4.8L/6L90E swap???

[87Skier]

Originally I was going to do a 5.3L from a 03-06 truck, but I haven't been able to find a good motor. Ended up finding a newer engine out of a 2013 Chevy Express 2500 with a 4.8L and 6L90E. It has about 50k miles, and for the engine, transmission, harness and computer he wants $2500.

It sounds like a decent deal to me, since the older 5.3's seem to be up around $1000 for just the engine if it has less than 150k miles.

I can't say I care all too much about power output, but I'm not sure if it will work with what I have. I'm trying to find all this out in the next couple days before it's gone.

First, it is a 2wd 4L90E, which I've heard has a completely different output shaft (36 spline instead of 4wd 29 spline). Since I need it to work with my np205 in my 72, this is an issue. Advance Adapters make a kit for the 4wd version but not the 2wd. What can I do about this?

Second, will it fit in my 72 jimmy without having to cut it to pieces?

Third, does this transmission still have a cable/linkage to shift from P/R/N/D?
Does it have manual shift controls for all the lower gears as well, or is this electronically controlled via the computer/inputs? Could this be run from a standard 72 column shift that has P/R/N/D/L2/L1 assuming that last few gears are not reachable?

Fourth, the engine is flex fuel and vvt. Does this make any difference to being able to swap the engine? Does the computer need to be told to ignore the fuel sensor?

Lastly, is there anything I should know before considering this engine and transmission?


I'm going to use a 205. I will not change my mind, and it will dictate the course of the engine swap.
Engine power isn't a concern and I'm leaving it stock and looking for better mileage over power.
The engine code is L20, and transmission code is MYD.

If the transmission won't work, should I still buy the engine? It would be $1500. Could I source a good used transmission for $1000? If so, I haven't seen one.

Thanks!

[mongocanfly]

You may be better off/much cheaper to keep your t350..and just do the ls engine swap..not saying it can't be done with the newer trans..but when you get done with adapters, controllers, shifters and whatall and more than likely new/modified driveshafts your going to be deep in your billfold just to get a couple more shifts ...my 2cents

In your post you say 6l90e at the top then on down you say 4l90e..

And don't knock a 4.8..they often get overlooked but can be made to put out some incredible hp numbers if needed

1500 is not a terrible engine price if complete with everything..I know its different realestate but I can pickup 5.3s around here complete with trans for a grand..buddy of mine bought a complete engine/trans combo last week for 900

[Overdriven]

My work van is a 2010-12ish 2500 express with 4.8 and 6spd auto. The gear selector is P R N D M 1, if I remember correctly. The M stands for Manual and there is a Up and Down switch on the gear selector stalk. You push the buttons to up or downshift, or at least as much as the ecu lets you manually select gears as it will override what you select in some instances. Sorry, I have no idea if there's any mechanical connection between the gear selector stalk and the trans.

VVT makes no difference for swapping, it just makes swapping in an aftermarket cam more involved. As for the Flex Fuel, the Flex Fuel sensor is under $50 and easy to plumb in if it can't be deleted from the ecu.

$1500 isn't a bad price for a 50k mile LS.

[87Skier]

It is a 6L90E, sorry about the typo. I'm used to typing 4L instead of 6L.

I don't think there is anything inherently wrong with the 4.8L. I think they are every bit as good as the 5.3L, but the 5.3L is far more common and seems to be one of those situations that it's worth more because everyone thinks they are better.

I did some more searching it appears that it uses a standard column shift and pattern. Looks like the Trail Blazer guys are swapping out 4L70's for 6L80/90. They have to add a controller and few other things, but it bolts in place and it uses the stock column. It's good to know that there are 3 drive options (D, M, 1). That will work out with my (D, L2, L1) column.

The primary reason I'm changing the engine and transmission is that my current setup really sucks. The 3.07's are great highway gears and get you moving fast enough when empty, but when I take my boat to the lake, and hit some hills or have to get out in traffic, it's a nightmare. I could just change the gears to 3.73 or 4.11, but then highway driving is awful.

