My 2006 2500HD I just drained and re-filled the Gear Box and here's what I found out. The OE Part numbers your Owners Manual calls out are discontinued or if you can find any is old and possibly broken down chemically and $45 a quart. I first wanted to use Valvoline but found after talking with them that the only OE spec'd fluid they have is sold directly and only to repair shops. The Synchromesh is not correct off the part store shelf since it's conventional not full synthetic. I ended up using Red Line MT-85. Took about 3.8 qts and I'll run it and recheck after a drive to work and back.
NV4500 Transmission Fluid Research & Findings
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AuroraGirl
Well-Known Member
What’s Gm originally say?
The callouts in the owners manual are for discontinued part numbers but it must be a full synthetic GL4 "ONLY" fluid. Mistake made is people get either a non-synthetic GL4 or a fluid that's rated GL4/GL5 and nothing can be in there rated for GL5 at all. Now regarding the discontinued Part numbers, if you do find them they are like north of $40 a qt and they have likely been sitting for a long time.
AuroraGirl
Well-Known Member
Hmmm. Seems it needs gl4 for a different reason than the sm465, since it must be synthetic. Wonder why it MUST be synthetic, maybe the viscosity?
My understanding for the NV4500 is there are carbon fibre synchro parts in there. Brass was used also in earlier models but research told me to use what's best if there's a chance CF is there since brass can handle more of a variance in syn.vs. conventional.
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Based on conditions like heavier duty towing and the fact that it remains heavier when it’s hot I’d say it’s ok to use but the owners manual states SAE 75w-85 GL4 synthetic. Also check your RPO in the glove box. NV4500 in mine is MW3 code. 5 speed with granny low 1st gear.
AuroraGirl
Well-Known Member
Didn’t they also offer a 5 ane 6 speed ZF trans? Is that why you say to check
Yes and those may or may not use ATF . I’m not positive though.
AuroraGirl
Well-Known Member
If they do it’s dexron iii which is now “manual transmission and transfer case fluid”
AuroraGirl
Well-Known Member
Any vehicle that previously required DEXRON®-III for a manual transmission or transfer case should now use P/N 88861800. This fluid is labeled Manual Transmission and Transfer Case Fluid. Power Steering Systems should now use P/N 9985010 labeled Power Steering Fluid.
Yes correct. Which MT does your rig have?
AuroraGirl
Well-Known Member
i have a 4l80e
But I was just contributing to this thread, I think manual Gmt800s are cool and sadly so rare
Oh ok . I messaged the moderator here about starting a new thread for MT owners to chime in and start talking about their rigs. These are rare and have their quirks. Haven’t heard back yet though if a new thread would be welcomed or not .
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