Technical Without starting an internet fist fight, is there a difference in synthetic gear lubes?

I was reading up or attempting to on synthetic gear lubes. There are a ton of opinions, mostly from non-engineer types. I know @Blues4U is a petroleum genius, so maybe he will chime in.

I have a later 8.8 posi going in the 55 and the Ford TSB calls out for synthetic 75W140 with a friction modifier.

Well, they range in price from $10-38 qt and I need 3. So, then I start wondering if the hype for stuff like Amsoil is worth the extra $ ?

It's a one time investment, since it is supposed to last the life of the rear differential. The intended use is mainly light driving and occasional towing of the race car and/or, the vintage travel trailer.

 

I guess at some level there are some small differences. I like Mobil Delvac synthetic gear oil. My personal experience is with the 75W90 in a large commercial operation. But it's available in 75W140. It's usually $35 to $39 per gallon. Keep the water out of it and don't break anything and it's a lifetime fill.

 

I was just wondering if the "Severe Duty Amsoil" is going to add any life over the cheap stuff.

 

Them thar is fightin words hombre,,,,,,gear oil is almost as controversial as motor oil and filters !
And don’t even get me started on Mary Ann or Ginger !

LoL

Tommy

 

You are right my friend.....

 

I would think the right answer is both ( Ginger and Mary Ann) why short change yourself .

 

No fight? But I had popcorn ready!!

 

Lol,,,,,I thought it would be fun to interject a little humor there .

It seems the most innocent of questions gets completely out of hand sometimes.
It’s kind of like Ford versus Chevy,,,,,great taste or less filling,,,,LoL.

And I didn’t even mention Mopar,,,,,,there might have been a cataclysmic shift of the universe,,,,LoL .

Tommy

 

Mila Kunis If you really want it for life spend some money.

 

OKAY, I have an OT late model with an 8.8. The owners manual says to use a synthetic 75W-140 GL5. So thats what I use, a major brand. Also use the Ford brand friction modifier. So I would say use the same in your project. (as your TSB)

 

Right. That's where I am at. With that said, is the cheapest 75w140 sufficient? You feel me?

 

my OT has the store brand synthetic in its 8.8. No issues

 

I won't argue about synthetic gear lubes, but I'll sure as hell argue the Ginger/Mary Ann question. In my opinion, "Both" would be the wrong answer. These recent photos should prove my point.

First, let's have a look at Mary Ann.



And now a quick peek at Ginger. Make it a quick peek, a longer look could damage your eyesight.

 

Aww man, I’ll never be able to watch Gilligan’s Island again!
As for rear end goo, give me whatever stinks the least while I’m wiping up the inevitable leakage.


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Yikes!

It was always Mary Ann for me......still a classy looking lady!

 

Yeah,,,,,but Ginger is 86 now and Mary Ann is 81,,,,,big difference from 55 years ago,,,LoL.
Even when I look in the mirror,,,,,I get startled and almost upchuck .

Tommy

 

Biggest part is to use the modifier, Ford brand works good. Regular gear oil is fine you just need to change it more often.

 

Amsoil makes great products, but for the daily driver you mentioned probably over kill. Most anything you put it there will get you more miles than you need. I doubt that the factory fill was super top shelf stuff. And if using a store brand now, if you find that you still have the car X miles down the road and you were concerned you could drain it and still be money ahead? The sprint car team I helped in the '70s always ran Amsoil in the quick change and the in/out box until went to a shifter rear. It's not in my daily driver as my grocery store trips just are not that abusive as they might have been 45 years ago.

 

In your case, Ford rear, Ford posi unit, use Ford recommended oil. Years ago purchase a 2 year old Ford Expedition 4X4, nice vehicle low miles, had a chatter in driveline when turning corners. Previous owner had all the fluids changed at a Ford dealership and wrong gear oil type installed. Took to a racing friend that had a shop, diagnosed it immediately, changed oil to correct Ford oil, problem solved. So..... Imo follow factory recommendation. Again IMO, Oil is not the place to pinch pennies. I am a believer in synthetic oil and use it in all my vehicles, but would not vary from factory recommendation in your case.

 

That’s what the friction modifiers are designed to eliminate. They are designed to eliminate clutch chatter in a limited slip/clutch style differential.


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Uhh Oh! Just recently completed rebuild of a Ford 8.8 with factory limited slip and was using a popular guide book on Ford axles for procedures. It did not specify either synthetic or 75w/140. However, it did recommend a break in procedure of approximately 500 miles with a drain and change at that point.

I have filled the axle assembly with lube and installed in project car, but it will be months before it sees actual use.

So, my question is......is the initial fill of 80/90 likely to be adequate for the break in period?
It does have friction modifier in it, supplied by Yukon Gear along with Phillips 66 lube they sent too.

Ray

 

Worked in dealerships for years, other then transmission fluid at jag and Mercedes.

everything else at every other dealership came out of 55 gallon drums from any one or more of the local suppliers.

if your not beating on it regularly then use what you have.

I noticed over the years the first oil change on a rear end gave you some black silvery goo every time no matter the manufacturer, IF the customer did regular fluid changes there after it always came out clean, albeit slightly darker but nowhere near the colour n stink of that very first change out.

big one is to use a friction modifier if your fluid of choice does not come with it already.

 

Ok, great input. Here’s the deal. I bought the rear end out of a salvage. Low mileage Exploder. I tore it down to shorten the long axle.
Now I need to service it back up. Up until 2000, they ran a 80/90 then a TSB came out that says basically change to 75w140 synthetic to extend the life. I did buy the Ford brand modifier recommended as well.

 

In your case I would assume the TSB is either to lengthen or completely get rid of the diff service interval.


Domestic brands love sealed for life stuff.
Talk to any “technician “ in the trade from around 2005 onward and ask them how many spark plugs or thermostats they have changed !

 

Question for all the experts
I couldn’t find Winters own brand gear oil up here for my new quick change so I called them and asked if Lucas synthetic 75-140 would do the trick.
Winters tech guy said yes.
The friction modifier never came up in the conversation in regard to the Winters wedge lock system.

So the question is (without another call to Winters ) is a friction modifier something to consider?
Or even necessary?

 

It won’t hurt if you put it in.
Won’t do anything except stink if you don’t need it
If you need it, we’ll, now it’s in there !

 

Larry it’s necessary if it’s a clutch type limited slip, if not then no you don’t need it.


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Look at Shell truck transmission and rear end lube, can't remember the name on it right now. If it will live in a truck rear, you're not going to hurt it or it hurt your rear.

 

Bought a few limited slip/positraction/sure grips/trak-lok rear ends over the years from guys convinced they were no good. Add a bit of the proper friction modifier and all but one lasted for years for the new owners.

 

Yum

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