LS Swap Dually Questions - First Timer

[Android04]

I've been reading through all of the facts and the internet for about a year now to prepare for this moment. This weekend I start the process of my LS Swap by pulling the motor from the donor vehicle. So here is what I got:

Donor: 2004 Yukon 5.3L 4L60E - Runs and drives like it's brand new
Transplant: 1985 2WD Dually 400sbc and TH400 are already out of it

Parts Already Ordered:
Dingo Motor Mounts
AC Delco EP381 Fuel Pump
Dorman PN692-027 Sender
Wix 33737 Single Return Filter
Fuel Line's and Russell Fittings
Fuel Injection Hose Clamps

Parts still needing (please suggest if I need anything else):
Poly Mount Inserts (suggestions?)
Standalone Harness (suggestions?)
EGR Block Off Plate (Needed?)
ECM Flash (Suggestions?)
87 Fuel Tank (Maybe)
Speedo Converter Box (Maybe)
Dakota Digital gauges (stimulus check haha)

Questions:
1) What oil pan should I run, I do plan to lower the truck after the swap is done and running reliably for a while? Holy-302-2?

2)Will I need to change out my cross member? If I recall correctly the dually has plenty of room.

3) Can I run my 85 Fuel Tank (brand new) with the 87 sending unit and pump? Or should I just order a 87 baffled tank?

My Dually is currently off in paint so I decided to use that space to pull everything needed out of the Yukon and start parting it out. I won't get it back for a month or so which gives me plenty of time to get stuff knocked out.

I know TONS of these threads are made, and once I have everything above I plan to start a build thread. I appreciate any and all help! I'm excited to finally start yet another journey. I'm basically building this as my daily and to pull a small trailer for our 4 wheelers and to maybe pull my 65 C10 to out of town shows.

[biketopia]

Are you dead set on using the stock ECM and harness? Are you doing any motor upgrades before transplant, or maybe after? Have you looked into doing a holley terminator x max? You get a new harness, engine and transmission management, self learning, and the ability to lap top tune everything, without additional HP tuners or EFILive credits. You also get a handheld to monitor engine paramters, or you can get a holley dash to see everything and people make a mount for them for those trucks. If you're leaving it mostly stock then stock harness and ECM are ok, but if you like to tinker and want to learn the holley the system, it's a very attractive choice. I'm not super familiar with the square body's, but I think you can actually keep the stock truck pan. There's block off's on Ebay for the EGR. Are you going though the 4l60, they can be made to last, if you're towing with it I'd suggest a huge cooler at a minimum, and maybe a build as well. I would also open up the engine and do a high lift truck cam to bring the torque in down low where you want it. A high lift truck cam from Summit, or Texas speed, isn't a massive cam, it's just their marketing. I put a low lift texas speed truck cam in my 08 and wish I went with the high lift version as it moves the torque curve down lower.

[Android04]

Originally Posted by biketopia

Are you dead set on using the stock ECM and harness? Are you doing any motor upgrades before transplant, or maybe after? Have you looked into doing a holley terminator x max? You get a new harness, engine and transmission management, self learning, and the ability to lap top tune everything, without additional HP tuners or EFILive credits. You also get a handheld to monitor engine paramters, or you can get a holley dash to see everything and people make a mount for them for those trucks. If you're leaving it mostly stock then stock harness and ECM are ok, but if you like to tinker and want to learn the holley the system, it's a very attractive choice. I'm not super familiar with the square body's, but I think you can actually keep the stock truck pan. There's block off's on Ebay for the EGR. Are you going though the 4l60, they can be made to last, if you're towing with it I'd suggest a huge cooler at a minimum, and maybe a build as well. I would also open up the engine and do a high lift truck cam to bring the torque in down low where you want it. A high lift truck cam from Summit, or Texas speed, isn't a massive cam, it's just their marketing. I put a low lift texas speed truck cam in my 08 and wish I went with the high lift version as it moves the torque curve down lower.

Thank you for responding.

I do plan to leave it stock and have looked at the Holley EFI stuff and would love to do it, but that will put me way outside of my budget for the swap. I did also look at some Texas speed options and such, but figured I might as well leave it stock for atleast a few years or unless the motor starts to get lazy.

The 4L60 will be gone through and beefed up, we have a local transmission guy who quoted me already for it. It will be going to him this Sunday.

[tinydb84]

Originally Posted by Android04

Parts still needing (please suggest if I need anything else):
Poly Mount Inserts (suggestions?)
Standalone Harness (suggestions?)
EGR Block Off Plate (Needed?)
ECM Flash (Suggestions?)
87 Fuel Tank (Maybe)
Speedo Converter Box (Maybe)
Dakota Digital gauges (stimulus check haha)

Questions:
1) What oil pan should I run, I do plan to lower the truck after the swap is done and running reliably for a while? Holy-302-2?

