Quote:
Originally Posted by BillGrissom
I recently looked at options online and at Autozone. I ended up getting the Autozone Dexron VI. Says it replaces Dexron III and is superior. However, forgot I bought AFT+4 at the same time for my Mopars, forgot and put 2 qts of the later in my 300D (85 CA, has your 86+ tranny). Doesn't matter. Most tranny fluid uses the same base oil and they just put in additives.
Similar questions for my 60's Mopars. Original isn't available, and Chrysler said "use Dexron III instead", back in the 80's. My 96 Voyager should use ATF+4 (today) and it has the exact same Torqueflite internals as my 60's 904 & 727 trannys, so I use ATF+4 in my old Mopars. Before that I used Type F (as many do), since I read it had more friction modifiers for firmer shifts. I since read that ATF+4 has the most friction (good), plus the Autozone brand used to say "fully synthetic". Many Chrysler V-6 (4 spd) minivan trannys were ruined because they said one could use Dexron III if the then-new ATF was not available. The slippier fluid caused the lockup converter to get confused and jump back and forth, wearing out the plates. GM wanted slippier fluid to give slower, smoother shifts since the un-schooled public thinks that is a sign of a good tranny. Actually, you want quick, firm shifts, which is what "shift kits" do.
In sum, I will strive to use Dexron VI in my old 300D's, but ATF+4 should be fine too. Mixing fluids does nothing bizarre. Then again, I am someone who uses silicone brake fluid and doesn't believe the bunk about bad things happening if a little left-over glycol fluid mixes in. I also know that Valvoline's DOT 4.1 "synthetic" brake fluid is marketing bunk (all brake fluids are synthetic).
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Hope Dexron VI works out. However,
note that viscosity of Dex VI is lower than Dex III. Possibly for fuel economy. It is possible that Dex III shears down to lower viscosity as it gets used while Dex VI is supposed to be more stable in viscosity with use.
A 96 Voyager should have a lock up torque converter unlike '60's Torqueflites. Lock up TC shudder tends to occur when friction modifiers degrade with use.
Type F has no friction modifiers. Atf 4+ has friction modifiers as does Dexron III, Dexron VI, Mercon, Mercon V. Friction modifiers can be designed to reduce friction under different conditions. ATF 4+ ihas more friction modifier than Dexron III.
Friction modifiers as currently used in ATF tend to reduce friction especially when clutches are almost engaged to avoid shudder of clutches, especially lock up torque converters. Old Type F tends to have friction increase as clutches are almost engaged. Type F when used where the lock up torque converter is supposed to use FM fluid causes grab-slip-grab-slip which feels like shudder.
All "approved by Chrysler" ATF4+ is supposed to be synthetic.
Ultradrive 4 spd transmissions did break down in 1989 and 1990's before ATF 4+, ATF 3+, ATF 7176 were available. These newer ATF's made to Chrysler specs have more friction modifier than Dexron III.
Friction modifier properties have little to do with whether an oil is synthetic, or has a certain viscosity.
Personally, I use generic Dexron III in my 1985 Mercedes. Recently, Dexron may be labeled "DM" for Dexron Mercon or "for older domestic cars" because transmisison fluids are seldom approved by GM as meeting Dexron III these days.
Brief History of ATFs - Bob Is The Oil Guy
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