5.7L Vortec vs. 5.3L Vortec

Performance wise, I bet the 5.3 and 5.7 are pretty close. What you'll notice is the longer wheelbase and 3/4 ton chassis. Should be a nice improvement over the avalanche.

Well, I bought it. Power unloaded is very similar, but I can definitely feel the flatter torque curve. The suspension is much stiffer, which is what I wanted. It doesn't wallow over bumps like the Avalanche did.

Towing performance with the TT will be proven in a couple weeks hopefully, otherwise it will have to wait until spring.

I used to pull my 5000lb. trailer with a '97 GMC 5.7, now I pull with a '11 GMC 5.3. The 5.3 will actually accelerate faster than the 5.7, 6 speed tranny verses 4 speed. Once up to speed the 5.7 had more passing power when I came upon a slower vehicle. The 5.7 had a lot more braking power than the 5.3. The 5.3 has very little even when pulled down into 2nd gear, so I end up using a lot more brake pedal with the 5.3.

Guy

I towed a 7000lb Sunline trailer with a 1990 R1500 Suburban for many years. It had the 5.7 TBI motor, 3:73 gearing and had the 700r4 trans with a torque converter lock switch installed . This combo towed very well and the TQ Lock switch was wonderful. The 5.7 pulled very well into the 3500 to 4K rpm range on long pulls and held speed very well ran cool. Ran this combo in 3rd gear TQ locked most of the time.

bfourman wrote:
If I end up with the 5.7 truck, it will get intake/exhaust and maybe a cam in the future.

A BlackBear tune, the MPFI conversion, and a very mild cam and it would rip! Plus it has a way more useable bed that the Av :B

my experience is I towed for years with my old 1998 chevrolet 2500 4x2 with the 5.7 and I believe it had the 4.10s. I towed all over the states with that truck and it ALWAYS had plenty of power. At the time was only towing 4500#s, but occasionally towed more and always handled it great. Unfort, at 170,000 miles transmission went out and I traded it in. Otherwise I never had any major problems with that truck or motor. I traded that truck in for my Tahoe which is a 2003 with the 5.3. Which others has stated, the biggest difference is you will hear the RPMS much more with the 5.3 versus the 5.7... I still have pulled up to around 6,700#s with the 5.3 but I know dam well the old 5.7 would have pulled it better. So yes you will notice the 2500 will handle your weight much better and in my opinion you will love towing with the older chevy 5.7 motor versus the newer 5.3 you have now.

My wife has a '06 1500 chevy 5.3 7000 GVWR 3.73 axle 4x4 truck with 295 hp. The older '02 5.3 put out even less.

When she bought the truck I had a old '90 model 2500 LD 7200 GVWR chevy 5.7 TB engine that cruised much easier with much less racket (rpms) than the 5.3 when pulling a 7500 lb trailer. The 5.7 was the L05 model and its peak torque came at 2400 RPM.

Yeah the 295 hp 5.3 would run off and hide (if your into drag racing) from the 5.7 TB engine when empty but put a load on it and the 5.3 has to be ran at 3500-4000 rpm to keep up with the old 5.7 which was loafing along at 2600-2800 rpm. Anything over 3000 rpm in the old TB 5.7 just made more noise.

The newer 5.7 Vortec has more grunt and more usable rpm and makes for a easier pull with a 6k trailer.

Honestly, while the ride performance would be better with the 2500, I don't think there is nearly enough "engine" performance gained to make that switch.

I towed a 5000GVWR HTT with a 94 Caprice with the 5.7L LT1 (260HP/330#-ft) and swapped to a 3.42 axle. It did fine towing, and at this time it was only four of us. I later had an 05 Suburban with the 5.3L (295HP/330#-ft) with the 3.42 axle. The Suburban with the tow haul mode actually towed that trailer better from every aspect. I honestly think 30 less HP and the high first gear of the 4L80E will make that 2500 seem like a dog compared to your Avalanche to get rolling.

wmoses wrote:
Not sure where the above numbers come from but my truck's engine is rated at - 315 hp (235 kW) @ 5300 rpm and 335 lb·ft (454 N·m) @ 4000 rpm of torque.

I also see numbers for the 5.7 as being 255 hp (190 kW) to 350 hp (261 kW) at 4600 rpm and 330 lb·ft (447 N·m) to 350 lb·ft (475 N·m) of torque at 2800 rpm, which is closer to the numbers given above.

Actually, the early 5.3L were rated at the 285. The 5.7L that went into the trucks was rated at the 255HP. The 350HP 5.7L was the LS1 that went into the F-Bodys, Corvette and GTO.

There have been several times I have had the Av spun up to 3500-4000 RPM on a long steep hill, and while that is within the operating range, it is too high for my comfort level.

I would love to trade it in on a Duramax or Powerstroke, but I do not want a vehicle payment on a truck that sits 80% of the time (I have a company car). If I end up with the 5.7 truck, it will get intake/exhaust and maybe a cam in the future. The 80e is a good trans, much more HD than the 60e. It is supposedly a rust free truck, and the engine/trans were rebuilt approx. 50k ago.

I'm familiar with the shortfalls of the treefiddy, and find them easier to work on than the newer LS engines, and much easier than a modern diesel.

My TT is an Aerolite, which IIRC is lower profile than most others.


Edit: Found out it has 3.73s. I was hoping for 4.10s. The Trailer Life guide for 2000 says a 3/4 ton 4x4 with the 5.7 and 3.73s is rated for 6800lbs, while my Avalanche with 3.73s is rated for 7k. Doesn't make much sense, but I would think a 3/4 ton leaf-sprung truck would handle the weight better.

I had 1990 Chev 1500, 5.7, 3.73, std cab, longbed - chipped, Flowmaster muffler and Thorley headers and K&N air filter. Replaced it with 2002 Chev 1500, 5.3, 3.73, ext cab, shortbed - totally stock.

Towed 5000-lb loaded 5vr. The 5.7 "felt and sounded" like it would out-tow the 5.3. But I timed both on several uphill onramps, full throttle, and the 5.3 won every time, but not be much.

The 5.7 felt stronger off the line but the 5.3 felt stronger midrange on up. MPG were roughly the same.