Wanting to buy a GMT400, how old is too old, and years to avoid? (discussion)

[mnewxcv]

Hi all, been lurking here for the past few months as I search for a decent truck in my area! I am looking for a long bed 4x4, probably 2500/3500 series, and have been thinking an OBDII truck would be preferred vs an older one. Do the older trucks have any issues that are unique to them, or to their age, and is there a point where a truck should be avoided because of how old it is vs assessing it based on condition? I know all GMT400s are getting up there in age. I've done a bit of searching the forum to gain some knowledge, and I do have a few questions.

On the older trucks, is the TH400/4l60e the same in the 1500 and the 3500? I know the 4080e is more desirable. Did 2500/3500s with the TH400 have any upgrades that the 1500 lacked, or were the early trucks really just a better chassis?
Are there any specific years to avoid? I have heard some people say to avoid 1996 I believe as it was the first year after a refresh, and that finding parts would be a little difficult since some of them are one-offs for that year only.
Would a good running 1988 truck have any additional specific issues vs a good running 1998 truck, or just issues that come with age, like gaskets, wear items, etc?

Thanks for reading. I've looked at a few trucks to buy but haven't taken any home yet. Finding the right balance between solid mechanically and solid cosmetically (plus body and frame) has been a little challenging. I'd love to hear what you guys have to say with some first hand experience!

 

[Jeepwalker]

Can I ask what your goals are for such a pickup? Are you looking for a 2nd pickup ...a 'project' truck that's in cherry condition because you love the style, are you looking to build, 'lift' a truck, do the tires, make a mudder or off-roader, etc? Or is this a first pickup you've ever owned and you just don't want to spend what the newer trucks are going for these days? DD? Are you looking ofr a regular cab, Ex Cab, 4dr?

What do you plan to do with the truck? How do you plan to use it? What is your mechanical skill level? Those answers might help us give you better advice.

But in general terms: the later year GMT400s (and the fewer miles), the more subtle refinement it will have over the early trucks. More power, more safety. But I have an 89 and it's been rock solid and I love it. But if I were personally getting into one today, I myself would start my search for a 98-97. OBDII is universal, more sophisticated, more supported by like phone-app software. Some will say avoid the 95's as they had unique wiring for the last OBD1 year. But if you never have a wiring or computer issue it's a moot point. Those are just general comments. There's nothing wrong with the early trucks. Lot simpler electronics. You just gotta spend a little time to understand the OBD-1 which is pretty easy. You only have 2 injectors vs 8. They don't give a lot of trouble.

 

[stutaeng]

Where are you located? Is rust an issue there? If not, you can't go wrong with with either. The drivetrain can always be overhauled, so long as it's not all rusted-thru.

The earlier ones have a but less power, but they have less electronics to worry about. Conversely, the later ones have a bit more power, but there are some things that seem to be common.

You need to focus to the 8 lug trucks it seems like. 88-90 8 lug are going to have the legendary TH400, and 91+ will have the 4L80e until production end.

I say 8 lug, because they made "2500" light duty (LD), which are closer to 1500 than 2500. Those were all 6 lug, is a way to tell. It's really confusing, I know. That's why I say stick to 8 lug.

Yes, 8 lug trucks are long bed, heavier, slower, get worse MPG, so they are better for doing work, towing, hauling. OTOH, they are more capable, rugged and durable. Conversely, at least in the city here, everyone and their buddy want to drive a RCSB or ECSB 1500 so the prices are actually higher than anything that I mentioned earlier. Which is you?

What are you using the truck for?

BTW, the TH400 is not the same as the 700R4/4L60/4L60e(5 or 6 lug). The 4L80e is based on the TH400, both 8 lug.

 

[HotrodZ06]

Alot depends on what deal you can find and the budget you have. stutaeng covered everything pretty well. Just be wary of really good deals. My 98 k2500 I paid $800 for is about to top $10k without counting labor. It pays to really check out prospective purchases before buying, the seller may be leaving something out or may not be aware of costly problems regardless of which year you are looking at.

 

[mnewxcv]

Good questions, I should clarify. This would be a second vehicle, not a daily driver.

I am looking for a 'work truck' to load up to and from the dump, do yard cleanup, carry lumber and supplies when I have projects. Somewhat regularly moving furniture or larger items (hence 8ft bed). Occasionally carrying a ton of something on a pallet. I'd like the ability to rent a trailer and tow with the truck, which is doable with any truck, but if I were to tow another vehicle I think a 2500/3500 would be a bit better for it. Nothing too crazy.

