck, I went ahead and changed the fluid early (12k miles) to get rid of any break in material and put in the 75w140 as I also tow our travel trailer.

I have always, in the past, used permatex gasket maker on the differentials and never had any problems with leaks or anything. In the interest of serviceability and access I used a Felpro RDS 55476 Differential Gasket. It certainly made the time (no waiting for it to tack up or cure) quicker, but I did have a couple of drips on the garage floor after a couple of days. When I checked the bolts they were not as tight as specified so i re-tightened them.

Is it common for a gasket to "pack down" and need the bolts re-tightened? They were looser than I remember leaving them.
I checked again at 24 hours and 48 hours after the re-tightening and things seem to be sealed up now. Will I need to keep checking them or will it stay sealed now?

Experiences?
thanks.

 

[dlundblad]

Hopefully Trav sees this.

 

[MolaKule]

Quote:
Is it common for a gasket to "pack down" and need the bolts re-tightened?

It is.

However, I clean all mating surfaces of oil with Naphtha and apply a thin film of Black RTV gasket sealer, wait a few minutes, then apply the gasket and bolt down. I have never had a leak with this procedure.

 

[tcp71]

I have a second gasket and some black and blue permatex on hand. If necessary I will just redo it with permatex or permatex/gasket combo. I will watch it a bit first. I did remove all the old rtv with a sanding wheel and cleaned with MG chemicals Safety Wash on the cover and differential mating surfaces. maybe just needed a re-tighten. I did notice some staining on the cover before opening it so not sure the factory RTV job didn't have a bit of a weep as well.

 

[demarpaint]

I like to use Permatex High Tack on a Felpro gasket after cleaning everything and jacking the vehicle slightly forward to stop the possibility of a tiny bit of residual gear oil running down the cleaned surface. Those gaskets haven't leaked yet. Try snugging it down a bit more, hopefully that fixes the problem.

 

[dustyroads]

Originally Posted By: tcp71
Is it common for a gasket to "pack down" and need the bolts re-tightened? They were looser than I remember leaving them.
I checked again at 24 hours and 48 hours after the re-tightening and things seem to be sealed up now. Will I need to keep checking them or will it stay sealed now?

Experiences?
thanks.

I used the Felpro gasket on my '13 last year. It was my first and only time using it, but no problems. I torqued the bolts to spec and just out of OCD, I retorqued a couple days later and I don't recall any tightening. The torque wrench immediately clicked on each bolt. No Permatex used.

Just my (limited) experience.

 

[Schmoe]

When I did mine, I used a gasket and sealer. Re-torqued after a couple of days because of thermal expansion and still got a small sheen kind of leak. A mechanic told me to take of the bolts, put sealer on the bolt threads, and then re-torque. I did that and it solved the problem.

 

[SOHCman]

I probably misunderstand, but I would stick with that 75w-140 man, the 75w-85 recommendation changeup sounds like a CAFE gimmick. Just like when they back spec'd the 90's Ford trucks to 5w-20..

 

[beanoil]

Lube Locker gasket user here.
Used to use FelPro, until I discovered this baby.
Clean the surfaces, install, torque, drop the mic.
LubeLocker

 

[CT8]

I run 75W-140 in the differentials. 2002 F250 and a 2015 F150

 

[tcp71]

I have a lube-locker in my cart on amazon. Haven't pulled the trigger yet unless the leak returns. I used some of my stash of 75w140 on this fill. I will continue to do so.

 

[tcp71]

Amazon.com for this one. Here's amazon.ca:

 

[WyrTwister]

$ 93.96 CDN ? That sounds VERY expensive for a gasket ! ??????????????