transmission Let's Talk Transmissions (Swaps & Modifications)

shaneman20 · November 13, 2017

Well, seeing as how I can't find much on this subject no matter what forum I go to, why not try to start the discussion here and see what kind of following I can get and see where we end up.

If you're reading this thread, chances are you have thought about modifying or swapping out your current transmission in your 2014+ GM truck. In my case, I don't mind my 6L80 in my truck. It does fine for what I do right now and it's holding up just fine, but I think the big issue is when you start to search for big power (like I'm starting to do), that 6L80 is not going to hold very much (or so we think). Now, let's all face it. We've seen posts after posts, comments after comments, photos, videos, etc. of guys with built motors with turbos or prochargers shooting down the quarter mile in search for the best time on these 6L80s. Some say they're completely stock, others have them built, and we all ask ourselves the same question: Reliability. How well are these transmissions going to hold up to the abuse on the track? Especially if you want to make it a fast street/strip truck and drive it back home to the garage afterwords.

We know for a fact that 6L90s can hold quite a bit of power. Even though I've mostly seen it in Camaro ZL1 applications, there is a guy on YouTube (GuitarmaggedonZL1) who is running a stock 6L90 on stock converter making 1000HP (give or take on an unloaded dyno) and the transmission hasn't puked all over the ground just yet. (Exaggeration, I know.) So, needless to say, a 6L90 swap sounds nice, at first... After you figure the extra length and weight (and in my case, relocation of the transfer case and getting custom driveshafts made), it starts to look a bit unpromising, but still not out of the ball park yet since it will be able to handle the power some are seeking, but where these newer transmissions lack significantly if you want to do boosted applications at the track (or even just launch control on N/A), no one has developed a transbrake. Very, very few forums are talking about this, and only one video exists of a guy in his BMW testing out a transbrake on a 6L80/6L90, and who knows how reliable it is.

So, now, you start to think: Well, gee. What can I do now? How about a TH400 or 4L80e swap?

So far, I've seen few posts on that as well. No one is talking about it, and I think the biggest problem people seem to be facing is the new PCM: E92. Also possibly the fact that the TCM on the newer transmissions is inside the transmission and whatnot, but whether that plays a part in this, I don't know yet. Now, adapting a TH400 or 4L80e can be done (most likely with a different bellhousing since the bolt holes are in a slightly different spot), but you run into the issue of getting it to speak/cooperate/communicate with the new E92, which I don't think anyone has tried. The only video I've seen of anything working in this application was on a 1320Videos video with a Nova where they were using an LT4 long block (built motor to 388 C.I.) and twin turbos, and it had a powerglide in it. Don't know if it was a manual valve body or computer-controlled, but what I do know is that they used the factory computer to run the DI injection system and piggybacked the rest to an MS3 Pro. After dealing with some issues, they were able to make that thing boogy to a 9 second pass at 148mph. So, these engines have potential to haul ass, but we just haven't figured out how to crack the system.

So, at this point, I'll just leave what I've discussed here and see where the thread goes from here, and I'm hoping people chime in and vendors are watching/listening. Even though the demand isn't hot for it right now, there's going to be a surge for good transmissions when people can buy these trucks/cars/motors/transmissions for pennies on the dollar. Unfortunately, I feel like we'll have to wait that long in order to see results, but oh well.

Just to give you guys an example: In the next year or two (2019 or 2020), I'd like to go turbo with my truck. (Doing all the supporting mods before going there minus built bottom end until I see where I can get with stock bottom end before sending a rod through the block or oil pan) Ideally, it'd be best to have a transbrake in that application with 2-step, but can't do it on the new transmissions. So, 4L80 seems to be the option, but I can't do that either because no one supports adapters or harnesses to make them work with the new motors/ECUs. That's the boat I'm in. I like to research everything before I go whole hog into something. Risk assessment, I guess.

