The Chevrolet Kodiak and GMC TopKick are a line of commercial trucks from General Motors, designed to take on jobs bigger than their pickup trucks can handle. The pickup trucks are sold in ½ ton (1500), ¾ ton (2500) and 1-ton (3500) payload and GVWR specs. The TopKick and Kodiak are a step above them, with 4500 and 5500 medium-duty trucks (think of box trucks, utility trucks or small buses) and go up to 6500, 7500 and 8500 light semis – these would either be used as heavy duty tow & delivery trucks, or light-duty semi trucks for local routes (a half-size smaller than something like a Freightliner Cascadia or Kenworth/Peterbilt long-haul truck).

The TopKick and Kodiak are instantly recognizable as GM trucks, sharing the same design language as the pickups they sell a million of every year. The first two generations use pickup truck cabs, while the 3^rd generation is a more unique design that still uses door stampings from the Chevy Express and GMC Savana vans. The 3^rd generation was also the first one to offer a pickup truck version of the 4500 and 5500, using a bed from the Silverado & Sierra 3500 dually.

GM manufactured these trucks for nearly 30 years, but discontinued production after all that 2008 business tightened the coffers and made them shift their focus to their core product lines. They did briefly make a Chevy Silverado and GMC Sierra 4500 and 5500 in the early-mid 2010s that competed with the Ford Super Duty and Ram 4500/5500 cab & chassis trucks, but these days partner with International Navistar to make a more traditional medium-duty truck, once again using a Silverado’s cab and headlights. The new Chevrolet Silverado 4500HD, 5500HD and 6500HD also uses a detuned version of the famous 6.6L Duramax Diesel, RPO code L5D (versus L5P for the pickups).

Every generation of the Kodiak and TopKick has offered a range of “big-block” gas V8s at the bottom end, and a Caterpillar diesel engine at the top end. If your truck has a CAT diesel, we would need an OEM part number off your original turbo in order to find an accurate match. Your original turbocharger should have a number plate on the intake side, and we can look up any of those numbers. If you cannot locate a part number on the turbo itself, you can also enter your engine serial number (ESN) on CAT’s website to get a part number directly from them.

The third (and final) generation of TopKick and Kodiak had the greatest engine variety yet. Base trucks had a Vortec 8.1L, the final iteration of Chevy’s “Big Block” line of gasoline V8s, and the top-of-the-line option was a Caterpillar C7 7.2L diesel. In the middle of the two were a variety of GM’s own Duramax Diesel engines, co-developed with Isuzu. 4500 and 5500 trucks used the same 6.6L V8 as the 2500 and 3500 pickup trucks – check our blog post about the 6.6L Duramax so you can look up the 8^th digit of your VIN and find out exactly which variant (RPO code) your truck has, and follow that link to the correct turbo.

6500, 7500 and 8500 trucks had a 7.8L diesel inline 6 as the base engine. There are multiple states of tune and emissions programming available, but the most common are the LG4 and LF8 variants. This engine is branded as a Duramax 7800 when it’s in these trucks, but the same engine is called the Isuzu 6HK1 when it’s under the “hood” of one of their FTR heavy-duty cab-over trucks (one step up from their popular NPR/NQR/NRR trucks). You can also find the 6HK1 or Duramax 7.8L under the hood of an Isuzu HTR, which is pretty much just a TopKick with an Isuzu badge on the grill. This engine has a reputation for reliability, but not necessarily performance. If you have a 7.8L, please check the number tag on your original turbo for a part number and search it on our website – it will likely match one of these 3:

Turbochargers Direct Remanufactured OEM GT37 Turbo For Isuzu 6HK1 & Duramax 7.8L LG4 TUR-102763-TDR

Turbochargers Direct Remanufactured OEM GT37 Turbo For Isuzu 6HK1 & Duramax 7.8L LG4 TUR-102799-TDR

Turbochargers Direct Remanufactured OEM GT37 Turbo For Isuzu 6HK1 & Duramax 7.8L LG4 TUR-102950-TDR

We carry a full line of replacement turbos for any CAT, Isuzu or GM diesel, as well as anything else that had one from the factory – new or remanufactured, and from OEM brands like Garrett, IHI, BorgWarner, Mitsubishi, or Factory Turbochargers aftermarket replacements that fit and perform like OEM at a better value with a better warranty. Contact us for knowledgeable assistance finding anything you need!