Not looking to modify it/lift it, but would consider putting a taller tire on it when it came time for new rubber. I would leave it mostly factory but would clean it up to make it look decent and take care of it mechanically and cosmetically.

I also want 4x4 so it can be a vehicle to drive in snowy weather (G80 preferred), which brings me to my location: New England, so yes, rust is an issue here. Another reason I look at the 2500/3500 is they seem to hold up a bit better in terms of frame rot, assuming they weren't plow rigs.

I'd prefer a regular cab long bed, but an extended cab in the right condition is fine too. Not looking for a crew cab long bed due to navigating it in cities with the long wheelbase. I also prefer the look of the cheyenne/work truck and am fine having a truck without power windows and locks, especially if that means one less thing to fail.

Thanks for pointing out the TH400 is not the predecessor to the 4L60, I must have misread that in my searches, and that eases my mind a little. Also in terms of engines, 5.7 seems like the best of all, but I'd take a 7.4 if the truck was otherwise clean. I'm pretty comfortable working on my own vehicles, but I am very aware of how age and corrosion can do turn routine service into a project when fasteners lose their shape or crumble. Hope to hear some more voices in here, it's all very helpful. I've looked at 4 trucks to this point but all had some flaw that kept me from taking it home.

 

[Canadian Rust Bucket]

Alot depends on what deal you can find and the budget you have. stutaeng covered everything pretty well. Just be wary of really good deals. My 98 k2500 I paid $800 for is about to top $10k without counting labor. It pays to really check out prospective purchases before buying, the seller may be leaving something out or may not be aware of costly problems regardless of which year you are looking at.

That's what happened to me. I bought my '95 with "just a leak in the gas tank" for $500, and now I'm into it for about $8k. There were so many issues lurking underneath.

Your use case is pretty similar to mine, but I went lighter duty with a 1500. I like the older years because they tend to be simpler. Less things to break, less things to fix. That's my two cents, anyway

 

[Erik the Awful]

The TBI systems don't have a lot of overhead for performance upgrades unless you plan on some mods. The Vortec injection can handle nearly 400 hp with a tune.
You can swap the engine in a TBI truck in a few hours. A Vortec truck takes twice as long.
'88-92 trucks have 700R4/4L60s with mechanical controls. '93-97 trucks have 4L60Es with electronic controls.
'88-95 has the boxy dash. '96-97 has the swoopy dash. I might be a year off on that.
Earlier trucks are five-lug. Later trucks are six lug. The eight lugs all have the same size pattern.
Earlier trucks can be stolen with a screwdriver. Later trucks have more built-in security.
Earlier trucks may have a 305 - and you'll have to decode the VIN or glovebox codes to avoid it.

 

[stutaeng]

Good questions, I should clarify. This would be a second vehicle, not a daily driver.

I am looking for a 'work truck' to load up to and from the dump, do yard cleanup, carry lumber and supplies when I have projects. Somewhat regularly moving furniture or larger items (hence 8ft bed). Occasionally carrying a ton of something on a pallet. I'd like the ability to rent a trailer and tow with the truck, which is doable with any truck, but if I were to tow another vehicle I think a 2500/3500 would be a bit better for it. Nothing too crazy.

Not looking to modify it/lift it, but would consider putting a taller tire on it when it came time for new rubber. I would leave it mostly factory but would clean it up to make it look decent and take care of it mechanically and cosmetically.

I also want 4x4 so it can be a vehicle to drive in snowy weather (G80 preferred), which brings me to my location: New England, so yes, rust is an issue here. Another reason I look at the 2500/3500 is they seem to hold up a bit better in terms of frame rot, assuming they weren't plow rigs.

I'd prefer a regular cab long bed, but an extended cab in the right condition is fine too. Not looking for a crew cab long bed due to navigating it in cities with the long wheelbase. I also prefer the look of the cheyenne/work truck and am fine having a truck without power windows and locks, especially if that means one less thing to fail.

