Swapping L86 6.2 8l90e into 72 k10

[barraza]

Picked up a low mile L86 8L90 4x4 to swap into a 1972 K10 Cheyenne pickup. Truck is an original paint survivor, i want to keep it relatively stock appearing. Has a mild lift, approx 3-4” done with Off Road Design custom leafs.

Why are my pictures sideways?? Sorry

[barraza]

My truck originally had a 350 engine, with a turbo 350 trans and a NP205 transfer case. The goal of this is to have a nice factory looking, easy driving truck. IE something i could daily drive, or my wife could hop in and feel comfortable driving. It is not going to be a hot rod, or too off road oriented with huge tires. The plan is to use factory parts where i can, and not spend a fortune. It is the extras on these swaps that can end up hundred dollaring you to death. This is the first test fit

[barraza]

Plenty of room for the 8l90e using the factory high hump tunnel

[barraza]

Plan was to use the transfer case that came with the 8L90e. It is a drivers side output, and of course the np205 is a passenger output for the front. After disassembling the new transfer case, i have changed my mind. While it appears it could be rotated, it would need several modifications. The new T/C uses a clutch pack to engage the front driveshaft, and it has an internal pump to provide hydraulic pressure to function. The pump looks like it would function if the oil pickup was moved to the other side of the case, which could probably be done with some minor tig welding. One mounting hole would need to be moved, but there appears to be enough material on the case to do this. The biggest issue is that the actuation clutch is designed to lock up shafts that are spinning about the same rpm. Like they would do in a stock truck that had the front axle spinning all the time. My truck has a Dana 60 front axle, and i do not want to keep the front hubs locked all the time.
I realize automatic transmissions have similar clutches, and they shift all the time, but they are locking up shafts that are much lighter than the guts and axles of a Dana 60. Also, automatic transmissions have much more fluid, a filter, and cooling capacity to keep anything from overheating. I’ll keep the np205.
An interesting fact, the np205 weighs 134 lbs, the new transfer case weighs 87lbs. This picture shows the pattern on the rear of the 8l90e. It is generally referred to as the “large round” pattern. It is shared with many later transmissions and or transfer cases. A 208 transfer case that was behind a 700r4 uses this pattern (on the transfer case, not the transmission). A Dana 30 case uses it, as do aftermarket cases like the Atlas.

[barraza]

Np205’s came in several styles, depending on whether they were attached to turbo 350’s, 400’s, or manual transmissions. Early ones had a figure 8 front attachment face, later they came with the “large round” pattern on the front. Other manufacturers had drivers side drops, and some were not even attached to the transmission directly, they were called divorced and had a short driveshaft from the transmission to the transfer case. Mine was attached to a turbo 350, and since its a 72, it has the figure 8 mounting face. So i have to convert from the figure 8 to the round pattern, and from the turbo 350 style 27 spline male input to the 32 spline female input. There are two 32 spline inputs, a short and a long. To attach to the 8l90e, the long input is needed because the shift rail of the np205 is on the front and it would require a lot of cutting into the 8L90e case for clearance. The large 32 spline input also has a bigger bearing on the front input, so the case needs to be machined. Not a complicated procedure, a local shop charged me 2 hrs time after i brought them a bare clean case. This picture has the original bearing sitting in the new larger bored hole

[barraza]

