Doing some LS swap homework

[Suburban_Tyler]

I'm sure LS questions are getting worn out. LS engines swaps are brand new to me. I'm interested in the how to's and peoples experiences and advices. Not so much criticism. What I have is a 1990 GMC R1500 Suburban. It has the tbi350 with a 700R behind it. The odometer shows 235,000. It still runs great but like all machinery, it eventually just gets worn out and tired with time. From what I have been looking at is a brand new engine with a controller and transmission with a controller over a salvage yard engine/ wiring harness/ ecm due to leaning towards a 6.2 and I don't know how much of a pain going through all of the wiring will be out of a used set up. I just think its more of my cup of tea. So I have a few questions that I will break down into sections. Just doing homework at the moment. I haven't bought anything yet.

1. If I was to buy the LS376/480 dbw that GM Performance offers with the engine controller, how difficult will it be to get all of my factory gauges including the check engine along with the battery light hooked back up? Anybody have a link to a wiring diagram for the 1990 Suburban?

2. From what I can tell the LS376/480 has just a single fuel line rail without a return. I assume I would need to do a corvette style fuel line that has the return on the filter? Correct me if I am wrong. What do I need to do with the pump and sending unit? If the return line is before the pressure regulator, how does the pump keep sufficient pressure to the regulator? Is the some sort of regulating in the filter? "I think" I read where somebody used a late model pump and replaced the factory in-tank pump with the higher pressure pump. Would the sending unit lines and flow enough fuel for the engine?

3. As far as a transmission goes 4L80E or 4L85E with a controller. I think my 700R is an electronic version with a electronic speedo. I don't ever recall seeing a speedo cable not that I really paid much attention every time I've been under the suburban which is usually only for oil changes. How much of a pain is it to get all of that stuff working and I would also like to get the cruise hooked back up. Anybody have knowledge with that? I know there is a FAQ with the cruise but I just didn't see the answer I was looking for. Or maybe I did and just don't realize it.
Thanks for any knowledge you can drop on me.

[83GMCK2500]

1. Wiring not hard. Someone here has posted links to a lot of factory diagrams. That GM Crate Engine package should have a harness with everything labeled.

2. Fuel also easy since you have a fuel injected 'burban. Any number of pump upgrade kits can be installed onto your pickup/sending unit and in your tank. With the crate engine it would be easiest to use the 'vette style filter/regulator. The meat & potatoes of this article apply to your questions. Ignore the car specific stuff, it is about swapping an LS motor in place of an earlier fuel injected motor.

3. I don't remember if 90 or 91 started the electronic speedos...You could have your 700R4 (4L60, technically by 1990) rebuilt to handle the LS motor, no problemo. If you do have a VSS (note, that does not make your trans electronic as you referred to) that is great, the ECM will want that signal. If you are still cable driven there are VSS adapters available.

[Suburban_Tyler]

Originally Posted by 83GMCK2500

1. Wiring not hard. Someone here has posted links to a lot of factory diagrams. That GM Crate Engine package should have a harness with everything labeled.

2. Fuel also easy since you have a fuel injected 'burban. Any number of pump upgrade kits can be installed onto your pickup/sending unit and in your tank. With the crate engine it would be easiest to use the 'vette style filter/regulator. The meat & potatoes of this article apply to your questions. Ignore the car specific stuff, it is about swapping an LS motor in place of an earlier fuel injected motor.

3. I don't remember if 90 or 91 started the electronic speedos...You could have your 700R4 (4L60, technically by 1990) rebuilt to handle the LS motor, no problemo. If you do have a VSS (note, that does not make your trans electronic as you referred to) that is great, the ECM will want that signal. If you are still cable driven there are VSS adapters available.

I will have to try to search a little harder on the wiring diagrams. I did find one for the factory 1990 ecm with google but beyond that I haven't seen what I am looking for. Does the ecm hook to the oil pressure and voltage gauges or is it more direct to a sending unit? I can understand that newer vehicles probably run through the ecm then to the gauge such as my 2005 Cummins truck does.

I will have to crawl under the Suburban and check for sure how the speedo is operated. I am ashamed of myself for not knowing 100% one way or the other. Even if it is an electronic speedo I was under the assumption that the transmission was electronic. I guess that is not true. Another reason that I assumed the transmission was electronic is that there isn't a kickdown cable hooked to the throttle body but this might be something I need to look closer at. I'm pretty easy on the ole burb but when I need to get into it it doesn't have a problem going down a gear depending on speed. The converter unlocks on hills all the time as needed but usually stays in overdrive.

[Suburban_Tyler]

So I went and looked at my transmission. It does in fact have wires coming out where a speedometer cable would normally be and the is also a kickdown cable hooked to the throttle body. I guess I just don't pay attention outside of general maintenance unless something is giving me trouble. So I take it that my speedometer is electronic but the transmission is not electronic??????

[83GMCK2500]

Correct. Here: read this. Specifically the end of the article when it talks about the 4L60-E Also, this has a good year break down as well: Novak's 4L60-E Article.

Speedo-drive is NOT indicative of hydraulic or electronic control mechanisms.

[Suburban_Tyler]

Is the same crossmember used in the transmission swap? I kinda have my sights on the 4L80E actually the 4L85E.

[jbristo67]

In

[Suburban_Tyler]

Still trying to find wiring diagrams for a 91 Suburban. I did find one for the engine to the ecm. I don't know if that's all I will need or if I need more than that. I feel that I will. Anybody have any links to threads or pages? I've used the searched function and read FAQ's. Maybe I overlooked something.

[83GMCK2500]

Originally Posted by Suburban_Tyler

Is the same crossmember used in the transmission swap? I kinda have my sights on the 4L80E actually the 4L85E.

Each of those transmissions use the same mount, so the crossmember won't change, but it might need to be moved forward or back depending on length of transmission. Orrrrrr, if you use the adjustable LS motor mounts you can just kick the motor forward a bit. Providing you have front clearance, which if you use electric fans you more than likely will.

Originally Posted by Suburban_Tyler

Still trying to find wiring diagrams for a 91 Suburban. I did find one for the engine to the ecm. I don't know if that's all I will need or if I need more than that. I feel that I will. Anybody have any links to threads or pages? I've used the searched function and read FAQ's. Maybe I overlooked something.

I take it you didn't stumble across this thread: PDFs of Square Schematics, Service Manuals, & GM Training Manuals

Scroll down to the line:

• 1990 GM RV & P Light Truck Wiring Manual | Mirror-1

[Suburban_Tyler]

What size stalls do you guys run in your torque converters? I know different setups have different requirements. Again on the 376/480 GM recommends a 3000rpm. Seems a little high to me but maybe that's just me. I would think on a heavier vehicle that something a little lower would be ideal.