K2500 Cab Swap To Increase GVWR

[JayY]

Hey guys,

Current truck is a 1997 K2500 RCLB 5.7 4L80E with 9.5 SF 14B 3:73's. Truck has suited my needs well as an around the house hauler, and I've invested a lot into the truck as it sits, so I doubt I'd be able to sell it and recoup half of what I have in it. My needs have since changed and need a little more truck. Ideally, I'd love to find the truck I passed up 6 months ago, but it's long gone, 8.1 ZF6 4:10 gears. I have an 8,000 lb tractor that I don't HAVE to move right now, but within the next 5 years, plan on needing to move it back and forth between some side jobs and eventually a small hobby farm (30-40 acres)


ANYWAY, this is where it gets interesting. Since the truck has been painted, relatively new interior pieces other than dash and door panels, A/C fixed, etc, I feel like I could swap in an 8.1 and a full floater and have what I'm after to handle the 12-15k total weight behind the truck. Whether the 4L80E would hold up is another story, nothing that an NV4500 swap couldn't fix. Where I'm having trouble is the limited tow rating attached to my current VIN number. Legally, I can't have over a 6,000 lb trailer as the truck sits, and that doesn't change when I throw parts at it. I had a thought of swapping a 3500HD cab to up the door sticker rating should I be pulled over. Of course the truck would be titled as a 3500HD but stay with my frame now to keep it an SRW truck for off road purposes. Any opinions, thoughts, comments? Completely stupid idea? I figure all in, I can be in a 8.1, axle swapped truck for under $15k if I keep my 4L80E, with mostly new parts. That's less than half the price of any new truck on the market, so I'm just trying to make good sense of it all. Thanks in advance!

 

[stutaeng]

Where are you located? What are the law's regarding something like this? Some places don't really care, you can register as you wish, or so I have heard.

I would not do the cab swap, that just seems shady. Those 3500HDs were like Class 4 trucks with BEFFY frames. BEEFY brakes too!
Even then, I think 12,500 or 13,500 lbs was the towing limit.

Even on the C/K3500s, I seem to remember they didn't go beyond 12,500lbs with 5th wheel towing. Bumper hitch was limited to 10,000 lbs. That's the highest they got... can't seem to find the Owner's Manual for my k3500, but lists 2500 also, as well as 3500HDs.

I would say look at the towing rating in your cab and configuration and use the 7.4 engine towing numbers. Regear to 4.56 if you need to. That's a conservative approach, but I don't you'll get to the 12.5k number.

The other difference is the 2500 Big block and higher trucks is they got hydroboost brakes. You should be able to converter easily.

Practically speaking, I would imagine you can get an GMT 800 with the 8.1 for less than $15k. I think even the 3500s with 6.0 were up there in those towing numbers, depending on gear ratio?

 

[JayY]

Where are you located? What are the law's regarding something like this? Some places don't really care, you can register as you wish, or so I have heard.

I would not do the cab swap, that just seems shady. Those 3500HDs were like Class 4 trucks with BEFFY frames. BEEFY brakes too!
Even then, I think 12,500 or 13,500 lbs was the towing limit.

Even on the C/K3500s, I seem to remember they didn't go beyond 12,500lbs with 5th wheel towing. Bumper hitch was limited to 10,000 lbs. That's the highest they got... can't seem to find the Owner's Manual for my k3500, but lists 2500 also, as well as 3500HDs.

I would say look at the towing rating in your cab and configuration and use the 7.4 engine towing numbers. Regear to 4.56 if you need to. That's a conservative approach, but I don't you'll get to the 12.5k number.

The other difference is the 2500 Big block and higher trucks is they got hydroboost brakes. You should be able to converter easily.

Practically speaking, I would imagine you can get an GMT 800 with the 8.1 for less than $15k. I think even the 3500s with 6.0 were up there in those towing numbers, depending on gear ratio?

