2002-03 GMC/Chevy LB7 3500 Dually build

[Springer-]

Back story ... I went and looked at a HMMWV and bought it. The plan was to do a Duramax conversion. On the way home I stopped and looked at a 89K mile 2002 Chevy 3500 Cab Chassis flat bed dump that was used its whole life a commercial plow truck at a golf course. Wouldn't start, had a bunch of work done to the engine, new injectors, new inj pump etc. Bought it for $2300 and had it towed home. Back to the HMMWV, I thought it had a GM 6.2 in it but it had been rebuilt and had a much better GP 6.5 that ran great. Decided not to part out the 2002 so I decided to fix it to replace my 97 F350.

I started by removing the dump bed because it was rusted pretty bad. Turns out the frame was rusted pretty bad also. Having been a plow truck I literally found a pile of salt under the passenger side seat. The cab was shot too. If I was going to do anything with this truck I needed a new frame and cab so I started looking for a parts truck. I found a 2003 GMC 3500 LB7 Cab Chassis dump truck used for landscaping and had never been plowed with. Kept in a fleet garage its whole life, all 300K miles of it. The engine ran, had a few dents but the cab was good and the frame was nearly perfect. Bought it for $3200.

Parted out the 2003 GMC, sold everything but the Cab and Frame for $2500. I also had the idea that I wanted a regular 8' fleet side bed on this build. I figured I could build a bed out of 2 beds. The F350 it would replace was my general purpose truck, it had a plow, lift gate and towed my trailer, etc. For this to replace my F350 I wanted a plow, lift gate etc. Also wanted a fifth wheel hitch that could be removed quickly without leaving anything in the bed.

I started this build in October 2019 and completed the majority of it by July 2020. I say majority because is anything custom build ever really done? I'm still working on it and the current projects is where I will pick up in real time and post progress.

here's the Chevy after I removed the flat bed dump. I set the fleetside bed on to check fitment, wheel protrusion, wheelbase etc. The Cab Chassis is about 5-6" longer wheelbase.

in this picture you can see the gap between the bed and the cab. When it was lined up correctly with the rear wheels, the gap was about 6".

 

[Springer-]

Here is the GMC I started with. I didn't have any pictures with the dump body on it but this is the cab I kept.

I ended up keeping both of these doors as well and fixing them. Although they were dented there was little to no rust on them.

Ultimately this is the Frame I am going to use.

 

[Springer-]

The cab was a pretty easy fix, we did the rockers and the drivers floor. Everything else was pretty solid, not bad for 300K miles.

 

[Springer-]

After we stripped both trucks, we transferred all the of the 90K mile drivetrain from the 2002 to the GMC frame. Since the frame had 300K miles we decided to replace all the suspension parts up front. New upper control arms, the lowers were good, all the ball joints, axle shafts, tierods, Billstein 5100 shocks etc. While everything was still easy to get to, we could see the rails that connected all the glow plugs were rusted off. None of the glow plugs had power going to them. I was pretty sure this was the reason the previous owner couldn't get it to run. I replaced all the glow plugs and the rails. All but 1 glow plug broke off. Rigid make an extractor set that works flawlessly to remove these and WAY cheaper than the specialty tools. Search Rigid 35585

We also did all the brake lines in stainless and replaced all the fuel lines with stainless. Replaced the fuel cooler.

 

[Springer-]

After we pretty much had the drivetrain complete we mounted the newly painted cab. The frame was coated with a rust protection oil causing the frame to look like fresh wet black paint.

I kept the Chevy nose because I preferred the look over the GMC nose and the hood was in better condition. After we got the nose back on and started mounting all the parts on the firewall and fenders, like the fuse box and main wiring harness we found nothing matched!! The cab harness was completely different than the fuse box. After further investigation GM completely changed the wiring harness from 2002 to 2003. The engine, transmission, ECU, TCU etc. were all 2002 and the cab was 2003. This was an unexpected dilemma.

 

[Springer-]

To solve the wiring issue I had to gut the GMC cab and replace it with the Chevy cab wiring, dash, heater core, steering column and air bag wiring. I also found out GM updated the radio mount in 2003 with a redesigned dash to 2 Din radios. In 2002 they had a 1.5 Din non-standard size. So I pulled all the wiring out of the 2002 dash and put it in the 2003 dash to fit the 2 Din radio. This would later allow me to put in a modern infotainment system. Another unintended benefit to this was being able to keep the Chevy gauge cluster with the 89K miles that matched the engine. Turns out the gauge clusters are different wiring too.

