GMT400 frame styles

[Horns]

Now I can not say I have any solid proof of this myself, but I do remember Draggin saying that the RCSB 1500's actually have a 1/16th thinner frame than all of the other 1500's.

Like I said, I have no personal knowledge to back that up, but if anyone knows frames, Draggin does.

 

[great white]

this all makes my head hurt... why cant they just make a 1500, 2500 and 3500... people who want a pickup for a grocerie getting, use the 1500... the 1500 will still haul! Just give the options motor/gearing/tranny... and then those who want something bigger buy the 2500 or 3500... i mean it sounds so simple, its not going to make any more sales! If the guy in the market for a truck, its the 1500HD vs the 2500 that's gonna make or break the deal! i think... ? sorry guys...

If it makes your head hurt then stop thinking about it....it is the way it is.

2500/3500's are targeted towards the working market and they generally know what weight rating they need. GM mixed and matched parts to give them options on balancing weight ratings with initial purchase price. It's about the bottom of the balance sheet in the working market. That's why most work trucks of this era tend to be rather "base optioned".

The 1500's are for the average joe blow who's looking to drive to work and haul some mulch on the weekend so they're all pretty much the same.

 

[MYT HI]

So between the 1500s and the 2500s is the frame taller? I know it is on a gmt800, that's part of the reason they sit so high


Sent from my 350 TBI powered iPhone

 

[DieselDetroit]

I'm loving this thread. Thanks for all the input fellas

I just went outside to look at my truck

1995 3/4 ton 4x4
6 lug rims
14 bolt rear end (now I'm confused)
GVRW 7200lb
396 diesel Detroit
4l80e

No mention of towing capability. Is that a function of GVRW ? Axle ratio? It's 3.73:1

 

[great white]

I'm loving this thread. Thanks for all the input fellas

I just went outside to look at my truck

1995 3/4 ton 4x4
6 lug rims
14 bolt rear end (now I'm confused)
GVRW 7200lb
396 diesel Detroit
4l80e

No mention of towing capability. Is that a function of GVRW ? Axle ratio? It's 3.73:1

1995 dealers package:

You must be registered for see images attach

1995 owners manual:

Odd, the online manuals don't have the chart for gearing/engine to trailer towing weight but my paper manual for my 98 does. My 98 is a K2500 8600 GVWR L65 TD with 4:10 final gearing and is rated for 8500 trailer weight in my manual.

Higher gearing, less GVWR and an L56 engine will drop that rating lower...

 

[DieselDetroit]

So 7000lb but it doesn't say if it's an l56/l65 or whether or not it's the light duty or heavier duty k2500

I'm guessing I'm going to be much less, probably 5-6000lb


Sent from my iPad using Tapatalk

 

[great white]

So 7000lb but it doesn't say if it's an l56/l65 or whether or not it's the light duty or heavier duty k2500

I'm guessing I'm going to be much less, probably 5-6000lb


Sent from my iPad using Tapatalk

Lets look at the 94 brochure since it's a little clearer:

You must be registered for see images attach

The yellow is the "light" 2500 as you can see by the 7200 GVWR. These could have been l56 or L65 although the GM documentation says all 8500 GVWR and under trucks only received the L56. We all know there are L65 engines running around in those trucks so that's not exactly correct. All 1500's were the L56.

Now, that's the MAXIMUM tow rating. Meaning: 4.10 gearing. It drops are you go to taller gears (IE: 3.73, 3.42, etc)

The red is the "heavy" 2500 as witnessed by the 8600 GVWR. All 8600 trucks had the L65. Again, maximum tow rating (ie: 4.10). The rating drops as the gearing gets taller.

The owners manual that came with your truck lays it out a little bit better than the dealers packages. The dealer packs are a little jumbled and sometimes wrong as they are usually printed before the model year is releases since the dealer uses them for ordering.

For example: my 98 K2500 TD 8600 GVWR (4.10) is rated for an 8500lb trailer but also for a CGVWR between 15,000-16,000 lbs. My truck weighs about 6700-7000 ready to roll so you you would think I have room for a 9000-9300 lb trailer. Except I'm only rated for 8500.

Confusing, eh?

The numbers in these years are kind of a mess. They really weren't that interested in testing their combos (costs $$$) so they sort of threw numbers out based on some calculations and dead reckoning.

It wasn't until later when the "towing wars" fired up that OEM's got really specific about weights. Mainly so they could brag one could tow more than the other.