KARNUT · November 13, 2017

It really depends on the miles you put on it and how often you plan to take to the track. Example I have a 25 year old modified truck. The first owner just installed a Whipple and a shift kit. At ten years and 80K miles the second owner rebuild the motor and stroked it and went to 10lbs of boost. When I bought it at 100K miles at 20 years old the trans got rebuilt with mild upgrades. At 25 years old that combo is still going. That’s with street tires and the stock 373 posi. One at of three times I drive it, I beat on it.

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L86 All Terrain · November 13, 2017

I have been thinking of modding my L86 for a long time, the most I would do is stage 1 TVS2300 to avoid all the necessary supporting mods and headaches with the stock computers. GM can barely tune these trucks let alone the aftermarket. With so much knowledge of the LS family computers and available techs, I think it would be crazy to try a full build on a new LT platform, especially when it is your daily driver. It would be a lot cheaper and less stressful to purchase a hail damaged/write-off 07-13 LS truck and build that as a track weapon. The techs are there, the computers can be tuned, wiring harness gurus are everywhere, you have the proper transmission already. You would spend more trying to make your current truck both a daily driver and a rubber burning sleeper than you would building a whole other truck. I can't even fathom the headaches involved in trying to make a built 4L60e work with a K71 trans module, and communicate with all the other electronic nannies they jam into these vehicles. If you could score a decent truck to build for even $8k, you will still be cheaper in the end, plus you wont ever be without your nice, new, warrantied truck. Just my 2cents. The support for LT isn't and will never be where it was with the LS family.

shaneman20 · November 13, 2017

38 minutes ago, 10SierraA.T. said:

I have been thinking of modding my L86 for a long time, the most I would do is stage 1 TVS2300 to avoid all the necessary supporting mods and headaches with the stock computers. GM can barely tune these trucks let alone the aftermarket. With so much knowledge of the LS family computers and available techs, I think it would be crazy to try a full build on a new LT platform, especially when it is your daily driver. It would be a lot cheaper and less stressful to purchase a hail damaged/write-off 07-13 LS truck and build that as a track weapon. The techs are there, the computers can be tuned, wiring harness gurus are everywhere, you have the proper transmission already. You would spend more trying to make your current truck both a daily driver and a rubber burning sleeper than you would building a whole other truck. I can't even fathom the headaches involved in trying to make a built 4L60e work with a K71 trans module, and communicate with all the other electronic nannies they jam into these vehicles. If you could score a decent truck to build for even $8k, you will still be cheaper in the end, plus you wont ever be without your nice, new, warrantied truck. Just my 2cents. The support for LT isn't and will never be where it was with the LS family.

This is kind of where I want to disagree. I know tuners have had issues getting into these new ECUs, especially the 2017+ vehicles, and it's kind of been a lot of headache for a lot of people already, but from headaches and pain and heartache of trying to become the next breakthrough thing comes success. These engines are still very new. Take into perspective that the Gen III/IV LS engines we know today was introduced in 1996 and used in production vehicles since that point, and look how long it took us to get to the point we are now.

I guess the things I'm searching after are things that are probably still another 5-10 years in the making.

The thing of it is going and getting a previous generation Silverado/Sierra and modding it or even getting one that's already been modified is kind of taking the easy way out, in my opinion. I'm a wrench. I want to get my hands dirty or at least get my hands on tools and work on things to produce results. Unlike a lot of people who are not venturing into the new world of LTX, I decided it was best to embrace what's new, help collect data and build on what will be a great foundation. Case in point, GM finally caught up to what everyone else was starting to do and that was the use of DI with port injection. While it may not be something that we can do with the stock ECU on these trucks/cars currently, the systems are being designed (or at least the hardware to do so) and we will see the same thing on these vehicles.

The thing is do you choose the easy way out because it's less stressful or do you embrace the new and plunge headfirst into a new, undiscovered world?

