I am going to change out the rear diff. fluid in my X next weekend. I don't do alot of towing but some. Its gonna be expensive. Has anyone used walmart's Super-Tech fully synthetic 75W-140? Its a GL-5 application grade. Motorcraft synthetic 75W-140 is $20/quart. Valvoline Synpower is $15/quart. Super-tech is $8/quart. The rear end takes 4 quarts plus the friction modifer. Thats $90 for a Motorcraft job or $40 for a Super-Tech job.
What do you'all think?

 

Just did this in my 2000 X and was told that I HAD to use the Motorcraft stuff @ $20.00/qt. I even added some limited slip additive too. I paid a mechanic to do this and am glad I did as he didn't get the seal tight and it leaked so he had to buy round two of the fluids! Good luck and if you decide to try anything other than motorcraft please post your result of happiness here so we all can learn from it.

Kevin

 

I bought the Valvoline Synpower Fully Synthetic 75w-140 from Advance. I had some heartburn with regards to buying the Super-tech for $8/quart. I just couldn't do it. A mechanic friend said "oil that thick, any brand would be ok". I disagree. There is a reason its $8/quart and everyone elses is $15 to $20/quart.

 

I am going to change mine with amsoil synthetic. I heard a friend got good gas mileage with it. Plus I got a chrome rear end cover which I am going to put on.

 

I used the Amsoil and their additive and still have chatter. I'm pleased with their regular oil, but the gear oil leaves much to be desired. I'll try royal purple next.

 

I used Super-tech on my X and it seems fine. but than again I don't do any towing at all. And I change it once per year along with my transmission and coolent.

The way I see it, I can do super-tech once per year, or the motorcraft at double the price and do it once every other year. My labor is free, well not free but I like to work on my x. The oil at the end of 2 years will costs me to same but even if the motocraft oil is better (I assume because of $) I just don't see it that much better at the end of 2nd year vs super-tech's once per year.

 

Changing your rear diff's fluid, whether syn or dino, annually or every other year is a bit overkill.

BTW... Did you notice that the OP was in May of 2004?

 

I didn't see the OP date until i posted. duh on my part.
Yes I understand changing out the rear diff once per year syn or dino is an over kill. I don't know if it is because I like to do everything at the same time so I don't have to keep a log of when and what i did. I firgue I am under the truck and getting dirty anyway why not just do everything and forget about it.

 

It seems to me that the OP doesn't matter as I was just getting ready to do the same thing and there is a thread about a whole bunch of work someone else is doing on his rig and that's part of it.. If I remember correctly I used Mobil synthetic on my '98 3/4 Suburban and it has the anti-chatter stuff right in it,no additive needed, and it worked great and I was pulling an 8500# travel trailer with for awhile..Never seemed to have a bit of trouble or noise. Put it in both the front and rear.Had a leak in the rear cover,so pulled it,cleaned them out, redid the gaskets in both and filled them with fluid..Really easy job,just takes a bit of time is all.

 

Just did mine with Royal Purple a month or so back. It was $12.50 a quart and has the friction modifier already in it. After about a week of regular driving the chatter I had went away.

As a side note, I don't know if it's related to the rearend oil change, but my rear pinion seal started leaking shortly after. Got it changed out and topped off with the remaining Purple oil I had left from the original change.

 

I also changed mine with RP to. I paid 16 a quart and the noise i had in the rear end went away.

 

I think the change to synthetic on my Suburban kept blowing out my rear axle seals; they were incompatable with the synthetic. The X's come with synthetic from the factory.

 

I nly run Royal Purple in all the fluids in the X and love it. I don't get any nose from the front or rear diffs. I also noticed a lower trans fluid temp after I replaced the trans oil.

I swear by it and we will turn over 200,000 miles this summer or sooner.

Bryan

 

Bryan, thats how i feel? Diesel or gas and have u replaced urtrans at all?

 

We are running a gasser but we can't really complain since we have had zero issues so far. Just the normal maintence schedule that is adjusted for a little longer limits.


Bryan