Duramax Swap Opinions

[Trenton]

I'm debating on swapping a Duramax into my '98 K3500 that currently has a 5.7L. I'm having electrical issues preventing the fuel pump from running, and I'm getting tired of putting money into an underwheling engine, anyway. I've always wanted diesel power in that truck. I think a 7000 pound, long bed crew cab 4x4 truck should really have diesel power.

I've seen many people do it, so I'm not asking how to do it. To the few that have done a Duramax swap, how well did the OBS frame hold up to the Duramax power?

Since my truck is a K3500, it already has the 9.25" front diff, 10.5" full float rear axle, and a pretty hefty frame. If i did the swap, I was thinking about swapping in the 11.5" AAM rear axle. The Duramax frame rails just look so much bigger than the OBS frame rails. I would hate to twist the hell out of the frame if I ever pull a 10,000+ pound trailer.

If anyone could give me some advice from experience, that'd be amazing! Thanks in advance!

 

[letitsnow]

Could you box the frame to make it handle the duramax better?

 

[618 Syndicate]

Are you gonna tune it? We have a lightly tuned LMM in a square dually and it's pulled a car trailer with about 8k without hurting that frame.

 

[Trenton]

Are you gonna tune it? We have a lightly tuned LMM in a square dually and it's pulled a car trailer with about 8k without hurting that frame.

Ideally yeah. I'd ideally like to be at 400 crank horsepower with some breathing upgrades and a tune.

And that truck sounds badass. Is it the factory square body frame, too?

 

[Trenton]

Could you box the frame to make it handle the duramax better?

Possibly, but it's already boxed around the front half of the frame, so I imagine that part is solid.

 

[618 Syndicate]

Ideally yeah. I'd ideally like to be at 400 crank horsepower with some breathing upgrades and a tune.

And that truck sounds badass. Is it the factory square body frame, too?

Yeah. A buddy of mine who passed away had it, and there's a few of us his widow trusts to drive it. LMM/6L90 combo from an ambulance originally.

 

[LB7OBS]

I have mine in a k1500 frame and it handles the torque and power fine, it’s been almost a full year of me daily driving mine, it’s a 400hp 700tq combo, I recommend a true track in your diff… gov lock didn’t make it far lol.. The dmax was designed for the gmt400 so it fit amazing with a small body lift for trans clearance (the k3500 should have the body lift from factory *i could be wrong)

 

[demps101]

technically. the lb7 duramax was supposed to go in the 98 or 99 chevys but a head gasket issue delayed the release of the duramax til 01. so the frame will handle it just fine

 

[1998_K1500_Sub]

technically. the lb7 duramax was supposed to go in the 98 or 99 chevys but a head gasket issue delayed the release of the duramax til 01. so the frame will handle it just fine

Sounds like a bit of an assumption there.

GM may well have intended some frame enhancements to enable that engine in a specific model GMT400. We'll never know because, unfortunately, it didn't happen.

 

[Sean Buick 76]

I would simply fabricate 2 or 3 extra cross members to bolt between the frame rails to stiffen it up.