1999 GMT 400 Suburban build anyone else building the same?
- Thread starter run2jc
- Start date
nitro_rat
Lunchbox Lockers
To me the best thing about a suburban is that there's generally enough room to put everything you need inside without "mods." Then it still works a family vehicle/people hauler or whatever when you're not "overlanding."
I would take a good look at the cooling system. Make sure the intake gaskets aren't leaking, the goofy heater hose connector on the front of the intake isn't leaking (a hose barb works great here), rear heater hose plastic "T" fittings will generally crack and break, ditto the plastic heater control valve. If there's a rubber heater hose block off on the right side radiator tank under the radiator cap, get spares in the "help" section of your FLAPS. It will split and leave you stranded at the worst time.
Brake system troubles are notorious on these rigs. You don't need a GMT800 master or any other hocus pocus. The rear brake drum hardware has usually been assembled and adjusted incorrectly at some quickie brake job place. Take your time (and maybe a service manual) and do them correctly. Replace the old rubber hoses and flush the old fluid out. It will stop fine.
Avoid cranking the torsion bars too high and your ball joints and cv axles will thank you. Your 99 should already have the good front axle actuator, that was a problem on the earlier GMT400's.
When your rear AC stops blowing cold and the front still works you'll need to change the expansion valve at the back. It will be corroded to the evaporator core and the rear AC lines will have to be changed. At this point you'll probably be ready to move on because the cost of the AC repair will eclipse the value of the truck...
All that said, I still like them. I've done nearly a million miles in the GMT800 Suburbans and can't say I like any of the newer ones any better!
I would take a good look at the cooling system. Make sure the intake gaskets aren't leaking, the goofy heater hose connector on the front of the intake isn't leaking (a hose barb works great here), rear heater hose plastic "T" fittings will generally crack and break, ditto the plastic heater control valve. If there's a rubber heater hose block off on the right side radiator tank under the radiator cap, get spares in the "help" section of your FLAPS. It will split and leave you stranded at the worst time.
Brake system troubles are notorious on these rigs. You don't need a GMT800 master or any other hocus pocus. The rear brake drum hardware has usually been assembled and adjusted incorrectly at some quickie brake job place. Take your time (and maybe a service manual) and do them correctly. Replace the old rubber hoses and flush the old fluid out. It will stop fine.
Avoid cranking the torsion bars too high and your ball joints and cv axles will thank you. Your 99 should already have the good front axle actuator, that was a problem on the earlier GMT400's.
When your rear AC stops blowing cold and the front still works you'll need to change the expansion valve at the back. It will be corroded to the evaporator core and the rear AC lines will have to be changed. At this point you'll probably be ready to move on because the cost of the AC repair will eclipse the value of the truck...
All that said, I still like them. I've done nearly a million miles in the GMT800 Suburbans and can't say I like any of the newer ones any better!
Yroundrdn
Observer
Very happy with the way ours turned out. I still have more to do but seems to be working out great so far. There is a build thread in the signature that is fairly complete. as for Nitro rat's comments, ditto on the heater hose and carrying and emergency block off. Did both of those and replaced the radiator. Brakes on mine have been fine but I did replace the calipers, pads etc. I just turned 200k and the G80 locker works great, trans is perfect and motor strong. I cut the front fenders and bumper to get the 285s in. For $27 I can get replacement fenders if I change my mind. All in all, very happy with it so far.
I just bought my 99 about two months ago replaced all fluids and changed out radiator hoses and new thermostat and cap flushed system. When I bought it they gave me a few maint record they had the oil cooler lines and distributor replaced. The ac takes Freon gets cold then the next day it’s gone so it might be the valve that is used to put Freon in I saw some leakage there. I plan on putting on a 4 inch lift and using it till then going hunting next week going to sleep in it , deer hunting in the hula wilderness muzzleloader I will start a thread when I start doing more stuff and I will keep up with you.
Frogprince
Observer
I run a K2500 GMT 400 Suburban. Picked it up last fall and have had some fun with it and some headaches.
After I purchased it needed a header on the passenger side (driver is going to be done here shortly), the Smog Pump grumbles and needs a valve and tube on the passenger side, and the AC pump was cracked
The biggest headache came from the the last trip. On our way down the mountain I heard a whine dependent on engine RPM. Turned out it rubbed a hole in the power steering lines that run up and into the frame (for cooling) and was leaking everything out. Shop that found the leak just bypassed 90% of the hose.
Mods so far done: Milestar Patagonia MT Tires (17" Humvee Rims), Wired in LED bumper lights on the rear bumper, Trailer Brake installed, LED Lights inside, LED Headlights
Mods pending: Brush Bar with Winch and LED Bar Light on roof or split next to the brush bar
After I purchased it needed a header on the passenger side (driver is going to be done here shortly), the Smog Pump grumbles and needs a valve and tube on the passenger side, and the AC pump was cracked
this is why I replaced mine. Other than that it has been routine maintenance needed (fluids, and fuel pump). It is due to go in for the intake gasket, injectors and the above mentioned header. Just haven't wanted to spend the extra money on it as of yet.
The biggest headache came from the the last trip. On our way down the mountain I heard a whine dependent on engine RPM. Turned out it rubbed a hole in the power steering lines that run up and into the frame (for cooling) and was leaking everything out. Shop that found the leak just bypassed 90% of the hose.
Mods so far done: Milestar Patagonia MT Tires (17" Humvee Rims), Wired in LED bumper lights on the rear bumper, Trailer Brake installed, LED Lights inside, LED Headlights
Mods pending: Brush Bar with Winch and LED Bar Light on roof or split next to the brush bar
nitro_rat
Lunchbox Lockers
On the 5.7 Vortecs, they will get an exhaust leak at the donut gasket. There are 3 "ears" on the flange. Remove the 3 nuts, slide the flange down the pipe. Use an angle grinder, cutoff wheel, torch, etc and shave the ears to about half their original height. Bolt it back up. Now it will compress the donut gasket enough to never leak again!