Thanks for pointing out the TH400 is not the predecessor to the 4L60, I must have misread that in my searches, and that eases my mind a little. Also in terms of engines, 5.7 seems like the best of all, but I'd take a 7.4 if the truck was otherwise clean. I'm pretty comfortable working on my own vehicles, but I am very aware of how age and corrosion can do turn routine service into a project when fasteners lose their shape or crumble. Hope to hear some more voices in here, it's all very helpful. I've looked at 4 trucks to this point but all had some flaw that kept me from taking it home.

That sounds like my truck use. I had (and still have a 99 2wd GMT 800) but needed the higher payload of a 2500/3500 and a long bed for doing home projects. Hauling lumber, a yard of sand, landfill hauling and stuff like that.

I looked at the square body's and they were ridiculous on price. GMT 800 HD's were still pretty high then. I found a rough GMT K3500 CCLB SRW with the 5.7 and it has served me well.

You'll like the 2500/3500, stick with 8 lug! The payload is great. The prices have gone up, but you can still find them in the country for good prices. Have you considered looking for a southern truck? Even if you fly to a southern state and have to drive it back home; the frames down here only have light surface rust, if any rust at all. Body panels don't really rust at all. I think $4000 to $5000 will get you a nice, rust-free truck with patience down here.

Besides that, your typical rubber hoses, tires and seals will likely require work by now.

 

[L31MaxExpress]

The TBI systems don't have a lot of overhead for performance upgrades unless you plan on some mods. The Vortec injection can handle nearly 400 hp with a tune.
You can swap the engine in a TBI truck in a few hours. A Vortec truck takes twice as long.
'88-92 trucks have 700R4/4L60s with mechanical controls. '93-97 trucks have 4L60Es with electronic controls.
'88-95 has the boxy dash. '96-97 has the swoopy dash. I might be a year off on that.
Earlier trucks are five-lug. Later trucks are six lug. The eight lugs all have the same size pattern.
Earlier trucks can be stolen with a screwdriver. Later trucks have more built-in security.
Earlier trucks may have a 305 - and you'll have to decode the VIN or glovebox codes to avoid it.

For the most part, good info.

That being said, I can swap a TBI or Vortec in the same amount of time. Vortec may actually be a little quicker because the accessory setup is so much easier to deal with than the early year stuff.

I did my first swap on my Vortec Express van in a weekend. Had the old engine out, all the externals swapped to the new engine, and the new engine back in during the first 6 hour day. The next day I had a few things to fix or clean up, get it timed, hook everything up and rebuild the ac. It ran the 2nd day. The 383 took much longer to swap, I had a harness to clean, repair and reloom, alot of engine compartment cleanup to work on, a suspension rebuild while I had the engine out of the way and more.

My brother and I replaced the shortblock in his 99 Suburban in a single day. Pulled the old engine starting about 8 AM, had it out by 9:00 AM. Took the old engine back to his garage, yanked the heads and intake, cleaned and transfered them to a spare short block that was in his garage, threw a LT1 cam in it. Adjusted the valves and resealed it. It is now Noon. Grabbed a bite to eat. We run to the nearby Dayco dealer and grab a S10 converter. Get back to the shop at 2 pm. Get the engine back in and we are hooking it up. Its now 4:00 PM, we realize the flex plate is backwards. Well out comes the 4L60E. 5:30 PM, flexplate swapped around and 60E back in. At 6:30 its all hooked up, oil and coolant in it. It fires then dies. Passkey relearn. We evacuate and charge the ac while waiting for the relearn. At 7:00 it is running and check all for leaks. Power steering pressure hose is leaking. My brother runs across the street to Autozone and snags a replacement. Its now 8:00 pm and we have $1,500 total and a days work into a very clean 1999 LS Suburban.

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I miss that Suburban. It drove and rode extremely well and had alot of get up and go for a heavy suburban.

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ALL years had the 305 as an option, all the way up to 99. GM built these in the light duty through 99 and as 1 tons until 2000.

95 has the same dash as a 96+, just no passenger airbag prior to 97.

All years have 5 lugs, 6 lugs or 8 lugs depending on the options and build. Not an early or late thing. 2wd 1500 is 5 lug, 4x4 1500 or LD 2500 is 6 lug and then 2500-3500 is 8-lug.

 

[User_name]

Everyone has pretty much covered everything imo. Just don't expect these trucks to be perfect. You will have to sink money into them.
Just remember that these trucks are getting long in the tooth.
I personally love the tbi engines if we're staying stock. (88-95)