Cliff notes at end

I took my tuck to the repair shop for a vibration noise, and my fears were confirmed. They believe that there is a worn main bearing or rod bearing on my 168K mile LM7. They don't want to dig into the engine at this time because they don't want to break something else or open a pandora's box of troubles. They said it should be fine for now but I wanted to get a second opinion. I have been wanting to build an engine for the truck, but this just pushes up my time frame , so I am shooting for next fall to do the swap. Should I be ok until then? I drive 500-750 miles a month, but come May/june I plan to pick up a new DD.

This leads me into my next question, Originally I was going to do a Gen IV 454, but I don't want to do the conversion. Then I was going to do a Gen III 408, but after talking to my family, I don't think it makes sense. I have a fast car, I plan on picking up a fairly fast car as a daily driver and the truck will then be use for hauling, as a back up vehicle and trips to the in-law's farm. So to have a high HP truck doesn't make as much sense, I just want good power for the HWY and reliability.

So I think I'm just going to do a built LQ9, but my question comes in, how much HP can I support on the stock fuel pump? Driveshaft? rear end? I know I will need a new tranny, as mine is stock with 168K on it. Can I still use my LT's into high flow cats, into a Y pipe as an exhaust? It's not that I need a ton of HP, but if i'm going to the trouble to swap an engine I want so some reward.


Cliff notes:
1: will a worn main or Rod bearing last for another 10K miles
2: how much Hp can I support on the stock fuel pump, Driveshaft, rear end?
3: Can I still use a Y-Pipe setup on a Built LQ9?

 

Is this vibration noise at idle or driving? An engine bearing is near the bottom of the list of things I would suspect to cause that.

Drain the oil and look for gold or copper colored flakes. Also cut open the oil filter and look for shiny metal. If there is a bearing problem you will see it there.

 

Learing from past experience, I keep 1 vehicle completely stock. I mess with the other ones. Maybe tune it, throw a lower stall yank converter in b/c you do some towing.

1) I doubt the vibration is a bearing. Could be anything really. What shop did you take it to? Checking the oil for shavings is good advice.

My G8 had a terrible noise at around 2k rpm. Grinding sound, very embarrassing. Changed out parts, took it to trusted sources, took the tune off of it, and it still made the noise. I was told several times it was a torque converter/transmission issue. Turned out to be exhaust pipes rubbing together because a weld broke.

2) My silverado is still running the stock fuel pump. 160k miles on it. I had a driveshaft made and speed balanced. Just put a tru trac and a lower set of gears in the rearend. The stock gears were a little worn, but still looked ok.

3) I'm running a 3" pacesetter y-pipe on the truck also.

 

The noise is at idling when the vehicle is at temperature, does not do it when cold. I thought it was the ac blower fan going out until I switched off the AC at a stop light light and the noise remained, not to mention you can hear it on the passenger side of the vehicle under the hood. They said they think it is the bottom end as it was coming from the underside on the lift. I also suspect one of the AC pulleys, but I thought they would have checked that.

I took it to the dealer because they have been a little better about finding noises then my regular mechanic, but I will take it to him for a second opinion. I am in need of an oil change soon so I will check out the oil for sure.

Zero2sixT
The truck has kind of been project vehicle, had it for 8.5 years now and done a tune, LT's, exhaust, and a range of other things. Problem is it has always been my daily (except 1.5 years when we lived downtown) so I've tried keeping many of the mods on the mild side. I think my wife and friends would like to see me get a new truck, but it is in good shape, paid for and I'd rather pick up an SS, G8, or something along those lines, throw an exhaust on it and call it good since I don't need a truck everyday. If I got a truck it would be a new 6.2, so my goal is to have the swap faster than a new 6.2l.
I'm looking at a modified LQ9 with a stock block and somewhat modified internals. I thought an 408 would be nice, but what I want it for and the longevity factor, a 370 will probably be just fine.

 

If its only there at idle, I don't think its an engine issue. But that is a guess. Dealership might be trying to get the shop to steer you towards the showroom.

If that were my truck, I'd keep it. Its a good looking truck. And I've always liked that body style. Wish I could've found one with the options my '03 has.

I'd prob run a bolt on 6.0 with a higher stall converter. Put the rest into the z o. Just seems overkill and a lot of money to build a 370 or a 408 only to out run a new, stock truck.

 

It could be more than at idle, it is a low enough noise that i cant hear it over the exhaust or other valve train noise.That was actually the weird thing, they said they didn't think I should do anything to the truck and run it until it gets worse then do an engine swap, which was not the response I expected. Lately I've got allot comments in the form "man the interior looks brand new" or "you just had this thing painted" which is nice since 75% of the paint is original, all one reason I don't really want to get rid of it.

I'm looking at one of the built 6.0's from Thompson motorsports, the price is about what I want with the power I'm looking for. I'm trying to find something that makes good power as to make the swap worth it to me but not overpower all the stock components.
Like this:
http://www.ebay.com/itm/495HP-370ci-...0164e0&vxp=mtr
Or
http://www.ebay.com/itm/425HP-6-0-LQ...015665&vxp=mtr

The Z is a different beast, I can't decide what I want to do with it. It came with an extended warranty until 2015, so I haven't done anything mechanical to it due to the valve guide issue. Once it runs out ill probably have the heads reworked to solve that issue, but don't know if I want to do a cam, headers, and tune and risk blowing it up in another way or just run it with ported heads and enjoy it as is.

 

Yeah, Im surprised they gave you that advice too. Its exactly what I would do. What dealership is that?

Heard good things about thompson. They have some good prices. Just can't beat the value of running a used 6.0. I paid $1200 for my longblock, plus the stuff he had laying around. It runs good and uses very little oil. I don't get much more than a small film of oil out of my catch can.

 

pull your accessory belts off first and run the engine at idle. You could get lucky, and it's just an idler or tentsioner pulley.

where abouts are you in Houston. PM me your number if you want some help . . .

 

It was Sewell Cadillac on the west side of Houston, the tech was very helpful, gave allot more then the standard type responses.

What I'm looking at now is a more or less stock LQ9 shortblock, but nicer heads and cam. So that if I keep the truck long enough, I can have the block re-worked and throw in a stroker rotating assembly. But it seems difficult to find some heads that fit a 370 and 408 effectively. Looking at some AFR's or PRCs. I think this would give me the power I want without a massive price tag. I'm sure if I look hard enough I can find a quality used longblock, but seem to have only a few less miles than mine.

I pulled the belt off and spun all the pulleys and didn't hear/feel anything out of the norm. But I will try running the engine. Back in 07 I had the tensioner fail catastrophically,but I don't really remember that noise. I still want to look at the AC belt and tensioner, I haven't really touched those since I have owned it.

I'm over on the westside, I'll let you know, most of my diagnostic time is the 5 min between getting our of the truck and running in the house after being out.

 

I took some videos, although it is not the easiest to hear, it is a low "wop wop wop wop" noise
Engine bay
Under Engine

In person it is more pronounced under the truck, but the air from the fan skews the noise on the video.