2005 TB 4.2L engine noise

[santon]

Hello guys,
I would be glad to get your opinion on the condition of the engine of my 2005 TB. I bought this truck 9 months ago with 240k km on the odometer. From the beginning, there was some weird noise, a kind of a knock coming from the transmission. I consulted several mechanics and attributed this noise to the torque converter. Later, the transmission was replaced for another, used one, together with its torque converter and the flexplate. The "knock" became less loud, however, it is still there. Here is the video with the sound of the noise. Now the truck has 270k km on the clock. It seems that the engine is burning oil - I added a lot since the last oil change. The PCV system was cleaned before the last oil change. I afraid that the engine is tired and on its way to go. Other than this noise and the oil consumption, it runs great. What can I expect from this engine? Could the knocking sound that I hear under the truck be a rod bearing noise? The transmission that I put is also not perfect, so I would like to decide what to do with this truck - try to sell it, prepare for the engine and transmission replacement or leave it as is and drive.

 

[Mooseman]

It could be piston slap, which some of these engines suffer from. It could also be an oiling problem. Does the noise go away at higher engine speeds? You should connect a real mechanical test gauge to see actual pressure because, as you may know, the gauge in the cluster is fake.

You could take an oil sample and send it to be analyzed but it may be expensive to send it to the USA if there isn't such a lab in your area. It would tell you if there is bearing material (rods) or aluminum (pistons) in the oil.

As a test, you could try using a thicker oil and see if the noise is reduced or eliminated.

I doubt it's the transmission or torque converter. To eliminate that, you could remove the TC to flexplate bolts and push the TC back and start the engine.

 

[santon]

It could be piston slap, which some of these engines suffer from. It could also be an oiling problem. Does the noise go away at higher engine speeds?

Not sure whether the noise changes at high engine speed. It is hard to hard to hear it at high speed.

As a test, you could try using a thicker oil and see if the noise is reduced or eliminated.

What viscosity of oil should I try? I am currently using 5W-40 synthetic of Castrol.

 

[Mooseman]

Oh so you're already at a higher viscosity. Not good. I would still get a real oil pressure reading.

 

[santon]

Sorry for reviving my old thread. I still have that knocking noise. When tested with a a stethoscope, the noise seems to originate from the transmission bellhousing. When I put the stethoscope on the engine's oil pan, I don't hear any noise. The knock is more noticeable on the hot engine than on the cold one. So, I am planning to do the following test: without removing a transmission, I want to disconnect the torque converter from the flexplate and slightly push the torque converter back. Then I will start the engine. If there is no knock then the noise is probably related to the transmission. As I understood, pushing the torque converter back should be easy. How hard would be moving it forward again to connect it to the flexplate?

 

[Mooseman]

It shouldn't be difficult at all to move it back. In fact, it's usually the way it goes when replacing the engine or transmission.

Have you looked at the flexplate for cracks using a boroscope? It's not an uncommon thing to happen:

<FIXED> Lifter noise & dull knocking (bottom end?) troubleshooting

And I also forgot to mention, there's a second crack opposite of the one... @Sparky will do man, may end up asking Brandon's father to borrow his extra truck until I can install the flex plate next weekend. It'll arrive Wednesday apparently. Kinda nervous now seeing how it has two cracks. Also...

gmtnation.com

Also check your oil pressure. Do not rely on the gauge in the dash cluster, IT'S FAKE. You have to use a test gauge.

Trailblazer oil pressure gauge doesn't tell you the oil pressure (4.2L engines) (YouTube)
Where to connect a real pressure gauge

 

[mrrsm]

Just some Cautionary FFT (Food For Thought)...

