Front differential leak, should I just redo the RTV?

[Apparition]

I have had the same experience as Tworley with the lube lockers. If you are planning on being in the rocks, stick with the RTV. If not the lube locker works great.

 

[sab]

I have never had leaks around the differential covers when changing the diff fluid on my 2005 LJ.
I feel like I do it by the book, razor blade & wire brush off the old RTV, then bead new RTV around the pan n leave for 24 hours before refilling.

Most gasket RTVs state in the directions to go finger-tight, wait a period of time (usually an hour) and then torque the screws. The reason for this is to get the RTV to spread out and cure a bit, so that when you do the final torque, the gasket has some firmness to it so that you can develop some torque before you squeeze out too much RTV. The mating surfaces have small ridges and valleys, and if you immediately torque the bolts, you can have small pathways for leaks.

Try just barely tightening the bolts a bit more, but be careful not to over-torque (stripping the threads.) This isn't always successful, but it's worth a try. I just did this earlier this year on a Subaru rear diff cover. Worked like a charm, which is good because the rear diff cover on those is structural and part of the mounting system, so it's a half-hour's work or more to remove it. If that doesn't work, when you re-do it, be sure to read the directions, and if it calls for a wait period before final torquing the screws, heed those directions.

 

[cpwolf]

Actual squish-out:
View attachment 520105
Well under 90%.

I also used the recommended two-step process. Finger tightened the bolts until the RTV squeezed out a little, evenly all around, and let it vulcanize for an hour. Then torqued the bolts, squeezing out more of course, and waited 24 hours before adding lube.

Looks like 23.2%

give or take .08%.

But I’m just eye balling it! Ha

 

[sab]

That is a lot of silicone. More than 90% of the silicone will be squished out or packed in the bolt holes.

I agree with Brianj5600 on this. I've built dozens and dozens of engines, transfer cases, transmissions, and differentials over the years, and I never use anything close to that size bead. On the production line for Harley and Polaris (both companies I've worked for as a design engineer), the tech setting up the RTV gun would be in trouble using a bead that size. It's wasteful, and the part of the excess that squeezes into the case can plug filters, if present, when it breaks off.

I'm going to need you to show me the math on that.

Ok. The sealing surface width on a Dana 44 is about .75". As you can see from the picture below, the bead width looks to be about 1/4":

The area of a circle 1/4" in diameter is pi x R x R, or 3.14 x .125" x .125", which is 0.049 square inches. So, if 90% squished out, that would mean that the thickness of the cured RTV remaining on the .75"-wide sealed surface would be:

.049 square inches x 10% ÷ .75 inches, or .0065"

In my experience, that thickness seems to be realistic. I concur with Brian5600's estimate of 90%.

Additionally, the RTV on the outside of the holes serves no purpose. Again, on production lines, that would not be there to save cost (every penny counts in vehicle cost to the bean-counters I despised.)

 

[sab]

Actual squish-out:
View attachment 520105
Well under 90%.

I disagree. There's a similar amount on the inside that squeezes out, too. Together with what's pictured on the outside, that could very well total about 90%.

I also used the recommended two-step process. Finger tightened the bolts until the RTV squeezed out a little, evenly all around, and let it vulcanize for an hour. Then torqued the bolts, squeezing out more of course, and waited 24 hours before adding lube.

Absolutely! As I mentioned above, following the directions for the sealant you are using is critical. On my sealant shelf, I have many types of sealants, and some require an extended waiting period and some don't. Silicone RTVs are the ones that most commonly require it. I use a Three Bond product (can't remember the number) for aluminum case halves (engines, transmissions, etc), and it doesn't require a long wait time...

 

[Zorba]

The bigger the glob, the better the job!

 

[nitrofalcon]

Thirded. They're reusable (within reason) and it makes future fluid changes much faster since you cut out the entire razor blade / wire wheel portion.

Razor blade and brushing is not fun. PITA!

 

[gasiorv]

View attachment 520108

I am actually in the market for a front Dana 60 and a RJ60 would meet the need if you have one sitting around.

 

[Apparition]

I am actually in the market for a front Dana 60 and a RJ60 would meet the need if you have one sitting around.

I do but I need it.

 

[nitrofalcon]

The bigger the glob, the better the job!

 

[Brianj5600]

I use very little RTV and don't use a bead. I smear a thin layer of what ever RTV isn't dried in the tube on the mating surface, bolt down the cover and let it sit overnight. If your surfaces are flat you almost can't tell there is any RTV on the mating surfaces.

If it makes a mess, try less.

 

[MikeE024]

The lubelockers are great--not trying to discredit them at all. I ran one for years and it held up really well even after removing/installing multiple times. I still have and use one for the rear cover. But if the diff cover is hit often and hard enough, the gasket can break/bend. The RTV at least has the ability to deform and bounce back during a hard hit. How much force to change that...I honestly have no idea. There are several of us who have had lubelockers on the front though and have gone back to RTV due to leaks.

I have had the same experience as Tworley with the lube lockers. If you are planning on being in the rocks, stick with the RTV. If not the lube locker works great.

I wonder if the thicker mating surface of my aftermarket cover is why my LL gasket hasn’t leaked on me. It’s taken some good hits.

 

[LJcooljay]

Definitely get a lube locker gasket. It appears to be leaking from the bolt hole and not the gasket area. I’d try pulling that bolt and wrap some Teflon tape on it, and then stick it back in there. See what happens. Or back that bolt off a little, apply some RTV around the hole/bolt, then tighten the bolt back up.

Hello all,
thank you for all the replies.


I ordered a lube locker gasket based on everyone's responses.
While I was waiting for it to arrive I took out that bottom bolt & picked out some old RTV from inside the hole.

like @[B]SouthernTJ2000[/B] mentioned.
I dabbed a little RTV or Teflon tape on the bolt (can't remember which)
months later still no leaks!

Next time I remove the diff. cover I'll be installing the Lubelocker but for now I'm still running RTV.

-In between all this I had to work on my transmission. I went with a lube locker gasket when reinstalling & love it. This brand seems to work great & no more razor blade scraping! definitely recommend for the 42RLE because of how "glued up" the pan can be & avoid bending it next time I drop it.

 

[MikeE024]

Hello all,
thank you for all the replies.


I ordered a lube locker gasket based on everyone's responses.
While I was waiting for it to arrive I took out that bottom bolt & picked out some old RTV from inside the hole.

like @[B]SouthernTJ2000[/B] mentioned.
I dabbed a little RTV or Teflon tape on the bolt (can't remember which)
months later still no leaks!

Next time I remove the diff. cover I'll be installing the Lubelocker but for now I'm still running RTV.

-In between all this I had to work on my transmission. I went with a lube locker gasket when reinstalling & love it. This brand seems to work great & no more razor blade scraping! definitely recommend for the 42RLE because of how "glued up" the pan can be & avoid bending it next time I drop it.

I just found my transmission pan all nicked and dented up, yet there were no leaks from the pan/LL even after I had the pan/LL off and on at least three times over the past year and a half. That's a pretty good sign imo.