What did you do to your NBS GMT800 Tahoe/Yukon Today?

[ivin74]

What sensor is taking direct readings indexed from the harmonic balancer?

I would like to know as well.

 

[Fless]

Took it for a drive halfway across town in freezing rain to pick up 4 nearly brand new Blizzaks for a friend.

 

[Rocket Man]

Took it for a drive halfway across town in freezing rain to pick up 4 nearly brand new Blizzaks for a friend.

Is the freezing rain sticking to the roads?

 

[Fless]

Is the freezing rain sticking to the roads?

Yes. It wasn't bad yet, just some slick spots, but when I got home the front of the hood and the mirror caps were covered.

 

[mountie]

Just returned from my mechanic... New starter / old was original/ failed/ ( why it was at shop)...replaced belts....new A/C belt tensioner....Mobil 1 oil.
( Tesioner wasn't bad, but it was original and it takes a beating down there.)
Yesterday I waxed wheels inside my garage, since it wasn't moving due to starter bad.

 

[Rocket Man]

Just returned from my mechanic... New starter / old was original/ failed/ ( why it was at shop)...replaced belts....new A/C belt tensioner....Mobil 1 oil.
( Tesioner wasn't bad, but it was original and it takes a beating down there.)
Yesterday I waxed wheels inside my garage, since it wasn't moving due to starter bad.

Looking good!

 

[iamdub]

The pulley and crankshaft are not machined with keyway/key? I am new to GM and we know there are some GM-specific quirks and features, but I would expect the removal and install of the harmonic balance pulley to be a fail-proof operation. With the pulleys and cam shafts being indexed with a key/keyway, there is only one position for the pulley which would not even matter if the timing chain/cam/crank were not messed with.

Just wondering... What sensor is taking direct readings indexed from the harmonic balancer?

Like I said, I am new to GM and eager to learn more. But right now, I am trying to wrap my head around why the computer would give a hoot where the harmonic balancer pulley is relative to the crankshaft, if the CPS reads off of the flywheel and timing is unchanged.

Thanks for taking the time to get me up to speed on things related to my "new-to-me" 04 Tahoe!

As Mark pointed out, the crank pulley is not keyed. There is nothing taking a reading directly from the pulley/balancer and so the computer does NOT give a hoot where it is in relation to the crankshaft.

even that, I don't understand?

The pulley bottoms out against the crankshaft. Once that happens, it's essentially "floating" as the only pressure applied would be a result of the belt.

Thrust bearings constrain the crank shaft in the forward/backward direction.

So... Hell if I know

Didn't even know a relearn was needed. I replaced mine while I had some bits apart and can't say I noticed any changes in how the engine behaved

It was just my guess since the clocking of the pulley doesn't matter and GM outlined this step for some reason. I'm not so sure the pulley bottoms out on the crankshaft. I think it presses on a certain amount, achieved when specified torque values are met. GM lists an engagement depth spec (something like a ~2mm range, IIRC). Yes, the belt does apply longitudinal pressure on the crankshaft. Maybe the positioning (and manufacturing tolerances) of the accessory drive was factored into their calculating of that engagement depth? Yes, there's a thrust bearing. But, it doesn't hold the crank so tightly that there's no movement. There at least has to be an oil gap.

The CKP sensor is very sensitive to the size of the air gap between it and the teeth on the reluctor wheel. On the old Vortec engines, particularly the 4.3, there was an issue with the CKP sensor misreading and, in more extreme cases, even contacting the reluctor wheel. It was primarily higher-mileage engines being spun to high RPM that had the worst of the problems. IIRC, they ruled it as "loose" manufacturing tolerances in that front cover allowing the sensor to be too close. They released a shim kit to space the CKP sensor out. The kit consisted of (IIRC) two .005" thick shims. You use one and test, then try the other if one wasn't enough.

A CKP relearn is necessary any time the sensor is disturbed or, especially, if shims were added. The PCM has to know the CKP's baseline so it can detect variances and respond accurately. I can see a slight "relocation" of the reluctor wheel being enough change to alter the base signal as expected by the PCM. Is it enough to cause a problem? IMO, not likely. But, for a ~2-minute process, why not have the accuracy?

 

[iamdub]

I would like to know as well.

None. See my guesses/opinions/oral diarrhea above.

 

[MADPINTO08]

Lights in grille

 

[Rocket Man]

Lights in grille
View attachment 361128

Are those RGB? I installed some in my bagged Silverado grill that are hooked to a controller along with my demon eyes that uses an app on my phone so I can CM them all to the paint color -it’s in the red spectrum which of course is illegal to drive with. I run them in a different color when I’m on the road.