Opinions On the 7.4 / 454 Suburbans and engine

Dogmann

Observer
I'm looking at a 99 suburban 2500, with the 454 Vortec and 4:10 rear end. What do you guys think of this year and engine ? Opinions?
 

random

Observer
I've always thought chevrolets were junk, but that motor ain't nothin but the truth. I've driven all up and down the east coast with a 250,000 mile 454 hauling 10-20,000.

Check the whole truck VERY carefully for electrical issues. I've never seen a chevy that year that didn't have any.
 

TankShooter

Expedition Acolyte
My family has had our 1999 1500 Sub since it was three years old. It has been reliable, but the things I have wanted are more power and a higher tow rating. I haven't ever needed either of them, it's just the good is good but more is better. 454s don't like revs because of the length of throw on the crankshaft, and they can scuff cylinder walls if you beat on them. That is a couple of years after the vortec heads came out so they had sorted everything out by that time. It's a pretty bulletproof drivetrain and there probably isn't a whole lot that it isn't capable of doing for you. It is the highest torque, most powerful, and lowest geared factory option for suburbans that year. As you well know you're going to pay a penalty at the pump, but if that's a compromise you can live with then it's good. If I needed to go heavier than the one I have, I'd go big block instead of diesel in that year. If you get it use the search engine in this forum to beef up the front end if you'll be doing serious off-roading. I'd say go for it and post up pics once you get started.
 

proper4wd

Expedition Leader
My family had that exact Suburban while I was in high school. It was "my" car most of the time and I drove that thing all over New England. Took it wheeling lots of times that my parents still dont know about! Loved the 454. The sound, power, everything... except the 9-11mpg. It had a Banks 4" single exhaust on it that I will never forget the sound of.

It had a few issues. Fuel filters clogging, distributor needed to be replaced, fuel gauge intermittently inop leading to a few times that I ran out of gas. Once in the middle of the woods that I had to walk a couple miles to the gas station in the middle of the night to get a can full.

It liked to eat front brakes too. Warped lots of rotors. But that might have been from towing the 9000lb trailer with no trailer brakes...

I miss that truck!
 

Jeep

Supporting Sponsor: Overland Explorer Expedition V
Gave those trucks nothing but severe duty. 454 and 4L80E had no issues whatsoever.

DSC00183.jpg
 

chilliwak

Expedition Leader
I have owned Chevys all my life and have nothing but praise for the vehicle. You can find lemons of any make, including Ferrari and Rolls Royce. I have an old 78 Chevy and it is still going strong. The 454 is a great motor. The `Burb´is a great truck!:Wow1: How can you go wrong?:)
 

FellowTraveler

Explorer
454 ?

The 454 "tall deck" is a good motor, 1999 K2500 Burb rocks, most if not all suspension parts and torsen bars are K3500 fitment too.

Blowers/turbos and a wide range of performance enhancements getting VE as high as possible will give better mpg's.

Electrical issues are always issues when the tech can't finger the problem a set of GM shop manuals for that vehicle will be all you need for successful repairs.

Be advised, this vehicle you question about has main drive/train harness coming through the firewall at the front passenger foot-well and if the front passenger stretches out by putting their feet forward and high up in the well the harness can be pulled at the ECM which is above the glove-box. When checking for electrical issues it's advised to check all the connections at ECM first.

Vehicle VSSB module is above ECM and can be hacked to correct speedo for optional tire wheel fitment.

If you want a diesel later then Cummins, Isuzu and earlier GM diesels are an easy fit.
 

rxm6

Observer
We have a 99 2500 pickup with the 454 vortec that has been a work truck all its life. We have had to have the heads redone twice and it usually burns through a quart of oil every month. Other than those issues it's been nothing but reliable at 11mpg :Wow1: It currently has 194k on the clock and shows no signs of slowing down.
 