KARNUT · November 13, 2017

This is kind of where I want to disagree. I know tuners have had issues getting into these new ECUs, especially the 2017+ vehicles, and it's kind of been a lot of headache for a lot of people already, but from headaches and pain and heartache of trying to become the next breakthrough thing comes success. These engines are still very new. Take into perspective that the Gen III/IV LS engines we know today was introduced in 1996 and used in production vehicles since that point, and look how long it took us to get to the point we are now.

I guess the things I'm searching after are things that are probably still another 5-10 years in the making.

The thing of it is going and getting a previous generation Silverado/Sierra and modding it or even getting one that's already been modified is kind of taking the easy way out, in my opinion. I'm a wrench. I want to get my hands dirty or at least get my hands on tools and work on things to produce results. Unlike a lot of people who are not venturing into the new world of LTX, I decided it was best to embrace what's new, help collect data and build on what will be a great foundation. Case in point, GM finally caught up to what everyone else was starting to do and that was the use of DI with port injection. While it may not be something that we can do with the stock ECU on these trucks/cars currently, the systems are being designed (or at least the hardware to do so) and we will see the same thing on these vehicles.

The thing is do you choose the easy way out because it's less stressful or do you embrace the new and plunge headfirst into a new, undiscovered world?

That depends on the money you want to spend. I’ve built plenty of vehicles modding from scratch. The truck from my previous post I bought off eBay for 7500$ dollars. Along with the stuff stated it’s lowered has custom interior and shows like a well cared for truck. It’s definitely cheaper to buy an older modded vehicle or mod an older truck than diving into the unknown. The guy I bought the truck from 5 years ago claimed he put 40K in the truck in the ten years he owned it. I may have 10K total. So when you finish your experiment let us know, someone will be glad to give you pennies on the dollar.

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shaneman20 · November 13, 2017

12 minutes ago, KARNUT said:

So when you finish your experiment let us know, someone will be glad to give you pennies on the dollar.

Thanks for giving me more incentive to work towards a goal, buddy.

KARNUT · November 13, 2017

Thanks for giving me more incentive to work towards a goal, buddy.

Just pointing out the reason that some of us taking ( the easy way out) buddy.

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L86 All Terrain · November 13, 2017

I hear your point, everyone wants to do something different or walk into uncharted territory, help push the aftermarket etc. I am just stating that what you want (a fast truck), could be had for FAR cheaper and it will still allow you to maintain the reliability and value of your current ride. Personally, I would not apply to be a shops "LT guinea pig". I am talking with a shop now about putting a stage 1 P1SC procharger or TVS2300 on my L86 but I would never go beyond that with a daily driven truck, so I am not against modding a daily, just building one. I have a 98 Silverado that is waiting this winter for a LSx 5.3L swap out of a donor Avalanche, and that is what I am going to go nuts on because A) I don't have to rely on it, B) it is mostly free (truck, engine and 4L60e), C) I can wrench on it at my own pace and not worry about how I am getting to work in the AM, D) The knowledge, expertise and parts are out there when you need it, because lets be real, no one can do it all on these computer chips they call trucks anymore, if they say they can they are liars. Even LS gods like Sloppy can't put together a wiring harness. Not trying to offend you or tell you what to do, or suggest a "lazy" way out. I am just pointing out you are taking a long, expensive and frustrating road willingly, simply to satisfy your own ego in it's regard to "taking the road less travelled". We do our best here to provide practical insight based on personal experiences to other users in order to help them make fact based, informed decisions regarding their vehicles. I respect your decision and way of thinking outside the box, however I think you will end up sinking tens of thousands into building your dream truck and being a shops R&D project, all whilst devaluing your daily driver. Look at Denali82's thread about his build, it took over a year, well over 20k usd, a second engine, a second 8L90 transmission, then finally a built motor and built trans to get the 700hp he was after. Is that something you are prepared to thrust yourself and truck into? It's not like you are going to walk into a shop with a built 4L60e on Monday and come out with a built drag truck on Thursday, keep that in mind. Granted Denali's result was awesome in the end. Ultimately your dream is possible, it is just the matter of how much money, and time are you willing to throw at it to get there. Would you be happier spending 20k to have a dual purpose truck, or 15k to have two, single purpose trucks? To each his own, let us know what route you take and keep us posted in a build thread. Especially if you can figure out how to make a 4L60e work with the new TCM's, be interesting and valuable research for sure. If you choose that route, all of us commend you and look forward to your findings. Cheers, and good luck Shane!

