...always somethin' ain't it?

 

Referance post: ( https://www.f150online.com/forums/ot...nion-seal.html )

 

Ok, got the right stuff (should be a movie ) $5.29ea w/tax. I guess you only add one bottle.

 

Has anyone heard of this? A friend of mine in Escondido, CA forwards this to me about synthetic fluids.

"With recent revelations on how gears inside differentials do with synthetic gear lube, I personally have plans to switch my axles from synthetic to a conventional gear lube at the next change.

What some of the axle manufacturers like Currie have discovered is the gears run hotter with synthetic than they do with conventional gear lube. That is surprising because the old IR temperature gauge says the pumpkin is cooler with synthetic than it is with conventional gear lube. What they figured out is that the synthetic gear lube stays cooler because it isn't sinking (absorbing) the heat out of the gears like conventional gear lube does. It surprised a lot of people. Currie has changed their policy on axle warranties to require only conventional gear lubes be used. If a failed axle comes in with synthetic gear lube from now on, they will void the warranty.

Yes, surprising to me too but I have had a few long conversations with several at Currie and they said it's not just them, other manufacturers have caught onto this recently too."

 

While I'm not convinced myself, and 100's of thousands of trucks out there have gone 250k mi. + on factory specified synthetic fluids...Eaton did tell me that if I were to use their TrueTrack LS carrier, I should not use synthetics because the helical gears would hold the heat in rather than to transfer it to the oil.

I would imagine that the difference is minimal and quality ring & pinion gears can more than take the heat. If I you were to switch over to conventional to keep the gears cooler or to run a TrueTrack LS, you might be "better off", but I would think the oil change interval should be greatly reduced. Not worth it to me.

Nice score on the Motorcraft FM, I thought it was closer to $12.

Another thing to consider man, since you're already dropping the diff. cover to drain and I assume clean the rearend, as well as pulling the pinion nut off...I would imagine that factory LSD is shot and due for a rebuild. It would be the ideal time to drop in a set of clutches / plates. If it is an 8.8" I would use the Cobra LSD rebuild kit as it has carbon fiber friction pads and is supose to extend the life something like 3x.

 

I'll look into this but the LSD seems to be hooking up just fine. I am waiting on my Dial Torque wrench to come in and when it does I'll install a new C-sleeve & set it up w/the good man made gear lube

My son wanted to change the fluid out anyway since it does have 250K on it so we did just that until next week or two.

Some pics can be seen @ my gallery (I just started one for the F150, original owner, I didn't have a digi cam when I got it). I think it's on the second page, you will see your favorite bottle www.street2mud.com/gallery

Thank for all your help, nice forum

 

If it still works, great. Seems like most of them are long gone by 80-100k mi. though.

 

Ya, about a month ago the roads were wet (I'm use to driving a CJ7 I-6, bought htis new & eventually gave it to my son when he was 16) & I don't drive it that much, got on it just a little and theread went out from under me, oops I would say it's working just fine as well as some other things I've done

 

I thought this was going to be hard the guy at the shop wanted 4 something for parts and 557 for labor for real wheel axel seal brake shoes and pads hardware and oil i laughed it took me about 2 and a have hours and costed me 127 buck thanks to all of you guys much appreciated btw i put black silocone oil sealer and a gasket on is this ok?

 

Has anybody had the issue of changing your diff fluid and then getting that rear end "shudder"? Changed fluid in my 8.8 3.55 and added modifier 75w 140 full syn also and about a month later I started to get the shudder when turning

 

Did you put in friction modifier from Ford? You are supposed to even if the gear oil says it already has it in it.

 

Yes I did but it wasn't motorcraft brand

 

Go to the dealer, get a bottle of Ford modifier, and put it in - or order it from Amazon:

 

Isn't it too late for that? It is seriously bad

 

A lot cheaper than changing the fluid again - or rebuilding the rear.