MrBeast

Explorer
the Vortec 7400 (454) that came in that suburban is one hell of an engine, there are also many things you can do to get more mileage and power out of it. Some of which are going with an upgraded ignition, headers, removing the cats and having the computer flashed to shut down the secondary O2 sensors. high flow intake elbow, filter and MAF

I had a 97 GMC 2500 short bed with the 7400 in it, I loved it, I did said mods to it with a true dual 3" exhaust and the thing would get 15 mpg on the interstate doing 70+ mph, selling it was one of the poorest decsions I have ever made.
 

Larry

Bigassgas Explorer
The 1996-2000 L29 7.4L big blocks are great engines. Much more dependable and durable than the 6.5L diesel of that era. L29’s had multiport sequential fuel injection, all of the latest sealing technology to prevent oil leaks and the “Vortec” style heads flowed very well. The advertised 290 HP rating at that time was very conservative. You can pull a lot more power out of one of these engines by just simply having a tuner add a hot tune calibration into the ECM and bumping up the fuel pressure 2 to 5 psi. The only other big block that surpasses an L29 in performance is a L18 8.1L which is similar architecture but a completely different animal.

The L29 doesn’t have any major durability issues other than the distributors can build up condensation and cause premature failures of the moving pieces. Easy fix is to install a $200 GM Performance Parts RamJet 502 distributor with upgraded internal components.

L29’s are known for cracking exhaust manifolds and their normal chemical dependency on oil. GM’s oil consumption spec was 1 qt per 100 gallons of fuel used was considered normal for any big block gas engine that era. While most went well beyond a 1,000 miles between adding a quart of oil many will need a quart every 1,200 to 1,500 miles. The stock 8.1L in my 2001 Silverado that I purchased new has used a quart of oil every 1,200 miles like clockwork since day I brought it home but the 8.1L in my 78 K10 doesn’t use a drop between the 3,000 oil changes which still surprises me.

Fellowtraveler’s comment on the passenger’s foot getting into the ECM wiring isn’t accurate on a 1996 or later GM anything, as the ECM began being mounted under the hood in 1996. I suppose the foot deal could apply to older TBI trucks with ECM's under the dash if someone hacked up the area installing a stereo or something and left harnesses exposed. I’ve never seen the under dash ECM or harness causing an issue on anything GM.


Ahh, the good ole trusty L29...
1188137921_4073dff6f5_o.jpg
 

Rush4x4

New member
I had a 99 GMC Suburban with the 454 and loved it. When gas prices went to 4 bucks a gallon I traded it in on an 02 Ram with a Cummins. I miss the Suburban, but I don't miss the mileage. My Cummins gets nearly twice the mileage. Only problems I had were with the fuel pump, one of the heater hose fittings rotted out, and the hydroboost unit started crapping out just before I traded it in. I do miss all the interior room, but it sucked always being the driver whenever we got together with anyone, especially with the mileage. If it'd been paid for though, I would've kept it instead of trading it in. It was a really nice ride.
 

proper4wd

Expedition Leader
All these posts make me want one again. Wish I had some good pictures of the old ride. She was a looker... gloss black, dark tint, LT package with tan interior and rear DVD, Centerline Hellcat wheels, classy billet grille with a silver bowtie in it instead of the gold.

I really do miss that truck!
 

bldeagle10

Explorer
not the same era but here is a pic of my 454 :D
201103131703000.jpg201103131703001.jpg
it is a 75 which I think was the first year they were introduced to the burbans? correct me if I'm wrong...

I wouldn't listen to the nay sayers about chevy's. as previously stated you get lemons with every manufacturer. I think it also has to do with how you drive the rig. my jeep has 330,000 miles on the original motor and complete drive train, nothing has ever been rebuilt. and it is commonly said that the 4.0 wont be reliable past 250k... at least it has been commonly said to me and I like to point at my odometer... I have personally had nothing but trouble with fords. while some of my friends have had nothing but troubles with their chevy's.....
 

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