Forum Discussion

darsben's avatar
darsben
Explorer II
Sep 21, 2015

Transmission Fluid

I have a Southwind on an 1989 CHEVROLET P30 CHASSIS. 454 ENGINE.
What transmission fluid should I use when I change it next week.
I am told Dexron III.
  • rgatijnet1 wrote:
    DEX VI will work fine.


    As stated Dex VI is backwards compatible with Dex III


    Dexron-VI

    The fluid specification for Dexron-VI was introduced in 2005, and was first used as the GM factory-fill automatic transmission fluid for model year 2006. All Dexron-III licenses expired permanently at the end of 2006, and GM now supports only Dexron-VI fluids for use in their automatic transmissions,[3] although fluids asserted by their manufacturers to meet Dexron-III standards continue to be sold under names such as Dex/Merc. These fluids are not regulated or endorsed by GM.[4]

    Dexron VI is of a slightly lower viscosity when new compared to the prior Dexron fluids (a maximum of 6.4 cSt at 100°C for Dexron VI and 7.5 cSt for Dexron III), but the allowed viscosity loss from shearing of the ATF during use is lower for Dexron VI, resulting in the same lowest allowed final viscosity for both Dexron III and VI (5.5 cSt).[5] The lower viscosity is intended to gain improvements in fuel economy by lessening parasitic drag in the transmission. Since Dexron VI is not allowed to thin out (lower its viscosity) as much as Dexron III during use, it requires the use of higher-quality, more shear-stable (less prone to thinning while in use) base oils.[4] The current GM specification that defines the fluid is GMW16444, which superseded the original specification, GMN10060
  • Valvoline makes dexron3 for napa and napa sells both. Some newer dexron 4,5 will not work in older trans models and dex 3 will not work in newer trans.
  • Dexron 3 available at most auto parts stores in my area. I use it in my levelers. Chuck
  • Gjac's avatar
    Gjac
    Explorer III
    It uses Dextron 111 but I doubt that you can find it anymore. The last time I changed mine I could not find it and had to use the "backward compatible"fluid. Walmart sells it.
  • That is the right answer. Transmission Fluids are 'backward compatible' except in a few rare circumstances. (Kinda like Dino Oil / half & half and 'New Oil' - synthetic).

    BUT...it is not true for fuel!! Early (1950 to mid 70) gas engines needed the additives -LEAD & stuff- that are not present in current fuel. If you drive a 1950's car, (as you know) you need to purchase and add LEAD to your fuel for that car!!