8.1L/4L80E swap into 84 Dually

[HotRodPC]

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

That's a Big NO.

 

[77 K20]

Are you going to do the returnless (fuel on demand) system that the newer 8.1's had? Think it started on '04 or '05 if I remember right.
Instead of having a return line and the pump running all the time the pump only supplied the engine with what it needed.
Thought it was an interesting idea. Don't know what is all involved in it. Might be nice to have less fuel lines, and they say it won't clog up the tiny fuel filter as fast. Some said the pump lasts longer also...

 

[1984dually]

Several years ago I installed a carbed engine in an 87 4x4 that was fuel injected. Swapped all the wiring and sending units for stuff off an earlier model. Should have got the tanks too. Ended up buying two new tanks from LMC truck(local yard wanted 200 ea. these were 129 ea)

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When I started I looked for a way to keep the dual tanks. Cleaned up the harness and installed it with a new dash switch. Bought a couple of 255lph high pressure pumps that fit where the tbi pumps were. Found a switching valve that was good for 65 psi(should hold more before bursting).

Turned around the fuel line on the engine so they would exit on the pass side front of the engine(easy access). Didn't want to run two fuel lines too the front so I got a 99 corvette fuel filter that is also a regulator. Put it just ahead of the switching valve. Return port goes to the return port on the valve. One steel line to the front. Plugged the return on the engine. Make for a clean install with no return off the engine.

 

[da_raabi]

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.

So is this basically what it takes to bolt up a 4L80E on a BBC? I've been looking for this bit of info for some time, sounds pretty friggin easy to me. Nice build too, too bad those 8.1s dont have ANY performance parts available without spending huge $$$. I looked at one for about 10 mins for my 80 Camaro and said Nope! when I saw the lack of a/m parts. Looks good!

 

[1984dually]

Swapping from a th400 to a 4L80E is pretty easy. Trans can be bought fairly cheap now. Biggest headache would be the controller(cost as much as the entire engine/trans harness from Howell). Or go manual shift.

 

[da_raabi]

Swapping from a th400 to a 4L80E is pretty easy. Trans can be bought fairly cheap now. Biggest headache would be the controller(cost as much as the entire engine/trans harness from Howell). Or go manual shift.

Interesting, I was planning on manual shift myself so thats no problem. Man, your build thread here just made my life a hell of a lot easier! You know there does not seem to be one definitive swap guide for 4L80Es into squares? I think you may have just fixed that problem...

 

[HotRodPC]

Interesting, I was planning on manual shift myself so thats no problem. Man, your build thread here just made my life a hell of a lot easier! You know there does not seem to be one definitive swap guide for 4L80Es into squares? I think you may have just fixed that problem...

We do have the luxury of having I think 4 members now who have done, 4L80-E swaps, one of them being a 4x4 too. Eventually, I'd like to get all 4 members info together and their input too along the way and compile the info including pics, parts #'s etc into a 4L80-E Swap thread and STICKY it in the Auto Trans section. If you're going manual VB in yours, that will be good input too.

 

[X-cabsquarebody]

Im kinda late to the party,,,, but I swapped an 8.1 into my crew cab 4x4 last winter. I tow cars and tractors, and haul more then driving it unloaded. My engine is an 01 model, with about 30K miles on it. Has not used a drop for oil and gets 7 mpg no matter what. I also have an 8.1 In my motor home. It gets about 12 mpg, and never used oil. I love the.power and torque of the engine. My truck is a 91 and came factory with a 4l80e, but I found a later model trans with 25K on it to swap in. I also have a 3rd 8.1 on my test stand that im going to put in a C10, backed with a nv4500.

So I guess you could say I like them. Still have a few bugs to work out, and hope to tweak the pcm for a little more mpg. But 3.73 gears are the main reason for my bad mileage.

Hit me up if you have some questions, happy to help of I can.

