7.4 -w /4.10gears

DOGMAN · May 12, 2004

What am I looking at in gas mileage in a 99 4x4 Suburban with the 7.4 & 4.10 gears Empty everyday & Towing a 22foot Very Heavy Airstream. The one I'm looking at has 30,000 miles and is very clean. What should I look for on these trucks- as far as problems? I've heard that brakes are a b*tch.

Anyone have a 7.4 with flows or glasspacks? I would love to hear what that sounds like in a 454!

LikeaRock14 · May 12, 2004

Heh, big blocks aren't meant for mileage, BUT, they do get decent mileage out of that 454. I have a 2000 Chevy C/K 3500 Crew Cab Long bed, 454 w/ 4:10 limi-slip rear. I have a di/so Flowmaster 3" muffler-back exhaust, K&N intake, and a JET chip. I noticed the main improvement after the intake, but now, when I'm cruising down the interstate going between 70 and 80 constantly, I actually average veeeeery close to 15 mpg, which really amazes me mileage wise. Around town and just short short trips, I average 11-12 mpg. We tow a 32 ft. gosseneck loaded down every weekend to the races, and it averages 8-9 mpg. EEK, yes it's bad, but I'm hoping with the soon-to-come Westers it'll run a helluva lot better mileage wise. I haven't had any single problem with this truck, more than pleased. The only complaint is it's a B*TCH to park. The burb won't be as bad w/ it being slightly shorter, but don't expect to drive it like a mini cooper

And as for exhaust, Flowmaster 70 series is the way to go. I NEVER EVER EVER get any kind of drone. When the windows are up w/ the a/c on, you seriously don't even hear it. It's mainly my dads truck, but it's basically my daily drive, especially since I need a new engine for my Blazer

Anyways, I made four clips, to give the basic ideer of what it sounds like. Keep in mind, it DOES sound better in person, but I think you'll still like it. I'm going to hopefully have it swapped for a dual out Spin Tech system soon, but I honestly couldn't be happier with the 70 series.

Here's the links:

Parked rev, about 10 ft. away

Slight rev, take off

Cruise by steady ( It's a HELL of a lot deeper and louder at cruise and takeoff than the clip makes it seem)

Hard downshift to 1st

R Dogg 56 · May 13, 2004

What am I looking at in gas mileage in a 99 4x4 Suburban with the 7.4 & 4.10 gears Empty everyday & Towing a 22foot Very Heavy Airstream. The one I'm looking at has 30,000 miles and is very clean.

What should I look for on these trucks- as far as problems? I've heard that brakes are a b*tch.

I've heard number falling in the 7-9mpg range when under heavy load, and 10-13mpg empty. Keep your foot out of it, and it'll be ok, maybe even better.

The drivetrain, while very reliable, has had issues in the past like driveshaft warping and cracks developing in the block. Transmission problems too, but I can't say for sure what they are at the moment. The brakes can be a problem if they've been abused for a while, and may not work well with the ABS. TSB's for these problems can be found on the Web, or issued through GM, although you may have to do a search or two to find them.

In any event, it sounds like a perfect towing vehicle, as the 454's were meant for work. Good luck!

GM GIMP · May 13, 2004

I had a '97 Suburban 7.4 with 4.10 ratio. My towing consisted of a '67 Camaro

with trailer & tools. About 7,000#s. My gas mileage was about 8 mpg. towing

and 13 mpg empty. It was programmed with Hypertech but that was the only mod.

I don't know about typical problems cause It never saw the dealer except to

replace the fuel pump under warranty. Brakes worked great. I traded it for a

'99 GMC 1500 ext. cab NBS and spent the next two years kicking myself. The Burb.

was awsome.

99-2door · May 13, 2004

I have a 96 c3500 ext. cab dually with the Vortec 7.4L , 4L80e and 4.10 G80

Complete dual system with 2 Flowmaster 40 series, no cats, headers.

I put an MSD 6A ignition box, and super conductor wires. The box really smoothed out the idle. Great truck I love the power this thing has while towing.

jobee454 · May 13, 2004

I had a 99 3/4 ton 4x4 454 5-speed and it was a great tow vehicle. Got about 8-10 loaded and 15 on the highway empty. It was 3.73 gears. The only complaint I had was that it used a quart of oil between oil changes (never smoked and didnt leak?????), and it had a rough idle. It was a power house and would run with any stock diesel down the road.

DOGMAN · May 13, 2004

I have a 96 c3500 ext. cab dually with the Vortec 7.4L , 4L80e and 4.10 G80
Complete dual system with 2 Flowmaster 40 series, no cats, headers.

I put an MSD 6A ignition box, and super conductor wires. The box really smoothed out the idle. Great truck I love the power this thing has while towing.

How does that baby with the 40 series sound ?

99-2door · May 13, 2004

I have a 96 c3500 ext. cab dually with the Vortec 7.4L , 4L80e and 4.10 G80
Complete dual system with 2 Flowmaster 40 series, no cats, headers.

I put an MSD 6A ignition box, and super conductor wires. The box really smoothed out the idle. Great truck I love the power this thing has while towing.

How does that baby with the 40 series sound ?

It sounds great, love that big block rumble. It is a little loud, but not so bad in the cab with the windows up. I regularly drive it up to 6 hrs in one day and it is fine to me. It is loud but smooth, none of that nasty popping like with glasspacks

Ben · May 14, 2004

Mine is 1996 3/4 ton 7.4L/4.1/LT265-75R16 Mich LTX-AT's.

Towing +8.5K lb boat/trailer from sea level to about 6.5K feet gets 7-8 mpg. Drive it HARD.

Empty or full with volleyball tournanment team (4 guys and 4 gals, 8 gym bags, 2 ice chest, ball bag, etc) highway normally get 12.5-13.5 mpg going 75-80 mph. Some times get 15.4 mpg. Not lots of times, but often enough to claim. What the heck was difference, unknown.

Normally commute & city get 10-11 mpg.

Normally freeway get 12-13 mpg.

My Sub weighs in at 7,400 lbs full liquids, me (190lb), +200 lb toolbox and misc stuff.

Air front tires to 70-80 psi all the time (LTX-MS LT265/75R16 E's) and rears 50 psi all the time (LTX-AT LT265/75R16 C's).

[edit]..... Home made cold, ram air system using OEM filter box and HD filter (not K&N), 2.5" dia dual Magnaflow, and a few other tweeks (180*F stat with holed drilled in flange, etc).