 

[Springer-]

To mount the bed I had to first make my own mounts. Being a cab chassis the rear frame rails are closer together so nothing matched the bed. The bed itself had issue with the bed crossmembers. The tops were good but the bottoms had some rust issues. I cut them in half and removed the bottom inch or 2. Then found some 2 x 4 x .125 steel fit inside perfectly. So I reinforced the bed replacing all the crossmembers. The crossmembers I used for mounting to the frame I used 2 x 2 x .125 and then used the same on the frame to make the mating mount.

To maintain the structure made a loop to go around the fuel filler. You can also see the fifth wheel mounts I made. The piece of 6 x 6 angle on the back is the mount for the lift gate. Mounts are the 1st, 2nd and 6th crossmembers. The 3rd, 4th and 5th are only on the bed and rest on the frame.

I must have raised the truck up and down 100 times to measure and fit the bed.

The fifth wheel mount match the bed perfectly and allow the fifth wheel mount to be bolted down from the bed. takes maybe 10 minutes to install and when removed it leaves nothing behind. All said and done I bet the bed would hold 2 tons and not bat an eye.

 

[Springer-]

The timeline doesn't exactly match the pictures, some times you needed something complete before starting the next step. Then you could go back and do something else and complete the rest of it later. This is the case with the bed mounts and bed construction. I started by positioning just the front and rear mounts. The did all the work to the bed. Then came back an finished all the mounts. So in the previous pictures that is actually after the next step but that wouldn't make sense until the next step was finished. So basically this isn't in perfect order but it does represent the way it was built.

After I had the two end mounts made and the bed mounted I started working on moving the fender wells. As you can see wheels don't line up with the wheel wells.

My pictures sort of swap side to side as I go but the process was the same. So I started by cutting it out around the wheel area.

Then I cut out the other bed wheel well much larger than required, both inner and outer.

I also cut out the fuel filler door. The cab chassis had dual tanks but no beds were made with dual fillers.

 

[Springer-]

Then I started lining up the fender well and taping it in place. Then I traced the cutout on the inside of the fender to know where to cut.

I then added the fuel filler door to the panel and trimmed the fender more. Test fitted the fender flair to make sure it as all going to work together.

Then I trimmed it to overlap about 1/2" all the way around. The fender was a bit weak so we replaced the edge.

 

[Springer-]

With the outer fender fitted it was time to do the inner fender.

The common rust area was fixed on the inner fenders and then positioned and fitted with the outer fender.

Tack welded the inner fenders in to start then fully welded the inners. They actually make up a lot of the structure of the bed and I didn't want to lose that.

I used a picture from later on to show the finished inner fenders. This is from a time after we mounted the fifth wheel rails in the bed. those are what is easily removeable.

 

[Springer-]

Once the inner fenders were done It was time to finish the outers.

What the pictures don't show is the amount of work fitting the inner and outer together and then sealing it all. I coated the seams above where the inner and outer meet with high temp axle grease, handfuls of grease smeared everywhere. Later on I also sprayed the inside the body with WaxOil rust protection.

As you can see in this next picture we have fitted the lift gate while the bed was in primer.

Here's the finished paint and dual tanks filler. Overall it came out much better than I imagined. In case your wondering, this is the first time I've ever done any body work remotely close to this extent. As kid I bondo'd rust holes to get past inspection but nothing even close to this.

 

[Springer-]

Below the body line we painted it with "Rock-it" paint.

We lifted the bed, painted the frame and the bed crossmembers. I built the fuel fillers and vents also. Then we oiled the frame.

 

[Springer-]

Installed the fender flairs.

This picture shows the wheel/tire protrusion compared to fender flair. Nearly flush, I considered putting a rubber extension but decided against it. The dually wheels fit nicely with the 3" fender flair. Nothing rubs inside and uses stock inner fenders.

Rear shot. Note I kept the dump truck rear hitch plate. It's 1/2" thick steel and the lift gate mount is welded to it. The lift gate mount is 6 x 6 x 3/8" steel.

Being in the north east with winters and salt on the roads etc, I installed ABS inner fender wells. I believe they were made by Rough Country.