So I decided on more gears. Originally my plan was to use a 4L60E that was a cast-in bellhousing, since I already have one, but it needs to be rebuilt, needs a new output shaft, and an output shaft speed sensor. I'll be into the 4L60 at least $1500, before its ready to go in, probably closer to 2k.

On the other hand, using a 6L80 (which is 1.675" longer than a turbo350) or a 6L90 (3.075" longer than turbo350), I shouldn't have to move the transfer case. I'm sliding the engine forward since my current setup essentially touches the firewall. If this were a 4wd 80/90 I would have to buy the Advance Adapters kit for about $700, then factor in the additional seals, bearings, and minor machining to be done to the 205 to make it work. That still puts me ahead of the 4L60 swap, but yes, in the end the turbo350 is a lot cheaper and easier.

[mongocanfly]

If you don't like the 3.07s now your gonna absolutely hate them with a 6l90e..the final gear in that trans is like a .667...with a 30in tire your only going to be turning about 1500 rpm at 65mph..(the taller the tire the more that rpm will drop)...I've got a nv4500 w/od gear of .75 behind my 6.0 and a 4.10 rear gear and I'm turning about 2200 rpm at 65...there's no way I would want a rear gear any higher than my 4.10s

[87Skier]

Yeah, I'll be changing those out with 3.73 or 4.11 a little after getting the engine and transmission in. 3.07s won't work with an overdrive transmission. It only works out to be about 1200 rpm at 60mph.

[First c10]

Not sure the above is accurate.
the stock trucks with the 6L transmissions either have a 3.07/3.08 or the option of a 3.42

I installed a 5.3/6L80E in my sons truck with the stock 3.08...I had to put a posi in it as it would light the one legger up!

Since the the trans has 6 gears 3.08 gears are like 4.11 in first gear.
If you were putting a 4L trans I agree you will need 3.73 or 4.11. but the 6L? I would wait till the truck is running you will be amazed as my sons truck is a rocket.

[87Skier]

Originally Posted by First c10

Not sure the above is accurate.
the stock trucks with the 6L transmissions either have a 3.07/3.08 or the option of a 3.42

I installed a 5.3/6L80E in my sons truck with the stock 3.08...I had to put a posi in it as it would light the one legger up!

Since the the trans has 6 gears 3.08 gears are like 4.11 in first gear.
If you were putting a 4L trans I agree you will need 3.73 or 4.11. but the 6L? I would wait till the truck is running you will be amazed as my sons truck is a rocket.

The plan is to get the engine/transmission in and driving round around, like you said.

I'm skeptical 6th would be usable in my Jimmy though. With 3.07's, 33's, and a 0.67 6th gear, at 60 mph, the engine would only be at 1250 rpm.

Worst case scenario though is that I would have to keep it in 5th, which would be around 1600 rpm.

I think I'll still probably have to change out the gears if I really want to use 5th and 6th, but it will definitely take off quicker with just the transmission change. The first gear ratio will be going from 7.74 to 12.37 (with 3.07 differential), so nearly doubling.

Changing to 3.73 gears. The first gear ratio goes to 15. And 6th gear, 60 mph, rpm goes to a little over 1500.

[First c10]

The size of the tire will change everything as I was not sure what tire you would be running. but remember you don't have to go into 6th gear at 60?
3.08 gear 33" tire at 70 MPH .66 OD =1449 RPM.
3.42 is 1609 RPM
3.73 is 1755 RPM
These numbers are with a locked converter which I doubt you will be locked in each gear, so they will be about 300/400 rpm higher(unlocked). My sons truck is more of a hot rod and it doesn't go into 6th till 65+ and wont shift above 4th gear until 50+
This can be set via the tune. Since I have a 6L I just bought my own HP tuners and play with it myself.
Also with the low gears the thing is going to shift through the first 3 gears very very fast. Good luck and keep us posted

[Daaaanz67]

Subbed.