2)Will I need to change out my cross member? If I recall correctly the dually has plenty of room.

3) Can I run my 85 Fuel Tank (brand new) with the 87 sending unit and pump? Or should I just order a 87 baffled tank?

I sent my harness out to be reworked. There are lots of people who do it online. You can buy a new harness for your on Amazon now too. After wiring mine up I think I'll do my own harness next time. It doesnt have as much to it as I initially thought.

Since you are staying stock you can send your computer out to have the VATS/rear O2 sensors removed. Again there are tons of people who can do it online.

I managed to get all my stock gauges to work (the speedo took a bit more work). Check out all the threads by aggie91 or LS1nova. They both have write ups on gauges and getting them to work.

For your specific questions-

I ran an Fbody pan. They are more expensive but I moved my engine down and back and wanted the most clearance possible. Lots of people use the muscle car pan since they are cheaper and a bit shorter.

Not sure which crossmember you are referring to but both the front and the trans crossmember can be used.

You could probably get away with the 85 tank as long as you keep the tank over 1/4 full. I would spend the extra few bucks and get the proper baffled tank.

[mongocanfly]

Having done a similar swap...(LQ9/NV4500)..
I used the Ebay adapter plates and stock sbc mounts...
Stock oil pan clears just fine...
I used the stock crossmember, but did have to move it and redrill holes..
I kept my stock tank and ran a inline pump...
I used a psi harness..where you plan to mount the ecm can be a headache..I've got mine wedged under the dash...with the factory ac box theres just not much room under there..I wanted to mount the ecm under the seat,but psi isn't long enough...I've since heard that BP automotive is long enough to mount ecm under seat, but cant 100% confirm it...I've always used psi, but my next build I'm going with bp..
I had a local guy unlock my ecm, then we put it on his dyno after i got the truck running...I highly recommended the dyno..it let's him fine tune everything ..it ran great with a basic unlock and generic tune , but what a difference after the dyno..
I used a Dakota digital speedometer converter box to go from pulse to cable..

[truckdude239]

2004 should not have an egr btw i think they stoped egr in 2002

[biketopia]

If you're confident in yourself, which you are doing a swap so you should be great, go check out lt1swap.com for harness info. There's a ton of info on de pinning and building your own harness. Just takes time, and a few tools. If you're balling on a budget I'd go that route before spending money on a new harness. Junk yards and for sale pages are full of harnesses for these things. LT1swap can flash your computer, and honestly there's probably someone right down the street from you that can do it too. Ask some people in the local scene, or stop by a shop and ask, someone is bound to know someone.

[LS short box]

If you change your mind on a cam upgrade you need upgraded valve springs and push rods. You didn't say many miles on the engine but if its a lot I would pull the timing cover check the timing chain for wear. Also if lots of miles maybe a new oil pump. Check oil seepage from the rear main seal and oil pan.
In regards to the oil pan I would not run a pan that hangs down below the cross member.
I like Howell Fuel Injection and Speartech harnesses. You can send them your ECM and they can reprogram as needed. They can set your shift points if you send them your tire diameter and gear ratio. Shift Works sells a trans tail shaft conversion that includes a mechanical speedo drive but its not cheap.
I would go with a baffled 87 tank. They aren't expensive.
My thoughts on LS swaps is that use as many "stock" parts as possible so if something goes bad parts are available at the nearest parts store.
Good luck with your swap.

[biketopia]

Needing new push rods and valve springs is not 100% needed in all cases. A low lift cam like mine does just fine with stock springs, if you go to the high lift version, all they recommend is a set of stock LS6 springs, still pretty cheap and readily available, no need to change push rod length either in my case.

[TrybalRage]

I know you already have the Dingo mounts, but I cannot recommend the Tejas Steelworks mounts enough. You get to keep the factory truck pan, they keep the motor high enough that the pan is flush with the crossmember and you can even run the 5.3 low mount AC pump.

I used them on my 85 with new clamshells on the crossmember and the motor dropped right in.

[mongocanfly]

Tribal..
do you have any pics of your low mount ac..?..I flipped thru your build quickly, but didnt see any..
There is no way I could do a low mount ac on mine without a nice sized frame notch..that's the last thing I have left to do on mine is hook back up the ac..I was gonna go high mount..