shaneman20 · November 14, 2017

20 hours ago, 10SierraA.T. said:

I hear your point, everyone wants to do something different or walk into uncharted territory, help push the aftermarket etc. I am just stating that what you want (a fast truck), could be had for FAR cheaper and it will still allow you to maintain the reliability and value of your current ride. Personally, I would not apply to be a shops "LT guinea pig". I am talking with a shop now about putting a stage 1 P1SC procharger or TVS2300 on my L86 but I would never go beyond that with a daily driven truck, so I am not against modding a daily, just building one. I have a 98 Silverado that is waiting this winter for a LSx 5.3L swap out of a donor Avalanche, and that is what I am going to go nuts on because A) I don't have to rely on it, B) it is mostly free (truck, engine and 4L60e), C) I can wrench on it at my own pace and not worry about how I am getting to work in the AM, D) The knowledge, expertise and parts are out there when you need it, because lets be real, no one can do it all on these computer chips they call trucks anymore, if they say they can they are liars. Even LS gods like Sloppy can't put together a wiring harness. Not trying to offend you or tell you what to do, or suggest a "lazy" way out. I am just pointing out you are taking a long, expensive and frustrating road willingly, simply to satisfy your own ego in it's regard to "taking the road less travelled". We do our best here to provide practical insight based on personal experiences to other users in order to help them make fact based, informed decisions regarding their vehicles. I respect your decision and way of thinking outside the box, however I think you will end up sinking tens of thousands into building your dream truck and being a shops R&D project, all whilst devaluing your daily driver. Look at Denali82's thread about his build, it took over a year, well over 20k usd, a second engine, a second 8L90 transmission, then finally a built motor and built trans to get the 700hp he was after. Is that something you are prepared to thrust yourself and truck into? It's not like you are going to walk into a shop with a built 4L60e on Monday and come out with a built drag truck on Thursday, keep that in mind. Granted Denali's result was awesome in the end. Ultimately your dream is possible, it is just the matter of how much money, and time are you willing to throw at it to get there. Would you be happier spending 20k to have a dual purpose truck, or 15k to have two, single purpose trucks? To each his own, let us know what route you take and keep us posted in a build thread. Especially if you can figure out how to make a 4L60e work with the new TCM's, be interesting and valuable research for sure. If you choose that route, all of us commend you and look forward to your findings. Cheers, and good luck Shane!

Now, I'm speechless. Lol. I guess I should clear one thing up a bit: This truck (once I start the build) won't be my daily driver because I realize problems and issues can and will develop any time you decide to tear into a motor/trans/etc.

Trying to acknowledge a lot of this. All I wanted to do was something that it seems no one is doing. It's been extremely "hush-hush" so to speak on nearly every forum, and I wanted to spark the conversation and at least get talking about it rather than "Just buy a 5.3L LS and a built 4L60 and go racing" because everyone does do that. I don't mean to make it seem like I'm doing this for my own ego, but rather chasing after things that no one else or very few are doing. Imagine if we just sat around and said the automobile was just fine the way it is or that the horse and buggy would do the job. Where would we be today? I apologize if it seems selfish in that sense, but I just wanted to get people talking. Throw information out there. It's better to talk about it and start growing an interest in it and find out if any others are personally interested in going down this road rather than choosing to stick where they are. And if you wish to stay where you're at with your LS platform and built 4L60/4L70/4L80/TH400, that's fine. I'm trying to pull people away from that, I just want to see if there is any interest in expanding on the LT platform and if there's any adaptability with some older stuff that we know works and will hold the power for the time being, if any of that makes sense.

