Big 'Ol Red

August 2020 Feature Clyde Turner

This article originally appeared in the October 2019 issue.

Take a look at this square body Chevy, because it’s quite an impressive comeback build that’ll really make you want to build your own similar project. Owned by Jose Morales, this old truck spent its time getting restored by Joshua Gruis at Jag’s Pro Truck Shop in Zimmerman, Minn. It’s a red 1983 Silverado that’s been completely rejuvenated with a couple of mods and tunes. In some ways, it might feel more like a 2005 (or newer). That’s because it obtained many of its new parts from a 2005 Silverado (the biggest components are the engine and transmission). However, Jose didn’t want a full “new truck” feel. He still wanted to keep 'Ol Red feeling like a stock 1983 square body in some areas, especially on the interior. In getting a closer look at this truck and everything done to it, we decided to interview the shop owner Josh who created it. Of course, this six-month project didn’t come easy; specifically, there were lessons to learn about making newer systems and components fit in an older truck.


Jose works for a local materials company in the greater Minneapolis area and puts his truck to heavy use. “It’s a very fun summer toy for him,” Josh says. With the suspension, tires, and wheels on this beast, it sure looks like one. The truck actually already had those mods on it along with the rest of those nice, clean ‘Ol Red looks on the outside when Jose brought it into Jag’s. Unfortunately, the truck was not doing so well on the inside. The truck’s original 6.2L diesel engine was very beat up and running on its last legs as it was literally spewing coolant everywhere.

“Its original 6.2L diesel was really hurting,” Josh says. “Jose wanted that engine fixed up, but we advised him that it would be expensive and that he’d be better off if he just did a swap.”

Eventually a major swap is just what they did. Jose didn’t want to go with that at first, as he complained that the truck would not feel like an ’83 model anymore. That’s understandable, as the engine and transmission are integral parts of the truck for obvious power-, personality-, and life-related reasons. However, after some serious thought and pondering on this matter, he gave in to Josh’s suggestions and felt a swap was the right way to go and fixing up an old engine would not be worth it considering the amount of work that needed to be done along with long-term costs (it’s an old engine with not much life left in it). Josh found a 2005 Silverado donor truck and they were in business and ready to go.

Meticulous Machining

Because it’s a swap, perhaps the most impressive aspect about this square body is how the new engine and transmission are able to work with the rest of the old powertrain. The 2005 truck had its LLY Duramax and the Allison 1000 transmission donated for the project. It took a lot of custom fabrication and machining of parts to get the new transmission to fit into the old transfer case.

“We had a custom output shaft built for the Allison to accept the NP208 right hand drop stock transfer case from the ‘83 Chevy,” says Josh. “We also had to have a clocking ring made to get the case to set at the right degree so the front drive shaft would clear to the Allison.”

Of course, it always helps to be able to rotate the transfer case for the happiest medium between belly clearance and front driveshaft angle. Eventually, Josh even needed to salvage the 42-tooth gear from the donor truck’s transfer case in order for it to work with the newer engine and transmission. He had it machined and pressed to fit on the NP208’s input shaft.

In order to make this swap work, Josh obtained many replacement parts from Precision Fabrication Plus, Inc., including cross members, a shifter cable and supports, and a throttle pedal support. The pre-existing mounts wouldn’t get the engine, A/C compressor and alternator all the way under the hood without a body lift. A body lift is a lot of work and drives up labor costs. It took Josh a lot of wiggling around of parts and components to try and get the hood to close safely with good clearance.

“I finally made it work,” he says. Josh and his shop also hand built a 4-inch exhaust, which was a bit of a trick to get around the transfer case with the right-hand drop drive shaft to navigate around. “It’s very tight to the t-case, frame, and body, but with the added supports, no vibrations occur,” the Jag’s owner adds.

Tuning & Restored Looks

The LLY Duramax was tuned with EFILive, giving the truck an extra jump in performance. The tune wasn’t big enough to require a transmission tune, and that worked for Jose; in attempt to preserve his truck as much as possible, he didn’t want ‘Ol Red’s transfer case or differentials changed out. Higher RPM from the transmission’s output shaft would definitely require that.

“I also made an adapter for the Allison tail housing to allow us to mount a speed sensor on it to read the gear for transmission output speed,” Josh says.

Of course, this was for safety precautions. A light tune was the best compromise between old looks and higher performance. To make the engine work well with this truck, Josh had the truck side of the wiring harness completed by Stand Alone Harness. “Ken Wolkens was extremely nice to work with and produced something that worked perfectly for our application,” Josh adds.

Jose wanted his square body to look as much like “new in 1983” as possible on the outside. Thus, Josh kept the dual factory fuel tanks in the truck, along with the lift pump and splitter valve. Impressively, with all this extensive reverse-engineering, the dual tank setup works well and almost like new. Josh also used the original dash and gauges, and they all work and function as desired.

Lessons Learned

Many of the lessons learned in this half-year project, both by Jose and Josh, were about doing the homework and really taking time with this swap. Of course, you can’t just throw any engine and transmission in a 1983 Silverado, especially because the older components generally can’t handle the higher power from the newer engines and transmissions without meticulous and serious amendment that often requires reorganization of your vehicle’s guts.

“Do your research,” says Josh. “You can’t do it all so fast.” That’s exactly right, because you’ll run into a lot of roadblocks in getting your hood to close, and Josh definitely ran into quite a few as he went through different approaches to get the hood to close.

You’ll have many moments where you’ll think you have the rebuild complete until it’s time to shut the hood, and then you have to back up and install everything over again. It’s frustrating! On a similar note, Josh learned another lesson about keeping the donor truck handy, even when you think you’re finished with it. Because it caught the attention of so many people who drove by and there were many good bids from people who wanted to buy it as a parts truck, he felt tempted to sell it. However, looking back, he’s glad he kept it around despite the space taken up and the bidder pressure.

Aside from important lessons learned, Josh picked up some serious inspiration from this project. “This truck drives amazing and after getting the chance to build this for Jose, I now want one for my own!” Josh says excitedly. From this, we know it’s clear that despite all the stress from trying different methods to reorganize the powertrain and other components on 'Ol Red, Josh lost absolutely no enthusiasm from doing a huge swap. Even though the truck is not exactly like it was when fresh out of the factory, it’s still incredible what came out of this restoration project.



Jag’s Pro Truck Shop

Precision Fabrication Plus, Inc.

Stand Alone Harness

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