Gear vendors o/d units - Chevy and GMC Duramax Diesel Forum
Transmission Shop Discuss the Allison OEM, aftermarket, and the ZF-6.

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post #1 of 8 (permalink) Old 06-25-2011, 06:52 PM Thread Starter
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Gear vendors o/d units

Part #3D0261A $3395.00
Automatic 5-6-Speed NV 261/263 Big Block Gas "Allison".
Replaces rear transfer case housing.
2001 and up big block gas.

Gear Vendors under/overdrive transmissions the most awarded auxiliary transmissions.

I just wanted to hear what anyone had to say about the units. I have wanted one for years, but am going to wait until I get my LBZ. Let me know what you have on them, thanks
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post #2 of 8 (permalink) Old 06-25-2011, 06:57 PM
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I doubt the OD unit will handle the torque of the D-Max.

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post #3 of 8 (permalink) Old 06-25-2011, 07:03 PM Thread Starter
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I was trying to find the details on torque, but the BASE UNIT will handle 1200+HP, and 30,000 Lbs GVW. You can order kits that will handle over 2000 HP, so I am pretty sure that it will handle the torque??? I am interested to find out more about the unit.


2009 2500HD, 4X4, CCLB, LTZ.

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post #4 of 8 (permalink) Old 06-25-2011, 07:05 PM
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i dont think the O/D unit would be much help, with the double overdrive the 6 speed Alli already has this would probably put your rpms way out of the power band

however the U/D might be useful for BIG loads

03 Chev CCLB
500HP on STOCK trans/fuel/turbo

built trans and lift pump coming soon!

special thanks to
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post #5 of 8 (permalink) Old 06-25-2011, 07:15 PM
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Will it hold? yeah.. probably

but you will engage the over drive unit for each of the 6 (or 5) gears.... making your allison a 10 or 12 speed transmission.

but only one of those gears is going to be taller than your tallest over drive unit

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post #6 of 8 (permalink) Old 06-25-2011, 08:08 PM
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These units will easily handle the torque & hp.
Not gonna help ya much unless you have gears 4.XX-5.XX. The 6 speed with 3.73's is plenty good.
Why are you wanting one?

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post #7 of 8 (permalink) Old 06-26-2011, 10:56 AM
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I have not seen one installed in a duramax but I have had to replace 2 main shafts ( GV ) behind stock Cummins. They snap pretty easy.
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post #8 of 8 (permalink) Old 06-26-2011, 10:56 AM
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My understanding was that those units are not for diesels since engine braking will damage the unit.
If you want overdrive, then get the suncoast 5-6 spd tranny conversion instead.

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