Mod to Stock 2005 GMC Duramax/Allison 2500

[RMccord]

I am contemplating 1 or mods to my 2500HD extended cab 2005 longbed Sierra duramax/allison.
The first is possibly putting a Borla 4" exhaust kit on it. I believe that it will alone reduce exhaust temps about 150 degrees. I suppose I might see a bit of additional power from the increased exhaust flow.
My questions to the group. Have any of you kept your unit stock for the most part but improved the exhaust system? If so would you do it again and what were the benefits you saw from doing it.

The other mod I am considering is at the air intake but all my reading has pretty much convinced me that the air intake of the GMC duramax is pretty dam good as it is.

Your thoughts and also suggestions for any other mods i should consider. I thought about airbags on the suspension and although it might make the ride a bit better I doubt that it would increase any of my capacities as they are mostly determined by the ability of the axle in the vehicle. Can beef every thing up but the axles have to be rated for the increased capacities that the other suspension features might bring into play correct.

THanks

[Countryfolks]

You may already have a 4" exhaust, our 04 does. I did change the muffler to a straight through type, no change in noise, nothing else obvious either. I did it to improve the air through put [lowered back pressure] and lower temps. I don't have gages so I can't say if it did or not. Air bags don't increase caps, just level the load.

Skip

[Cat320]

I just measured my exhaust...looks like about 3 3/4"...I guess GM would call that 4. My truck is 100% stock. As Skip said, adding airbags, booster springs and other gizmos won't increase your cargo capacity, just level the ride (and add more weight).

[Jim Rose Paschal]

I have a 2005 Chev. Duramax/Allison. I also have a 335RLBS. I just returned from 23 states plus Canada with a completely stock truck. I went over the mountains at any speed I desired without any overheating. I averaged 11mpg driving most of the time with cruise at approx.2000rpm.

[Gonfishin]

Hi Bob, I have done what you are thinking about doing. I have an 05 Duramax that I went with a 4 inch exhaust and Ride Rite air bags. I can not say for sure about the exhaust temp drop because I installed my gauges at the same time as the exhaust. I can tell you that I have hit 1250 deg occasionally while pulling the Monty. Like you I heard the exhaust would lower egt's approx 150 to 200 deg. If I am not mistaken factory diameter on the 05's is 3 1/2 inches. I think you would see the most benefit from doing the exhaust and {cat delete}

[mobilrvn]

Haven't put the larger exhaust on our '06, but can't wait. Seems like the EGT runs fairly high when compared to our old '00 F-350. Besides the air bags, we have a rear stablizer bar. Never drove without it, so can't say it was an improvement, but it handles much like our F-350 did which had duallies. Let us knwo what you think when you get the larger exhaust system.

[Cat320]

quote:Originally posted by Jim Rose Paschal

I have a 2005 Chev. Duramax/Allison. I also have a 335RLBS. I just returned from 23 states plus Canada with a completely stock truck. I went over the mountains at any speed I desired without any overheating. I averaged 11mpg driving most of the time with cruise at approx.2000rpm.

Don't want to hijack the thread, but what kind of speed were you getting at 2000 rpm?

[Montana Sky]

Bert,
2000 RPM's run me at 70 mph.

As far as mods go, I wont be using any. The only thing I might change is adding airbags to help level out the truck. Headlights are a tad on the high side. The thing to remember about adding modifications to any truck, your factory warranty could be voided. Just a personal choice that only you can make.