And also, if it seems like I was being egotistical, I was really trying not to be, but when you're passionate about something and what to embrace whatever it is you have, you'll do what it takes to go further, so I've found.

flyin99 · November 15, 2017

Hey Shane....

I know RPM Transmissions has done some 4L swaps into the new Camaros, as I've been in one. Looks completely factory, from the shifter and gear selector, etc. I don't know the cost, as I bet it was $$$$$$$, but I do know they are able to do them in Camaros. I inquired about this swap, for my 14 Silverado and was told it was indeed, NOT plug and play by any means, but.........."is" possible........may be expensive though...they just asked what power I was making and what I wanted to do with the truck, etc.....I haven't followed up any more than that....... Just fyi

shaneman20 · November 15, 2017

15 hours ago, flyin99 said:

Hey Shane....

I know RPM Transmissions has done some 4L swaps into the new Camaros, as I've been in one. Looks completely factory, from the shifter and gear selector, etc. I don't know the cost, as I bet it was $$$$$$$, but I do know they are able to do them in Camaros. I inquired about this swap, for my 14 Silverado and was told it was indeed, NOT plug and play by any means, but.........."is" possible........may be expensive though...they just asked what power I was making and what I wanted to do with the truck, etc.....I haven't followed up any more than that....... Just fyi

Hey man! It makes me wonder if the Nova I seen running a TT LT4 setup using the factory ECU to run injectors and the MS3 Pro to run everything else including the powerglide would actually work. It'd be a freaking hassle to deal with, but it makes me wonder. The good thing is that in my neck of the woods, we have a very well-known tuner that could probably pull it off, but it's just a matter of execution. It's still years down the road and I'll end up pushing this 6L on an N/A setup to start with, but looking into a TH400 or a 4L would be a thing to look at before diving head-first into it.

Also running an MS3 or some flavor of would possibly allow you to run a second set of injectors, but again, more hassle and that's another story for another time...

flyin99 · November 16, 2017

We've got a good tuner down here, as well. If you're ever down this way (Central KY)....James Short...http://www.shortuning.com/...Look him up......really knows the LS stuff for sure. Love your truck, by the way!

shaneman20 · November 16, 2017

6 hours ago, flyin99 said:

We've got a good tuner down here, as well. If you're ever down this way (Central KY)....James Short...http://www.shortuning.com/...Look him up......really knows the LS stuff for sure. Love your truck, by the way!

I've heard nothing but good things about James. I'll keep him in mind as a back-up to David Griffin. And thank you for the compliment!

truckguy82 · November 16, 2017

On 11/13/2017 at 1:04 AM, shaneman20 said:

Well, seeing as how I can't find much on this subject no matter what forum I go to, why not try to start the discussion here and see what kind of following I can get and see where we end up.

If you're reading this thread, chances are you have thought about modifying or swapping out your current transmission in your 2014+ GM truck. In my case, I don't mind my 6L80 in my truck. It does fine for what I do right now and it's holding up just fine, but I think the big issue is when you start to search for big power (like I'm starting to do), that 6L80 is not going to hold very much (or so we think). Now, let's all face it. We've seen posts after posts, comments after comments, photos, videos, etc. of guys with built motors with turbos or prochargers shooting down the quarter mile in search for the best time on these 6L80s. Some say they're completely stock, others have them built, and we all ask ourselves the same question: Reliability. How well are these transmissions going to hold up to the abuse on the track? Especially if you want to make it a fast street/strip truck and drive it back home to the garage afterwords.