 

[HotRodPC]

So I guess you could say I like them. Still have a few bugs to work out, and hope to tweak the pcm for a little more mpg. But 3.73 gears are the main reason for my bad mileage.

Hit me up if you have some questions, happy to help of I can.

So what gear ratio do you think is going to improve your mileage?

You'd be another that can put some input into a 4L80-E swap thread when the time comes. Stay tuned for that.

 

[X-cabsquarebody]

So what gear ratio do you think is going to improve your mileage?

You'd be another that can put some input into a 4L80-E swap thread when the time comes. Stay tuned for that.

My motorhome has a 4.56 gear, weighs 14000 lbs, and gets almost double the mileage. My truck weighs in at 8500 lbs and when it locks the converter in 4th gear at 60 mph, my RPMs are at about 1800. I have been advised that a gear swap to 4.11, 4.56 would help my truck.

I have 2 91 crew cabs that have factory 4l80e trans. So when the time comes for for the trans sticky, I will do what I can to contribute.

 

[1984dually]

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Most may or may not know the problems with the acc drive system when installing an 8.1 in an earlier truck. Most common swap thread out there cuts the frame for ac compressor and exhaust clearance. Getting the front drive off a Kodiac/Topkick as well as the g vans solves the ac problem. Changing the front brackets moves the compressor to the upper drivers side and the Alt to the pass side. What I have yet to see mentioned is the fact that you need to change EVERTHING on the front of the engine(including the balancer). Everything is moved out about 1in. I got lucky and found another engine with a hole in the oil pan that had everything I needed. All the stuff is available from a gm dealer or a workhorse dealer. For exhaust I used the headers off the pryer 454(hooker) but had to move 1 tube that hit the oil pan. Don't think that would be a problem with most other brands. One other thing is the compressor off the side will not fit the truck brackets. Used one off a 96-99ish vortec engine.

 

[HotRodPC]

My motorhome has a 4.56 gear, weighs 14000 lbs, and gets almost double the mileage. My truck weighs in at 8500 lbs and when it locks the converter in 4th gear at 60 mph, my RPMs are at about 1800. I have been advised that a gear swap to 4.11, 4.56 would help my truck.

I have 2 91 crew cabs that have factory 4l80e trans. So when the time comes for for the trans sticky, I will do what I can to contribute.

OK, that makes sense to me. I figured as much. Just that MOST will be thinking taller gear like a 3.54 or 3.42 will be better. It's so hard to convince people that a lower gear can in fact for a fact net you better mpg. They're all looking for lower rpm when they're not thinking of ALL THINGS CONSIDERED. As in Weight, Wind drag, Tire Size, Transmission Model, What is the vehicles main purpose, what is the main or most used driving condition etc etc.

1 good example, is my C20 with 3.21 rear gears and Th400. For what I use that truck, I'll bet anyone, I'd get much better mpg with 3.73's. I'd actually get better with 4.10's but for the occasional 140 mile round trip to my dads, I'd settle for the 3.73's unless I got an OD trans, then I'd 4.10's since I have them already, but if I had a choice and was having to buy a carrier and gearset, I'd go with 4.56's.

 

[77 K20]

I have 4.10 gears in mine and get better mileage than others I know with 3.73s.

 

[X-cabsquarebody]

Danny, I skipped the a/c part on my swap. I just removed the compressor and hope to find the brackets later . I haven't been able to located any yet. I would like to know we're you got yours, parts #s would would be great.

If your going to run a manual fan, the 8.1 fan will not fit in the 454 shroud. I'm using a Vortec 454 fan, works great. I would suggest pulling the crank sensor and lubing it with some anti seize. I was told to do this to make it easier the pull when its in the truck. It turned out to be good advise, cause it went out.

 

[1984dually]

Can do on the part numbers for the brackets. Will dig them up and post the first of the week. Going racing this weekend. On the engine fan I am using a 6.2 diesel radiator and shroud. Fan fits the hole good. Pulling the crank sensor makes sense. No easier time to do it.