View Full Version : 2003 H2 Hummer 6.5TD Swap - Mileage, Power, etc.
12-23-2011, 11:51 AM
I hope this is the right place to post this... I've got a 2003 H2 Hummer that I'd like to swap the gas guzzler out for a more fuel efficient diesel option. On a recent 450 mile round-trip in the hill country, I averaged around 12.2 MPG and that was babying it. I have a couple 6.5TD engines that came from a '92 and a '94 C3500. It's my understanding that the 6.5 should bolt directly up to the 4L65E without modification, so this is an attractive option considering I already have everything I will need for the swap. I guess my general question pertains to fuel economy. I've heard of guys doing the H2 Duramax swap and pulling as much as 22 MPG with good driving habits. Now I realize that the 6.5 isn't as powerful as the Duramax, but it's still a reliable and efficient diesel power plant, but I don't know if the 6.5 will have any difficulty moving this 6600 lb. H2 around given it's power output. What kind of numbers can I expect out of this type of setup? If anyone has experience or tips/suggestions for this swap I would really appreciate the info, as well as any other resources (online or otherwise) that could be provided to me. I have also been looking at info on the 4BT swaps into H2's, however as stated I already have two 6.5's and lots of spare parts from those two trucks at my disposal. Thanks in advance and happy holidays to you all.
12-23-2011, 12:49 PM
I'd say that the weight of the vehicle would put you around fully loaded Burb weight...so look to see what kind of mileage the 6.5TD burbs get and probably drop 1-2MPG due to the full time 4WD.
I'd chose the 92 as it's mechanically injected, which simplifies the swap but you will have to figure out how to make the sensors work with the factory gauges, if its possible. You would also need a transmission controller to control your factory transmission. I think you would run into more issues using the Electronically injected 94+ 6.5TD's, which are far from simple.
I think you're gonna need to buy a new flexplate and torque converter to fit your input spline count (not sure on the 97+ transmissions), you should be able to use the factory 700R4 flexplate (these are externally balanced and have to use a specific plate) and get a custom converter built for the bolt circle of the flexplate and fit your transmission and the stall speed. Otherwise the transmission can be adjusted from the TCU or through a custom tune for shift point and other variables.
The 6.5TD can be modified to run pretty good, but the best you can hope for is for first gen D-Max performance. You should be able to obtain 14-16MPG consistently if you drive it right. It won't be a speed demon, but with a healthy IP, high pop pressure injectors, plenty of air coming in and lots of space for exhaust to leave and it shouldn't be far off from the performance you get now. If you've got it running right, tuned to perfection, beefed up bottom end and gauges aplenty, you should see close to 250HP and 500TQ and handle more than stock limits and be nearly as reliable.
Just don't get your hopes up! but it sounds like you know what these engines are like anyway.
01-06-2012, 03:56 PM
Appreciate the reply, Koots. I've done more research and I am heavily leaning towards the Duramax powerplant now. I'm sure I'll find something for these 6.5's before long. Hope you're having a good new year so far. I'll check back around here when the fun begins.
01-06-2012, 10:02 PM
My feelings on the 6.2/6.5 is that they work great as a simple, economical diesel. They don't work well doing serious towing (requires heavy cooling mods to work well), they don't work well in extra heavy rigs either.
Something like a 1/2 ton RCSB or RCLB or a swap into a car, is an awesome place for these engines.
Otherwise, look for a 5.9L Cummins. Unless the D-max proves to be an easy swap into the chassis. because it sits in the HD trucks and would probably still work with all your electronics.
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