 

[Springer-]

The last step before mounting the lift gate was a spray in bed liner, in this case Line-X.

The "finished" product.

 

[BillEBoy]

Awesome work, sir. From experience I suggest the same treatment on your inner panels as you did the frame...WaxOil/Fluid Film inner rocker cavity, bed bottom, bed supports, inner bedside panels...anything you can reach. Not sure what gun you have but definitely worth investing in something with a 360 degree wand. Looking forward to following along

 

[Springer-]

Awesome work, sir. From experience I suggest the same treatment on your inner panels as you did the frame...WaxOil/Fluid Film inner rocker cavity, bed bottom, bed supports, inner bedside panels...anything you can reach. Not sure what gun you have but definitely worth investing in something with a 360 degree wand. Looking forward to following along

Thanks for the suggestion. We did all the body panels with Waxoil and my friends shop sprayed a different oil product very similar to Fluid Film called New Hampshire Oil Undercoating and we did the inside of the cab with that. We did inside all the bed crossmembers with NHOU and sprayed the underside of the bed with Waxoil. The truck was literally dripping with oil when we finished.

 

[Springer-]

Future upgrades include replacing the Dash wiring with a 2002 Tahoe harness that includes the wiring for electric windows, locks and mirrors. I also have the doors from the Tahoe with electric windows, locks and mirrors to install. My cab chassis doors are all manual. The biggest problem with the manual is not being about to control the passenger side. I never realized how handy that is until they were gone.

I couldn't find pictures of the Tonneau cover I put on but it was a tri-fold hard cover. To fit it with the lift gate I had to modify the top of the lift gate posts. I did find pictures of those. The cover would have been flat on top. I had to drip it down for the end to sit flush on the bed rails of the truck. This is after the modification. I had to modify the posts of the lift gate to match.

Here it is in place and you can see the tonneau cover on the right.

With the cover closed. I have LED lights mounted inside the cover that lights up the bed very well. I couldn't find those pictures either but someday, in the summer, I take new pictures to post.

 

[BustedCrank]

Bravo on the bed work.

 

[East_coastTJ]

great build, I really like those rear flares, not as wide as a dually bed but good coverage

 

[Springer-]

When I rebuilt the frontend on this truck the only thing I didn't do is the torsion bar bushings in the crossmember. It clunks and makes all kinds of noise every time I stop, accelerate, hit a bump, turn or anything. As annoying as this is I know the front wheels are not going to fall off. It handles well and has good shocks etc. It was always in the plans to replace the IFS with a solid axle. I purchased a WFO 3" lift solid axle conversion kit. Due to the scamdemic I couldn't get the required coilovers and had to put the kit on hold. I did however pick up a 2005 Ford F350 frontend. While waiting for the coilovers I rebuilt the frontend. it was pretty rusted so I pulled it all apart and sand blasted it and had it painted.

In the rebuild I kept all the stock axles but replaced the universals. I also rebuilt the pumpkin and installed a Eaton Truetrac differential. Since this is a street driven personal truck and not a 4 wheel off road truck, I didn't go all out on the frontend with bracing etc. Everything is new Spicer or Ford except the brakes rotors and pads, I went with PowerStop.

This is the current state of the frontend. Just replaced the steering link and outer tierods.

 

[Springer-]

great build, I really like those rear flares, not as wide as a dually bed but good coverage

The cab chassis rear end is almost 12" narrower than the regular dually rear end. The concept of the truck is to be completely custom but completely stock looking. If I want to talk to GM truck mechanics all I have to do is pull up at the service department and they all come out of the woodwork asking questions like what model is it, when was it made, etc. People have followed me into gas stations to ask about the truck.

 

[BillEBoy]

Thanks for the suggestion. We did all the body panels with Waxoil and my friends shop sprayed a different oil product very similar to Fluid Film called New Hampshire Oil Undercoating and we did the inside of the cab with that. We did inside all the bed crossmembers with NHOU and sprayed the underside of the bed with Waxoil. The truck was literally dripping with oil when we finished.

Right on. Well worth it to protect the investment, much harder pill to swallow seeing it corrode than the first dent lol. What are the ultimate goals for the truck?

