Diesel World


- Tech · Camrose · Alberta · General Motors Corporation

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.

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