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Royal Purple Max Gear 75w90 Gear Oil

Market Price $22.99 You Save 13% ($3.00)
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  • Item 45003
  • MPN# 1300

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    Features & Details

    • Fully Synthetic
    • Friction Modifier Included
    • Protects Against Wear
    • Reduces Gear Whine
    • 75w90 Weight
    • 8.8" Ford Rear Ends Require 3 Quarts
    • For 1979 to 2017 Mustangs
    Pure Performance. Maximize performance from your Mustang's drivetrain with Royal Purple Max Gear oil. This fully synthetic oil is the perfect complement to new gears, lubricating better and ensuring your differential keeps working its best whether it has gone a thousand miles or a hundred thousand.

    Protect Your Investment. Made with Royal Purple's innovative Synslide® additive, Max Gear oil is perfect for upgrades or routine service. It's the gear oil of choice for greater wear protection and lower temperatures for every car, from daily drivers to track-day toys. It prevents corrosion and meets all warranty requirements, so adding Royal Purple Max Gear oil is great for peace of mind when it comes to your Pony.

    Includes Friction Modifier. Unlike other oils, all viscosities of Max-Gear® are formulated with hypoid friction modifiers necessary for use in clutch or cone type differentials. No additional additives are necessary.

    Application. Royal Purple Max Gear 75w90 weight oil is recommended for use in 1979 to 2017 Mustangs and is compatible with other oils. Three (3) quarts of gear oil are required to fill a 8.8" Ford rear end.

    Fitment: 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Details

    What's in the Box
    • (1) one quart bottle
    Installation Info
    Tech Specs
    Will it fit my Mustang?
    • Boss 302 - 12, 13
    • Bullitt - 01, 08, 09
    • Cobra - 93, 94, 95, 96, 97, 98, 99, 01, 03, 04
    • Cobra R - 93, 95, 00
    • EcoBoost - 15, 16, 17, 18
    • GT - 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11, 12, 13, 14, 15, 16, 17, 18
    • GT350 - 15, 16, 17, 18
    • GT350R - 15, 16, 17, 18
    • GT500 - 07, 08, 09, 10, 11, 12, 13, 14
    • LX - 87, 88, 89, 90, 91, 92, 93
    • Mach 1 - 03, 04
    • Other - 79, 80, 81, 82, 83, 84, 85, 86
    • V6 - 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11, 12, 13, 14, 15, 16, 17

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    7 Questions / 6 Answers

    Ask a Question

    For 6th gen with Torsen 3.73 the owners manual list 1.5 liters and like 3 oz of friction modifier as capacity. Why are 3 quarts needed?


    • Hello! From my understanding it does vary slightly, but its about 2 quarts of gear oil and a bottle of friction modifier which is about 4 oz and you should be good.

      Ryan H

    Helpful (1)

    Will this bottle of solution make shifting a manual tremec (2010) 5 speed shift smoother? Does it affect the shifting in a good way?


    • The Royal Purple Max Gear 75w90 Gear Oil will improve shift quality, especially in colder weather. The primary benefit is reduction of friction and wear.

      Rob D

    Helpful (0)

    I'm confused, so to clarify when changing Gear oil do I need 2 or 3 quarts?


    • Three (3) quarts of gear oil are required to fill a 8.8" Ford rear end.


    Helpful (0)

    On the bottle and in the part description it states - Friction modifiers included, no additional additives are necessary. Is the Ford modifier really required?


    • If you are changing gears or even adding new gear oil, it is always a good idea to add friction modifier to help the performance of the gears.


    Helpful (0)

    going to change my diff to a lsd with 4.10 gears, i have an 08 v6 wondering what the difference between the 75w90 75w140 gear oil which would be recommended


    • The differences in the Royal Purple Max Gear Gear Oil, 75w90 and 75w140 would be the viscosity of the oil throughout a temperature range. For moderate driving applications, 75w90 would be best, however, if the vehicle is driven in more extreme driving conditions, the 75w140 would be best for that application. If you are using the vehicle for a particular application, please give us a call and we would be happy to recommend a weight which would be best suitable for your application.


    Helpful (0)

    How good will this work for the MT82 transmissions.


    • This Royal Purple Max Gear 75w90 Gear Oil is meant for your rear differential, and should NOT be used in your transmission.


    Helpful (0)

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    Customer Reviews (52) Write a Review

    Overall Rating 4.8

    out of 5 stars

    Installation Time:Less than 1 Hour

    Installation Cost:0-$100

    • Performance Gain 4.567567 4.6
    • Fit 4.756757 4.8

    • 5/5

      January 09, 2010

      it works like Jesus, 05 Mustang GT

      The shop that installed my 4.10 Gears gave me a skeptical look when I told them to use this stuff instead of their regular oil, he made it seem like it doesn't make a difference. But on the same conversation he was warning me he has installed hundreds of rear gears on mustangs and most of them have a weird hum that has been rectified with the newer Mustangs, so he warned me some people don't like it. When I got my car back there was no humming or any of the other issues he warned me about, so like Jesus, if you believe it works then it works.

      R. Hidalgo

      Year: 2005 Submodel: GT

      Helpful (7)

    • 5/5

      August 24, 2010

      Good stuff

      Works as it should. Fluid is not as viscous as I had imagined and this is good because clean up was easy. Took about 2 bottles to fill up my 7.5'' differential (98 V6).I recommend you use "Right Stuff" gasket maker for sealing the differential cover.


