Hello,

A few days ago, I searched this site for information on the proper way to torque a differential cover screw on a 1995 F350. I did not find what I was looking for. In my case, I have a Sterling (Ford) conventional differential (S168N / 4.10 / 10.25 ring gear) that I have changed the differential fluid from 80W90 to 75W140 full synthetic. To do this, I removed the differential cover. To reinstall, I am using a LubeLocker gasket and twelve new differential cover screws from Ford that I will torque to 19 lb-ft, unless somebody says something to convince me otherwise.

Here is what I have gone through, to come to this conclusion.

The 1995 Ford Powertrain / Drivetrain Service Manual, on page 05-02C-11 clearly says to torque the rear cover screws to between 28 and 38 lb-ft of torque. These numbers are clearly stated in two other places in the manual for this particular Sterling (not Dana) rear axle. This seemed high to me, as normal torque for a clean 5/16"-18 HHCS in Grade 5 is in the 17 lb-ft range, and a Grade 8 is in the 25 lb-ft range. Why then, would the Ford screw call for so much of a higher torque?

I searched the internet in general, and sure enough, there are a lot of instances where people have been breaking off differential cover screws. So, I decided to perform an abbreviated test. The test is shown in the attached pictures, and hopefully is self explanatory. In short, the Ford differential cover screws did not fail until about 50 ft-lbs was applied. This makes it seem as though it would be fairly safe to torque the new screws to 28 to 38 lb-ft.

However, when I removed the existing cover screws, they all consistently broke loose at 19 lb-ft (Black sealant was used. Not a gasket.). There was absolutely no leakage around the differential cover. This is why I have chosen, for the moment, to only torque to 19 lb-ft.

Any thoughts?

Thank you,
Greg

 

Just torque them in a cross pattern until theyre gudentight and you'll be fine.

You probably can't find anything on google because nobody ever puts that much thought into it.

 

What he said...and 19 lbs is more than adequate.

 

I just use the right arm torque to it feels good gauge. Never broke a bolt or had a leak.

 

228 in lbs

 

That's right!


I wouldn't use a gasket though. Rtv like factory.

 

I've always used RTV too, but i used one of the lube locker gaskets, much nicer, and you can refill with oil instantly without fear of leaking. Much less clean up too to replace it.

 

how does a gasket effect filling? I will always pull the cover when servicing . The bottom of the diff needs cleaned out for a proper service.

 

You're supposed to wait an hour or so for rtv to setup before refilling with oil. I use three bond 1184 and wait 15 minutes but still it's alot cleaner. I always pull the cover and clean it too.

 

It's coated in the same stuff good water pump gaskets and idi oil cooler gaskets are. Not just a paper gasket

 

Does your wrist click yet?

 

No.....but sometimes my butthole will pucker-up

 

10 char

 

LMAO it goes on and fluid in. No wait and never had a leak.

 

I have used the FelPro gasket on my last three diff oil changes and they worked just fine for 150,000 miles. RTV is too messy and has to be cleaned every change. It's all personal preference.