L83 Underdrive crank pulley installed!

Spurshot · March 2, 2015

I could believe the hp claim on an engine running 6000-7000 rpm with all the lights on loading the alternator, power steering pump, water pump, and A/C running.

Back in the 70s I was making 5-6" diameter alternator pulleys to slow them down. The water pump is another draw on power.

SILVER SLED · March 2, 2015

I had an under drive pulley on my 07 TBSS. I don't know how much hp it gained but I definitely noticed a seat of the pants diff when driving and it did seem to free rev a bit quicker.

bdbake01 · March 2, 2015

Is this a torque to yield like most high clamp LSx bolts? If so, you'll think u r about to flip the truck over before you get to the spec'd 120deg past first torque. Did that on my LS1. WOW.

SILVER SLED · March 2, 2015

Does this pulley require a diff serpent belt and and a/c belt? What percent does it under drive?

TJay74 · March 2, 2015

Yes, it will require both main belt and sometimes the AC belt as well if the AC is under-driven.. Usually the pulley company gives you the Gates belt # to use.

8thsense · March 2, 2015

All I needed was a breaker bar, simple puller and and socket to loosen the belt tensioner. I locked the engine at the flywheel , from uder the truck. Yes, the crank bolts are torque to yeild but you can use an ARP bolt, if you wish to use a high quality torque crank bolt.

Couple of my GM trucks in ther past, I got 14 rwhp on the dyno, after I changed the pulley out.

It seeems our trucks work off some kind of engine load map, that kicks in the DOD 4 banger mode. So if the engine feels less load, then it seems to hold 4 banger longer and MPG increases. Less load also helps mpg and that comes from lighter/smaller diameter crank pulley (easier to turn) and slowing down all the accesories that the engine has to turn by around 25%.

I had a UD pulley on one of my older 2004 4x4 silverado and ran it for 168K miles till I sold it. I contributed never having any accessory`s fail (wp, alt, steering or idler pulley)in that time, due to turning everything a little slower. I dynoed 14 hp gain on that 6.0 engine from the UD pulley and my average MPG was up. So for a few hundred bucks, it more than paid for itself.

dbannerz71 · March 5, 2015

Any update or effects (positive or negative) due the installation of the underdrive pulley. This has really peaked my interest as it appears to be a low cost maintenance free way to get more power and possibly mpg improvement. I'm close to pulling the trigger on this but id like to know more from anyone with a K2 series (2014/2015) truck of this has some impact electricly or with the AC in the summer time. Thanks in advance. It would also appear that this pulley drives both the main serpentine belt and the AC belt...is this correct?

timber74wolf · March 7, 2015

So I am new to the forum. I have been lurking around and reading a lot of threads. I was wondering if there was an under drive pulley for the new 14 trucks and low and behold someone installed one.

I have ran under drives on my past 3 GM trucks. 1990 Chevy with a 5.7, 2004 GMC with a 5.3 and my parents Chevy Avalanche with a 5.3. On all the trucks the Under drive pulley worked great.

So with that being said... Here is my question. Is it only the Crank pulley or is there a Crank and Alternator pulley setup?

Sure wish the set from my 2004 would fit since I removed it before I traded the truck for my 2014.

dbannerz71 · March 7, 2015

I believe the serpentine belt apps around and drives the alternator as well. So if you replace just the crank pulley it would under drive the alternator and everything else that the serpentine belt wraps around. Having said that my question is do you need to get a smaller belt to go from the crank pulley to the AC? No one has answered that yet. Was hoping to hear from the OP that installed one.

Last C5 · March 7, 2015

I believe the serpentine belt apps around and drives the alternator as well. So if you replace just the crank pulley it would under drive the alternator and everything else that the serpentine belt wraps around. Having said that my question is do you need to get a smaller belt to go from the crank pulley to the AC? No one has answered that yet. Was hoping to hear from the OP that installed one.

Typically underdrive pulleys are made to underdrive the main belt by 10 or 25% and only require a new main belt. Some companies like ATI and others make pulleys that underdrive both the main and the AC belts and both belts need to be replaced. So it depends on whose pulley you buy whether you'll need one or two new belts.

dbannerz71 · March 7, 2015

Typically underdrive pulleys are made to underdrive the main belt by 10 or 25% and only require a new main belt. Some companies like ATI and others make pulleys that underdrive both the main and the AC belts and both belts need to be replaced. So it depends on whose pulley you buy whether you'll need one or two new belts.

Gotcha. As far as the one that was posted to have been used and the link provided to amazon, I can't tell if it would under drive the AC or not. Its made by UPD...

http://www.amazon.com/UPD-Chevrolet-Truck-Underdrive-Pulley/dp/B00U4F1Y5G/ref=sr_1_1?ie=UTF8&qid=1425254472&sr=8-1&keywords=2014+GM+truck+underdrive+crank+pulley

Last C5 · March 7, 2015

Gotcha. As far as the one that was posted to have been used and the link provided to amazon, I can't tell if it would under drive the AC or not. Its made by UPD...

http://www.amazon.com/UPD-Chevrolet-Truck-Underdrive-Pulley/dp/B00U4F1Y5G/ref=sr_1_1?ie=UTF8&qid=1425254472&sr=8-1&keywords=2014+GM+truck+underdrive+crank+pulley

I can't tell from that Amazon description either. I'll be checking out ATI's new product for the LS9 or waiting for them to produce a product for the 6.2 . ATI is currently listing the pulley below as a new product, but they don't have an application chart on it yet.

SK128H6 LS9 WET SUMP LONG SNOUT