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I have a stock 1989 GMC 2500 6.2L diesel powered Suburban, and was wondering how easily one could replace the original engine with a Duramax.

Philip Baler

Camrose, Alberta Canada

“Easily” is a relative term. For someone well-versed in auto mechanical and electrical systems, it can be somewhat easy to perform a conversion like you propose. It’s still work, but relatively easy.

There have been a few ’80s GM trucks converted to Duramax/allison power. New motor mounts would need to be custom fabricated to get the engine to sit between the frame rails, and the engine itself will easily fit into the engine bay. We’ve long thought that the Duramax engine packaging was actually designed to fit the 1990s GM body style trucks (GMT400), which have a similarly sized engine bay when compared to your 1989 model. The turbo exhaust downpipe will interfere with the right-side frame rail, but a little careful frame rail trimming will allow the exhaust to clear without compromising frame strength.

Physically installing the engine, transmission, fuel supply system, cooling system and exhaust system are the easy parts. These all-electronic engines and transmissions require a lot of wiring along with a handful of computer modules. It’s all perfectly doable, and we found during a conversion of a 1989 Chevy that the process became easier once the decision was made to strip nearly all of the original vehicle wiring and replace it with wiring matching the model year of the engine/ transmission package being installed.

Numerous companies have been working toward a standalone electronics package that would allow the Duramax to be installed in just about any vehicle, though their target market is largely the marine folks. PPE (ppediesel.com) is offering such a package, as is Banks (bankspower.com). Some of the West Coast hot-rod Duramax conversions you may have read about incorporated the PPE system.

If you stick with the GM electricals and electronics, we recommend installing a steering column matching the model year of your engine/trans package. The fairly minor amount of modification required to install a newer column is well worth the effort because you’ll have the correct electrical control of the Tow/haul feature, turn signals, cruise control and Passlock security in the ignition switch assembly. In addition, the new steering column will provide the correct cable-shift components for the Allison.

We recommend modifying the original dash to accept the new instrument gauge panel. If done well, the new dash will look great, help during the de-bugging process and allow you to benefit from the new gauges and Driver Information Center once the truck is on the road.

You should visit thedieselpage.com/ features/clarkdmconversion.htm, a web resource that discusses a 1987 Chevy C30 with a Duramax/allison conversion. Good luck, and let us know what develops.

Once the cheap and easy items are eliminated (like the fuel filter change or fuel line leaks), you may need to consider the most often discovered cause - injectors.