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 > Towing with a 99 GMC Suburban 7.4L

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MegaCab_PL

Rockland County, NY

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Posted: 02/13/18 09:42am Link  |  Quote  |  Print  |  Notify Moderator

Where is BenK - he is an expert on GMT400 Burbs with 7.4 ?

IIRC - 4.10 was rated at 10k, 3.73 was rated at 8K

Either way, 9k is going to be a lot for it, but for $ 1,500 I'd get it to have around.
It's still a beast with 2 k payload.

kw/00

Florida

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Posted: 02/13/18 12:13pm Link  |  Quote  |  Print  |  Notify Moderator

I don't see an issue, the price is really good, and for a few hundred u can fix the cooling issue or at make it much better. I have a friend who found a sweet deal on a cheap tow rig, sold his HD truck and got out of that payment and paid cash for the other and was debt free.


A truck, a camper, a few toys, but most importantly a wonderful family.

DaveF-250SD

Ridgecrest, Ca.

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Posted: 02/13/18 01:20pm Link  |  Quote  |  Print  |  Notify Moderator

I think it would be a good vehicle to have around your property to haul things around to save wear and possible damage to your new truck. If it runs hot and slow with a 5,000 lb. trailer, something is seriously wrong with it. A friend of mine has a class C motorhome with a 454 that probably weighs 10K empty, and he never has any issues with overheating, even in the middle of summer. My own '78 GMC 1 ton SRW 454 pickup (have to update my signature) runs very cool under all conditions, empty and pulling a car on a trailer, just under 7K pulled weight, and can do 65 up any hill or mountain pass I encounter while towing.


2004 F-250 XL Super Cab short bed 4x4 V-10/4R100
1977 Chevrolet Scottsdale C-20 Trailering Special 454/TH400

blt2ski

Kirkland, Wa

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Posted: 02/13/18 03:26pm Link  |  Quote  |  Print  |  Notify Moderator

Scott, I came back from Duvall at 40-45k gcw in dump truck. Mind you it is a 175/330 non turbo 7.3 V8! Fortunately, 7 forward gears. In 1st which is 10.08-1, 2800 rpm at switch back motor starts slowing down to 2100 as I straighten back up, motor speeds up.....thought I was going to have to back down with 5 yrs of soil in truck, 12k equipment trailer behind me!
Needed clean shorts after that.
Never as of yet have I stalled that rig on a hill! My auto trans 454s, stalled them out all the time. One was a 4ad, into 4lo, no big. Rwd dually, burned up transmissions every 30k like clockwork, with 5k fluid fluid change.....talking COMPLETE fluid change including fluid into the TC!

Marty


92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
00 Chev C2500, V5700, 4L80E, 4.10, base truck, no options!
92 Red-e-haul 12K equipment trailer

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Lwiddis

Hearst San Simeon SP

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Posted: 02/13/18 06:36pm Link  |  Quote  |  Print  |  Notify Moderator

So Fireguard and RJS refuse to comment on sales to those that are not firefighters. Interesting.


2015 Winnebago 2101DS TT & Tahoe LTZ, 300 watts WindyNation solar-parallel & MPPT, Trojan T-125s. TALL flagpole for US flag. Prefer USFS, COE, BLM, NPS, TVA, USF&WS, state & county camps. Bicyclist! 14 year Army vet - 11B40 then 11A - old MOS 1542 & 1560.


wnjj

Cornelius, Oregon

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Posted: 02/13/18 06:59pm Link  |  Quote  |  Print  |  Notify Moderator

blt2ski wrote:

Scott, I came back from Duvall at 40-45k gcw in dump truck. Mind you it is a 175/330 non turbo 7.3 V8! Fortunately, 7 forward gears. In 1st which is 10.08-1, 2800 rpm at switch back motor starts slowing down to 2100 as I straighten back up, motor speeds up.....thought I was going to have to back down with 5 yrs of soil in truck, 12k equipment trailer behind me!
Needed clean shorts after that.
Never as of yet have I stalled that rig on a hill! My auto trans 454s, stalled them out all the time. One was a 4ad, into 4lo, no big. Rwd dually, burned up transmissions every 30k like clockwork, with 5k fluid fluid change.....talking COMPLETE fluid change including fluid into the TC!

