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L18 8.1L swap resource thread

She is in her final resting place before major surgery of being a parts doner . Quick rinse under hood got 5lbs of dirt out and she is clean and all there .

last pic is the 3 here and running . i have 1 parts truck ready for scrap / 1 94 waiting for this ones 8.1/4L80-e and 1 running 02 8.1 / 4L80-e not sure yet maybe in to new plow truck build .


7796.jpg7797.jpg7794.jpg
 
Another one on the hook today . This one is at my friends storage lot . Its got 211,xxx miles runs good body shot and frame shot . Another good parts doner tho . Already ownend it just had to pick it up today .

Up to 4 c3500hd/ 2005 2500hd / 02 motor with spun rod bearing but run good . I think i have an addiction problem .

I am even thinking swap my 2wd c10 from the 5.3 to one of these

7801.jpg
 
Wes Harden said:
I am slowly getting that 8.1 out of the van. To much life getting in the way of shop time.

Few question, any one use the factory instrument tach, if so what did you use for the signal.
I have ordered a throttle cable throttle valve off ebay, GM17096144, and am looking at https://www.summitracing.com/part/trans-dapt-performance-products/2566/853047#instructions for the spacer, is this the correct spacer?
Click to expand...

Spacer for the 7.4L throttle body? I used the one linked below however it’s showing as discontinued.
 
Wes Harden said:
I am slowly getting that 8.1 out of the van. To much life getting in the way of shop time.

Few question, any one use the factory instrument tach, if so what did you use for the signal.
I have ordered a throttle cable throttle valve off ebay, GM17096144, and am looking at https://www.summitracing.com/part/trans-dapt-performance-products/2566/853047#instructions for the spacer, is this the correct spacer?
Click to expand...
You’re talking the wiring for the squarebody gauge but tach signal from the 8.1?
 
Wes Harden said:
Few question, any one use the factory instrument tach, if so what did you use for the signal.
I have ordered a throttle cable throttle valve off ebay, GM17096144,
Click to expand...
Are you bringing over a newer transmission with the 8.1 and just need to make an old cluster work, or are you using old transmission and cluster and need to double adapt?
 
GWeakland620 said:
You’re talking the wiring for the squarebody gauge but tach signal from the 8.1?
Click to expand...
yeah I want to keep my factory gauges esp the tach. since no HEI to signal the tach I am hoping the ecu has a suitable source.
Blue85 said:
Are you bringing over a newer transmission with the 8.1 and just need to make an old cluster work, or are you using old transmission and cluster and need to double adapt?
Click to expand...
yeah going to up grade to the 4l80e, I believe i'll need to have the electronic t case output signal. Speedo is not that important, I could use a gps driven motor to work my factory gauge or just get a gps speedo. I do like my tach.

So who has put a np205 behind a 4l80e ? did it need any clocking how is the front drive shaft clearance ?
 
Wes Harden said:
yeah I want to keep my factory gauges esp the tach. since no HEI to signal the tach I am hoping the ecu has a suitable source.

yeah going to up grade to the 4l80e, I believe i'll need to have the electronic t case output signal. Speedo is not that important, I could use a gps driven motor to work my factory gauge or just get a gps speedo. I do like my tach.

So who has put a np205 behind a 4l80e ? did it need any clocking how is the front drive shaft clearance ?
Click to expand...
Gm did factory 1 year 4L80 & 205 . Also 90-91 electric speedo .
 
Wes Harden said:
yeah I want to keep my factory gauges esp the tach. since no HEI to signal the tach I am hoping the ecu has a suitable source.
Click to expand...
My Howell harness came with a lead labeled tach signal. You have to run a special resistor, but then you use that as your signal and run the rest of the squarebody wiring. I can see what pin it uses for the signal if you want.
 
When I had my ECM reprogrammed, LT1swap.com set the ECM to read as 8 cylinder so it would make the tach read correctly.
I remember they said it could be changed to whatever you wanted.
 
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