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Discussion Starter · #1 ·
Hey guys. I did some research on the different types of transmission fluids and I was surprised to see just how many different types there are. I'm going to have my transmission fluid, filter and gasket changed soon and I want to make sure that the correct fluid goes into my transmission.

I know that Impalas need Dexron-IV, while newer Chrysler vehicles use ATF-IV and Fords use Type-F. Are these basically the same fluid?

Also, I'm wondering if shady mechanic shops are throwing Dexron-III into our transmissions, because it is cheaper and they have plenty of it lying around. Plus they know that it will screw up our transmissions down the road giving them the business of having to overhaul your transmission.

I wonder if many of the transmission problems that are plaguing the 8-generation Impalas are due to the transmission being sensitive to Dexron-III?

Maybe a transmission expert like Kingnuttin can shed some light on this issue?
 

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Discussion Starter · #2 ·
I went to GM today to buy the fluid, filter and gasket and it seems that GM uses Dexron-6 now? I was looking for Dexron-IV, but the guys said that they only make Dexron-6, so that's what I bought.
 

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they skipped right from dexron III to VI there never was a Dexron IV or a V.
Also I believe type F was something used decades ago, Ford uses Mercon.

Many fluids are dexron III/Mercon dual compatible
 

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I'm no expert, but I do know a thing or two. Like Dwayne said, there was no 4 or 5, the main difference between 3 and 6 is, 3 was conventional, 6 is synthetic. What that means for your transmission is more consistent viscosity, and resistance to thermal breakdown. So using 6 will help prolong the life of the transmission in any GM transmission that calls for 3 or anything beyond. Ford type f I'm not sure about, Chrysler ATF+4 is supposed to be ok in dex 3 systems, but I don't know about vise versa. Then the Japanese companies all have their own fluids as well. They must be doing something right though, they're transmissions usually don't have a serviceable filter, yet they tend to last the life of the car...

Anyway, dexron VI is what you need, settle for nothing less. And don't let them put in any additives!
 

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Discussion Starter · #5 ·
Whew. I'm glad I bought the right fluid. I bought a 5L jug of Dexron-6, which should be enough for a drop pan and filter and gasket change. I wont do a powerflush after reading about the damage that it can do. My transmission is still shifting fine and I would really like to keep it that way. What would happen if the shop were to throw in Dexron-III into these cars?
 

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You may need a bit more. A pan drop on these trans typically takes 6.5 litres of fluid to refill.

If the shop used DexIII, the trans would work fine, it would just have a lower quality fluid depending on what brand was used. I actually still use DexIII fluid but Amsoil synthetic, top quality stuff. Amsoil does make a DexVI fluid, same stuff just thinner to meet DexVI viscosity requirements, DexVI is thinner to try and improve fuel mileage.

Lots of shops buy the Mr Transmission or Petro Canada ATF in my experience, because of its cheap price. The local trans builder here would be selling $3500 built transmissions and putting in cheap Mr T ATF because we couldn't talk the customers into Amsoil ATF for the $100 difference, despite it being a tremendously better fluid. I could never understand it.
 

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Yeah, drain and fill is about 7qts, so get a couple more liters. And like will said, dex 3 won't kill it, but it would be best to change it sooner than later if you did have it in there. It will break down much faster.
 

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Actually most dexron III shears down and gets thin with use so the Dexron VI isn't really thinner in actual use, it just starts thin and being a better base fluid is able to hold that viscosity.
 

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Actually most dexron III shears down and gets thin with use so the Dexron VI isn't really thinner in actual use, it just starts thin and being a better base fluid is able to hold that viscosity.
The cst viscosity at 100*C fluid temperature should be a maximum of 6.4 for DexVI, while Dex III should be maximum of 7.5. Higher numbers = thicker.

How the viscosity changes as the fluids age is another story
 

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In actual practice most Dexron III shears down that far pretty quick so most of it's life in the vehicle is spent well below the new 7.5 number.

I said that mostly so people don't go thinking that a switch to VI will gain them mileage.

I do believe that EPA testing of new vehicles was part of the reason to start so thin, .01 is meaningful at the manufacturer level.
 

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Discussion Starter · #11 ·
I guess I'll grab another 1.5L bottle then.
 
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