Geartrain noise in 4L60E second gear causing "knock" retard

[Fast355]

On a side note, I was driving home tonight with the windows down on the service road, next to an elevated highways retaining wall and ran it WOT from 0 through 75 mph. The whine I am hearing may even be accessory whine as its there in 1st gear too.

Ramjet timing tables woke this pig up. Also noticed a strong correlation between the 0411 MBT map and the Ramjet maps. On 93 octane a vortec 350 should have no issue at 30-31° of timing.

[sherlock9c1]

Do you have an underdrive pulley laying around that you could install to see if that changes the sound and the knock? Are the belt and tensioner in good shape (maybe it is slipping)?

[Fast355]

Do you have an underdrive pulley laying around that you could install to see if that changes the sound and the knock? Are the belt and tensioner in good shape (maybe it is slipping)?

Tensioner was replaced 23k miles ago with the engine and it has an underdrive pulley already installed. Belt was replaced with the underdrive pulley when the cam went in, about 1,000 miles ago. The clutch fan has already hit the spare parts shelf as well.

I wonder if it could be that Duracrap alternator that I had no choice but to install in middle of nowhere USA when the original started discharging at idle.

[Fast355]

So I found something interesting looking at the knock sensor calibration.....Specifically Burst Knock. I am going to do some datalogging with it limited to 1° and see what I see. I notice many guys just disable it on the LS engine and my TBI/TPI/CPI always had it disabled

[Fast355]

I am CERTAIN the knock sensor is lying to me though. At 3,500 rpm in 1st gear, heavy throttle PE @ 12:1 afr, commanding a mere 19° of advance, I was getting 7.8° of retard, that gradually tapered off as the rpm climbed, to less than 1° at 5,200 rpm.

[Fast355]

Now I am getting somewhere. Removed 2° additional CTS compensation at 205+ and ran with the burst knock at 0. Only saw a few brief points of 2° retard and that was mostly in OD when the TCC locks. Going to need that 3.73 G80 sooner than later. Now that I have the P0128 code turned off, I'll stick my 170°F thermostat back in. That will safely bring me up from 24-25° of timing to 28-29° by keeping the engine and IATs lower.

[pmkls1]

Speaking in terms of pure speculation I am going to say that your problem most likely isn't related to the noise you are hearing regardless of the source. This is based on your experiences with timing changes etc. It sounds to me like you are on the right track with tuning and lowering coolant temps etc. Just my 2 cents on the noise, if the trans does have a 2nd gear specific noise then it would probably be in the rear planet and/or captured bearing as well as sunshell flex. I understand your desire to upgrade to a 4L80E, but just remember that they are heavier, take more power to operate, and are relatively more expensive generally speaking. They also have their inherent flaws to deal with. If you can build a trans then I'd say build a solid 4L60E instead. You can throw upgrades that basically just increase pressures and clamping forces at the trans all day long. But, if you don't actually upgrade the internals and have stock frictions that have seen slippage and been abused, then nothing is going to improve the function of the trans and you might actually be worsening the problem.

[EagleMark]

I like burst knock, especially on high advanced spark tables. It's a anticipated knock for like cruising highway speed lite throttle and a quick accelerate it will keep you out of knock. Does not effect WOT. Great for heavy rigs. So when you get this issue fixed don't rule out leaving it off.

[Fast355]

Speaking in terms of pure speculation I am going to say that your problem most likely isn't related to the noise you are hearing regardless of the source. This is based on your experiences with timing changes etc. It sounds to me like you are on the right track with tuning and lowering coolant temps etc. Just my 2 cents on the noise, if the trans does have a 2nd gear specific noise then it would probably be in the rear planet and/or captured bearing as well as sunshell flex. I understand your desire to upgrade to a 4L80E, but just remember that they are heavier, take more power to operate, and are relatively more expensive generally speaking. They also have their inherent flaws to deal with. If you can build a trans then I'd say build a solid 4L60E instead. You can throw upgrades that basically just increase pressures and clamping forces at the trans all day long. But, if you don't actually upgrade the internals and have stock frictions that have seen slippage and been abused, then nothing is going to improve the function of the trans and you might actually be worsening the problem.

I have made up my mind on the 80E and have a core to build already. The 60E is a TRASH transmission, I have had one built professionally by a reputable performance shop (killed it in 15K) and had 3 others that I built with good components. You hit a point where you end up destroying cases on them or other hard parts with relatively little power. You just cannot make them hold up in a 6,000 lbs vehicle making 450+ TQ with a 2.6 STR converter. 80E has better gear spacing and the durability is well worth the slight power loss. The build I am looking at copying on my 350 made 490 ft/lbs of torque at the flywheel. With a 2.6 STR converter I will be looking at over 1200 ft/lbs torque spikes to the input shaft. The 60E does not stand a chance against that.