4.8/4l60e to lq9/4l80e
 

Ok here's the deal. I have a 1999 GMC Sierra 1500 (new body) that currently has the 4.8. I'm thinking of doing a 6.0 lq9 swap but want to get a little info first before tackling it since it is my dd. Ok I have done a little research already.

I want an lq9 not an lq4 first off. I know that the lq9s came out of ss silverados, escalades, ssR's, and trucks with the vmax package (denalis I believe were lq4's may be wrong though). Based on my research these engines only came with the 4l65e behind them and since my truck isn't 4wd I cant really use it, correct? Not only that I want the strength and reliability of a 4l80e anyways.

So my question really is what all will I need (and need to do) to convert an orginal 4.8/4l60e truck to an lq9 with a 4l80e setup?

Will the lq9 pcm need to be reflashed with 4l80e firmware?

Finally is converting the 4l65e harness to the 4l80e the same as converting a 4l60e to a 4l80e? 4l60e and 4l65e are electrically the same correct?

True they only came with 4l65e but there are 2wd versions out there, 2wd Vmax and SSS trucks. The SSR had an LS2 which is 6.0 as well.

You are basically looking at two diferent swaps at the same time. The engine part is easy, all you need is to have the PCM flashed. You also need a segment swap for the 4l80e. It may be easier for you to pull the entire harness while you are in there. The 4l60 and 65 are exactly the same externally.

That's what I'm hoping to do is get the harness and everything from whoever I end up buying the motor from. Then all lq9motors should be set up with a 65e harness which will need to be converted to run an 80e correct?

As far as mounting the transmission goes should it mount the same or will I need a different crossmember and mount? I will also need a trans yoke that will fit the 80e right? That should be able to be pulled from a 2500hd truck. Will the original flexplate and converter off of an lq9 work on the 80e as well, or will I need to get those from a 2500hd truck as well?

Your flexplate/converter combo needs to be matched.
either 6 bolt 80e converter with a 6 bolt flexplate
or the 3 bolt 60e flexplate with a hybrid 80e aftermarket converter.

Yes you will cut the crossmember, and have to deal with the yoke.

So I'll have to cut the crossmemeber does that mean it will have to be moved back? The driveshaft can stay the same length right? I'm assuming that the lq4 six bolt flexplate and converter will fit on the lq9 since they are almost the same engine.

you will need to cut your cross member and move the center of it back 6" to the middle of the mounting hole and for wiring search for 4l80e wiring you just switch 2 wires in thepkug and leave one unplugged. Next you will have to run an extra wire to your computer for the extra speed sensor which is easy the connectors come apart and you are right about the flywheel and spacer. The yoke just try to find you an old 2500hd 4l80e driveshaft ahnd get the front yoke off and get a conversion ujoint part number posted on one of these post on the 4l80e conversion.

is this a ECSB. the DS will stay the same length, I just had to trim around a half of an inch of the turbo 400 yoke i bought.

No, sorry shoulda mentioned that. It's a Single cab shortbed. Just as long as I don't have to weld anything because I have never done it, even though I would like to learn.

Can the 4.8 radiator be used with an lq9 with out there being any cooling issues? I'm gonna try to run some TBSS fans I'm getting from a guy up at work.

rad should be fine.

Ok last thing and I'm done till I get closer to the swap... Btw these are two loaded questions, I understand.

I'm 19 and have never done a swap before, but I have a fair amount of knowledge and understanding of how an engine works and what it is composed of. I'm very good with electronics so the electrical aspect shouldn't be that bad. I have several friends that have done swaps and rebuilds who are going to help me with this project. It also helps to work at a Chevy dealership where I have access to SI and the knowledge from techs. One tech who has done this said it isn't very difficult but then another one said it would be a complete mess. With the research I have done and the help from people on here it doesn't seem that difficult especially because on every other guy's sig it say blah blah blah 6.0 swap. I understand there are alot of you guys on here that have been doing this sort of thing for longer than I have been alive, but then again there are a fair amount of young guys on here that do this too. So here are my last two questions, how difficult of a project am I looking at? And. I have an old truck to drive ( that I have done a fair amount of mechanical work on myself) as a back up, but could this thing be knocked out in a week or less with the right tools and the correct parts?

If you have all the parts already and you just need to bolt it in, you could swap them out over a weekend. Being 2wd makes the trans swap much easier.

yes a week? probably a long few days. Motor should be just a swap. tranny a bit more work.

I once had a guy tell me a 80e swap wouldnt work and it will burn up. He worked at a junk yard...

See the thing was I went to ask the tech that does motor swaps and motor work about the swap and he was the one that did it to his personal truck. He said it wasn't difficult but when I asked him how the 4L60E would hold up he said he didn't have many problems but his was an lq4 plus I know I wont help but to keep my foot in it. He said talk to the trans tech about it. So I went to him and asked if I could swap a 4L80E and he said it would be a total mess and that there are two extra sensors and all this stuff. He said he knew a guy that tried it and it wouldn't run but I'm sure he didnt modify his harness correctly or reflash his pcm. I'm NOT AT ALL saying he doens't know what he is talking about when it come to working on a factory set up, but as far as swapping there are alot of guys that seem to be more knowledgable on here. The fact is I do not think many people would attempt this kind of thing if it was that big of a hassle.

Thought I was done. So the ds shouldn't change on a rcsb? As far cooling lines what kind of mod will have to be done? And on the crossmember the platform that the trans physically sits on is what will have to be moved back right? What do I do, cut it and have some more length welded to it? I don't see how the whole crossmember can be moved back seeing how the abs motor and fuel filter are in the way. Are there any pictures of the modified crossmember? Better yet will a 3/4 ton crossmember bolt right up? Sorry guys I have been looking through the 4L80E swaps but just cant find anything that is specific enough for my application.

I just cut my trans cooling line the bottom one and flared the end then put a piece of hose in between the 2 pieces to extend it hasnt leaked yet. The driveshaft stays the same like i stated before just get the 400 yoke or go to the junk yard and get A 2500hd 4l80e drive shaft and get the front yoke off of it and put it on yours with the ujoint I put a part number on one of the write ups on this swap.The cross member has to be cut wide enough for the tranny and the center has to be moved back 6" to the center of the tranny mount hole there are pics floating around here im at work cant post mine.

How much welding is involved? Idk how to weld, I would be having one of my dad's old employees do it. He said he is good but does it take much intricate work to get it to fit?

Thanks alot man. I guess they eliminate that little perch too (I'm not talking about the mount the thing directly underneath that's welded on top of the c/m) that the 4L60E sits on is that just not needed on 80e because they sit down lower?

No, you still need the mount bushing, but with the 4l80e its a few inches back, hence the different crossmember.

Dont buy any of that. But at least you see what it looks like. and the wiring swap is really easy!

I wasn't talking about the mount/bushing I was talking about that metal perch (or are we meaning the same thing but calling it something different) that is welded on top of the factory crossmember of my truck. It sits on top about 2 1/2 inched high then there is the mount and then the trans. Yeah, I'll have my dad's old welding guy modify mine with square tubing. It doesn't seem that difficult. I just hope nothing goes totally south on the whole thing.

square tubing? Just cut that section outta of the crossmember and slide it back 6 inches. Leave the hump in it. Dont move it up or down, just straight back. Then put some pieces of flat strap on each side and weld it all. Add gussets if you want as well.

I know this thread was about 2 months old, but if you haven't finished w/ your conversion, THIS should help out. Not sure if you've found this thread yet, or not. You can pick apart modifications to suit your needs...and if you read through the entire thread, a lot of guys have already done that for you. Hope this helps...