'99 Silverado 4.3 to 5.3 Swap with 4L80e bonus

Discussion in 'LSX + Carb Swaps' started by stutaeng, Nov 18, 2020.

  1. stutaeng

    stutaeng I'm Awesome

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    Hello, finally starting on my 99 Silverado ECSB 1500 2wd 4.3/4L60e/3.42 NBS. I've had it since my college years and has been pretty reliable, but has had very low oil pressure and the tranny is acting up. No money for a engine/tranny rebuild, but would like to put some life back into it. Finally retired it from being a daily driver and can work on it as I have time nights and weekends.

    Decided to finally pull the trigger on a 5.3/4L80e swap. I know this is a NBS, but it should be pretty close to the 96-00 OBS. This is my first large project, so it's going to go slow...I'll post photos as I go along, and links to other forums that are useful.

    Trying to go for a stock swap/setup, where possible, on a budget. Goal is to make the truck reliable again to use it on out of town work across the state. May need to tow a 6x12 trailer, so regearing will most likely be required, especially with the tranny swap. Nothing fancy or exotic for this swap.

    Wish me luck!
     
    Last edited: Nov 18, 2020
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  2. stutaeng

    stutaeng I'm Awesome

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  3. stutaeng

    stutaeng I'm Awesome

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    I bit of progress. Pulled the engine and transmission from the truck.

    Took off wiring harness from 5.3 and accessories. Oil pan gasket is leaking a bit, I'm going to pressure wash it and change gasket.

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  4. stutaeng

    stutaeng I'm Awesome

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    Well, little update.

    I dropped in the engine and added some of the accessories. The donor engine was from an 04 suburban and I got the ECU, harness and fuse block. But I foolishly cut off the tranmission harness. And someone had already cut the off the 02 harness because they took the cats.

    I also realized that the '99-'02 and '03-'06 have different interior cab wiring and AC wiring I believe is different. Don't know how that's going to shake out yet...

    Currently trying to weed out tranny/O2 wiring from the 4.3 and will try to integrate into the 5.3 harness.

    Re-pinned the tranmission connector for the 80 also. Gotta add that other input shaft speed sensor.

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  5. stutaeng

    stutaeng I'm Awesome

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    Darn, realized the other day that the 99-02 and 03-06 have different O2 connectors as well. I'm not sure if the current O2 from my 4.3 are even going to work with the 5.3. Looks like I can only use my original transmission connector harness now.

    For the O2 I'm down to either splicing pigtails or getting a complete harness from connector to ECU. Later option is going to be tough, as the trucks I've seen at the wrecking yards don't have the catalytic converters and O2 sensors are almost always cut off. Any advice?
     
  6. stutaeng

    stutaeng I'm Awesome

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    Got the tranmission under the truck, but the rain delayed me getting it bolted to engine. I think that's okay, as I had a chance to understand converter spacing in more detail...

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  7. stutaeng

    stutaeng I'm Awesome

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    Well, not much progress, but some updates. I got another complete harness, DBW throttle body and matching ECU from a 2000 truck. I'll have to get the ECU tuned to my application. I don't know if I should run the EGR or not. The 2000 harness has a connector for the EGR, but the L59 intake & exhaust manifold don't have the provisions for EGR. I have another manifold with EGR, so I can go either way.

    I had to redo the transmission connector repin, and took some photos while I was at it. Also repinned the ECU connector. So I will focus on doing that. This is specific to the 99-02 truck ECUs with Red/Blue connectors, but similar to the 03-06+ Blue/Green.

    Step 1: Undo the gray connector on the transmission. Remove wires S (white,) T (tan,) & U(brown.)

    Wire U will now go where S used to be. Now you have 2 "extra" wires, S (white) and T (tan.) Remove these wires from the loom to the first branch of the wiring harness. Apply a little dap of rtv silicone to the empty connectors.

    Solder your new speed sensor, and this will now be your new output speed sensor on your 4L80e. You can see with the new pigtail, you have plenty of wire for the new connector.


    Step 2:

    a.) Go to your Red ECU connector and look for the Tan wire. It is on #42. Remove this pin and relocate it to pin #23. Same Red connector.
    b.) Go to your Blue connector and look for the White wire. It is on #79. Remove this pin and relocate it to the Red connector pin #22.

    That's it for the electrical portion. All you have to do it get your ECU reflashed.

    Useful links I followed:
    https://lt1swap.com/4l60e_4l80e_harness.htm


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    Last edited: Jan 21, 2021
  8. stutaeng

    stutaeng I'm Awesome

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    Step 2 Photos:

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  9. 1997

    1997 I'm Awesome

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    Nice work.
    Dick’n with those ECU and trans pins/connectors/harnesseses is tedious at best.
     
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  10. stutaeng

    stutaeng I'm Awesome

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    Thanks!

    It's not that bad honestly. If you can swap one wire, you can swap all of them.

    But you just want to take your time and have a little patience. Probably took me 45-60 minutes at most.

    I know they sell those adapters and a new VSS sensor that goes all the way to the ECM, but you still got to add the pins. And this method costs just $10 for the new VSS sensor pigtail. Wiring is all there already, LOL.
     
    Last edited: Jan 21, 2021
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