Rear Dif Gear Lube for 2002 F150

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Nov 22, 2005
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I know my 2002 F150 specs/factory fills synthetic 75w140, but is that thick of an oil really nessicary? Would I see any negative effects if I switch to synthetic 75w90? Would I see any fuel economy increases? When I do tow with the truck I would say it is only moderate in weight, i have a 14ft enclosed trailer that I haul my motorcycles and gear in.
 
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They probably spec the 75w140 because they need a good thick oil to dissipate the heat and provide adequate protection. I would say that a really good synthetic 75w90 would be just fine. Amsoil makes a very tough gear oil if you are looking for a sugguestion.
 
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Use the factory recommended weight in a full synthetic flavor. There is a reason Ford specs 75w-140 in that vehicle. Follow it!
 
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Do you tow? I would keep that in mind. I know Amsoil makes a 75w-110 but has anybody else come out with a dino or syn of that weight? I would feel more warm a fuzzy with the 110 over a 90 wt.
 
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I just put Valvoline Durablend 85w-140 in my buds 04 F-150 heritage, but it doesn't get that here and he's moving to Florida so I didn't see the need for a full syn lube.
 
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I have a 2002 F-150 and swapped out the factory rear diff fill with Mola's Speciality Formula 75W-90 Synthetic gear oil. In my driving circumstances I did not notice a difference in my mpg. I don't tow but I can load my truck to the max and beyond sometimes. Sad to say after 6 months I developed a leak in the rear diff. The installer who put Mola's diff fluid in insisted upon me supplying Permatex Ultra Blue RTV Silicone. I'm not sure that is compatable with synthetic diff fluid. Ford uses a black silicone RTV sealant that works. Anyway I had Ford reinstall their 75W-140 gear oil with their RTV brand sealer and all is good. I don't think you will save many mpg between 75W-140 and 75W-90. Maybe if you tow then Amsoil's 75W-110 might save you some mpg. Whimsey
 
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 Originally Posted By: Spartuss
Use the factory recommended weight in a full synthetic flavor. There is a reason Ford specs 75w-140 in that vehicle. Follow it!
X2 \:\! I would throw some Royal Purple MaxGear 75W-140 in it.
 
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 Originally Posted By: Whimsey
Ford uses a black silicone RTV sealant that works. Anyway I had Ford reinstall their 75W-140 gear oil with their RTV brand sealer and all is good.
Actually, Ford uses TA-29 (gray) RTV at the factory and specs either TA-29 or TA-32 (clear) for rebuilds. \:\!
 
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 Originally Posted By: Ben99GT
 Originally Posted By: Whimsey
Ford uses a black silicone RTV sealant that works. Anyway I had Ford reinstall their 75W-140 gear oil with their RTV brand sealer and all is good.
Actually, Ford uses TA-29 (gray) RTV at the factory and specs either TA-29 or TA-32 (clear) for rebuilds. \:\!
actually no they use black.
 
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They do not spec black for replacing diff covers, and every factory diff cover I have pulled off has had gray RTV.
 
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cause every one ive pulled off has black, on mustangs, F-series, E-series, panther chassis, rangers. o and according to the FACTORY service manuals it specs TA-30 which is black in a caulking gun.
 
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General Specifications Item Specification Lubricants and Sealers SAE 75W-140 High Performance Rear Axle Lubricant XY-75W140-QL (vehicles with the trailer towing option or 4:10 ratio) WSL-M2C192-A Additive Friction Modifier XL-3 EST-M2C118-A Premium Long-Life Grease XG-1-C or XG-1-K (Canada CXG-1-C) ESA-M1C75-B High Temperature Nickel Anti-Seize Lubricant XL-2 ESE-M12A4-A Silicone Gasket and Sealant TA-30 WSE-M4G323-A4 Threadlock and Sealer TA-25 WSK-M2G351-A5 Stud and Bearing Mount TA-27 WSK-M2G349-A1 Lubricant Capacities Additive Friction Modifier XL-3 118 ml (4 oz) Approximate axle fill capacity 1.7 liters (3.15 pints) to the bottom of the fill hole with the axle at ride height
 
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TSB 05-23-3 • YL3Z-4662-CA - Pinion Bearing Spacer for Axle Noise Repair 1997-1998 9.75 axles (Includes Time For Road • XG-14 - Gear Marking Compound Test To Verify Concern (Irs • 4067 - Differential Shims 0.241² to 0.307² Axle)) (Do Not Use With 4010D Or 4010D4) • SAE XY-75W140-QL - High Performance DEALER CODING Synthetic Rear Axle Lubricant CONDITION • XL-3 - Additive Friction Modifier (Limited Slip BASIC PART NO. CODE Axles Only) 4209 14 • 205-506 - Seal Protectors (Rotunda Tool) • W710084-S439 - Wheel End Nuts (1997-2005 F-150, 1997-2005 • 390266-S100 - Differential Slave Pin Bolt (9.75² Expedition/Navigator) axles) • 387426-S100 - Differential Slave Pin Bolt (8.8² 9.75 REAR AXLE HOUSINGS WERE axles) • 4B422 - Axle Circlips • ZC-21 - Metal Surface Cleaner • TA-29 - Ultra Silicone Sealant • TA-27 - Stud and Bearing Mount Retaining • F3TZ-4121-AA - Fluid Tag (REQUIRED IF FLUID And just to verify, I just checked two Ford in my driveway, guess what, both gray.
 
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Whatever works, I normally use Motorcraft TA-32 clear. Works like a charm with <1 hour setup time.
 
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