Marty


Maybe not practical on a steep slope, but could you unload the equipment and drive it up and/or help the truck with it?

blt2ski

Kirkland, Wa

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Posted: 02/13/18 07:52pm Link  |  Quote  |  Print  |  Notify Moderator

wnjj wrote:

blt2ski wrote:

Scott, I came back from Duvall at 40-45k gcw in dump truck. Mind you it is a 175/330 non turbo 7.3 V8! Fortunately, 7 forward gears. In 1st which is 10.08-1, 2800 rpm at switch back motor starts slowing down to 2100 as I straighten back up, motor speeds up.....thought I was going to have to back down with 5 yrs of soil in truck, 12k equipment trailer behind me!
Needed clean shorts after that.
Never as of yet have I stalled that rig on a hill! My auto trans 454s, stalled them out all the time. One was a 4ad, into 4lo, no big. Rwd dually, burned up transmissions every 30k like clockwork, with 5k fluid fluid change.....talking COMPLETE fluid change including fluid into the TC!

Marty


Maybe not practical on a steep slope, but could you unload the equipment and drive it up and/or help the truck with it?


I probably could have removed the bobcat and mini trackhoe. That would be 9000 lbs between them. That would have put me at a weight I could have kept going 1 to 2 gears taller.
But as mentioned, you can have all the HP/torque in the motor you want, but if it can not get to the ground in a practical manner, you're screwed! I've always had better luck towing with a properly setup drivetrain in a lower HP rig like this Navistar, than a higher power, but improper, usually transmission setup rig.

Marty

BenK

SF BayArea

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Posted: 02/13/18 10:15pm Link  |  Quote  |  Print  |  Notify Moderator

It will do it, albeit since older, a bit slower up the steeps

Waiting for mine to die or wear to the point just have to rebuild... [emoticon]

Will keep mine for a long while. Hate payments, can afford to buy one out right, but their prices are insane to me. It is a truck to me, not a car. Know that trucks are designed with margins for work, not like cars...

I have 4.1's and suggest you consider it if it doesn't have it now

Flush EVERYTHING with synthetic. Mine has been on synthetic's since new and MolyB (2 micron) additive in everything except except for the 4L80E and Diff (anything with clutches will be ruined with such a low co-efficient friction modifier). Make sure power steering (also is the power brake source) and MC (DOT4, non-silicone)

Change out the engine thermostat to a 180* and I've drilled a 3/32" dia hole in the flange...as the tiny <1/64" dia OEM hole is too small and temp over shots when really, really hot)

Change out the fan clutch to a 'SEVERE' duty. OEM is 'standard' and some have found to have a 'HD'. HD and severe duty fan clutch of that era couples up to 90% of shaft RPMs. Standard best is around 50%-60% shaft RPMs are coupled. Also, since so much is coupled...the bearings are beefier and SEVERE duty has the biggest bearings. It will ROAR when it kicks in and surprised me the first time. Can see the dash temp gauge needle drop like a rock when it kicks in

Know other TV's computers have backed off via their torque management and mine still provides 'Power Mode' when they start to slow...of course naturally aspired...forced fed has that advantage and if they have a good cooling system with lots of margin... Also, mine handles...more so compared to newer which are so tall because the fashion statement crowd thinks taller is more capable...my track is +10.5" wider than stock to boot, so cornering is something different...

Make sure the radiator has the 'short' neck and is in good order. The 'short' neck has the 7 fin ATF, in tank, radiator (liquid to liquid).

Depending where it has been parked/kept/etc...leaf & debris build up between the AC and radiator partially blocks air flow. Creates mystery heating/cooling issues. I blow mine out with 100 PSI air every so often

Duct tape the intake holes on the engine bay side of the air ducting to the filter box. I've made my own ram, cold air intake that is in parallel to the OEM intake routing.

