Why Dex/Merc III?

[efosterw]

Replacing the tranny in my 96 XJ Sport and I keep reading that XJ guys recommends Dex/Merc III over ATF +4. My mechanic says either is fine and mentioned that the tranny we're installing probably always ran ATF +4 and that he would normally go with that (does it really matter what the tranny has used in the past?) What makes D/M III so highly recommended? Mechanic says that D/M III is a more generic transmission oil and that ATF +4 was more specialized.

[4.3LXJ]

It all really depends on what the clutch material is made out of. The ATF is not just oil and detergent, but friction enhancers for said material. If it is the wrong enhancer, it will cause the tranny to slip

[drakan1908]

My Grand must use ATF4. You cannot substitute dexron for it. So there must be something different. I would look in the owners manual, if you have one, and run what is recommended.

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[XJ Wheeler]

The way I heard about it is Dex III is what they used back when they were selling these things and later in Chrysler stopped selling their own Dex III so they switched over to ATF4 because they sold that. Beyond that I figure use what it did when new.

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[abebehrmann]

I'm pretty sure it was just the 00-01 XJs that specifies ATF+4 for the transmission.

My 99's owner's manual specifies only Dex/Merc III for the transmission/transfer case.

[efosterw]

My Grand must use ATF4. You cannot substitute dexron for it. So there must be something different. I would look in the owners manual, if you have one, and run what is recommended.

Sent from a van down by the river



Glad I found an owners manual while picking at the junkyard a few months ago :)


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[abebehrmann]

Just an add-on.

I asked my friend who works as a mechanic for a Jeep dealership and he said that they originally came with Dex/Merc III, but if you were to take your Jeep into the dealership to have the transmission flushed today they would use ATF+4. Hypothetically both should work, but sometimes switching between ATF fluids can inexplicably cause problems.

[efosterw]

Just an add-on.

I asked my friend who works as a mechanic for a Jeep dealership and he said that they originally came with Dex/Merc III, but if you were to take your Jeep into the dealership to have the transmission flushed today they would use ATF+4. Hypothetically both should work, but sometimes switching between ATF fluids can inexplicably cause problems.



Thanks! Are you saying that changing between Dex and ATF can cause problems?


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[efosterw]

Just an add-on.

I asked my friend who works as a mechanic for a Jeep dealership and he said that they originally came with Dex/Merc III, but if you were to take your Jeep into the dealership to have the transmission flushed today they would use ATF+4. Hypothetically both should work, but sometimes switching between ATF fluids can inexplicably cause problems.



Got my tranny replaced and requested Dex/Merc. That's what my owners manual called for, so that's what we used. The tranny was a salvage in good shape... guessing it probably used Dex/Merc, but who knows?!?


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[efosterw]

The way I heard about it is Dex III is what they used back when they were selling these things and later in Chrysler stopped selling their own Dex III so they switched over to ATF4 because they sold that. Beyond that I figure use what it did when new.

Sent via messenger pigeon. I talk, he types.



Owners manual called for Dex/Merc, so that's what I used.


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[4.3LXJ]

That is the right stuff

[abebehrmann]

Thanks! Are you saying that changing between Dex and ATF can cause problems?


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Sorry, just now seeing this. He said that he'd personally never had any problems switching between the two types, but he's heard others tell stories about some acting up. Basically said there shouldn't be a problem with it, but if you can avoid it why chance it.

[Tbone289]

I'm pretty sure it was just the 00-01 XJs that specifies ATF+4 for the transmission.

My 99's owner's manual specifies only Dex/Merc III for the transmission/transfer case.

Dexron/Mercon is specified in the owner's manual and service manual for '00-'01 XJs. As far as I know, Dex/Merc was the only factory fill ever used in the XJ AW4 and Chrysler began specifying ATF+4 as a "substitute" because dealerships no longer stocked Dex/Merc.