Has it been done in a GMT800, specifically an 03 and later? I drive a 6 speed Ford F250 for work sometimes and the vast improvement in driveability with the 6 speed over a 4 speed 4L60/4L65 can't be dismissed. Not looking to blaze trail on this, or reinvent the wheel if it's a major undertaking. It was just something I've wondered about as opposed to having the 4L60 built. Thanks in advance.
6 speed Auto conversion
- Thread starter mattt
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My initial thought is that is would be a challenging swap, as the 6 speed (and maybe the 4 speed, as well) is computer controlled (computer inside the transmission), and this would have to be matched up with the truck's other related computer control systems.
Folks on this Forum with much more direct knowledge than me on this topic will chime in.
Folks on this Forum with much more direct knowledge than me on this topic will chime in.
TollKeeper
Full Access Member
I have been looking at this a lot myself. There are a few that have done it, but at major cost. The tail crossmember is in the wrong location to support the trans. The driveshaft is to long? or short? (cant remember). TCM does not shake hands with the rest of the modules in the truck without reprogramming because of VIN's, and looking for a specific TCM that isnt there.
And then because of the way the way the final drive is on the 6L80, you would also have to regear the front/rear diff.
The next issue is that the 6L80/6L90 will only talk to a 58x crank trigger. You have a 24x.
And then because of the way the way the final drive is on the 6L80, you would also have to regear the front/rear diff.
The next issue is that the 6L80/6L90 will only talk to a 58x crank trigger. You have a 24x.
swathdiver
Full Access Member
time and money better spent building a bullet proof 4l60, unless of course you have quantities of both to spare.
The swap can be done. If I remember correctly, the mount is not much different from a 4l80e mount (going off fuzzy memory). I know it has been adapted to the the autotrac transfer case using a factory adapter as well. Controlling it is a challenge. When I took the Holley EFI training course a couple years ago and the 6L transmission came up. They said they do have 6L transmissions running with Holley control but as of then (right before covid hit) they had no release date or plan for a release of it.
There is this controller that has been used many times for a swap like this and I am really considering it. I just want more people to iron out the daily driver related bugs first.
There is this controller that has been used many times for a swap like this and I am really considering it. I just want more people to iron out the daily driver related bugs first.
GM 6L45E 6L50E 6L80E 6L90E TCM2650 transmission controller harness
GM 6L50E, 6L80E 6L90E, Transmission Control Module. TCM-2650 transmission controller GM 6L45E 6L80E 6L90E transmission controller and wiring harness.
www.zerogravityperformance.com
This company offers a GMT800 swap kit as well. They are gaining popularity in the trailblazer ss community for 6L80 swaps. They seem to offer good results in that community but they are expensive.
Their old website here has tons of useful information about the transmission as a whole:
Their old website here has tons of useful information about the transmission as a whole:
Yeah the price is a huge shocker. I am hoping as more people figure out the electronics side of the transmission, the controllers will start to come down in price.
I agree with him on everything except the 60e part. Before I spent any money on a 60e, I would swap in an 80e instead. The upfront labor IMO pays off in the end of never having to worry about even a built transmission failing.
Tonyrodz
Resident Resident
Big $$
I could see the price adjusting as more figure out the electronics side of things over time.
I see your point that a 4L80e is more stout than a 4L60e, but for a 2004 Tahoe, I don't think the 4L80e is the right transmission. My factory trans is currently at 333k mileage, so they can be made to last with proper care. The plan is to do some upgrades, and hopefully swap internals to turn it into a 4L65e. Not sure what upgrades yet as that's to be determined for what's hopefully another 300k transmission
I have driven 2 different 4L80e's in 2500HD trucks I used to own and I was never jazzed up with how they shifted, and the gearing spread.
Yeah, for sure....Big $$. I believe that is with them providing the transmission itself. I believe they have another option that is between $2500 and $2900 with you supplying the transmission itself.
Mudsport96
Full Access Member
The gearing spread is better than the 60e. The problem is 1st isnt as steep so it makes an already underpowered tahoe feel even more sluggish because you get less of an rpm drop on the 1-2. A good converter would fix that. As for the shifts a transgo hd2 kit fixes that as well.I could see the price adjusting as more figure out the electronics side of things over time.
I see your point that a 4L80e is more stout than a 4L60e, but for a 2004 Tahoe, I don't think the 4L80e is the right transmission. My factory trans is currently at 333k mileage, so they can be made to last with proper care. The plan is to do some upgrades, and hopefully swap internals to turn it into a 4L65e. Not sure what upgrades yet as that's to be determined for what's hopefully another 300k transmission
I have driven 2 different 4L80e's in 2500HD trucks I used to own and I was never jazzed up with how they shifted, and the gearing spread.
If you were looking for a middle ground upgrade, im 76.34% sure a 4l70e drops in place of a 60 and 65e. Think its just a repin of a few wires, and leave the input speed sensor unplugged since a vehicle with a 60/65e wouldnt look for it anyways.
Supposedly a stronger case design and beefier internals but same outside dimensions.
TollKeeper
Full Access Member
Your not the first person I have heard about the 4L70 being a almost direct swap. I -think- PCMofNC even makes a adapter plug, to make it plug and play.
Been researching this 4l70 v 4l65 and I'm not seeing much difference in them. Same gear ratios, and mostly the same internals, with some minor differences. The electrical differences are as described with the ISS being in the 70 and not necessary when used in place of a 4l60 or 4l65. Looking around for a 4l70 for sale and they are few and far between. Can anyone else make the case for going 4l70 vs the 4l65? Thanks.
swathdiver
Full Access Member
The 4L70 Supermatics were used behind the 2007-2009 6.0 motors in the half ton pickups and behind the Avalanche and Suburban 6.0 L76s in 2007-2008.
They are more stout than a 4L60/4L65 but these can be built to handle plenty of horsepower. It is not necessary to swap out a 4L60/4L65 to a 4L70 when more strength is desired as all of those features can be retrofitted.
The Novak Guide to the GM 4L60-E (Late Style) Automatic Transmission
Explore the 4L60-E transmission — GM’s advanced electronically controlled overdrive automatic. Technical details, identification, and swap compatibility.