Positioning the engine
It sounded relatively easy to drop the engine in, and the first test fit looked great, but the devil is in the details. I wanted to keep the transfer case in the stock location, so the driveshafts could be reused, and the shifter would be easy to come through the floor in the stock location. Unfortunately, when i put the radiator support back on, the fans were too close to the front of the engine. I didn’t want to cut the firewall for clearance. The drivers side is much tighter than the passenger side. I decided to massage the firewall behind the drivers side head for a little extra room, it cant be seen so i guess i can live with it.
The first photo is oil pan clearance to the crossover steering drag link, the second picture is clearance between the firewall and drivers side cylinder head. Third photo is lifting the passenger side suspension with the hoist to check for oil pan clearance. Everything feeds into the engine placement. Put it to far forward and it would need a shallower oil pan, which is one of the $500 things that sneak up on you. My final position is hard to exactly say, as far rearward as possible. The 3 holes from the original mounts are almost centered in the 4 bolt pattern of the 6.2, but i redrilled the factory engine crossmember holes rearward on the frame 1.25 inches. The transmission crossmember moved rearward 1 7/8” . I made my own mounting plates for the engine out of 1/2” aluminum plate, and used the original engine crossmember with the center cut out and replaced with a 3/8” plate, bent to fit the oil pan as tight as possible.

[regan wilson]

Nice truck.

[ls1nova71]

Any updates? Been searching for threads on GenV engines in 4x4's and not finding much.

[barraza]

Originally Posted by ls1nova71

Any updates?.

Yes its running and driving now. Got held up by advance adapters being back ordered on transfer case input shafts. Ill try to gather some pictures and post an update soon. If you want to know anything specific, let me know.

[FamilyTruckster65]

Nice build.

Can you share on what you had to do for a shifter? Also what wiring harness and ecu/tcu set up did you go with?

Thanks!

[barraza]

Originally Posted by FamilyTruckster65

Nice build.

Can you share on what you had to do for a shifter? Also what wiring harness and ecu/tcu set up did you go with?

Thanks!

The shifter for the 8l90e was believe it or not the easiest thing of all. The shift arm the the turbo 350 bolted on the 8l90 with no modifications at all. The frame pivot for the linkage needed one of the two bolts moved a little, it would depend on where exactly the engine ended up. The original column shifter needed to be adjusted slightly and it works fine.

I am using the stock ecm and tcm. My wiring harness was reworked by Mitch at Swaptime. Unfortunately, i would hesitate to recommend him. Way to long to do, and way to hard to get in touch with him. If i was doing it again, i would do the harness myself, and either do the programming myself or send it to Speartech.

[FamilyTruckster65]

Most excellent. Thank you for sharing. When I am ignorant, I like to over complicate things. I really helps to see what others have done to solve the things that come up.

[cornerstone]

I'm doing the same swap in a 72 C10, and am just about to the point of hooking up the shifter. Glad to hear it was a breeze! That's one less thing to rack my brain over. Thanks!

[barraza]

Running and driving now.

[barraza]

Need to update and add pictures to this thread, but haven’t had time. If anyone has a question i can answer though

[FamilyTruckster65]

Well done! It is looking like a clean install. Thank you for sharing.

[barraza]

I had a couple of PM questions about the radiator, so I’m putting a couple more pictures here. This is the drivers side, the fans attaché directly to the radiator. A little trimming allows the front of the radiator to almost touch the front surface of the core support. Moving it as far forward as possible leaves plenty of room between the engine and fans. The 2018 truck water pump is offset to the drivers side, so the lower radiator hose runs across from the water pump to the lower radiator outlet on the pass side. All of the hoses i used are factory 2018 truck. Also in this picture the upper mount is visible, it is the molded in bracket next to the hose. It just needed a spacer to attach to the core support. The lower radiator attachment is a peg on the radiator, that fits into a hole drilled on the lower core support with a bushing. These fans move a ton of air, and are controlled by the factory ECU. They are PWM, so they run at slow speed when only a little cooling is needed, and ramp up speed as demand increases.
This radiator has a small hose on the upper pass side that circulates water through the overflow tank, the overflow is also connected to a small hose near the thermostat. A tank like this is required because it bleeds air from the system and there is no cap on the radiator itself.
I was looking for a foolproof system that was guaranteed to work, be reliable, and not break the bank. I really had no idea any of it would work until i mocked it up, and it turned out being one of the easiest parts of the whole project.

[6600DURAMAX]

So for clarification the radiator and fan setup is from a 2018 Chevy 2500HD style pickup ?

