Weighing transmission rebuild and upgrade options

I'm looking for some input on what to do with the trans in my 193k mile 09 CE. It's ok at the moment, but I'd like to come up with a plan to replace it with something rebuilt and upgraded. I want to buy or build something that can handle 400ish ft-lbs, and is as reliable as possible. I also want to avoid extended downtime.

My original plan was to get a decent core from Pick n Pull and have that upgraded to 4L70E specs. Then just swap it into the truck over a few days. But I've since found out there were some changes to the internals starting in 2009, and that's on top of the fact the H3 and Colorado use their own unique valve body. So finding a cheap donor probably isn't going to happen.

The 6L80E swap sounds ideal. Good value, strong, fairly easy to come by, and nearly plug and play. But it looks like there's potential reliability issues with the cut down output shaft. (Lack of heat treatment). Has anything improved on that front in the last year or two?

I don't mind spending a bit extra to get a quality solution. I really like the 6L80 idea. I'm just not sure what's really available on the market right now.

If the 6L80E swap was nearly plug and play, you'd see plenty of threads about people doing the swap. It's the 'nearly' part that causes issues. Your best bet is research the 4L60E upgrades people have done in their H3, order the parts. Find a local trans shop to rebuild your transmission with your upgraded components. Downtime may only be a few days or a week.

See this thread:
https://www.hummer4x4offroad.com/fo...m-built-4L60E-transmission-wish-list-thoughts

Thanks. That was a good read. I'm definitely going to make some notes from that.

I only meant the 6L80 is plug and play in the sense you don't need to modify the chassis or driveline geometry. Most of the 6L80 threads I've read are at least a year old, so I wanted to bring it up in case I missed some new development.

200k on a OEM tranny is pretty good. Even a slight upgrade should prove more than enough for moderate off roading. I had my 01 Silverado recently rebuilt at 150k but it had seen some hard towing and no extra cooling in the desert heat.

More transmission related threads to read:

https://www.hummer4x4offroad.com/forum/showthread.php/13503-4L60e-Valve-body-replacement-question

https://www.hummer4x4offroad.com/forum/showthread.php/13399-Transmission-Pan-Question

https://www.hummer4x4offroad.com/forum/showthread.php/12175-Tranny-dead

https://www.hummer4x4offroad.com/fo...-Cooler-Thread-Number-3-install-with-pictures

I was happy to see the previous owner put in a standalone transmission cooler. I need to go through and make sure all the lines and fittings are still in good shape though.

Does anyone know if the ATSG guides cover the H3 and Colorado transmission customizations? I'd like to know exactly what's unique about these transmissions, if for no other reason than my own education.

Jeff V. said:

I'd like to know exactly what's unique about these transmissions, if for no other reason than my own education.

Click to expand...

Someone who knows more about this will have to confirm the following:
I believe the differences that the H3 4L60E transmission has (compared to a 'regular' 4L60E) include a valve body with the corner that's different, and a shallow pan and filter. I also believe that the 4L60E from an I-5 H3 won't work in a V8 H3 because the pilot bearing is different. I can't comment on using a 4L60E out of a Colorado in a H3.

I am in a similar situation right now. My alpha has 250K miles on it, but is still working great. The problem is that I have a P0717 code. This is a input speed sensor which is inside the transmission. From the looks of it, it seems that the whole trans needs to be dropped to replace it and I was pondering upgrades. I am currently running 38in Toyo M/Ts on my Alpha and was thinking of upgrades I can do so I don't break stuff later down the line.

