Dexron IV same as Dextrol III ?

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Lee4212

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'05 Impala 3.4 v/6,base. 66,000 miles. The trans has a small seal leak at the axle so i got some Dextrol IV (parts store says it is compatible) in my car. Can it be used or what,isn't it a synthetic? Manual say's Dextrol III "H" rating. Some places say the IV is backwards compatible with what i have in the car. I added 3/4 quart of the IV until it get's repaired next week. Only lost about 3/4 quart in a month.
OH....are both axles the same length or how can i find out what the "CORRECT ones are since the drivers side has 2 lengths or so i am told. Thanks everyone !! WONDERFUL site !
 
Dexron VI is more or less the same thing as Mercon LV, and is nothing like Dexron III. I'd stick with Dexron III if that's what your car specs. It's cheaper and easier to come by as well, IIRC.
 
Originally Posted by NothingNew
In your application there is no problem using Dexron VI instead of Dexron III. GM came out with a TSB stating so.


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In another posting I voted to keep using Dex III in a 30 year old RV transmission, but in this case you can go to Dex VI as described above. I checked your 05 owners manual and indeed it asks for Dex III. However, starting in 2006, the Chevy Impala owners manual asks for Dex VI. I recently looked at products and prices and found AC Delco Dex VI at an auto store at the same price as Castrol Dex III.

By the way, Dex VI , Not Dex IV.
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Yea use newer fluid like Valvoline maxlife. Holds up a little better and can be had for less than $18 a gallon at walmart.
 
Mercon V is a better substitute for Dexon III than Dexron VI. Dexron is a very light oil like Mercon LV. I had to research this when I changed the trans fluid on my 4Runner which called for Dexron III.
 
Ignor my previous post. Had to make some corrections...

Mercon V is a better substitute for Dexron III than Dexron VI. Dexron VI is a very light oil like Mercon LV. I had to research this when I changed the trans fluid on my 4Runner which called for Dexron III.
 
Originally Posted by ka9mnx
Ignor my previous post. Had to make some corrections...

Mercon V is a better substitute for Dexron III than Dexron VI. Dexron VI is a very light oil like Mercon LV. I had to research this when I changed the trans fluid on my 4Runner which called for Dexron III.



No it is not. The proper replacement is Dexron VI. After a couple thousand miles mineral based Dexron III products will shear and be lighter than Dexron VI and since VI is a synthetic based fluid it handles the heat better than III and can be used in service longer.
 
Originally Posted by ka9mnx
I think you better look again...

He is correct, that is the proper replacement. dexron VI is more shear stable than dexron III and after brief service the two will end up at roughly the same viscosity. It's part of the spec for dex VI.

Besides, the owners of the specification have also said it is the proper replacement .
 
Originally Posted by Lee4212
'05 Impala 3.4 v/6,base. 66,000 miles. The trans has a small seal leak at the axle so i got some Dextrol IV (parts store says it is compatible) in my car....


I think you meant, as others have stated, you purchased some Dexron III.

Also, the leak at the back (the tail shaft seal) is easily replaceable. I usually replace the Universal joints while I am down there.

Dexron VI is the recommended replacement and has better and more stable chemistry than does Dexron III(H).
 
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If you're looking to stick with Dexron III, instead of switching to Dexron VI, you might want to consider an Allison TES 295 approved fluid.

Mercon V is not a substitute for Dexron VI. If i t was, I have 3 applications that call for Mercon V - I would have used it across the board. I run TES 295 in both my GM applications.
 
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When Mercon and Dexron III came out in the 90's they were virtually identical in spec. Both were a syn blend and both companies were looking for a lifetime fluid fill. When Ford came out with Mercon V it was a full synthetic lifetime fill that addressed cold winter operation and fuel economy. GM, a little later, came out with Dexron V which addressed the same issues Ford had but was quickly replace by full synthetic Dexron VI. Both have very high VI and don't shear all that much. The difference between Mercon V and Dexron VI is GM chose to go to a lower viscosity oil where Ford went to a slightly lower viscosity oil. Not long after GM and Ford came out with their new ATF's they discontinued licensing for the older fluids. When they did this they were forced to use the "suitable for use in" "acceptable for use in" "replaces..." verbiage for their discontinued products. ATF products now sold as Dex/Merc no longer carry the licensing because it is no longer available.

When I did my research (a lot) on replacement ATF for my 4Runner (Dexron III) there were pros and cons for both Mercon V and Dexron VI (like here). Either WILL work as a suitable replacement. After my research I chose Mercon V because of the viscosity of the finished product (the only real difference between the two) more closely matched the viscosity of Dexros III. Either would have worked in my application, and yours.
 
Are DexronVI fluids suitable to use in Ford Mercon LV applications?
I ask because ST makes one that covers both and so do a few other companies (I think).
 
Originally Posted by SirTanon
As I mentioned above, Dexron VI is more or less the same thing as Mercon LV, and as I understand it, are essentially interchangeable.



If memory serves VI is a blend of group III/IV/V with additives and LV is a base oil which meets performance of group III and additives. So in theory VI will meet LV requirements but not nessary the other way around.
 
A great THANKS to all for the information, i'll stay with the VI. Runs great...body starting to go at the front fenders and the usual age stuff but motor is a champ so far. Oil changes every 2500 miles or less...alot of short trip driving (work is only 8 miles away). The site and all the information makes my mind go goofy.
 
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