Rear gear oil questions

wera44

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8.8 with 4.10 gears, 75w90 or 75w140 and regular or synthetic? Ill run friction modifier with either oil choice.
 

Win

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I used 75w90 royal purple in my last rear end I had built. I've also heard great things about Lucas also.
 

Rallim

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Does gear oil really change anything? I've seen people recommend different things, but I've never heard of anyone giving any reasons or what effect any different ones would have. Far as I'm concerned they just make sure the bearings don't explode.
 

Win

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I felt that when I had the chance to upgrade I did. It was new so I felt start right and keep it right.

like right when we got her 11 5.0 I got amsoil to put in it.

yes royal purple is syn. Go do some reading on

www.bobistheoilguy.com
 

RichV

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Synthetic keeps the temps down. It's great for racing and towing where you have a lot of load on the rear end.
 
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wera44

wera44

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Manual said synthetic 75w140 so that's what I ordered and I'm going to run friction modifier even though the gear oil comes with it in it.
 

Goldmember

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Mobil 1 75W140 for me. Works just fine. My dad has dealt with his share of 8.8's, and his advice on friction modifier is to add a little at a time until you've got it right. I think you're supposed to use 4 oz, so 1 at a time until things are working properly. I haven't used any FM and there's been no issues; can still get both of 'em spinning.

Then again, mine is a stock weekend cruiser, so not much load/stress put on anything. If you're racing, might have different needs.
 

robb15033

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75W/90 Amsoil with added friction modifier. Motorcraft or Amsoil friction modifier only ones I use.
-One example I found was that our Mustang shops are all using the same product unified: Amsoil in the differential. Similar to shops choosing FRPP gear sets exclusively.
 

robb15033

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Does gear oil really change anything? I've seen people recommend different things, but I've never heard of anyone giving any reasons or what effect any different ones would have. Far as I'm concerned they just make sure the bearings don't explode.
Differential fluid is where it all starts when acceleration is endured. Gears wrestle and spin with superior fluid, eliminating inertia is the core of a machine moving withe little to no effort, and transferal of energy.
 

JerZeyStangz

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I am running Amsoil 75w90 gear oil. It can run up to 300,000 miles with no drain. And I am using Motorcraft Friction modifier. I did this when my rearend got rebuilt from scratch with the Ford racing 3.73 gears, it has clutches, new bearings etc...

The rearend is so quiet I can hear the transmission and exhaust, and I can roast both tires off idle, no one tire fires.
 

Win

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I am running Amsoil 75w90 gear oil. It can run up to 300,000 miles with no drain. And I am using Motorcraft Friction modifier. I did this when my rearend got rebuilt from scratch with the Ford racing 3.73 gears, it has clutches, new bearings etc...

The rearend is so quiet I can hear the transmission and exhaust, and I can roast both tires off idle, no one tire fires.


Agreed I'm a huge fan of amsoil! Switched our 2011 5.0 when we first got it.
 

Handz

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I dont trust royal purple.

I use only motorcraft OEM gear oil and Fiction Modifier in my Diff.
 

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