Just to weigh in,
the 4l60 in in the H3 is the same old 4l60e.
The H2 got the 4l65e, which has 5 pinion planeteries which are stronger but the chance of you breaking the 4 ponion planeteries on the 4l60e on a stock H3 are minimal.
The 2008+ models (some 07 models) get an ISS located inside the trans. This can be added to people buying a 4l60e without it.
The H3 has a unique trans pan and filter. The valve body is the same iirc.
The I5 and V8 are different, input shaft depth, torque converter and bellhousing are different

As for the 6l80e swap,

If you got a 4x4 trans, all is needed mechanically are a tcase adapter, resplining the output shaft, a 6l80e TC and bellhousing
Electronically the tbms harness and programming
You will need to add paddle shifters or something to be able to use manual shift (stock shiftet only allows you to drop to 1st)
Need a button to activate tow mode
Figure out how to get the trans to shift out of 1st in 4LO (communication issue)

Probably 4K in total cost but you get a trans thats much tougher than medium built 4l60es. Add another 500 to get the paddle shifters

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I had my CE trans built to exceed 4L75 specs using OEM parts with the exception of some aftermarket items which I believe to be superior to OEM such as the pack, 1-2 accumulator, etc.. While gathering parts for the rebuild, I found two new valve bodies ( # 24237219 ) and bought both. I used one for the rebuild and sent my original to the guys at Valve Body Pros to have it gone through even though I had not had any problems with it. Apparently they didn’t have to do much to it because they didn’t charge me a lot. So, I have two valve bodies on my shelf in unopened boxes, one new and one rebuilt. Since these things are scarce, I’m going to keep one for a spare but if someone out there gets in a bind and needs one, PM me and maybe we can work something out.

Here's what I think I've learned from combing through various threads and parts catalogs. Amrg covered most of it. I'm just sharing what I've read, so please don't take this as me contradicting anyone. I'm still pretty new to GM transmissions so I'm just trying to learn and understand.

V8 H3 and V8 Colorado are completely interchangeable from 2009-2012. V8 Colorados aren't exactly common though. There was no V8 Colorado in 08.
I5 and V8 have different input shafts, bell housings, and valve body assembly.
Per ATSG GM added the internal ISS to all 4L60Es in 2009. Dunno if this is related to the valve body assembly part number change that also occurred in 09. But Amrg is saying this occurred in some 07s and then from 08 onward?
I've also read the ISS changed the geometry of some of the internal parts, so you can't just install the sensor in an older trans.

I can't find a part number for a bare valve body casting. All the part numbers are listed as a complete assembly with solenoids and springs. What I'm wondering is if you can strip down an older I5 body core and then install the various solenoids and such to upgrade it to 09+ V8 spec or better. The complete assembly may be discontinued, but maybe it's possible to cobble one together? I might try to get in touch with ATSG and see if their manual has this information. I've got no problem spending the $40 on the book if it does.

I've got six self serve junkyards within 30 minutes of me, so that's gives me a lot of potential options. I'm wondering if a core 09+ 4L65 or 4L70 plus a 'custom' I5 valve body and new wear parts might make a cost effective solution.


As far as the 6L80 goes, I've got a fair amount of background hacking on the digital side of cars. I'd love to take a crack at the gear selection problems. Having a proven output shaft is a much bigger concern for me.

https://m.youtube.com/watch?v=QjI6psqCQN4

Precision Transmission has several interesting transmission teardown videos.

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The 6L80E swap is something many people here would love to see/do.

The only people that I know of that are actively working on it is Outfitter Designs. But I'm not sure how quickly they are working on it because I have been continually bugging them every 3 months for a year and a half now, asking for updates. I think the last I heard was that it was expensive to tool a new output shaft & they weren't sure on the strength of the output shaft with the re-spline, taking away much or possibly all of the heat treating.

It may be years before they release a kit, if at all.

I haven't had the time to read through this, but the pictures and diagrams look very informative.

http://www.wwdsltd.com/4L60/4L60ERepairs.html

Iirc the output shaft resplining was approx $100 from moser.

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IMHO that's a bargain. It just seems there was some concern about the durability of it since the heat treated layer was ground away.

Jeff V. said:

IMHO that's a bargain. It just seems there was some concern about the durability of it since the heat treated layer was ground away.

Click to expand...

Yes it is. But I wonder how much it would cost for a heat treatment?


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