godmadechevy

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?

Atomic

iTrader: (42)

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.

godmadechevy

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?

charcold-bowtie

iTrader: (10)

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.

godmadechevy

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.

Pewter53

iTrader: (36)

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.

charcold-bowtie

iTrader: (10)

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.

godmadechevy

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.

charcold-bowtie

iTrader: (10)

rad should be fine.

godmadechevy

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?