Swapping in 40k 4.8 in Moms '05 Z71 Tahoe

[redhat]

This Monday, will be swapping in a low mileage (40k) 4.8 Gen III LS, LR4 to be exact into Mom's 2005 Z71 Tahoe. Tahoe was a southern truck and has 240k miles. Last 3 years in New York, oiled yearly, and in great shape.

The 240k 5.3 in it has bad lifters, makes some violent upper end noises and is definitely down a couple of cylinders. I bought this little 4.8 for my Regal, but figured for her daily driving and use, a SBE low mileage motor would be perfect. Plus time was never on my side for getting this project going.

Since the motor is out, will be replacing:
- new serpentine
- valley cover gasket, knock sensors, knock sensor sub harness, knock sensor gaskets
- plugs and wires
- thermostat
- exhaust manifold gaskets with ARP hardware (stock LS bolts love to break)
- upper and lower radiator hoses (did heater hoses and those connectors earlier this year)
- oil pressure sensor
- manifold flange gaskets, studs and nuts
- PCV
- intake gaskets
- oil pan gasket
- oil pickup tube o-ring

Have a local tuner that will be able to flash a 4.8 Tahoe tune to the PCM. From what I've read, a 4.8 will run on a 5.3 tune but use lots of fuel.

This 240k 5.3 uses a quart or so over 5-6k OCI, has strong 40PSI of oil pressure at hot idle and has no bottom end noise. So I will pull the heads, new LS7 lifters, boost cam, pushrods, MLS head gaskets and we will be hitting it with a nice healthy 15lbs of boost and it'll go into the Regal. The rings have got to be worn about perfect for some boost. I'd feel a lot less bad about scattering the guts of a 240k motor versus a young gun. But I doubt that'll happen. Probably will make some good power out of that old girl.



Should be fun!

 

[eljefino]

do it!

 

[clinebarger]

If the knock sensors on the low mileage LR4 & harness are in good shape with no corrosion....Reuse them!

The LR4 & LM7 calibrations are VERY similar for what it's worth......

 

[Nick1994]

How sure are you it has 40k miles?

I have a feeling junkyards lie all the time.

 

[redhat]

Originally Posted by Nick1994
How sure are you it has 40k miles?

I have a feeling junkyards lie all the time.


The 4.8 was pulled from a 2003 thru 2005 (I don't know the year) 3/4 ton Chevy Express van. I know the guys at the junkyard this was pulled at pretty well. So at that point it had 30k on it. My buddy Dave bought it and put it in his Silverado that he blew up the motor in. About 10k later he swerved to miss a deer and totaled the truck. He pulled the motor and I bought it for my project.

Here is a pic feom then under the valve cover.

 

[skyactiv]

My brother worked for an HVAC company that had Chevy vans either with a 4.8 or a 6.0. He said the 4.8 V8's were dogs and got worse fuel economy than the 6.0's because you were always on the gas pedal on the 4.8.

 

[53' Stude]

Originally Posted by skyactiv
My brother worked for an HVAC company that had Chevy vans either with a 4.8 or a 6.0. He said the 4.8 V8's were dogs and got worse fuel economy than the 6.0's because you were always on the gas pedal on the 4.8.



Migh be a a so so engin but my co worker has two Silverado trucks with 4.8 and never had any issues

 

[redhat]

In a 3/4 ton Express van (4.8 never came in 1/2 ton 1500), between a 4.8 and a 6.0, you could potentially have a difference of 30hp and 80-100lb/ft of torque. If a van had a lot of stuff in it, I could see that.

But anything is better than a 5.3 down a couple of cylinders, will probably seem like a power house compared to present. 4.8s will do a lot of things, they are just as strong and tough. They are a 5.3 with flat top pistons, and a shorter stroke.

 

[bdcardinal]

The 4.8 is a good engine. May not make a ton of power in stock form, but they can handle boost really well. One of my friends has one with unknown mileage in a early 80s Fox body LTD that makes 700+rwhp with a ebay turbo and a huge meth shot. The engine has never skipped a beat but the rear doors and trunk no longer close straight.

 

[redhat]

Originally Posted by bdcardinal
The 4.8 is a good engine. May not make a ton of power in stock form, but they can handle boost really well. One of my friends has one with unknown mileage in a early 80s Fox body LTD that makes 700+rwhp with a ebay turbo and a huge meth shot. The engine has never skipped a beat but the rear doors and trunk no longer close straight.


Haha I love it! Love foxboys and boosted LSx ones are awesome!

 

[Nick1994]

Originally Posted by redhat
Originally Posted by Nick1994
How sure are you it has 40k miles?

I have a feeling junkyards lie all the time.


The 4.8 was pulled from a 2003 thru 2005 (I don't know the year) 3/4 ton Chevy Express van. I know the guys at the junkyard this was pulled at pretty well. So at that point it had 30k on it. My buddy Dave bought it and put it in his Silverado that he blew up the motor in. About 10k later he swerved to miss a deer and totaled the truck. He pulled the motor and I bought it for my project.

Here is a pic feom then under the valve cover.

That's a good looking engine...

 

[MuzzleFlash40]

The 4.8 is a strong engine for being a "mid level" engine. 295 hp and 305 tq compared to it's direct competitor which would be the 4.6l ford making 240hp and 290 tq. The only issue I have with mine is it has the 3.42 gear matted with the 4speed auto, I wish it had atleast a 3.73.

 

[redhat]

The deed has been done. The 4.8 runs great. The 5.3's cathedral ports were caked full of oil. Just some additional evidence to the fact that she was definitely using some oil.

