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Opinions on 99-03' GM BBlks 7.4/8.1 and SBlk 5.3/5.7

Actrac

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Chester, CT
Hi, Newbie here. I'm looking to purchase a used Chev. Suburban. The 2500 series usually have BBlks, 7.4/8.1's. Are these engines good? Is one better than the other? I'm actually thinking I would prefer a 2500 series with a 5.7 for better fuel economy. I will not be towing often or heavy loads. The truck will be loaded with tools daily, but that is normal. Any opinions are greatly appreciated.
 
The big blocks are good and reliable but for what it sounds like you need the 5.7 or 6.0 would be better. Mileage in the big blocks will ba about 10mpg
 
I love my 8.1 dually. I get 11.7 MPG driving to work.. 75% highway doing 80, 25% city doing 35. tows like a raped ape too!
 
OK, Thanks for the input, now there is a 01'/1500/5.3L Suburban that's priced well, trans is rebuilt at 110K, vehicle has 133K total, Is this engine OK, I guess I could crate motor 5.7 when the 5.3 craps out, any thoughts?
 
With Proper / Basic Maintenance, the 5.3L should Last over 300k.

I'd take a Look at the Trans Fluid to See how it Looks / Smells, Check the Oil, and if those things and a Test Drive are all Good, you should be Fine.
 
I had an '03 8.1 4x4 reg cab and drove 95% highway. 11 MPG most of the time. Loved the power! Used more oil than I liked and that was considered normal for that motor. Wife had an '02 5.3 Tahoe with 4l60 trans that had problems fixed with reverse under warranty but we had it for 65k and no other troubles. Now have an '07 5.3 Tahoe at 75k and it's been pretty much trouble free except a u-joint. The 5.3 is actually a better motor for mileage than the 5.7 and has plenty of power. I'd avoid a big block in any case unless you don't mind bad mileage. '00-'02 5.3 did have some cold piston slap issues but it didn't seem to affect the life of them.
Welcome to The Truck Stop! :welcome2:
 
A 5.7L does not directly swap in place of a 5.3 due to different motor mounts, and stepping down to a 5.7L from a 5.3L would be a HUGE drop in power, torque, AND milage. If you load it down alot you may want to look into a 2500 with a 6.0L, but if it is a thousand pounds or less in the BURB I would ad in some airbags and go with a 1500 and enjoy teh better milage. And there are to many LS engines to list that have surpassed 200K miles and needed nothing but a water pump. The 5.3L has proven to be ALOT more reliable than the 5.7L VORTEC ever was.
 
We have ~280K miles on a 8.1L and it still gets just over 10mpg unloaded and 8mpg loaded heavy, always burned a qt of oil/ change. Plenty of power and has been rode hard and put away wet its whole life.
Had a 6.0 make 180K rode pretty hard before it was totaled.

The only weak link in a 1500 burb with a 5.3 is the 4l60 behind it. They can do just fine driving around with light loads but loaded heavy they can fail pretty quick.
 
Can the 4l60E be upgraded to the 5.3L easily? The trans in this Sub. has just been re-built, so I should get some service out of it. In the meantime, I would buy a good/re-built 4l80E/ or whatever you folks tell me would be good upgrade, then I would ready when it craps out.

It's sounding like this 01' 1500 Sub will do for me, price point is good, condition is V.G., 2 owner [same family], never towed, Mobil1 oil since new, etc. Money is tight, 2500's w/ small blocks are not around, better avoid the 8/10 mpg senario, gas will most likely be 4.50 a gal by winter.

What ius best way to beef up rear suspension? I will put 5-600 lbs of tools in to stay, so I would mind having it stiffer in rear. I will then load it up more from time to tome, it would be nice to keep it up a bit. Thanks for advise, much ap[preciated
 
I do not know for sure if the 4L80 and 4L60 are a direct swap but I suspect it would be possible. Might need a body lift though. Air bags in the rear should do it. Most of the carpenters/remodelers around here went that way on 1/2 tons.
I agree a 6.0/4L80 2500 would be ideal but harder to find. 13-14 mpg though.
 