I’m in central NC. Unfortunately the door sticker still doesn’t change and I guess that’s the biggest obstacle I run into. I know the truck will handle it and stop it if I upgrade to hydro boost, which I would do if I did the 8.1 swap. I’m the kind that’s usually overly cautious when towing, and this wouldn’t be an every day load. Maybe 2-3 times a month tops. The reasoning behind the 8.1 swap was to keep from losing my ass selling this one, which I know will be inevitable at this point. And, I do kind of have an emotional attachment to the GMT400 body styles, dad had one growing up and I learned to drive in his 96. So in a way, I hate to part with the truck since I’ve done so much to it, just wish it had a little more grunt, but just trying to stay legal while doing it!

 

[Supercharged111]

Why bother with the cab? Just nab the door and the ID tag from the donor cab if you want to pull a fast one.

 

[stutaeng]

I was suggesting that buy another truck, LOL.

Keep yours!

 

[JayY]

Why bother with the cab? Just nab the door and the ID tag from the donor cab if you want to pull a fast one.

I was way overthinking about them matching the VIN

 

[stutaeng]

Is your trailer a bumper pull or 5th wheel? I was looking at the 2004 Towing Guide (as an example only) and everything pumper pull 2500HD/3500 seems to stop at 12,500 lbs or so. You have to get into 5th wheel and only the 8.1/6.6TD gets you to the 15k range. Since the GMT900 is deeper (and therefore more rigid) than a GMT400, I don't think it would be a good idea to tow that amount with your truck, even with the 8.1 swap.

Maybe a C/K3500 frame may do it, as the newer 2500HD and the older C/K3500 had roughly the same GVWR from the factory. I seem to recall the C/K2500 had a slightly thinner frame than the C/K3500? Only you can make that judgement if you want to go that route.

Good luck.

 

[Supercharged111]

JaYy how thick is your frame? It's either going to be 1/4" or 3/16" thick. Being an 8 lug I'm inclined to thinking it'll be 1/4". I wouldn't be opposed to putting 12k behind that, but in stock form I don't think it's going to do all that hot. Probably gonna need bags or at least 3500 leaves with the upper overloads, more power, and hydroboost brakes. 9.5" rear end I believe is still good for 6000# in 8 lug configuration.

 

[JayY]

Is your trailer a bumper pull or 5th wheel? I was looking at the 2004 Towing Guide (as an example only) and everything pumper pull 2500HD/3500 seems to stop at 12,500 lbs or so. You have to get into 5th wheel and only the 8.1/6.6TD gets you to the 15k range. Since the GMT900 is deeper (and therefore more rigid) than a GMT400, I don't think it would be a good idea to tow that amount with your truck, even with the 8.1 swap.

Maybe a C/K3500 frame may do it, as the newer 2500HD and the older C/K3500 had roughly the same GVWR from the factory. I seem to recall the C/K2500 had a slightly thinner frame than the C/K3500? Only you can make that judgement if you want to go that route.

Good luck.

Yes I understand all that, I’m just trying to get as close as possible. The truck frame will handle it fine, I’ve watched these trucks take way worse abuse than this for years. Just trying to avoid the legal battle. Thanks

 

[JayY]

JaYy how thick is your frame? It's either going to be 1/4" or 3/16" thick. Being an 8 lug I'm inclined to thinking it'll be 1/4". I wouldn't be opposed to putting 12k behind that, but in stock form I don't think it's going to do all that hot. Probably gonna need bags or at least 3500 leaves with the upper overloads, more power, and hydroboost brakes. 9.5" rear end I believe is still good for 6000# in 8 lug configuration.

Yes I understand this, just looking to see if anybody has gotten around the legality of the low rating these trucks came with. I know what I need to do to get it to physically handle the weight, just looking to see if I can swap GVW stickers from a larger truck to stay legal. Just wanted to see if anyone done it before and what everyone thought on the cab swap.