Leaking differential cover: repair with gasket or RTV

[1fastTbird]

I have a small leak coming from the differential cover on my 75k mile 2006 GT. The cover has never been off and the fluid never changed, so it's a good time to get fresh gear oil in there anyway. I have never pulled off a differential cover, but I can't imagine a job getting much easier than that.
My question is do you guys prefer RTV or a gasket to seal it back up? I am leaning towards RTV.
Is there a particular gear oil and or friction modifier that you prefer? What about technique for refilling?

 

[07 Boss]

I always use ATV to seal it back up.

When you drain it I always leave a couple of the top bolts loose, almost all the way off, and then remove the other bolts. This makes it a neater job because then you can pry the bottom of the cover open without having the whole thing come off. Then once all the oil drains out you can remove the cover all of the way.

I have a fill plug (and drain plug) on my cover so it is a little easier to fill than the stocker, but either way get one of those tubes that screw onto the bottle and it makes it real easy to fill. also when you lift the car put the jack stands under the frame so the axle hangs down. If you hold the car up with the axle you don't have as much room to maneuver.

You can use whatever oil you want just pay attention to the recommended weight, I've use both synthetic and dino oil back there. Just be sure you add the proper 4 or 6 ounces (can't remember off the top of my head) it requires.

 

[Uncle Buck]

RTV FTW

Wear gloves. This is a smelly job

 

[1fastTbird]

Thanks for the prompt responses, I really appreciate it. I may pickup one of the Ford oem GT500/Boss 302 finned covers and use the upper plug for the diff cooler to fill.

 

[46addict]

I have the same issue but I'm not sure if its just a leaking cover or if I have a bad pinion seal.

 

[Dad]

I actually prefer both. Clean your metal surfaces thoroughly with brake cleaner, apply a thin bead of RTV to both metal surfaces, put on the gasket, hand tighten the bolts and walk away. Come back after a few hours, tighten to the correct spec and add correct diff oil.

 

[Gabe]

Did a diff service on the fiancee's Shelby.
I used black RTV, worked great, months later still no leaks.

 

[grywll42]

Just ordered ford friction modifier from AM 11 bucks free shipping, I think it's like 50 bucks at the dealer

 

[Gabe]

Just ordered ford friction modifier from AM 11 bucks free shipping, I think it's like 50 bucks at the dealer

Always Google first.
Amazon has it for $8.49 with free shipping
Amazon.com: Genuine Ford Fluid XL-3 Friction Modifier Additive - 4 oz.: Automotive

 

[AR Stang]

Black RTV, but don't go crazy with it.

Some people snug the bolts, and then tighten to full torque later, but I have never had an issue taking them down to full tightness from the start and filling with oil right away.

 

[JEWC_Motorsports]

Like everyone else, black rtv.

 

[skwerl]

Black or gray RTV. My mechanic prefers gray. I bought a tube of gray from the parts store and it was half dried up because it was so old. Also let it set up completely before scraping off the excess. It peels right off when it's dry.

I don't know any mechanic who uses the gasket on the Ford rear ends. They often end up leaking.

 

[swflastang05]

I used black RTV for decades then learned about Lube Locker gaskets (from Scott on this forum), I'll never go back to RTV again! Lube Locker FTW

https://lmr.com/item/LLR-F880/lubelocker-Mustang-88-Rear-Differential-Cover-Gasket

 

[1fastTbird]

I was all ready to go buy some RTV but swflastang05 had me at "hello." I am going to give the Lube Locker a try. The job is dirty and stinky enough and saving time vs RTV sounds enticing.

I appreciate all of the feedback.

 

[nyuk98GT]

1fastTbird,

+1 for the Lube Locker gasket. One came with my FRPP cover kit and it is holding well - no drips from the perimeter at all.

RTV is certainly proven to work but the gasket is a very tidy option. I don't know if it is reusable but I wouldn't hesitate to get another one if the rear end ever needs to be taken apart.

HTH,

Chris

 

[dre256]

I just did my rear on my 03 GT. Same rear, I got a GT500 rear cover used on ebay for 50 bucks. They have a few new still for like 80 or cheaper. Fill on the cover makes the job so much easier. GT500 cover does need longer bolts than stock as it is thicker. Can pay 20 bucks online for them, I went to tractor supply and got class 5 bolts for a few bucks. I use black RTV sealer on my jeep and worked great. This time on the mustang I tried lube locker gasket from LMR for 20 and worked well too

 

[Bill220]

I'm leaning towards the gasket, if that's what is on there now.

 

[travelers]

We use the black RTV at work on rear covers and a lot or other gasket areas with no leaks or problems.

 

[Bill220]

I'm afraid of overtightening those two bolts and ruining the rear end. I might just leave the stock cover on. Not like I need it.

 

[nyuk98GT]

Bill220:

From the installation guide that came with the FRPP cover:

The girdle-to-housing bolts are tightened to 20 to 25 lb-ft.

The load bolts are tightened to 5 to 10 lb-ft [60 to 120 lb-inch] (DO NOT OVERTIGHTEN these bolts). The jam nuts are tightened to 25 to 30 lb-ft.

You could just leave the load bolts 'untightened' (that is, not touching the bearing covers) and then snug up the jam nuts. But, I think you should get the benefit of the load bolts and you'll be successful if you're careful and double-check your work. Go for it, Brother!

You can get a torque wrench from the rental tool crib at AutoZone. But you should have a good torque wrench in your toolbox if you're working on your car.

HTH,

Chris