The big blocks are torque monsters and will pull a house down but they do have their inherent problems, the most obvious of which is MPG. ;)

The Vortec 7.4's (1996-2000) are known for problems relating to bad injectors (good new ones will cost you $300+), bad fuel pressure regulator ($50+ and you must remove the plenum to get to it, a bit of work, better do it while you're in there upgrading those rotten Multec injectors with some nice Bosch 4-holers), and a few other misc. issues. High mileage units can display problems with worn rockers as they are nonadjustable (the bolt simply torques down) but you can convert them to adjustable with a cheesy kit; I ended up replacing them with roller tip adjustables and stock style studs. Distributor body is plastic and often cracked around the tabs that the cap screws go into, making tune-ups a pain. Distributor body/bushing also wears out and lets the shaft flop all over the place causing timing errors.

The first 8.1's from 2001-early 2003 are kind of known for a number of annoying problems but the aforementioned oil usage is a big one. However I read something really interesting on 3500HD.com from a guy that loves his early 8.1's and says he found some kind of port in the intake while rebuilding one of his, he bent the direction of the port so it can't suck oil but can still pass crankcase vapor; says he was using about 1 quart per 1000 miles and now it uses none. If you want to look up his posts the member name over there is AVERY.

Anyway above all, if you're wanting MPG, you could probably do better than a big block. If you want raw stump-pulling power with no questions asked, well, big block is the way to go. :D

Richard
 
The big blocks are torque monsters and will pull a house down but they do have their inherent problems...
However I read something really interesting on 3500HD.com from a guy that loves his early 8.1's and says he found some kind of port in the intake while rebuilding one of his, he bent the direction of the port so it can't suck oil but can still pass crankcase vapor; says he was using about 1 quart per 1000 miles and now it uses none. If you want to look up his posts the member name over there is AVERY.
Well THAT'S damned interesting... I'd be all over that if I was still into them. I never could understand why a new and very meticulously maintained motor would use so much oil...
 
Mine is down a quart usually around the 3500-4000 mile mark. Been like that since I drove it off the lot, hasn't changed any since.
 
No reason to swap in a 4L80E as it won't be a straight forward swap and would require a custom PCM program to make work. The 4L60E can be built up pretty stout with just a few drop ins while it's apart. Put a beast sunchell in it, good RAYBESTOS clutches, a set of blue plates for the 3-4 pack, new reverse input drum, wide kevlar band, corvette servo, TRANSGO shift kit, SONNAX 1-2 accumulator and a SUNCOAST single disc converter and you would have a good shifting and stout unit for not alot of money(about a $1200 in parts, and the rest is labor). They can be built up alot stouter, but this build worked well for me in a daily driver I did in a 93 2500 with a ported roller motor I built.
 
Mine is down a quart usually around the 3500-4000 mile mark. Been like that since I drove it off the lot, hasn't changed any since.
Could be they had it figured out by '05 Mike. My early (Dec '02 build) '03 used a qt in about 1500 from day one and after 50k a bit more when I traded for the '05 LLY.
 
Yes - all the mentions of high oil consumption I've seen in the 8.1's are the early years, 2001-early 2003. That's what bums me out about them since if I were to buy a GMT4xx 3500HD with the 8.1 that would only be 2001-2002 since after that the model was discontinued.

Richard
 
Having highmiles on our we have started to gum up a couple plug tips lately but still doent use more than a few qts/yr (how often we change it) we just check it about everytime we take it for a run but the AC is out and it too hot to drive it too much in the summer.

Just installed a new radiator in it and the truck wont run over 180-190 both ECT and tranny temp.

I'm debating as to whether or not i want to buy it from the farm as a personal beater, seems like i have enough of those though lol.
 
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