 

[Springer-]

One of the difficulties with the frontend is the wheels. No one has an answer as to what to run or how match the fronts and rear. Stock is 16" x 6.5 with 8 x 6.5 bolt pattern. The Ford D60 front is 8 x 170 bolt pattern and in a dually configuration the adapter is 8 x 200 bolt pattern. My stock rear is 8 x 6.5 bolt pattern and I don't want to change that. The stock GM 16" wheels wont fit over the brake calipers. The only answer I get is to run regular 17" wheels on the front. This would affect the diameter of the tires compared to the rear and mean different rims so 2 spares. I didn't like that answer.

The only set of wheels I could find was 2008-2010 GM Dually was available in a steel 17" x 6.5 with 8 x 6.5 bolt. The offset is only 5mm different so the rear wheel set will only be about 1/2" wider, 1/4" in both direction. I bought one for testing purposes and used a 2x4 to space it out to make sure it would clear the calipers.

Once I was sure it would fit then came the issue of the wheel adapter for the dually. One of the options was to redrill the hub bearing to 8 x 6.5 but that still didn't solve the problem of a dually adapter that would fit over the hub center. So I designed my own adapter to space it out 3.5" and to be open in the center to clear the hub. I still have to make an adapter for the center now so I can move the selector out the end of the wheel adapter.

It's a hub centric wheel and I bored out the center so I can bolt the hub manual lock to it. You can see the hub in the center inside where the manual hub lock would go. I'm going to make a spacer to move it to the wheel adapter. Mock up in the next picture.

Here is where the manual hub lock will go when it's done. FYI, I am also keeping the vacuum hub lock and making my own controller so the manual lock is a backup system.

 

[Springer-]

I went with PowerStop brakes. They are basically rebuilt and powder coated calipers, drilled and slotted galvanized rotors and their brake pads. I've had good results on my car with their pads so I decided to use their complete kit. I swapped out the ABS brake sensors for GM right angle passive that my truck uses.

 

[Springer-]

I think that brings me up to date with the truck build. There's a few other little things that I will post when I get some pictures in nicer weather.

The next step is the manual locking hub adapters. I hope to make them this weekend or next week. I have to buy 5 more of the rims but I don't need them until I am mounting this front end. If all goes well I'll start that in the spring or early summer. I'm sourcing the vacuum parts now for the ESOF system but that isn't a requirement to install the front end.

 

[Springer-]

What are the ultimate goals for the truck?

It's just my around the house personal truck. Go to the dump, plow my drive way, move stuff, tow my trailer. It's replacing a 97 F350 that I had for 13 years. I loved my F350 but this is 3 times the truck and just better in every aspect. I bought the truck for $5200 with a new engine in it and put the lift gate on for $600. Drove it for 13 years and about 25K miles, tires were brand new when I bought it and still on it when I sold it. Did minimal work on it and sold it for $4000 when I got the GMC 3500 built. Since completing the GMC in July of 2020 I've put on 11K miles. The F350 best mileage was about 9 mpg. The GMC LB7 is close to 15 mpg.

 

[arse_sidewards]

I bought a lift gate for $50 once.

It was $50 because the entire bed it was attached to rusted out and took the attachment points for the liftgate with it because they bedlined it and whatever usage neccessitate the lift gate inevitably tore up the bed-liner and rust got all behind it. This matches all my other experience with the stuff. I'm sure it's fine for a 1/2-ton that just sees furniture, mulch and beer coolers.

 

[Steve300xcw]

I'm sure it's fine for a 1/2-ton that just sees furniture, mulch and beer coolers.

AND he's back

 

[Springer-]

Today I was test fitting parts on the front end that need to be sent out for powder coating. I'm using the WFO 3" SAS kit. It includes all the hardware but I don't trust Nylock nuts. If it isn't a pinched lock nut I'm not using it.

I checked the "Tracinator" fitment. It's probably overkill for my application but it should be bulletproof for me. When compared to any quality product and even stock it was only $100 more than the next closest and I still like the design of this more. Even some of the cheap ones were only 2-300 less and still relied on a factory style ball joint. When I took my front end apart this was the most worn out ball joint and I went looking for an "upgrade". At $650 it's not cheap but it is well made and will out likely outlast me.

 

[Springer-]

I was also working on the manual hub spacers, or at least the design. I think I have it, now I have to make them. I use a proprietary system called "NAD" ... "Napkin Aided Design".