In the past the ideas of swapping the 4L65e to the 6L80e were rightfully met with resounding No’s, and don’t try. At recently as 6-7 years ago this swap was a $7,500-$10,000 endeavor.
From what I’m seeing that’s changed dramatically in recent years. Swaps from $2,000-$4,000 seems very possible mostly depending on price paid for a 4wd 6L80e trans.
Wiring harnesses/stand alone TCM can be bought for less than $1,000 that will mate your trucks system to the new TCM to run the transmission.
The transmission is 0.021 inches longer, this should be nominal enough that the existing drive shafts should be able to handle without trouble. Likewise the H3 guys have already proven that the existing mount location of their 4l60e matches the locations on the 6l80e
That leaves the last piece of the puzzle, mating the splines on the trans output to the transfer case. I do not know exactly what the spline count is on either side, I also don’t know if the 03-07 vs 08-09 share the same transmission spline counts.
- On one hand if they do share the same spline counts then the 6L80e should be a direct swap.
- On the other hand it may be possible to buy the transfer case input shaft for an 08-09 and make it work on the 03-07 transfer case. I am not aware of how the electronics on the transfer case changed from 07 to 08 but simply swapping the complete 08-09 transfer case may not be feasible.
This leaves the why, there are many reasons to do the 6 speed swap.
-Improved step ratios mean smoother shifts
- Better 1st to get the truck moving and for off-roading
- Two over drives for improvements on fuel economy.
-Simply put the truck feels a lot stronger and durable with the stronger 6l80 design, it’s no secret the 4l65 is a small unit that’s inadequate for the weight and mission of the H2.
-Capable of holding up to 500HP and about 10,800 lb tow rating.
-0-60 would be greatly improved as more ratios are available as well as significantly quicker shifts.
I may start looking into this much more, the stock trans (with stock sized tires) is good for about 120-140k miles which is inadequate in my opinion, it should really be triple that which I think the 6L80e can do.
I have a date set to get my truck regeared later this month, following that I plan on going to PCM of NC, which I am routinely near, and the H3 guys will know, to have the truck tuned and plan on talking through this for more ideas.
For the price and gains it’s a real no brainer. I might have also forgot to mention I have a spare H2 transfer case laying around which would be helpful.
The only other road blocks I am seeing is complete walk through on these, which will mean some learning curve will exist, most Corvette and Camaro guys talking about trans conversions are going from 6L80e to 4L80e to hold their 750HP setup. And then most of the guys doing 4L60e to 6l80e are doing 2wd setups which, while closer to the money, still leaves some questions.
From what I’m seeing that’s changed dramatically in recent years. Swaps from $2,000-$4,000 seems very possible mostly depending on price paid for a 4wd 6L80e trans.
Wiring harnesses/stand alone TCM can be bought for less than $1,000 that will mate your trucks system to the new TCM to run the transmission.
The transmission is 0.021 inches longer, this should be nominal enough that the existing drive shafts should be able to handle without trouble. Likewise the H3 guys have already proven that the existing mount location of their 4l60e matches the locations on the 6l80e
That leaves the last piece of the puzzle, mating the splines on the trans output to the transfer case. I do not know exactly what the spline count is on either side, I also don’t know if the 03-07 vs 08-09 share the same transmission spline counts.
- On one hand if they do share the same spline counts then the 6L80e should be a direct swap.
- On the other hand it may be possible to buy the transfer case input shaft for an 08-09 and make it work on the 03-07 transfer case. I am not aware of how the electronics on the transfer case changed from 07 to 08 but simply swapping the complete 08-09 transfer case may not be feasible.
This leaves the why, there are many reasons to do the 6 speed swap.
-Improved step ratios mean smoother shifts
- Better 1st to get the truck moving and for off-roading
- Two over drives for improvements on fuel economy.
-Simply put the truck feels a lot stronger and durable with the stronger 6l80 design, it’s no secret the 4l65 is a small unit that’s inadequate for the weight and mission of the H2.
-Capable of holding up to 500HP and about 10,800 lb tow rating.
-0-60 would be greatly improved as more ratios are available as well as significantly quicker shifts.
I may start looking into this much more, the stock trans (with stock sized tires) is good for about 120-140k miles which is inadequate in my opinion, it should really be triple that which I think the 6L80e can do.
I have a date set to get my truck regeared later this month, following that I plan on going to PCM of NC, which I am routinely near, and the H3 guys will know, to have the truck tuned and plan on talking through this for more ideas.
For the price and gains it’s a real no brainer. I might have also forgot to mention I have a spare H2 transfer case laying around which would be helpful.
The only other road blocks I am seeing is complete walk through on these, which will mean some learning curve will exist, most Corvette and Camaro guys talking about trans conversions are going from 6L80e to 4L80e to hold their 750HP setup. And then most of the guys doing 4L60e to 6l80e are doing 2wd setups which, while closer to the money, still leaves some questions.
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