One important consideration before doing this is to remember that IF the Center Flex-Plate Bolt Pattern is substantially fractured and broken out around and adjacent to the end of the Crankshaft ...AND... Once you remove the Three 120 Degree Torque Converter Bolts located in the Outer Orbit of the Flex-Plate...There will be NOTHING left to restrain the loose Flex-Plate from coming completely loose once the Engine is being Started and revved due to the energy imparted by the Small Gear of the Starter Motor directly clockwise to make the Flex-Plate turn counter-clockwise at the Outer Fire-Ring Gear.

For the sake of argument... Prior to Starting The Engine after removing the Three TC Bolts... It might be a better approach just to perform a gradual *Push-Pull* against the outer areas of both sides of the the Flex-Plate Ring Gear using a Large Flat Blade Screw Driver. First, pry out the Dual Rubber Plugs loose from underneath the center bottom location in between and then pass the Flat of the Screw Drive through the Two Holes in front of and from behind the Flex-Plate and see if it substantially moves.

If the Flex-Plate is Cracked enough to allow it to be easily moved with the prying efforts... you will have identified the issue as a Cracked Flex Plate...without risking damage to the inside areas with the Engine and Interior Bell Housing while Running. Technically, the Mechanic performing THIS action was risking serious injury if that Flex-Plate had been Badly Fractured and then had suddenly broken loose where it was Cracked around the Center:

In cases where the damage reaches this extent, Bad Motor Mounts and Failed Thrust Bearings at the #5 Crankshaft Mains Journal will be "The Smoking Guns".

 

[santon]

An update - we disconnected the torque converted from the flexplate. The flexplate does not have cracks. Started the engine - no noise at all! So, now I can say for sure that there is no rod knock. The noise is coming from the transmission, probably from the torque converter of pump. The transmission works OK, the noise is not that loud, but I have the new torque converter and I think I will try to replace it. I just need to find a solution for supporting the transmission - the transmission jack, or an adapter for the regular floor jack. Thank you guys for suggesting this test, a special thanks to @Mooseman and @mrrsm.

 

[mrrsm]

Your BFF for the 4L60E is THIS style of "Safety Belt" Scissor Trans Jack and the means to jack up and support the Front Frame of the SUV tall enough to be able to slide out the Transmission once this Red Thing is lowered as far down as it will go. Rear Wheel Chocks are an absolute MUST for Safety throughout this entire debacle:

450 lb. Low Lift Transmission Jack

Amazing deals on this 450Lb Low Lift Transmission Jack at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

And for controlling and REALLY Elevating the SUV... THIS Ramp and Jacking Stand can help:

2 Hydraulic Vehicle Ramps 4,400 lb.Capacity Portable Car Repair 5 ton jack | eBay

Hydraulic Ram Hydraulic. Safety used for 2 ton vehicle. when the jack all the way down. We have more than 20 years experience in Auto Repair Produce area. Buy directly from the factory from the factory with the low price now!

www.ebay.com

Also, in the past, @m.mcmillen (The Legendary Mac) has recommended using an EXTRA Long 36" X 1/2" Drive Extension to mate up with a 15mm Deep Socket and a 1/2" Drive Ratchet or 1/2" Drive M18 Milwaukee "FUEL" Battery Power Drive Tool when undoing the Two Top Trans 2 Bell Housing Bolts for an "Over The Transmission Point Of Access" difficult to access position during this PITA R&R.

Remember to listen for the "Double Clunk" from the Slow Rotation and Pushing-insertion of the Torque Converter to achieve having it completely inserted as far back inside the Bell Housing and Transmission Fluid Pump Shaft as it will go.

 

[santon]

Thank you @mrrsm for this information.
When removing the transmission, do you guys recommend to disconnect the transfer case first? It adds some significant weight to transmission. I have seen that some people remove the entire transmission as one piece including the transfer case while others disconnect the transfer case and then remove the 4L60E.

 

[azswiss]

I would remove the transfer case. The problem is not total weight so much as it is the fact that the trans/t-case combo will be unwieldy to maneuver, especially on the install. Also, depending on the size of the trans jack you use, stability could be a problem.