[TrybalRage]

Originally Posted by mongocanfly

Tribal..
do you have any pics of your low mount ac..?..I flipped thru your build quickly, but didnt see any..
There is no way I could do a low mount ac on mine without a nice sized frame notch..that's the last thing I have left to do on mine is hook back up the ac..I was gonna go high mount..

No pics because I haven't gotten around to getting a compressor yet. The donor motor didn't come with one, unfortunately. But keeping the swap motor AC without notching the frame (or a small notch for the hoses) was one of their goals with the design.

If you're on facebook, visit the Square body LS swap group: https://www.facebook.com/groups/267895843406925

I stole some images that other folks put there:
https://imgur.com/a/HKsOW6E

[gmc684x4]

Muscle car pans are deeper then the fbody pan although the sump front to back is shorter
The holley pan or its knock off are a lot like the fbody pan with a shorter front to back sump length

[Android04]

Thank you everyone for the replies. The swap has 115k miles on it and have drove the donor vehicle around for a couple weeks to make sure no issues. Great Oil Pressure, no over heating, etc.

As for balling on a budget, that is the case two kids and multiple vehicles but I do think I plan to go with a BP Harness. I'm also just going to order a 87 tank to avoid the issues once the motor is in. I have a pretty tight budget I've set aside so Dakota's are way out the window. I know all of my gauges work, so now that is my game plan to get everything needed to make those work.

What about cruise control? My 85 has it and in the harness break down you can pick with or without CC. I plan to call them once I get some downtime from work this week. Dingo mounts weren't that expensive so I may look at Tejay's and just sell the Dingo's.

Again thanks everyone for the help so far. Getting closer and closer..

[biketopia]

Is your donor DBW or DBC? If it's drive by wire I think it's fairly "easy" to make work. I'm sure it's about the same work if it's DBC but you'll need the factory cruise cable and box as well.

[gmc684x4]

I would ask your tranny guy about a 4l80e swap
A stock 4l80e is already 1 ton rated

Your building a 1 ton I would think you will use as a 1 ton load wise trailers campers etc .

4l60e is a light duty 1/2 ton tranny
As Clinebarger stated in a tranny thread
He can build a tough 4l60e for about $5000
Compared to a built 4l80e for about $2500

http://67-72chevytrucks.com/vboard/s...d.php?t=812006

[ls1nova71]

Originally Posted by Android04

What about cruise control? My 85 has it and in the harness break down you can pick with or without CC. I plan to call them once I get some downtime from work this week.

A 2004 Yukon will be DBW, and an '85 Chevy truck with factory cruise will already have the switch you need. If the swap harness has the cruise control wires, it's as easy as hooking them up to your switch already in the truck. Under the dash where the cruise switch wiring plugs into the underdash harness you will find there are 4 wires in that connector. Basically you would need to cut the gray, dark green and dark blue wires there and wire them into the wires provided in the LS harness. The colors will probably be similar, but if they aren't, they should at least be labeled. Gray will go to the 'on/off' wire, dk green to the 'resume/accel' and dk blue to the 'set/coast' wire. The fourth wire will be pink and needs to be hooked to an ignition source so that it has 12v whenever the ignition is on. You "shouldn't" have to do anything with it, but you never know what has been done to a truck in 35 years, so you would have to verify it to be sure.

[Android04]

Originally Posted by gmc684x4

I would ask your tranny guy about a 4l80e swap
A stock 4l80e is already 1 ton rated

Your building a 1 ton I would think you will use as a 1 ton load wise trailers campers etc .

4l60e is a light duty 1/2 ton tranny
As Clinebarger stated in a tranny thread
He can build a tough 4l60e for about $5000
Compared to a built 4l80e for about $2500

http://67-72chevytrucks.com/vboard/s...d.php?t=812006

Thank you for the thread and suggestion, I will ask him on Sunday when I drop it off.

[Android04]

Originally Posted by ls1nova71

A 2004 Yukon will be DBW, and an '85 Chevy truck with factory cruise will already have the switch you need. If the swap harness has the cruise control wires, it's as easy as hooking them up to your switch already in the truck. Under the dash where the cruise switch wiring plugs into the underdash harness you will find there are 4 wires in that connector. Basically you would need to cut the gray, dark green and dark blue wires there and wire them into the wires provided in the LS harness. The colors will probably be similar, but if they aren't, they should at least be labeled. Gray will go to the 'on/off' wire, dk green to the 'resume/accel' and dk blue to the 'set/coast' wire. The fourth wire will be pink and needs to be hooked to an ignition source so that it has 12v whenever the ignition is on. You "shouldn't" have to do anything with it, but you never know what has been done to a truck in 35 years, so you would have to verify it to be sure.

Perfect! That's what I like to hear. Thank you for the knowledge