Transmission Fluid Question

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Nov 20, 2009 | 05:06 PM

Danspeed1

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Joined: Nov 2009

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From: Orange County, NY

Transmission Fluid Question

I know similar questions have been asked because I used the search function... but I just wanted to be sure so I will ask once more.... I have a 1985 F350 6.9L Diesel 4x4. Today I changed the transmission fluid and transfer case fluid. I bought Alldata which told me to use either Dexron or Mercon. I imagine that the information I am receiving is from "back in the day." Is Mercon equivilant to todays Mercon V?(5) or was I supposed to use something else?

Also, I am not sure if my rear end is posi or not... If it is not posi, would it hurt anything if I added the posi gear additive (friction modifer)?

Sorry for the seemingly stupid questions, I just don't want to make any expensive mistakes!

Dan

Nov 20, 2009 | 05:43 PM

bashby

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From: Charles Town, W bygod Va

I believe mercon V is full synthetic, all you need is dextron 3/mercon. It wont hurt anything to add lsd additive to a non lsd rear. You can check the tag on the rear, it will say 3L55 for 3.55 limited slip or just 355 for non lsd.(of course the #s wont neccasarily be 355 unless thats your gear ratio) usually the first # is obscured by the mounting bolt so it may look like L55 or 55

Nov 20, 2009 | 07:51 PM

fellro86

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From: Marengo, Iowa

Most stores now just call it dex/merc now. I believe Dex III Mercon is the full proper name, but the labeling is generally just dex/merc. Merc V probably would work, but is overkill. ( yes, full synth.) The additive won't hurt anything if there is no clutches in there. That is all it is for, is to make the clutches grab like they are supposed to.

Nov 21, 2009 | 02:23 PM