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Rear Differential and Trans. fluid.

Discussion in 'Chevy Trucks' started by Barkleymut, Jan 22, 2004.

  1. Barkleymut

    Barkleymut PlowSite Veteran
    Messages: 29

    I have an 03 2500HD 6liter 2WD. I don't plow but I pull a heavy trailer 6 to 9K lbs. all year. I am switching to Amsoil oil for the engine and want to do the best for my rear end and tranny too. Should I just stay with the intervals in the owners manual and use the regular lubes or should I step up to the Amsoil trans and differential fluids? I've never changed the auto tranny fluid in a truck before. I can't imagine its too hard, or is it?
  2. porkhead1

    porkhead1 Member
    Messages: 70

    IMO, Amsoil for the engine is great.......:) As for the tranny oil, the first time changing it, its pretty messy unless your tranny pan has a drain plug in it. If you don't have a drain plug, put one in the first time you drain the oil & change the filter. Pulling that heavy a trailer all year, I would recommend at least changing the std. tranny oil every 25k miles. If your truck doesn't have an aux. tranny cooler :realmad: by all means get one! Heat is the #1 killer of auto. trannys. Get the biggest cooler that will fit between the grill & radiator, install so that the oil from the tranny goes into the radiator first, then into aux. cooler & back to the tranny. Regardless of whether you use reg. tranny oil or synthetic, get a cooler. As for the rear end, IMO, use the Amsoil. Does your truck have a locking or posi differential..? If it does, you may need some GM Posi Additive when you make the change. Until you can get the oil changed in the rear end, check to make sure that the oil level in there now comes up to the "fill" hole. The factory likes to save some $$$ by not filling them all the way to the top. If you plan on having the truck for a long time, keep up on the maintance....you can't make any $$$ with it in the shop for repairs

    Good luck

  3. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    Even if you have a limited slip(check the option codes for g80 or if your truck came equiped with a "locking rear diff") But use synthetic in the rear by all means. Amsoil will work fine. If you are towing extreamly heavy I believe that GM recomends going to a heavier oil in the rear......check the manual.

    Synthetics only real advantages are better cold temp flowing(not an issue in a trany IMO) and better resisance to heat brakdown and better resistance to break down. The resistance to high heat is just and "insurance" thing in most fluids and operating conditions.....if your not going to try for extended drain intervals or in the cold were you want the oil to flow then synthetic dosnt offer any advantage.(in a motor or trany or anything, it depends on the situation) A symisynthetic with a good additive package(its all about the additive package IMO not the base) will offer you almost all the benifits of a full synthetic at a fraction of the cost. I personally run Schaffer's 7000 Supreme semisyn in my truck. It didnt make sense to me to run a full synthetic in my application because I wasnt going to do extended drain intervals since I run a BOMBed Duramax and thus have a higher level of soot production and thus I need to get the oil outa the motor more frequently.

    I personally believe that amsoil trany fluid is to slick. And not its not because its synthetic......the base has nothing to do with if a fluid is "too slick" or not. The additive package for the amsoil synthetic ATF dex replacment is too slick IMO. The only advantage synthetic ATF offers in a trany is that it will brake down from heat less. As long as you dont get the trany realy hot and you change the fluid based on the way you work the truck(sounds like your in the severe service group) you will be fine......if you want the extra measure of protection of hight heat break down from synthetic i would recomend going with a fluid other than amsoil in the trany JMO.

    I plow snow and it is JMO but i think its better to change the fluid often so synthetic would get very pricey so I just do more frequent changes of regular dino ATF.
  4. JMR

    JMR Senior Member
    Messages: 567

    Rear diff fluid is already synthetic lubricant(GLS 75w-90). So Amsoil would be fine. For the trans IMO don't use synthetic. GM uses DEXIII. Flush the trans when changing fluid and change the filter. Dropping the pan only gets 1/3 of the fluid out of the trans. Flushing gets 99 %. Why would you mix 2/3 old fluid with 1/3 new. I always change the filter too. Would you ever change your oil and not change the filter? JMO