10Lxx vs 8Lxx vs 6Lxx Replacement for 4L65

[justirv]

I've pulled the trigger on a 4L65E rebuild. It's going to be a little beefier than stock, but not by much. The next level up was a $900 increase... I suggested to my builder that the $900 wasn't in my budget and upgrading me for free was likely not conducive to paying his bills and he agreed... While he's in there... He's replacing my rear main seal, and I am waiting on an estimate to replace the pan gasket. You have to pull the transmission and transfer case for both repairs...

Now, firstly, I want to thank everyone that responded, especially @strutaeng for mentioning gearvendors, @acesttz for mentioning True Blue Motorsports, and @drdave81 and @strutaeng for mentioning performancetrucks.net. That said, I appreciate everyone throwing the brakes on to help prevent me from doing something stupid. But it is frustrating to ask for information and simply told it is a bad idea. It is much *less* frustrating for people to offer up information where people have considered/tried to do it and gave up or failed. To that end, I'm adding what I found in case anyone else tries to look into this, so they will know what they are up against:

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The 6Lxx transmission were different than to 4Lxx transmissions in that the transmission controls were actually built into the 6Lxx transmissions. That meant that using a standalone transmission controller was almost impossible, because it would still need to talk to the TCM *in* the 6Lxx.

The 8Lxx and 10Lxx were problematic -- as replacements for the 4Lxx -- because they, too, had their own, separate transmission control modules (TCM). This mean R&D had to be invested in deciphering how their TCM's worked so there could be translation between the year models for which they were made, and the year models for which the 4Lxx were made. As of this update, there is a company out of Houston, Texas that will do the conversion for GMT900s, but not the GMT800s. There was a commentator on the installer's FB page saying the GMT800s were for the "poors" or close enough. So I suspect these guys are never going to build a standalone controller for the GMT800s.

Ultimately, as others have said, anything is possible if you spend enough time and money. But my time was in short supply this go-around, even though I did have *some* coin to spend. So I've got a built 4L65E, or will have in a couple of days.
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Thanks for the detailed follow-up, please let us know what internal upgrades you made, and your impression when you get some miles on it.

 

[S33k3r]

...and your impression when you get some miles on it.

I suspect my number one impression will be the fun-to-drive factor. Even with it slipping in 2nd and 4th, it was WAY fun to drive. But I'll definitely report back!!!

 

[S33k3r]

@justirv,

Here's the info from the shop:

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New gaskets, seals, filter, clutches, steels, Transgo sk kit, borg Warner forward sprag, corvette servo, Sonnax wide band,
heat treated sun shell, Sonnax pump spring, aluminum accumulator pistons, hi per blue molded pistons
***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****

 

[justirv]

@justirv,

Here's the info from the shop:

***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****
New gaskets, seals, filter, clutches, steels, Transgo sk kit, borg Warner forward sprag, corvette servo, Sonnax wide band,
heat treated sun shell, Sonnax pump spring, aluminum accumulator pistons, hi per blue molded pistons
***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****






View attachment 435299

Thanks S33, we always appreciate closure with a full report.
You should be happy with the results. Not sure of your intended use but a quality 40k cooler with stainless braided line set will add miles/years to its life. I made the mistake of adding a cooler and keeping my original lines when I had mine rebuilt. Blew a stock cooling line at highway speed and fried the 3/4 clutch pack in less than 30 secs.

 

[S33k3r]

I've been driving on the new transmission and it's pretty good. Doesn't have the get up and go my daughter's 2003 Sierra Denali seems to have; I suspect that's because she has 4.10 gears and I have 3.73 gears. That, and hers weighs a fair bit less than the Escalade does.

Not sure of your intended use but a quality 40k cooler with stainless braided line set will add miles/years to its life.

It's on the list to do. Sooner, rather than later, but I still have to fix the AC. Unless heating issues become a problem -- which I am keeping an eye out for -- I have to fix what is broke, first. eFan conversion is on the list as well.

 

[justirv]

I've been driving on the new transmission and it's pretty good. Doesn't have the get up and go my daughter's 2003 Sierra Denali seems to have; I suspect that's because she has 4.10 gears and I have 3.73 gears. That, and hers weighs a fair bit less than the Escalade does.



It's on the list to do. Sooner, rather than later, but I still have to fix the AC. Unless heating issues become a problem -- which I am keeping an eye out for -- I have to fix what is broke, first. eFan conversion is on the list as well.

Good luck on the AC. There's a lot of info here for that. The e-fans will help decrease the AC vent temps at low speed and in traffic. I went with the 2010+ oem setup with 7 and 9 blade fans, more efficient than the earlier 2005 style. OEM harness and relays or Nelson makes a nice fan harness.

 

[the 18th letter]

My 2007 Tahoe has the 4 Speed transmission. Honestly, from what I have heard it is a better, more reliable transmission than the 6, 8, or 10 speeds.

I put over 175k so far on mine and never changed the fluid or added a cooler to the transmission. I was disappointed at the amount of mods needed on my 6 speed in hopes of just delaying the inevitable break down.