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Old 03-13-2021, 09:07 PM   #1
barraza
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Swapping L86 6.2 8l90e into 72 k10

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
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Last edited by barraza; 03-13-2021 at 09:20 PM.
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Old 03-13-2021, 09:36 PM   #2
barraza
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Re: Swapping L86 6.2 8l90e into 72 k10

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
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Old 03-13-2021, 09:44 PM   #3
barraza
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Re: Swapping L86 6.2 8l90e into 72 k10

Plenty of room for the 8l90e using the factory high hump tunnel
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Old 03-13-2021, 10:26 PM   #4
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Re: Swapping L86 6.2 8l90e into 72 k10

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.
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Old 03-13-2021, 10:46 PM   #5
barraza
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Re: Swapping L86 6.2 8l90e into 72 k10

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
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Old 03-13-2021, 11:24 PM   #6
barraza
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Re: Swapping L86 6.2 8l90e into 72 k10

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.
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Old 03-14-2021, 09:13 AM   #7
regan wilson
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Re: Swapping L86 6.2 8l90e into 72 k10

Nice truck.
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Old 06-13-2021, 09:37 PM   #8
ls1nova71
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Re: Swapping L86 6.2 8l90e into 72 k10

Any updates? Been searching for threads on GenV engines in 4x4's and not finding much.
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http://ls1tech.com/forums/conversion...71-c-10-a.html
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Old 07-01-2021, 10:55 PM   #9
barraza
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Re: Swapping L86 6.2 8l90e into 72 k10

Quote:
Originally Posted by ls1nova71 View Post
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.
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Old 07-02-2021, 08:10 PM   #10
FamilyTruckster65
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Re: Swapping L86 6.2 8l90e into 72 k10

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!
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Old 07-04-2021, 04:13 PM   #11
barraza
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Re: Swapping L86 6.2 8l90e into 72 k10

Quote:
Originally Posted by FamilyTruckster65 View Post
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.
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Old 07-04-2021, 07:06 PM   #12
FamilyTruckster65
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Re: Swapping L86 6.2 8l90e into 72 k10

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.
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Old 07-12-2021, 10:52 PM   #13
cornerstone
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Re: Swapping L86 6.2 8l90e into 72 k10

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!
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