[57taskforce]

Subbed. I'm doing the same to my K/20

[boynton]

I have this set up (6.0/6l90) in a 2wd truck and had to use a high hump Trans. I'm am currently building a 6.0/6l90/np205 in a 72 blazer. The back of the motor (where I set it up) is about 2-3 inches from the firewall. It looks like this is the best place for it so the trans fits in the high hump without issues and everything clears the mounts. You will also need a new cross member up front for the motor. The pan is super close to the cross member even though I swapped it. This is another reason my motor sits where it does. I agree with first c10. I am running 3.07s in both trucks. As he stated you can tune anything with these new motors/Trans. If you tune your minimum speed for your shifts it doesn't matter what setup you run, the 6 speed will work. As far as the shift linkage it is all electronic. I used lokar's linkage adapter.it hooks right up to your column. I am using a stock column as well. You can see the 2wd in the one owner short step.

[87Skier]

I ended up getting the engine and transmission. Ordered the transfer case adapter, and am in the process of gathering everything to swap the output shaft of the transmission. I just need to track down a few more parts and figure out which style of output shaft I need (there was a change between 2012 and 2014).

I am planning on picking up another 4x4 crossmember and modifying that to fit the engine. I've seen at least one other person do the same. Right now the truck is running and driving, and don't want to tear it apart until I have everything ready so I will probably be taking careful measurements and will move the crossmember fore or aft a few inches to fit the engine.

Originally I was going to go with an off-the-shelf bolt-in crossmember, but after talking to a few difference companies, it was clear they only work if you lift it at least 2". I will be keeping it stock height.

An important note for anyone doing a GEN IV swap:
You only need the gas pedal (no TAC module) and OBD II port from the cab.
Unless you intend on keeping the body control module, you will need to buy a CAN bus cruise module if you want cruise control. Like this one: paceperformance

There are other cruise control kits. The CAN bus makes it easy to setup since you only need the two CAN wires that are connected to the OBD II port. Pretty much everything is wired into the ECM (brake signal, Vehicle speed, etc...), so the module pulls almost everything from the CAN bus.

I have not yet confirmed this but this will likely be the case:
The TUTD (Tap up and tap down) transmission shifting system can be operated via the CAN bus or the wired input. By default, it runs through the body control module over the CAN bus, the TCM must be enabled to use the wired input. This will allow you to use a simple switch with a couple resistors to shift it manually.

If you are using an E38 ecm LT1swap.com has an ECM pinout diagram: pinout This also has the wires that can be removed. I will be confirming that each wires goes to the location described before removing any.

The TCM pinout is attached. Note that XCM is the transfer case control module. It is an extension of the CAN bus to transfer case. These wires aren't necessary unless you are using a newer transfer case that has a control module.

If you have a turbo350 and 205, and plan on buying the advance adapters kit for 6l80/6l90 to 205, it is longer.

Bellhousing Flange TO transfer case mounting flange length for the transmission and adapter:
This is for the figure-8 (non circular) NP205 only!
Turbo350 and adapter: 25.125"
6L80 and advance adapter: 28"
6L90 and advance adapter: 29.4"

The turbo350 to np205 adapter is 3.5"
The 6L80/90 adapter is 4.7" (according to an email from AdvanceAdapters)

I'll probably split the additional 4" of the drivetrain length between moving the engine forward and transfer case back. It's unlikely that you can move the engine far enough forward to avoid having to shorten or lengthen driveshafts.

[boynton]

FYI for my advanced adapter kit I only had to change the input shafts for the transfer case. Mine is a 6l90 (I don't have it together yet so don't quote me on this).

[87Skier]

I have a 2wd 6L90 (36 spline), so I have to change to the 4wd shaft (29 spline).

[boynton]

Ah ha yes I am using a 4wd 6l90 sorry. Thanks for all of the bonus info!

[First c10]

Keep us posted as I am interested in the TUTD setup for my 6L80

[87Skier]

Originally Posted by First c10

Keep us posted as I am interested in the TUTD setup for my 6L80

It took longer than I expected to get around to this. If anyone is curious about the TUTD for the 6L80/90 you don't have to do a lot to get it working if you are doing a swap. Here's what you'll need to do:

1. Run a new wire

Parts:
Wire (18-20 awg)
Weatherpack/Metripack crimper: Amazon
6L80/90 connector: Mouser
Cable seal: EFI Connection

GM didn't hardwire the TUTD. You'll need to add a connector and wire to the transmission harness. See this document from Speartech: Speartech

2. Use a prebuilt switch, like this one: Speartech

OR save yourself about $130 and do it yourself

Parts:
8.25k ohm 1% tolerance resistor: Digi-key
4.42k ohm 1% tolerance resistor: Digi-key
1.5k ohm 1% tolerance resistor: Digi-key
Momentary rocker switch (anything will do here): Digi-key

Wire it up according to the attached schematic. I'll let you decide if you want it all inline and clean or if you want to hot glue the components into the small box or something, but solder everything.

