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Old 01-03-2019, 07:50 AM   #1
Kcorey
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LS 6.0/4l80e swap - What tcase and fuel system ?

Hello all. I have a 1970 k20 cheyenne i am wanting to swap a 6.0 LS and 4L80E transmission into. Couple questions , what transfercase have all used to retain the 4wd i know i am going to have to have driveshafts made? Also i am planning on using a pacific fab engine crossmember, what transmission xmember have others used? My truck has a aux tank from the factory, what have you guys done to supply the engine with fuel while using the factory tanks? Thanks
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Old 01-03-2019, 09:54 AM   #2
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

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Hello all. I have a 1970 k20 cheyenne i am wanting to swap a 6.0 LS and 4L80E transmission into. Couple questions , what transfercase have all used to retain the 4wd i know i am going to have to have driveshafts made? Also i am planning on using a pacific fab engine crossmember, what transmission xmember have others used? My truck has a aux tank from the factory, what have you guys done to supply the engine with fuel while using the factory tanks? Thanks
as for the transfercase, the 2500 non HD that the 6.0 and 4l80e come out of use either a NP261 manual shifted or NP263 electronically shifted transfercase. it would be easiest to go with either of those, the 261 being the easiest as to not have to run any wiring for the push button transfercase selection.
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Old 01-03-2019, 03:45 PM   #3
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

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as for the transfercase, the 2500 non HD that the 6.0 and 4l80e come out of use either a NP261 manual shifted or NP263 electronically shifted transfercase. it would be easiest to go with either of those, the 261 being the easiest as to not have to run any wiring for the push button transfercase selection.
He will not be able to use the NP261 or NP 263 transfer case... the front drive shaft is on the wrong side..... the 72 uses a passengers side front drive shaft.... the 89-91model 241C out of a k-20 burban with a turbo 400 or 4L80E will be the right one.. passengers side drop with electronic vss....
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Old 01-03-2019, 08:29 PM   #4
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

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He will not be able to use the NP261 or NP 263 transfer case... the front drive shaft is on the wrong side..... the 72 uses a passengers side front drive shaft.... the 89-91model 241C out of a k-20 burban with a turbo 400 or 4L80E will be the right one.. passengers side drop with electronic vss....
actually you are correct, i believe they went driver side drop in 73 or maybe 76.
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Old 01-03-2019, 08:47 PM   #5
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

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actually you are correct, i believe they went driver side drop in 73 or maybe 76.
All of the solid axle trucks are passenger drop. Drivers drop started with IFS in 1988. There were some overlap years with the V series trucks that went to 91.
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Old 01-03-2019, 09:14 PM   #6
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

A np241 will fit a 4l80 and be pass side drop...can be found in 91 burbs I know
Really no need for a engine crossmember...you can use adapter plates and it'll bolt right into the small block mounts..can do the same with the trans crossmember if you get the right one...
On the fuel ,I use vett style filter reg and a walbro 255 inline pump
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Old 01-03-2019, 09:36 PM   #7
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

I was reading some threads where they say you need a different engine crossmember ? I’ll have to look for a 241 out of that truck. I was also reading about using the corevette regulator , will have to figure out plumbing to utilize both the fcurrent fuel tanks . Install the fuel pump right inline with the current supply line? It will draw OK from the stock pickup of the tank?
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Old 01-04-2019, 04:28 PM   #8
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

Im not sure what your reading on crossmembers... but with adapter plates a LS will bolt right in where a smallblock does and use the smallblock motor mounts...you may need to swap/modify the oilpan for axle clearance though...

And No...dont use your stock fuel lines...you'll need to upgrade to high pressure fuel lines...I have my pump p mounted above the tank and it works just fine...I'd keep it as close to the tank as possible....you'll need a return less fuel system to run the vett reg and you'll need a return port back into the tank no matter what...you can modify your tank for a in tank pump but I'm not dealing with dual tanks either...
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Old 01-04-2019, 06:31 PM   #9
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

You can also use a np205 out of 85 and up square body trucks with sm465 and 400 turbo trucks as as they are 32 spline female input shafts
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Old 01-09-2019, 12:25 PM   #10
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

From my understanding the crossmember has to do with running the stock ls ac compressor with the engine in certain locations. Will you be running ac?
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Old 01-09-2019, 02:16 PM   #11
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Talking Re: LS 6.0/4l80e swap - What tcase and fuel system ?

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You can also use a np205 out of 85 and up square body trucks with sm465 and 400 turbo trucks as as they are 32 spline female input shafts
you cannot use this one because it has the mechanical speedo cable... the 4l80e uses a electronic speed sensor to shift the transmission...
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Old 01-09-2019, 08:38 PM   #12
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

I plan on running ac . The truck came with factory air so I would like to retain that feature
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Old 01-10-2019, 10:51 AM   #13
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Re: LS 6.0/4l80e swap - What tcase and fuel system ?

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I plan on running ac . The truck came with factory air so I would like to retain that feature
Well I will be tackling this myself in the near future. My understanding is with conversion mount adapters you gave to put the engine in the forward position with stock crossmember, frame stands, and stock low mount ac on the ls. I have seen a few 2wd guys extend the engines frame stand so they could move the mount reward without moving the actual engine. In my mind I’ve had two thoughts on this, slice and dice a 2wd crossmember from a square body and move it back on the frame rails creating plenty of clearance for the compressor. The second is the same but with the 4wd crossmember, but dictated by amount of lift and in my case crossover steering. I’m opting for a square body 4wd crossmember slid back 2 inches which will allow my frame stands to be closer to the position of the stock ls mounting, Ofcourse this is all theory as I haven’t put my crossmember under the frame yet.
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