differential oil change synth vs dino

[Tannerm]

My 97 f150 4x4 probably needs it. Its got 178k miles and doubt its been done in a looong time if ever. Front (8.8) calls for 75w90 and rear calls for 75w140 with friction modifier (8.8 3.55 LS. Rear end code H9). Should I use syn or Dino oils in them? My differentials don't chatter or anything but I just wanna replace the oil for peace of mind. Will also be doing the same in my 99 5.0 explorer 2wd.

[DFWtechie]

I went ful syn on my difs yrs ago and love it. I also run full syn in the engine a trans. just let the gasget maker dry for atleast 2-4 hrs before refilling the dif's

[Lone Star Performance]

Yep^^

[One zero]

And don't get the friction modifier on your skin or anywhere other than into the fill hole. It stinks to high hell and takes a week to get off.

[91CoupeMike]

And don't get the friction modifier on your skin or anywhere other than into the fill hole. It stinks to high hell and takes a week to get off.

Only if you use the right kind, the shit they sell at parts stores isn't even close to the ford stuff.

[91CoupeMike]

I personally don't see the need in spending the extra money on a syn oil.

The old stuff was on its way to lasting 200k and you don't have any issues.

Why change it up?

I use the regular $7 a qt valvoline or castrol. But that's just me, it's just gears and bearings, not your engine.

[LS1Goat]

As greenbullitt would probably tell you. Nothing really beats motorcraft synthetic gear oil and friction modifier.

[Tannerm]

Well i went to 2 autozones, 1 O'Reillys, and Walmart... No one has effing Dino 75w140! So alas I had to go full syn in the front and rear pumpkin. Plus the explorers rear. Oh well. I'm a mess but its done if Walmart had more, I woulda cheaped out and got there super tech syn 75w140 if they had more then two qt... Thanks alot gents.

[Tannerm]

As greenbullitt would probably tell you. Nothing really beats motorcraft synthetic gear oil and friction modifier.

I run that in my truck. Been happy with it. The explorers used Mobil 1 since before me and didn't want to change it.

[kingjason]

So I was reading around the other day while setting up the cable on my OX locker. If I can find it there was an article talking about synthetic diff oil blowing up bearings in 4x4s. They are a very well respected locker company and did a lot of tests as they were having premature failures. I cant remember if it was tearing up small parts on the lockers or what it was. It may have been ARB but I will look in a minute.

[Skidonenko]

Does ford still recommend 80w90FEHP in anything new? They were crapping rear axles left and right with that weight 5 years ago. In the front diff I guess it wont see near the the use of the rear, but 75w140 with a bottle of XL-3 was what worked in everything (more XL3 in the superduty axles).

[kingjason]

For some reason Auburn, Hi-9 axles, and Currie were all voiding the warranties if synthetics were used. I read the 10 page post and it appears it got pretty heated with manufactures, and others chiming in. At some point those three were losing a lot of ring and pinions, burning up rear ends, and limited slips etc. They switched back to dino and no more issues. Something about the synthetic staying cooler in the pumpkin but not pulling the heat from the actual R&P. I do not believe they actually backed it up with any real science.

I agree with the comments here about dino diff oil working great for hell 200k or more in cars. I am a big synthetic guy though with regards to my engines. I just don't see it being that beneficial in a rear end.

[dumpycapri85]

I agree with the comments here about dino diff oil working great for hell 200k or more in cars. I am a big synthetic guy though with regards to my engines. I just don't see it being that beneficial in a rear end.[/QUOTE]

Yep . Don't fix it if it ain't broke .

[Baron Von Crowder]

For some reason Auburn, Hi-9 axles, and Currie were all voiding the warranties if synthetics were used. I read the 10 page post and it appears it got pretty heated with manufactures, and others chiming in. At some point those three were losing a lot of ring and pinions, burning up rear ends, and limited slips etc. They switched back to dino and no more issues. Something about the synthetic staying cooler in the pumpkin but not pulling the heat from the actual R&P. I do not believe they actually backed it up with any real science.

I agree with the comments here about dino diff oil working great for hell 200k or more in cars. I am a big synthetic guy though with regards to my engines. I just don't see it being that beneficial in a rear end.

The air cooled bug guys did a similar test, something to do with the syn oil either not picking up the heat that the dino did or vise versa. IIRC, the head temps went up with the syn oil.