3. Retune your transmission:
You need to tell your computer you are running a 'Hardwire' TUTD, and setup the forced shift speeds. I used HPTuners. Also, these numbers are for a tall geared vehicle, setup your speeds for your vehicle. See the hptuners pictures.

I set mine to engage TUTD when the gear select is D4 (second position for my transmission), and a button press is detected.

[boynton]

Great info. Thanks for the update!

[First c10]

That is awesome!
Thank you!!

Originally Posted by 87Skier

It took longer than I expected to get around to this. If anyone is curious about the TUTD for the 6L80/90 you don't have to do a lot to get it working if you are doing a swap. Here's what you'll need to do:

1. Run a new wire

Parts:
Wire (18-20 awg)
Weatherpack/Metripack crimper: Amazon
6L80/90 connector: Mouser
Cable seal: EFI Connection

GM didn't hardwire the TUTD. You'll need to add a connector and wire to the transmission harness. See this document from Speartech: Speartech

2. Use a prebuilt switch, like this one: Speartech

OR save yourself about $130 and do it yourself

Parts:
8.25k ohm 1% tolerance resistor: Digi-key
4.42k ohm 1% tolerance resistor: Digi-key
1.5k ohm 1% tolerance resistor: Digi-key
Momentary rocker switch (anything will do here): Digi-key

Wire it up according to the attached schematic. I'll let you decide if you want it all inline and clean or if you want to hot glue the components into the small box or something, but solder everything.

3. Retune your transmission:
You need to tell your computer you are running a 'Hardwire' TUTD, and setup the forced shift speeds. I used HPTuners. Also, these numbers are for a tall geared vehicle, setup your speeds for your vehicle. See the hptuners pictures.

I set mine to engage TUTD when the gear select is D4 (second position for my transmission), and a button press is detected.

[First c10]

87skier,
How did you wire your TCC lockup? I just rebuilt my 6l80 and have to do a fast relearn and you have to apply the brake an my relearn aborts after a little bit because it doesn’t see the brake applied. I have wired it every way I have read and nothing.

[87Skier]

I've been having some trouble with this as well. Not sure if you are using HPTuners or some other platform, but mine will only use the brake signal (light blue wire going to ECM and TCM) when the engine is not running.

I'll update when I get a chance to work on it, but as far as I can tell this signal will originate in one of two ways:

1. Either the light blue wire also goes to the BCM and it has to send out a signal (unlikely)

or

2. We need to use the brake position sensor. If you happened to follow the E38 pinout on LT1swap.com, you will notice that pins 26 (signal), 42 (low reference), and 54 (supply voltage) in connector J1 are "Not used". This is where the brake position sensor should be wired in. I went ahead and ordered one, but I won't have it until next week.

I've been struggling to find exactly how the programming in the ECM is setup. It is unclear how the brake position switch (3 wire), and the brake switch (1 wire) work. Some reports indicate that a faulty brake position switch could make it hard to impossible to shift from park, faulty brake lights, and the cruise control system not working. But it doesn't sound like these always happen with one another.

I did find that you need to relearn the pedal park status in the ECM/BCM so you will need a GM tech2 scanner. For now I'll just actuate it in my hand to see if it triggers the brakes applied signal without the BCM present. I'll update next weekend.

[First c10]

I have HP Tuners and cannot locate where in the scanner it will show if the brake is applied or not applied.
Do you know where to find this in the VCM scanner?
Cant wait to see what you find.

[87Skier]

Should be this one. You can add the other channels and see what shows up.

[First c10]

Holy crap, I must have missed the whole brake tab or file. I am assuming yes means applied?