Now that they've gone right off the deep end with towing weights, so SAE came out with the J2807 standard for tow ratings. Now OEM's can't toss out a big number without proving it: http://www.caranddriver.com/feature...-sae-trailering-standards-explained-tech-dept

As to your 6 lug 14 bolt: thats a semi floating axle. A full floating axle also has a 14 bolt cover.

What you have is a 9.5" ring gear:

You must be registered for see images

its a fine axle, but not as heavy as the 10.5" that would be in an 8600 GVWR truck:

You must be registered for see images

Guys call them "14 bolts" because it's easy to look under the truck and count the bolts. It's a "slang" term, just like "OBS" or similar abbreviations. GM identifies them by the ring gear size.

If you look back up to the chart, you can see the difference in the GAWR between the 9.5 and the 10.5 axles. About 1200 lbs difference. That's another 1/2 ton and a bit over the 9.5 rating.....that's pretty significant.

 

[someotherguy]

The LD/HD nomenclature isn't 100% B.S. If you look at an 8600 GVWR 2500's window sticker, it says "heavy duty" - that's what differentiates it in name from a 7200 GVWR 2500, and since they are very different trucks with the 8600 being considered a "regular" 2500 - you have to find something to call the other one. It's true the GMT400 lineup didn't have any "heavy half" though many people refer to the 1500 w/F44 heavy duty suspension as such; it does come with the 9.5" 14 bolt SF and an extra leaf in the rear spring pack, while the 7200 GVWR 2500 has the same 9.5" 14 bolt SF, the overload leaf in the spring pack is yet a little thicker and a little longer. Having fun keeping it all straight yet? Anyway since the 7200 GVWR 2500 shouldn't just simply be referred to as a "2500" because that's misleading, gotta call it something, so 2500LD only makes sense. Because yes, other than the heavier rear axle, rear spring pack, 6 lug bolt pattern, and a few small gussets on the frame brackets - it's a 1500 with some upgrades.

I've had examples of all of these (and more) at my disposal at one time to compare. I did also try to do frame thickness variations but without any precision measuring tools it was inconclusive. Simply throwing a cheap set of calipers on surface rusted frame rails didn't seem accurate at all.

Richard

 

[great white]

The LD/HD nomenclature isn't 100% B.S. If you look at an 8600 GVWR 2500's window sticker, it says "heavy duty" - that's what differentiates it in name from a 7200 GVWR 2500, and since they are very different trucks with the 8600 being considered a "regular" 2500 - you have to find something to call the other one. It's true the GMT400 lineup didn't have any "heavy half" though many people refer to the 1500 w/F44 heavy duty suspension as such; it does come with the 9.5" 14 bolt SF and an extra leaf in the rear spring pack, while the 7200 GVWR 2500 has the same 9.5" 14 bolt SF, the overload leaf in the spring pack is yet a little thicker and a little longer. Having fun keeping it all straight yet? Anyway since the 7200 GVWR 2500 shouldn't just simply be referred to as a "2500" because that's misleading, gotta call it something, so 2500LD only makes sense. Because yes, other than the heavier rear axle, rear spring pack, 6 lug bolt pattern, and a few small gussets on the frame brackets - it's a 1500 with some upgrades.

I've had examples of all of these (and more) at my disposal at one time to compare. I did also try to do frame thickness variations but without any precision measuring tools it was inconclusive. Simply throwing a cheap set of calipers on surface rusted frame rails didn't seem accurate at all.



Richard

Largely semantics IMHO.

Although GM does throw the "HD" moniker in sporadic places. You can even see it in the chart I posted above. It never was "hard and fast" like the 3500HD was though.

GM was a little "skitzoid" with names/addons back then. Wouldn't surprise me at all to find "LD" listed somewhere also.

Agree on measuring rusty frames. Largely pointless. The only documented difference I've ever seen is a different frame modulus between 1500 and 2500/3500. Even the steel is rated at the same strength. But the combination of steel and modulus is what determines frame "strength".

 

[83GMCK2500]

So between the 1500s and the 2500s is the frame taller? I know it is on a gmt800, that's part of the reason they sit so high


Sent from my 350 TBI powered iPhone

I didn't see this question answered. The reason that the body is higher on the -800 chassis is because there is a body lift incorporated into the design/construction of the frame. Translation, they welded/rivetted the mounts higher on the frame, or used taller mounts. RPO: HVY = Identification, 2 inch body raise, H.D. model