Well for the last day and a half i've been slowly changing out all of the driveline fluids. Today I did the rear diff. The cover was pretty rusty to begin with but after some sanding, scraping, and cleaning I was able to clean it up a bit. Here's a pics before I pulled the cover off:



No, my diff was not leaking. The oil you see if from the engine actually haha (next project to take care of). As I drive on the highway, the drips are being thrown all over the underside of my truck. On the bright side, my entire undercarriage has a nice oil film on it protecting it from the winter elements, especially salt

Side Note: It makes is much easier to do if the spare tire is removed. I'm glad I took the couple minutes to take it off. Definitely saved my back being able to sit up underneath. Using a 1/2 inch socket all of the bolts can be removed. Once the bolts were removed I used a putty knife, working from the bottom up, to separate the cover from the axle. Suggestion: Leaving the two top bolts in makes it much easier to controllably drain without the cover coming crashing down in the oil pan.



If you change yours, make sure you clean out the oil in the bottom valleys of the diff. There are a couple places where small amounts of oil sits. Using a rag I was able to get all of the oil out.



The teeth seem to look just fine. The fluid, however, was definitely due for a change.



The inside of the cover had some grime on it. Nothing a little rubbing with a towel can't take care of.



Using sandpaper I was able to remove all of the existing sealant from both the cover and the axle. I used a rough grit to remove the large pieces, then a fine grit to remove any deep scratches left by the rough grit paper, and lastly I used steel wool to smooth everything out. Make sure to cover the diff with a plastic bag to make sure the pieces of sealant being removed don't get into the gears and crevices.




This is the results I got after some sanding and cleaning. Be sure to remove all traces of old sealant to ensure you get a good bond with the new sealant. Also, I used a good cleaner on all mating surfaces to make sure no grease or oil was on the surface.



This is when I applied the new RTV. I used blue because it's what I had on hand in my shop. Any type of gasket maker should be acceptable. They do make a black RTV that is very resistant to oil and high temps. Perhaps i'll try that next time.



Before placing the cover back on I sprayed a coat of paint on it just to add a little rust protection in the future. Last, but not least, don't forget to torque the bolts down. I torqued mine to 35 ft lbs after reading guzzles instructions.

This is cheap insurance for your axle. If you haven't done this lately, head on out and do it. It's easy and can be done in a couple hours. For those that want more detailed instructions check out guzzles website. Those are the ones I skimmed through before doing the work myself.

Welcome to guzzle's Ford PSD Web Pages

 

Looking good Clay I need to do this. What fluid did you end up using? Do you have an open diff or the LS?

 

Thanks! I ended up getting the Valvoline 85-140 synthetic blend from autozone for $7/quart. I looked for 75-140 like the manual requests, but I couldn't find it anywhere. Unfortunately, I have an open diff, but on the bright side I don't have to worry about adding LS fluid. One thing I forgot to mention, since it's cold outside, i'm leaving the diff empty over night to allow the RTV to dry. I did leave a shop light on the diff cover hoping that some heat will absorb and help with the drying process.

 

Clay, when I do mine I will have to to tape a note on the steering wheel to remind me to fill the diff. Seems the older I get the more forgetful I get.

 

Thats a good idea. Luckily I put the new oil next to my keys as a reminder for tomorrow morning.

 

im very disappointed to not see a smilie face again! come on man get with the program!

 

Dang it, I forgot again!! I may have a surprise for you tomorrow. Stay tuned

 

Just a question but why the Blue RTV silicone?? That is sensor safe RTV and tends not to fare well with GL-5 hypoid gear oil. Red or Grey RTV are both high resin content and work great with GL-5 oil. Just my $.02

 

i use blue cause i got a buncha it on sale one time. works good for me, i dont run my diff fluid more then a year anyhow.

 

I had several tubes of it already in my toolbox. I wasn't aware about the issue with GL-5 fluid. I'll keep that in mind the next time I change the fluid. I'm too lazy to go back and change it haha

 

Good job on the pics and step by step. This isn't a hard maintenance to perform at all.

 

Thanks! I think the hardest part for me was scraping and sanding off all of the old rtv and even that is easy.

 

nice job on the pics and write up, i know you said you had an open diff but does the valvoline syn oil already have the friction modifier in it or do you still have to add it?

 

This is what I found online:

http://www.valvoline.com/pdf/Durablend_Gear_Oil.pdf

If for some reason the pdf can't be viewed, this is what the back of the bottle says:

Recommended for all hypoid differentials (conventional or limited slip)

To be honest, i'm not sure if it has the friction modifier in it. I would guess it doesn't. The best way to find out is to change the fluid and drive the truck to see how the diff reacts on turns. It the tires chirp a little bit, friction modifier would need to be added.

 

Clay thanks for the reply i am in the process of buying all new fluids and collecting the required parts needed over the winter so when spring hits or i find a heated garage i can swap them out.