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post #1 of (permalink) Old 07-29-2019 Thread Starter
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New here, considering an 8th gen, but I have some questions

I'm considering looking at 2009+ 8th gens for my next car, but I have some questions regarding performance, feel, reliability, and ease of DIY repair on the 3 V6 engine/transmission options.

As I understand it, pushrods are typically simpler and easier to work on than DOHC motors, and considering that these big V6s are in a FWD engine bay, I'm conserned about work space and reliability of the motors when repairing things myself.

Which motor would you suggest if I wanted one that was gonna last a long time and be the easiest and cheapest to repair without feeling sluggish and wasting tons of gas?
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post #2 of (permalink) Old 07-29-2019
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Originally Posted by Fiives View Post
I'm considering looking at 2009+ 8th gens for my next car, but I have some questions regarding performance, feel, reliability, and ease of DIY repair on the 3 V6 engine/transmission options.

As I understand it, pushrods are typically simpler and easier to work on than DOHC motors, and considering that these big V6s are in a FWD engine bay, I'm conserned about work space and reliability of the motors when repairing things myself.

Which motor would you suggest if I wanted one that was gonna last a long time and be the easiest and cheapest to repair without feeling sluggish and wasting tons of gas?
I recommend looking at 2012+ model years with the LFX 3.6L engine and 6T70 transmission. Yes, it's an OHC engine, but it seems to have a very good reputation, as does the 6T70 transaxle.

Here's a list of engines I culled from Wikipedia for the years you mention.

LZ9 3900, 2006–2011
LGD = LZ9 flex fuel, 2009–2011
LZ8 = LZ9 w/DOD, 2007–2008
LZ4 3500, cut-down 3.9, 2006–2009
LZE = LZ4 flex fuel, 2006–2011
LFX 3.6L, 2012–present

These are all 60 V6's, so none of them are particularly tightly squeezed into the engine bay - none of them are fat like the 90 Shortstar (3.5L LX5 DOHC V6) in the related w-body Oldsmobile, Intrigue.

The 3.9 and 3.5 were both cam-in-block push-rod motors. The 3.9 LZ9 was a new design, and the 3.5 LZ4 was a cut-down version of that. These 2 motors replaced the older 3.4 LA1, but they were subsequently replaced by the 3.6L LFX, which was used in the last of the gen8 w-body Impalas and is still in use in the newer gen9 Epsilon2 Impalas.

The only knock I've heard on the 3.6 is changing the rear plugs, but there's a Youtube video that shows a neat trick wherein the guy turns the COPs 90 to get them out - voila! - no need to pull the intake. (Sorry, don't have the link handy.)

My limited experience with the 3.9/3.5 series was the LZ4 in my Pontiac G6. They were known for a coolant leak in the crossover pipe on the passenger end of the motor, but seem to otherwise have a decent reputation. I did the fix on that, and it wasn't too difficult other than dealing with the power steering pump pulley, as I recall.

As for the 3.9, the LZ8 DOD version (displacement on demand = active fuel management = shut-down cylinders) lasted only 2 years. The DOD stuff was a problem in the 8-6-4 Cadillacs 35 years ago, and it's a problem in the more recent V8 LS4 Impalas. I would definitely avoid this.

HTH.

And welcome aboard!

Doug

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post #3 of (permalink) Old 07-29-2019
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Fiives, Welcome.

I owned a 2012 Impala LTZ previous to my 2014 LTZ now. I must agree with Plano-Doug, the 3.6 V-6 is the way to go. The engine produces good power and the transmission felt solid in my 2012.

I drove over 45K in two years in the 2012 and loved the car. Plenty of room, good gas mileage for a full size car and it was comfortable. The only problem I had from mine was two of the three BLIN door actuators failed and made a horrible racket until replaced. I replaced them myself and the job was a bit challenging but nothing anyone with basic mechanical abilities could not do. There are YouTube videos showing the procedures.

Good luck with your research and upcoming purchase.
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post #4 of (permalink) Old 07-29-2019
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Another vote for the 12 and newer with the 3.6. We bought our 2012 new, have had no major issues with it(knock on wood) and have somewhere around 170,000 miles on it. Changing the plugs on these cars is a 30 minute job, have changed ours twice. My wife is the primary driver in our car, she averages 25.6 mpg with mixed driving, not too shabby for a 300 hp v6 with a good number of miles. I can get on the interstate with it and get around 30 mpg if I keep it around 75. One complaint from some was with oil consumption, some of these cars do burn/lose a half qt or more every 3000 miles. We went over 150,000 miles with never having that issue, but a more recent change earlier this year had us around a half qt low with between 5000 and 6000 miles. Still honestly not too bad. The wheel bearing hubs are prone to failure, but they are not much trouble to change. If not for the wife hitting a pothole, think we would have made it to around 100,000 before having to replace either.

I have no first hand experience with the 3.5 or the 3.9.

Finding a used car with a 3.6 at a fair price that has been taken care of might be an issue, but then that goes with any used vehicle.
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post #5 of (permalink) Old 07-29-2019 Thread Starter
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Thanks for the great replies guys. Ill definitely be trying to get a 2012+ one then.

If i cant find one at a good one in my budget, is the 3.5 or 3.9 the better one to get?
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post #6 of (permalink) Old 07-29-2019
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I agree on the 2012. Mine looks good, runs great and plenty of power even with 180k. Repairs have been minor, t-stat, hub bearing and blower control module. Depending on the terrain it gets 32 to 35 mpg on the highway with the air running.
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post #7 of (permalink) Old 08-01-2019
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Such a nice choice
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