[barraza]

Originally Posted by 6600DURAMAX

So for clarification the radiator and fan setup is from a 2018 Chevy 2500HD style pickup ?

It’s technically from a 2018 GMC Sierra, 4wd, because that is what my engine was out of. I’m not sure what if any differences there are between the 2500 and 1500, but i think i ordered for a 1500.

[barraza]

Little update:
With my current setup, i found i had a battery drain. Took a while to find, but the radiator fans draw power even with everything turned off. Not sure why, maybe it has something to do with the speed sensing they feed back to the ECM. Anyway, instead of powering them with direct battery power, they must be run by a relay switched by the key.

They were using about 40milliamps of power each. Enough to drain the battery in a few weeks.

Another thing to consider when using the 8l90e trans. It has a VERY low first gear, 4.56, and with overdrives, you end up with a wide gear range. There is no reason to use low axle gears.

I love this engine and trans. Best modification i have ever made.

[HYPR]

Originally Posted by barraza

Little update:
With my current setup, i found i had a battery drain. Took a while to find, but the radiator fans draw power even with everything turned off. Not sure why, maybe it has something to do with the speed sensing they feed back to the ECM. Anyway, instead of powering them with direct battery power, they must be run by a relay switched by the key.

They were using about 40milliamps of power each. Enough to drain the battery in a few weeks.

Another thing to consider when using the 8l90e trans. It has a VERY low first gear, 4.56, and with overdrives, you end up with a wide gear range. There is no reason to use low axle gears.

I love this engine and trans. Best modification i have ever made.

I'm doing a similar install on my C20 Custom Camper with the L83/6L90E.
I like what I read about you leaving the LT water pump in place. I did notice you kept the original AC system instead of upgrading to a Vintage Air GEN 5 Sure Fit System. How did you address the Variable Displacement GEN5 LT AC Compressor? As I understand these are not compatible with each other.

[Hart_Rod]

Originally Posted by HYPR

I'm doing a similar install on my C20 Custom Camper with the L83/6L90E.
I like what I read about you leaving the LT water pump in place. I did notice you kept the original AC system instead of upgrading to a Vintage Air GEN 5 Sure Fit System. How did you address the Variable Displacement GEN5 LT AC Compressor? As I understand these are not compatible with each other.

Curious about this as well. TIA

[ls1nova71]

Originally Posted by Hart_Rod

Curious about this as well. TIA

There is a plug on the back of the compressor you just apply power to whenever the clutch is engaged, that will lock it in full displacement. That said, with VA, it may work, it may not. It will likely work but maybe not to it's full potential due to being too much displacement for VA. They are sized for the compressors they use and work best with the correct one. Would probably do better when hooked up to an original factory air set up since they used a bigger compressor.

[Hart_Rod]

What did you do for your fuel system? PWM or return style? TIA

[barraza]

Sorry, I haven’t check in for a while.

Regarding the fuel system: I used a tank and fuel pump from a 96 impala ss.

One of the goals of the whole effort was to to make this truck effortless, ie worry-free. The impala/caprice tank fits up into the frame where the spare was, and the filler neck was extended to poke out at the rear corner of the bed.


I did this for a couple of reasons. First, gasoline is crap now. You never know when you are getting ethanol. Second, i am using a stock impala ss fuel pump with its corresponding reliability.

The impala pump is inside a baffled section of the tank, is submerged, and is quiet. The tank is plastic, the lines are plastic, and they connect to the stainless lines that came with my engine. The fuel gauge works like normal.

There was a very minor amount of trimming of the frame required, 1/4” maybe??

The LT direct injection engines have a high pressure pump inside the engine, and apparently only need a steady supply of fuel at a reasonable pressure to work fine. I used a pressure regulator / return that is commonly used on LS swaps and is generically know as the corvette regulator. It’s off of
C5 vettes.

Everything works flawlessly