8.1L/4L80E swap into 84 Dually

[1984dually]

Hello, just joined up and a few have expressed an interest in the swap. I will do my best to show what was involved and feel to ask any and all questions.
Truck is a 1984 Chevy Dually that we have owned for 20+ years. Been through several engines during that time from a 454(several),482in gen 6, and even a 1970 400hp Cadillac. All backed by a 400 trans. It is used to pull an enclosed car trailer housing my Drag car. Was either going to buy another truck or spend the money to upgrade the drivetrain and interior in the 84. 84 won. Engine is a 2003 8.1L from a GMC. Trans is a 4L80E from a 4500 topkick. Installation was pretty straight forward. Used the clamshells from the 454 and it bolted in on the stock mounts. You do need to grind a little off a boss close by so the clamshell will fit flush with the block. Trans mount was slid back until the front cross member holes lined up with the rear holes in the frame. Drilled the rear holes in the frame(4), stretched the trans mount holes about 3/8 in and bolted it in. Shorten the front drive shaft about 3.5 in. Nuff for now. Will get into the shift linkage and cooler lines next. thanks for reading

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[84k20]

Damn that thing is hugeee looks good so far!

 

[foamypirate]

That's awesome! Looking forward to seeing the progress. Should be a beast!

 

[HotRodPC]

That'll be a good running truck !!! Just keep the oil jug and the gas can handy. You'll need them both.

 

[1984dually]

First problem that cropped up was the trans cooler lines. Turned out it wasn't that much of a problem. Found these fittings on ebay

http://www.ebay.com/itm/6AN-4L80E-G...pt=Race_Car_Parts&hash=item35bc3d2b69&vxp=mtr


Be aware that the fittings are different from 97 up and 96 down. Both available from Sweet. Braided lines to the frame and steel hard lines to the front. All braided line through a filter and to the cooler.
Up next was the linkage. All these years of playing with chevys and the column linkage was never a problem. They decided to move the linkage 4in farther back as compared to others in a 4l80E. They did move it right across from the front cab mount. Drilled out the upper rivets/welded the original bracket on to a 1/4 steel plate and bolted it to the frame. Had to stretch the rod to reach, Works good.
Next will be the fun part, Fuel system and complete rewire of the truck.

Thanks for looking

 

[HotRodPC]

Really? I never noticed or heard of the manual valve linkage being in a different location.

 

[Rollin_Thunder]

That engine looks gigantic in there. And to think I thought my 454 was big. So what kind of mileage and power do those put out?

 

[1984dually]

Really? I never noticed or heard of the manual valve linkage being in a different location.

I always thought they were in the same place too. Was a surprise when I seen it. Can't remember anybody mentioning that on any other site either

 

[1984dually]

Opinion around is by trashing the torque management system and all the other ecm mods it should go over 400hp with increases torque and mileage. We'll see when it get going down the road. Looking to keep up with a couple of buddy's and their diesels.

 

[89Suburban]

Great project. Subscribed.

 

[HotRodPC]

Opinion around is by trashing the torque management system and all the other ecm mods it should go over 400hp with increases torque and mileage. We'll see when it get going down the road. Looking to keep up with a couple of buddy's and their diesels.

I hope you're right. I'd like to see this go real good. I've often wanted to hear good things about the 8.1 but all I ever hear is major gas hog, like 6mpg and drinks damn near as much oil as it does gas.

My step bro bought a used one and I said uh oh, oh no and he asked why since it's low mileage, like 32,000 when he bought it, it's got many many good miles left. Told him what I'd heard. 6 months later he took his loss on it and got rid of it. He said 5 mpg towing his little single axle enclosed trailer for work and 8mpg empty, adding 2 qts of oil between oil changes between 3,000 and 4,000 miles. It was an early one though, 02 or 03 IIRC.

 

[77 K20]

I hope you're right. I'd like to see this go real good. I've often wanted to hear good things about the 8.1 but all I ever hear is major gas hog, like 6mpg and drinks damn near as much oil as it does gas.

My step bro bought a used one and I said uh oh, oh no and he asked why since it's low mileage, like 32,000 when he bought it, it's got many many good miles left. Told him what I'd heard. 6 months later he took his loss on it and got rid of it. He said 5 mpg towing his little single axle enclosed trailer for work and 8mpg empty, adding 2 qts of oil between oil changes between 3,000 and 4,000 miles. It was an early one though, 02 or 03 IIRC.

I had heard all of this also 6 or 7 years ago when I was looking for a truck to tow my 5th wheel (needed more room in cab with the addition of another daughter). I was looking for a duramax but came upon a 8.1L instead. It was roughly $12,000 cheaper than a duramax so I bought it.

Using 5W30 regular oil it did use oil. I switched to Mobile 1 high mileage 10w30 synthetic. Useage dropped by about half and I have better oil pressure now.

At the beginning I thought the truck was gutless at least for passing on the highway. Got a custom tune by BlackBear performance and it really woke the engine up (removed torque management and did a bunch of other things).

But one difference from most other trucks is I have the manual trans- the ZF6. It has been great for towing and also better for power and gas mileage.

I have been using Fuelly to keep track of gas mileage for the last almost 12,000 miles. I have averaged 11.7 mpg. Best tank without towing has been 16.5 mpg, and the worst one when towing has been 7.1 mpg.

 

[1984dually]

Have some buddies who pull 24ft enclosed car trailers weighing in a 10000lbs =/-loaded.
1 2013 Dodge 6.7 1 2012 ford 6.7 1 2006 dodge 5.9. All pull good. Been with all of the at one time or another and fuel mileage has been running around 11-12 loaded. We travel and it his hilly here. Running the number with cost of a diesel conversion vs the 8.1L gas the numbers are better with a gas at 9mpg. Take a long time for me to recoup the cost difference. Would I like a diesel? yes but if I can get the same mileage as
77K20 I would be thrilled. More coming later.

 

[HotRodPC]

I agree. You guys do math like I do. This is why I never had a Diesel, well a good one anyway. For the mileage I drive, and the cost difference, the value was not there for me. Also, maintenance it much higher and the fact I feel very confident working on any gas motor, and know just enough about Diesel to get myself in over my head, and being able to do my own work saves thousands. Then you hear, but a diesel will run 400,000-500,000 miles and you only get max 200,000 out of a gas motor. Maybe true, but I can also buy 2 gas motors for the price of 1 diesel, and being I bought a new truck every 8-16 months, I RARELY got over 25,000 miles on a truck and was getting a new one. All I ever paid for was oil changes and I only did that cuz I can't see tearing up a motor and neglecting just cuz it won't be mine in a few months.

But I sure wouldn't mind a Cummins 6BT conversion into a square now days.


I did have a 95 K2500 X cab with 6.5 TD/NV4500 I bought brand new, had it 6 months and got rid of it to qualify to buy another house. Had to get out of the payment for debt to income ratio. Then after getting the house and finances adjusted, bought a 96 Crew Cab Dually 6.5TD/4L80-E. At any rate, I don't even really count those, didn't have them long.

 

[torchred]

Are parts exchangeable between the 8.1 and the 4.8/5.3/6.0?