1977 Square Body GMC C3500 Dually L92/4L80E Swap
#1
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Hi, I figured I should share the L92/4L80E convertion I'm doing on my 1977 crew cab GMC dually. The truck used to have a 350ci SBC with a SM465 transmission but I'm tired of shifting and ready for more power. I use this truck for my shop and do a ton of towing with it. I was going to go with an LY6 but ran into an amazing deal on this L92/4L80E. The motor will stay stock for a little wile at least until I get bored. I'm utilizing the stock radiator and fan shroud with an Avalanche fan and clutch. Here's some pictures of the truck.
![](https://scontent-a-iad.xx.fbcdn.net/hphotos-frc3/1465212_511943422246176_694906930_n.jpg)
![](https://scontent-a-ord.xx.fbcdn.net/hphotos-prn1/t1.0-9/1623732_10151864762211035_1877517940_n.jpg)
![](https://scontent-b-iad.xx.fbcdn.net/hphotos-ash3/1000601_508665349240650_697691222_n.jpg)
The old 350 SBC/SM465 next to the new L92/4L80E
![](https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-prn2/t1.0-9/1958007_10151950043541035_473510421_n.jpg)
This is the exhaust I'm running, I built it out of some leftover exhaust pieces I had around form past projects.
![](https://scontent-a-ord.xx.fbcdn.net/hphotos-ash3/t1.0-9/1796650_10151903587046035_1103013378_n.jpg)
Here's the engine and trans set in the hole.
![](https://scontent-a-iad.xx.fbcdn.net/hphotos-frc3/1465212_511943422246176_694906930_n.jpg)
![](https://scontent-a-ord.xx.fbcdn.net/hphotos-prn1/t1.0-9/1623732_10151864762211035_1877517940_n.jpg)
![](https://scontent-b-iad.xx.fbcdn.net/hphotos-ash3/1000601_508665349240650_697691222_n.jpg)
The old 350 SBC/SM465 next to the new L92/4L80E
![](https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-prn2/t1.0-9/1958007_10151950043541035_473510421_n.jpg)
This is the exhaust I'm running, I built it out of some leftover exhaust pieces I had around form past projects.
![](https://scontent-a-ord.xx.fbcdn.net/hphotos-ash3/t1.0-9/1796650_10151903587046035_1103013378_n.jpg)
Here's the engine and trans set in the hole.
![](https://scontent-b-ord.xx.fbcdn.net/hphotos-frc1/t1.0-9/1979491_10151950047546035_608607014_n.jpg)
Last edited by MuscleCarDynamics; 04-01-2014 at 07:23 PM.
#5
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I used an external walbro 255 fuel pump, later down the road I might put it in the tank but I didn't want to pull the bed off the truck. I am using a PSI harness on this project. This is the first time I've used them and I don't know if I will on my next harness (I hate the plastic wire covering). I've used speartech and the GM performance harnesses and I think I like speartech's the most out of all of them.
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#18
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It's all buttoned up and even got the AC system hooked up and running again (AC is a must for me living in FL). I did the intake like this to shield the filter form water coming off the tires in the rain as the truck doesn't yet have inner fenders. The trans wasn't shifting and seemed like it was stuck in 2nd gear in default so I sent the ECU and TCU back to PSI and I'll have it back tomorrow.
![](http://i90.photobucket.com/albums/k280/musclecardynamics/get-attachment_zps5de44f66.jpg)