      Year: 1998 Submodel: V6

      Helpful (6)

    • 3/5

      Installation Time: Afternoon

      October 02, 2011

      Good product but 75w-90 wrong for 2002 Mustangs with 8.8 rear end

      Purchased 75w-90 based on American Muscle web page stating it was the correct fluid. Order was on the way before I checked owner's manual. Ford specs 75w-140 for the 02 Stang and the data tag on the differential cover says "Use only 75w-140". Called American Muscle they said the 90 weight would be OK. Could have chanced it, but was able to exchange the 90 for 140 weight at a local retailer at no cost. Put in the specified 75w-140 and all is good. Be aware that you need to drop the sway bar to reinstall the cover without making a mess of silicone gasket sealant. Royal Purple products are great


      Year: 2002 Submodel: GT North Salt Lake, UT

      Helpful (5)

    • 5/5

      Installation Time: Afternoon

      March 07, 2012

      Rotal Purple Rocks!

      Took me a little while to do the rear diff oil change, it was my first time though but it feels amazing! 100% recommended


      Year: 2003 Submodel: GT Brownsville, TX

      Helpful (4)

    • 5/5

      April 22, 2010

      Good stuff

      I love how this stuff come with friction modifier already, less stuff to hassle with. Just did a girdle install and use the Max Gear RP oil and have no complaints. I have liked all the RP stuff I have used in the past as well.


      Helpful (4)

    • 5/5

      April 16, 2010

      Good Stuff

      I was looking for this gear oil at my local auto motive shops and they where all asking this really crazy prices for this stuff. I usually make some purchases through American but never thought they carried gear oil. When I checked I was amazed at the price. I recently had 3.73 gears put on my car with the Royal Purple Gear Oil and could not be happier.

      Art Torres

      Helpful (4)

    • 5/5

      Installation Time: Less than 1 Hour

      November 26, 2012

      Synthetic Solution

      Best price I could find on Royal Purple full synthetic gear oil. Better than local price; better than any other online price I found. And I found a great source of Mustang stuff to boot!


      Year: Pre-79 Submodel: Other Texas, USA

      Helpful (3)

    • 5/5

      Installation Time: Less than 1 Hour

      April 25, 2012

      Gear Oil

      Great price on the oil. Great quality. Worth the buy.


      Year: 1987 Submodel: Other Malvern P.A

      Helpful (3)

    • 5/5

      Installation Time: Afternoon

      October 20, 2011

      Good Gear Oil

      I put this in the 8.8 rear of my 98 GT. Right away I noticed a quieter and smoother ride, but not much in the way of performance gains. The only tricky part was getting the new oil into the diff. It was hard to get the bottle lined up to pour it in because of the mufflers and the driveshaft. But other than that, it was a good choice for the price.


      Year: 1998 Submodel: GT

      Helpful (3)

    • 5/5

      August 08, 2011

      Smooth running!

      I just changed the diff fluid today. I did it at the same time as the tranny fluid. I dont have any scientific results but I can say there is minimal resistance in the drive train. I run all royal purple and I feel confident that wont have any fluid related problems. I changed it at 70k and the old fluid seemed like it would be good till 100k. I saw 3 different numbers from diff fluid intervals so I went with the shortest one.


      Year: 2006 Submodel: GT

      Helpful (3)

    • 5/5

      June 10, 2010


      eliminated the 2nd to 3rd synchro crunch in my six speed miata. Shifts like butter now


      Helpful (3)

    • 5/5

      May 11, 2010



      DAVE W

      Helpful (3)

    • 5/5

      January 17, 2010

      RP ATF

      Great Stuff


      Helpful (3)

    • 5/5

      November 11, 2007


      Good oil, looks like I bought mine just in time before the price jump. I wouldn\'t call it a jump really, I was surprised to get such a deal once I saw it going for 11 to 12 bucks a bottle at an O\'reilleys auto parts store. ;)

      Robert L.

      Helpful (3)

    • 5/5

      Installation Time: Less than 1 Hour

      October 31, 2017

      Works great

      Great product already has the friction modifier in it so it's prefect for rear gears changes only thing is you'll only need two for a 8.8 rear end where the website says it takes three


      Year: 1986 Submodel: Other

      Helpful (2)

    • 5/5

      Installation Time: Less than 1 Hour

      August 09, 2013

      Must use!

      Swapped to a set of 4.10 gears on my Cobra and used this to refill the diff housing. Was easy to add and haven't had any gear whine or anything. A great product from Royal Purple, i use it for all my fluids in my Cobra.


      Year: 2001 Submodel: Cobra Malven, PA

      Helpful (2)

    • 5/5

      Installation Time: Less than 1 Hour

      March 22, 2013

      Great Product and A MUST HAVE

      This fluid is a must have when you are changing out gears!!!


      Year: 2012 Submodel: GT500 Malver, PA

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      April 10, 2012

      Gear oil

      The gear oil works like it should. The way my car drives has not changed, but now I just know my car is running smooth. Also when filling make sure you have a hand pump.


      Year: 2002 Submodel: GT Pasadena, CA

      Helpful (2)

    • 5/5

      April 24, 2010

      nice stuff

      works well ,no chatter around turns

      nick z

      Helpful (2)

    • 5/5

      January 27, 2010


      Does exactly what it is supposed to do. No problems here


      Helpful (2)