Trans fluid for a built trans?

Dozerboy

Well-known member
Jun 23, 2009
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TX of course
Been a while since it was discussed it seems and I can't find a straight Dex3 anymore. What's recommended for a truck used only for towing and spirited driving on the weekends? 600hp and Suncoast if it matters. I see the common Allison fluids are available, but everything else seems to be a Dex/MERC fluid.
 

KyleC4

Tech
Dec 30, 2016
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Bay Area
Years ago a guy at GM technical assistance center told me that Dex 3 is still offered but it’s sold as Manual Transmission and Transfer Case fluid. I don’t recall the part number for it though. They kept formulating it cause Tremec said they only wanted Dex 3 in their transmissions. I think some transfer cases as well still call for it. But I know most people will see red fluid drain out and just pump Dex 6 back in just cause they know it’s not Auto Trak fluid. Last service I did at home for a customer I used that new Transynd formula 668 I think. Napa had a deal on it in gallon jugs and it came out to less than $7 a quart
 
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Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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Been a while since it was discussed it seems and I can't find a straight Dex3 anymore. What's recommended for a truck used only for towing and spirited driving on the weekends? 600hp and Suncoast if it matters. I see the common Allison fluids are available, but everything else seems to be a Dex/MERC fluid.
valvoline Dex/Merc is Dex3. Mike told me that years ago and its all i used in the truck after.
 

Bdsankey

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Feb 1, 2018
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I've run anything that is Dex 3 approved and they don't really seem to care. Mike's direction to me awhile back was "what ever the hell is cheapest at the parts store as long as it says Dex 3 you're golden". That advice hasn't let me down yet.
 
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Dozerboy

Well-known member
Jun 23, 2009
4,565
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TX of course
valvoline Dex/Merc is Dex3. Mike told me that years ago and its all i used in the truck after.

I just found this at Walmart for $18 a gallon. While I hate Walmart and it might not be the boutique brand I'll take it. NAPA has is listed for $22 if yall hate Walmart more then I do.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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That’s what I run and the clutches looked good after years of 1000hp. But not really sure if fluid makes that much of a difference 🤷‍♂️

He told me, synthetics are too slippery and would cause more wear on c3's. now the last time i talked to him about that was like 2015ish or when ever the G3 clutches came out because we were mulling around the idea about running a different fluid in the truck for the G3's. He just had a worry it would kill the red Alto's sooner that were still in the rest of the trans. Things have clearly changed since then. id bet a synthetic isnt as big an issue anymore but i dont know enough. @[email protected] would know.

I just found this at Walmart for $18 a gallon. While I hate Walmart and it might not be the boutique brand I'll take it. NAPA has is listed for $22 if yall hate Walmart more then I do.

sweet! im all for the cheapest place i can get oils. i think a gallon of Dex3 was 30 bucks at oreillys last time.
 

1FastBrick

Active member
Dec 1, 2016
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Junkyard
Walmart is usually hands down the cheapest for oil's.

I haven't purchased oil or trans fluid from a regular parts store in probably 12 years.
 

Bdsankey

Vendor
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Feb 1, 2018
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Neenah, Wisconsin
I think fleet farm is around $14/gal for Fram branded dex/merc. The last cash and carry build we did that is the fluid they used. Seems to be holding up well.
 

JoshH

Daggum farm truck
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Feb 14, 2007
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Literally any generic dex/merc fluid will work. I buy it in bulk from a local oil supplier in 55 gallon drums.