The 5.3 looks gunky, I'd be pretty inclined to believe that its first 160k miles of its life, it wasn't changed often enough. Plus I think it idled a lot.

Think I might have Mom and Dad religiously put a quality synthetic in this thing from here on out. Maybe 6k Mobil 1 5W-30 OCI. She does a lot of stop and go.

 

[350Rocket]

My brother worked for an HVAC company that had Chevy vans either with a 4.8 or a 6.0. He said the 4.8 V8's were dogs and got worse fuel economy than the 6.0's because you were always on the gas pedal on the 4.8.

Depends on the vehicle it's in. My half ton 4x4 1500 4.8 gets 19mpg vs 9mpg in my friends 1500hd 6.0. Typically the 6.0 has a terrible reputation for mileage and the 4.8/5.3 are decent as long as they're not overworked.

 

[350Rocket]

The 4.8 is a strong engine for being a "mid level" engine. 295 hp and 305 tq compared to it's direct competitor which would be the 4.6l ford making 240hp and 290 tq. The only issue I have with mine is it has the 3.42 gear matted with the 4speed auto, I wish it had atleast a 3.73.

I usually leave mine in 3rd unless I'm on the highway doing 70mph+. If it had 3.73s I could use overdrive more often.

Mine has plenty of power but has to rev a bit to make it.

 

[350Rocket]

This Monday, will be swapping in a low mileage (40k) 4.8 Gen III LS, LR4 to be exact into Mom's 2005 Z71 Tahoe. Tahoe was a southern truck and has 240k miles. Last 3 years in New York, oiled yearly, and in great shape.

The 240k 5.3 in it has bad lifters, makes some violent upper end noises and is definitely down a couple of cylinders. I bought this little 4.8 for my Regal, but figured for her daily driving and use, a SBE low mileage motor would be perfect. Plus time was never on my side for getting this project going.

Since the motor is out, will be replacing:
- new serpentine
- valley cover gasket, knock sensors, knock sensor sub harness, knock sensor gaskets
- plugs and wires
- thermostat
- exhaust manifold gaskets with ARP hardware (stock LS bolts love to break)
- upper and lower radiator hoses (did heater hoses and those connectors earlier this year)
- oil pressure sensor
- manifold flange gaskets, studs and nuts
- PCV
- intake gaskets
- oil pan gasket
- oil pickup tube o-ring

Have a local tuner that will be able to flash a 4.8 Tahoe tune to the PCM. From what I've read, a 4.8 will run on a 5.3 tune but use lots of fuel.

This 240k 5.3 uses a quart or so over 5-6k OCI, has strong 40PSI of oil pressure at hot idle and has no bottom end noise. So I will pull the heads, new LS7 lifters, boost cam, pushrods, MLS head gaskets and we will be hitting it with a nice healthy 15lbs of boost and it'll go into the Regal. The rings have got to be worn about perfect for some boost. I'd feel a lot less bad about scattering the guts of a 240k motor versus a young gun. But I doubt that'll happen. Probably will make some good power out of that old girl.



Should be fun!

Sounds like it was a good call switching and taking the 5.3 for your project. I carry a lot of weight in my 4.8 truck and it does okay. At 202k miles it hasn't had any knock sensor issues yet (or anything else attached to the engine except water pump and spark plugs). I'm curious if you had to do any of that stuff in 240k on the old one? Mine is an 05 also. Btw afaik the 05s have gen 4 rods despite being a gen 3 engine.

 

[Blinker]

The Z71 Tahoe was never equipped with a 4.8. Having driven a few 4.8 Tahoes in the past (rentals), they are a dog. The 4.8 is fine for the Silverado, but in the heavy Tahoe body it is gutless. Good luck.

 

[350Rocket]

The Z71 Tahoe was never equipped with a 4.8. Having driven a few 4.8 Tahoes in the past (rentals), they are a dog. The 4.8 is fine for the Silverado, but in the heavy Tahoe body it is gutless. Good luck.

I'm sure the Tahoe weighs less than my Silverado does with all the equipment in the back and survey bars, tools etc. I do wish it had a 5.3 because it would be better but it's not bad. For some reason it will blow the doors off our 2013 4 door Silverado with the vvt 4.8 (same gear ratios). It's slow compared to the 02 2wd we had with the 5.3, especially in normal driving (cable throttle feels more responsive vs my electronic throttle body).

When I got the cab corners and rocker panels replaced I had the cap, box liner and wooden racking, plus all contents removed and it was like a completely different truck. It would spin the tires without trying hard (even with the torque management).

 

[clinebarger]

Depends on the vehicle it's in. My half ton 4x4 1500 4.8 gets 19mpg vs 9mpg in my friends 1500hd 6.0. Typically the 6.0 has a terrible reputation for mileage and the 4.8/5.3 are decent as long as they're not overworked.

9mpg is a little low, They typically get around 12mpg. If you put a 6.0L in your truck....You'd get close to the same 19mpg. A 4L60E is quite an efficient unit compared to a 4L80E then you got the bigger differential & lower gears + the additional weight of a crew cab 2500.

I put a LQ4 6.0L in my dads 2003 Tahoe to replace the leaky L59 5.3L, Still gets the same 16mpg average it always got....Just more grunt.

I'm swapping back to a 4L60E in my Camaro because the 80E is so power hungry.

 

[Snagglefoot]

The Z71 Tahoe was never equipped with a 4.8. Having driven a few 4.8 Tahoes in the past (rentals), they are a dog. The 4.8 is fine for the Silverado, but in the heavy Tahoe body it is gutless. Good luck.

Define gutless. The two vehicles are within 300 lbs of each other. It’s like having your cousin Eddy in the passenger seat and suddenly it’s gutless?