Keeping the intake charge important to always have power mode available.

Change out the air filter with the OEM optional "HD" and just drops into the OEM filter box. It is about 2" larger in dia.

Read diff is the EXACT same as the 1 ton dually of that year...except for the cylinder and MC (dia's are larger and DO NOT lose the short rod between the MC and booster...almost impossible to replace and is a junk yard thing) and change them to that 1 ton dually

Check if you have the 3.5" wide rear shoes...those are the same as the 1 ton dually...mine came that way and why parts folks always ask how wide your rear shoes are....no matter what

Manually adjust the rear shoes often, as the proportioning valve is off....not sending enough to the rears. Decided to NOT touch that and just manually adjust them

Pulling is common and is due to the rears not in the braking game...in a pinch...apply the E-Brake pedal a bit to move the shoes into the game

I like Praise Dyno, but the GM Parts "Dura Stop" rear shoes almost as good to provide "Nose Bleed Braking"

Super Tune the fronts...as the slides stick...I've made a special grease gun with a hypo needle to poke in high temp brake grease (filled with MOLYB)...and make sure to change out the slide O-Rings

Spark Plugs...have modified with by 'cutting back' the ground electrode

SS WIRE ignition RF suppressed wires...I like copper over Platinum plugs and change them around 50K miles or so

Copper inserts on the dist cap::Gater Back serpentine belt

Change the Serpentine tensioner...they typically last in the 60K miles or so for me

NOTE that the newer TVs, not just GM but most all, has "Torque Management" and this era Suburban does NOT, so it runs with that pack well, or at least mine does...to even taking them when "The Boy Racer" kicks in when challenged by another Boy Racer...

Know that there are most things forgotten and will noodle that for a while...

Plans for the day that, gosh darn, just have to rebuild...

  • A 'built' engine that will pass 1996 SMOG, I live in SF Bayarea
  • 1,000 HP 4L80E, but only going to use less than half depending on what the engine builder can do and still pass SMOG...so it will last a looooong time...these 1K HP unites are warrantied for 3 years, so going to last
  • A gear spliter OD with a 0.75 OD ratio...gear spliter, so it will insert itself in-between each gear to make 8 gears...times 2 in LOW
  • New diff ratio in the 4.8 or maybe 5.x for a final double OD to the axles in the 2.x range


All of the Internet searches finds +500 HP 454's, but are for carberators...no good ones found to date for a Vortec...yet...or will bite the bullet and have one built. Engine builder passed on and am looking right now

Also, if it has the F60 option (check the glove box label listing all options it left the factory with) and you will have a 'Snow Plow' prep package that begets 1 ton front torsion springs. Since it comes with the 6,000 RGAWR as the 1 ton dually of the same year...tongue'n cheek refer mine as a K3500 Suburban...

If me...I'd buy it and have two Sub's and make the choice of which one to be the parts one...



[image]
mysub mysuburban


-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

Lwiddis

Hearst San Simeon SP

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Posted: 02/14/18 10:10am Link  |  Quote  |  Print  |  Notify Moderator

Lines on this SUV are still beautiful...clean.

Grit dog

Black Diamond, WA

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Posted: 02/14/18 01:37pm Link  |  Quote  |  Print  |  Notify Moderator

DaveF-250SD wrote:

I think it would be a good vehicle to have around your property to haul things around to save wear and possible damage to your new truck. If it runs hot and slow with a 5,000 lb. trailer, something is seriously wrong with it. A friend of mine has a class C motorhome with a 454 that probably weighs 10K empty, and he never has any issues with overheating, even in the middle of summer. My own '78 GMC 1 ton SRW 454 pickup (have to update my signature) runs very cool under all conditions, empty and pulling a car on a trailer, just under 7K pulled weight, and can do 65 up any hill or mountain pass I encounter while towing.


Agreed. It shouldn’t be overheating, but make sure it’s something easy to fix and not a head gasket or something

* This post was edited 02/14/18 01:47pm by Grit dog *


03 Arctic Fox 860
07 Dodge 2500 deezul

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