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75/140 owners manual vs 75/90 tag #5326673 01/18/20 11:36 PM
Joined: Dec 2018
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BigGee Offline OP
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During some recent maintence on my truck(2003 f-150 4wd),I got the recommended fluids from the owners manual, for transmission (Motorcraft Mercon v), transfer case (Valvoline Dexron/Mercon),front differential (Supertech 75/90),rear differential (Valvoline 75/140).All of these were the factory fill with 285,000 miles on them and surprisingly the old oils looked good.While changing the rear diff. on reassembly I found a tag that states 75/90 fluid only! .I refilled with the 75/140 without concern but I do think it is odd that the manual states a different viscosity than the tag on the rearend. Any others seen this before?

Re: 75/140 owners manual vs 75/90 tag [Re: BigGee] #5326705 01/19/20 12:59 AM
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mpack88 Offline
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I actually did a post wondering if I should use a 75w140 in my leaky differential until I get it rebuilt. but my owner's manual says use a 80w90. Both our trucks should be an 8.8. No one in my post had any objection to using the thicker stuff but the thinner stuff wouldn't hurt it either. If still a concern for you I would call Ford.

Re: 75/140 owners manual vs 75/90 tag [Re: BigGee] #5326768 01/19/20 05:52 AM
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ka9mnx Offline
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Ford has waffled on rear axle fluid specs. In the early 2000's the API changed the specs for axle oil (I think they added the 75w-110) which made the upper viscosity for 90 lower. In response to this, Ford changed their rear axle spec to 75w-140. With their newer vehicles it seems they are back to 80w-90. I'm using SuperTec synthetic 75w-140 in both my Ford's with no complaint.


2005 Ranger 3.0 - SuperTech Syn 5w-30/Motorcraft
2000 4Runner 3.4 - SuperTech Syn 5w-30/Toyota
1997 B2500 Van 3.9 - M1 HM 10w-30/Mopar
1993 F150 4.9 - SuperTech Syn 5w-30/Motorcraft
Re: 75/140 owners manual vs 75/90 tag [Re: BigGee] #5326871 01/19/20 08:55 AM
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CT8 Offline
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75w -140 is a better oil for rear ends worked harder. Think of it as a heavy duty 90.


2015 F150 2.7
2018 F350 6.2
Re: 75/140 owners manual vs 75/90 tag [Re: CT8] #5326873 01/19/20 08:59 AM
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4WD Offline
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Originally Posted by CT8
75w -140 is a better oil for rear ends worked harder. Think of it as a heavy duty 90.


And 140 might be made from better base stock and other
Significant price jump for M1 90 or M1 140 … but read somewhere it’s 30% PAO and stronger add pack.

Re: 75/140 owners manual vs 75/90 tag [Re: BigGee] #5326954 01/19/20 10:29 AM
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tcp71 Offline
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My 09 9.75” differential called for 75w140. In 2015 the spec changed to 75w90 (or 80w90?) for fuel mileage reasons I think. I changed the oil after break in on my 2016 ( also a 9.75” axle) at 20k miles with 75w140. It does need to tow 7000lbs through the mountains in the summer so I have no problem with the heavier hot temp rating.

Either would be fine if you don’t tow heavy. If you do work the truck hard, I would go with the 75w140.


2016 F150 Eco: Edge 0w40
2005 Sienna 3.3: NAPA 5w30 syn. (varies)
Re: 75/140 owners manual vs 75/90 tag [Re: BigGee] #5327040 01/19/20 12:09 PM
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bullwinkle Offline
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The 140 is tougher, at some microscopic loss of MPGs due to extra drag (mainly when cold). I'm debating whether or not to change out the 80W90 in the MGM in my sig when I install the trailer hitch & Air-Lift air springs in it, along with the oversize transmission pan & auxiliary cooler.


06 Ram 3500 CTD 4X4(FG Venturi), 93 GMC C3500 6.2, 89 F-450 7.3, 98 XJ 4.0(XG8A), 05 xB(XG3600), 18 Transit 3.7, 03 Merc Grand Marquis 4.6 2V(XG2)
Re: 75/140 owners manual vs 75/90 tag [Re: BigGee] #5327052 01/19/20 12:22 PM
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Whimsey Offline
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My 2002 F-150 4X4 and 2005 Explorer with the 4.6 V-8 both called for 75W-140 in the rear diff with no options given. It worked great. I still have the 2005 Explorer.

Whimsey

Re: 75/140 owners manual vs 75/90 tag [Re: BigGee] #5328136 01/20/20 06:30 PM
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BigGee Offline OP
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I did use the 75/140. In most cases if you go by the book you will be ok,I do use the truck pretty hard,I had already bought it and didn't have enough 75/90 to do the job.I was really surprised on how clean all the oils were with that many miles and years on it.

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