We know for a fact that 6L90s can hold quite a bit of power. Even though I've mostly seen it in Camaro ZL1 applications, there is a guy on YouTube (GuitarmaggedonZL1) who is running a stock 6L90 on stock converter making 1000HP (give or take on an unloaded dyno) and the transmission hasn't puked all over the ground just yet. (Exaggeration, I know.) So, needless to say, a 6L90 swap sounds nice, at first... After you figure the extra length and weight (and in my case, relocation of the transfer case and getting custom driveshafts made), it starts to look a bit unpromising, but still not out of the ball park yet since it will be able to handle the power some are seeking, but where these newer transmissions lack significantly if you want to do boosted applications at the track (or even just launch control on N/A), no one has developed a transbrake. Very, very few forums are talking about this, and only one video exists of a guy in his BMW testing out a transbrake on a 6L80/6L90, and who knows how reliable it is.

So, now, you start to think: Well, gee. What can I do now? How about a TH400 or 4L80e swap?

So far, I've seen few posts on that as well. No one is talking about it, and I think the biggest problem people seem to be facing is the new PCM: E92. Also possibly the fact that the TCM on the newer transmissions is inside the transmission and whatnot, but whether that plays a part in this, I don't know yet. Now, adapting a TH400 or 4L80e can be done (most likely with a different bellhousing since the bolt holes are in a slightly different spot), but you run into the issue of getting it to speak/cooperate/communicate with the new E92, which I don't think anyone has tried. The only video I've seen of anything working in this application was on a 1320Videos video with a Nova where they were using an LT4 long block (built motor to 388 C.I.) and twin turbos, and it had a powerglide in it. Don't know if it was a manual valve body or computer-controlled, but what I do know is that they used the factory computer to run the DI injection system and piggybacked the rest to an MS3 Pro. After dealing with some issues, they were able to make that thing boogy to a 9 second pass at 148mph. So, these engines have potential to haul ass, but we just haven't figured out how to crack the system.

So, at this point, I'll just leave what I've discussed here and see where the thread goes from here, and I'm hoping people chime in and vendors are watching/listening. Even though the demand isn't hot for it right now, there's going to be a surge for good transmissions when people can buy these trucks/cars/motors/transmissions for pennies on the dollar. Unfortunately, I feel like we'll have to wait that long in order to see results, but oh well.

Just to give you guys an example: In the next year or two (2019 or 2020), I'd like to go turbo with my truck. (Doing all the supporting mods before going there minus built bottom end until I see where I can get with stock bottom end before sending a rod through the block or oil pan) Ideally, it'd be best to have a transbrake in that application with 2-step, but can't do it on the new transmissions. So, 4L80 seems to be the option, but I can't do that either because no one supports adapters or harnesses to make them work with the new motors/ECUs. That's the boat I'm in. I like to research everything before I go whole hog into something. Risk assessment, I guess.

Whats wrong with the 8l90?

the z06 uses it, the new zr1 uses it, and a lot of people are making big power on t, seems to be holding up fine.

don’t think you’d need start thinking about th400 or 4l80’s until you’re beyond 1200hp

at which point your truck is so heavily modified that there’s no point in doing it to ‘14+ anyway, not like you’d care about interior appointments or gas mileage at that level

shaneman20 · November 16, 2017

3 hours ago, truckguy82 said:

Whats wrong with the 8l90?

the z06 uses it, the new zr1 uses it, and a lot of people are making big power on t, seems to be holding up fine.

don’t think you’d need start thinking about th400 or 4l80’s until you’re beyond 1200hp

at which point your truck is so heavily modified that there’s no point in doing it to ‘14+ anyway, not like you’d care about interior appointments or gas mileage at that level

Biggest flaw with the 6L80/6L90 and 8L90 is you can't use a transbrake...yet... That, and I don't know if you'd want to with a 4.03/4.56 first gear on what would be an otherwise tall final drive. You'd just break traction every time. In a boosted application, you'd just have to have a high enough stall to get a vehicle up on the 2-step and footbrake the hell out of it.

Both the 6L90 and 8L90 are good for handling power and that's obvious with a lot of Corvettes and Camaros sending it with no issues (that I'm aware of) down the quarter mile, but if you decide to go with a procharger (or an centrifugal supercharger) or turbo, you're pretty much limited in options on these new vehicles unless it's a stick.