Duramax Diesel Conversions

[More Power]

Recently, I've received a couple of requests for more information concerning a Duramax/Allison conversion in the 1990s 2 Wheel Drive (GMT400) body style trucks, asking whether the motor/engine mounts we offer would work. The answer is YES, but the transmission mount crossmember would need to be modified. Member Gordon Marks kindly sent me a couple images of his modified transmission crossmember, which explain how he accomplished his installation. Thanks Gordon!

Note: The factory 4WD GMT-400 (1990s) transmission crossmember works perfectly without modification in 4WD trucks. It appears the 2wd TRUCKS/SUVs have a somewhat different frame rail dimension when compared to the 4WD models. Mock-up the installation before committing to welding on the added material. You may find you need to adjust the height up/down a little to get ~ 3/4" clearance between the rear of the transmission and the transmission tunnel.

You can see from these photos that Gordon flipped the modified 2WD crossmember upside down and mounted it below the frame rails. Be sure to use lock-washers and thread locking compound just to be sure. Jim

[More Power]

I received this message and photo from Patrick yesterday. You can expect to see his truck on the road somewhere in Massachusetts before long!

Jim

From: PatrickS
Subject: The Diesel Page - Duramax Conversion Mounts
Date: Mon, 24 May 2021
To: The Diesel Page
Jim,

The mounts arrived today and I was impressed with the quality of the parts. After work I bolted them up and, while an involved process, I got the drivetrain in. The mounts were worth every penny.

Patrick

2000 K2500, CrewCab Shortbox

[DayRadebaugh]

I have a low mileage '99 Suburban with a 6.5. I saw the discussion of the conversion to Duramax, but it said it was intended for only the '88-'98 models. Am I correct in thinking that the difference would be in the dash-instrument cluster only?

Thanks

[DmaxMaverick]

It depends on the body style you have, GMT-400 or GMT-800. 1999 was a transition year, and I don't recall how the Suburbans were released, if they were a half-year release, or if there was a difference between the weight classes. 2001 was the first model year for the Duramax. GM has always found a way to defy any direction of logic during these times. A GMT-800 (1999+) would be the simplest, with very little accommodations to consider.

[DayRadebaugh]

It depends on the body style you have, GMT-400 or GMT-800. 1999 was a transition year, and I don't recall how the Suburbans were released, if they were a half-year release, or if there was a difference between the weight classes. 2001 was the first model year for the Duramax. GM has always found a way to defy any direction of logic during these times. A GMT-800 (1999+) would be the simplest, with very little accommodations to consider.

Thank you. Would you happen to know how I can tell the difference? From what little reading I've done, I'm guessing mine is a GMT 410.

[DmaxMaverick]

I suppose I was asking the question. Which do you have? I simply don't recall what GM did during that transition, and I don't know what the equipment and RPO stickers should show to determine it. As sure as the sun rises, when you have it all figured out, an odd duck will show up. If yours looks like previous 1990's models, then it's a 400. If it looks like more modern models up to 2006, then it's an 800. It's important to the simplicity because a later model will fit the instruments and harnesses you'll need, rather than shoehorning everything. Look at the panoramic picture at the top of this page. Which grill looks like yours? The trucks on the far left and right are GMT-800 trucks, with different models mixed in between. Lil' Red is a GMT-400.