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How to install TRUE down pipe - Done - soon to be in the DIY section

34K views 66 replies 31 participants last post by  chingon 
#1 ·
Installation vehicle- 04.5 LLY with MBRP 4" full exhaust with catless pipe.

I haven't noticed any immediate change in EGT's, but it does seem they drop faster. I'll have to keep an eye on them to be sure. The stock down pipe is MUCH heavier than the new one.

Here are the tools you’ll need.
10mm open end wrench - This one for the 3 bolts holding the heat shield on the turbo.
7/16” open end wrench - This one for the clamps on either end of the down pipe itself.
14mm socket and wrench for the retaining bolt on holding the down pipe in place
WD40 to spray on new flange and old bolts
Gloves and a cold engine
I also had to do some machining on mine to make it fit so you may need a dremel as well.



DO NOT attempt this on a warm engine. Just starting your truck for a few seconds cranks the exhaust temp to 200+ degrees. Also use some mechanics gloves or be VERY CAREFUL because the heat shielding around the turbo and down pipe is VERY SHARP..I have the cuts on 4 fingers to prove it.

First thing you need to do is remove your front pipe and either remove it completely or just unbolt it and move it back like I did mine. If you have a cat on yours then it might be better to remove it all together since you loosen the 4 bolt flange anyways, on vehicles that have that flange. The front pipe mounts to the down pipe with a band connector and you’ll the 7/16” wrench to remove it.



Once the front pipe is out of the way that gives you free access to the down pipe from underneath. You can see the retaining bolt that holds the down pipe secure. Use the 14mm socket and wrench to remove it.


You don’t need to remove your transmission dipstick completely, but you do need to loosen the bracket holding it to the block so you can move it around, you’ll need this in future steps. There are two nuts holding it down, just loosen them and the bracket slips out on top keeping the dipstick in, but able to move around.

Now go on top in the engine compartment and using the 10mm wrench remove the 3 bolts holding the turbo heat shield on the top. Just lift the shield up and lay it back out of the way. It was more of a pain trying to remove it completely and just easier moving it out of the way.


Now you can see the down pipe and where it connects to the turbo housing. Use the 7/16” wrench and unloosen that nut on the clamp. Remember, righty tighty, lefty lucy.


Now the down pipe is loose on top and bottom. To get it free you’ll need to put your hands on it and wiggle it back and forth to get it to come out of the turbo housing. It fits inside of it about a quarter inch. Just keep wiggling it side to side and it will work it’s way out.

Once that is removed from the housing move your transmission dipstick to the other side of the cooling lines shown in the picture. This moves it enough out of the way to get the stock pipe out of there through the bottom. Don’t waste your time trying it another way. I spent hours on this just so I have this down. If you find a better way then let us know.


The stock down pipe will come out the bottom with some twisting and turning with no problem.



Now comes the fun part. After trying to install this several times and the retaining hold and bolt would not line up with the new pipe I had to resort to using my dremel. I widened the hole that is on the new downpipe just enough that it doesn’t hurt the integrity at all, but enough that the bolt will fit through it. Instead of a perfect circle in the first picture I had to make it more of an oval shape pointing towards the flange.



Ok, once the hole was big enough for the retaining bolt to fit I snaked the new pipe up from the bottom and loosely put the bolt on so I could move it around if I need to. Before you put the pipe in there clean the flange that will go inside the turbo housing very good and get any over spray off of it. It helped me to put some wd40 on that flange as well to help it slide in there. I still had to wiggle it back and forth, but it went in easier with the wd40.


Once you have the new pipe flange inside the turbo housing, fit the band clamp around it and tighten it down. If the pipe is not all the way flush or is off the clamp will not go on properly and you will have a leak. Take your time because it can get frustrating.


Now the top is tightened so you can go back underneath and tighten the retaining bolt now because it was basically loose so you could move it around and it kept it lined up.
Then reinstall the dipstick bolts while you can reach.

Reinstall your front pipe whichever one you have and connect it to the new downpipe and tighten loosely. Connect the 4 bolt flange to the mid pipe and then tighten the downpipe clamp down.

Once the bottom is done go back on top of the engine and move your dipstick back to the left side of the cooler lines and reinsert your dipstick. Replace the turbo heatshield on top of the turbo with the three 10mm bolts you removed in the beginning.
I think that’s it….



If I forgot something or you have any questions let me know
 
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#2 ·
I'm surprised there are no comments.. this is a multiple thread discussion, but anyways..

unless there is something I need to change or add or answer I'll be moving this to the DIY section soon.
 
#3 ·
Ooooo...you want comments and such?!?!

I think everyone was waiting til it was finalized...you had "still adding" posted up, so I think everyone was still waiting.

Did you notice any EGT drop afterwards??

Different Exhaust / Turbo sound?
 
#4 ·
Thanks alot for that post, very helpfull. I'm buying a Banks pipe on Wed and planned on doing it myself. Got your section printed and ready to go!
 
#5 ·
did you have to get a different front pipe piece after this becasue it is a little smaller at the beginning and made to fit into the old pipe???
 
#7 ·
deadsquirrel;2007255; said:
did you have to get a different front pipe piece after this becasue it is a little smaller at the beginning and made to fit into the old pipe???
the flanges on either end of the new down pipe are exactly the same size as the stock ones..meaning it will fit your stock catted pipe and most after market front pipes as well.
 
#8 ·
I'll keep an eye on my egt's this week, but so far they've been all over the place. I think they are lower then they aren't, I think they are higher then they aren't.

previous EGT's on my truck are:
Idle in gear wth A/C is around 500
Idle in gear with no A/C is around 450 or a little lower
Idle in park usually goes down to 300 or so- my timer shuts down abotu 330
Highway cruising is between 500 and 800
On the pedal they go over 1000 at times in short bursts

most trucks should be pretty similar to this or just lower or just higher.
 
#10 ·
How about the sound?? Any change overall??
 
#11 ·
01Duramax6spd;2007307; said:
Who's pipe is that? How much did it run?
from what I understand Diamondeye is the manufacturer/originator and it's being sold from multiple vendors as other names and such. This particular one was about $229 although some may have snuck in and got one when they listed it wrong.

it's a solid peice and put together well save for the machining I had to do for the retaining bolt.
 
#12 ·
Mad Maxx;2007324; said:
How about the sound?? Any change overall??
well.. I could almost sware my turbo whistle is louder, but it could be my imagination. I've been driving a turbo car lately so I'll have to get back to you on this one as well.
 
#13 ·
briano;2007332; said:
from what I understand Diamondeye is the manufacturer/originator and it's being sold from multiple vendors as other names and such. This particular one was about $229 although some may have snuck in and got one when they listed it wrong.

it's a solid peice and put together well save for the machining I had to do for the retaining bolt.
I was one of the lucky ones that was able to sneak in on a incorrect listing(RPMOUTLET.COM), picked mine up for $169.00, next day the price was $229.00!!!
 
#15 ·
Now you can see the down pipe and where it connects to the turbo housing. Use the 7/16” wrench and unloosen that nut on the clamp. Remember, righty tighty, lefty lucy.


Just noticed that comment in your thread. You mean loosen the nut correct? I've never heard unloosen before?
 
#16 ·
Thinkmoto;2007810; said:
Now you can see the down pipe and where it connects to the turbo housing. Use the 7/16” wrench and unloosen that nut on the clamp. Remember, righty tighty, lefty lucy.


Just noticed that comment in your thread. You mean loosen the nut correct? I've never heard unloosen before?
long day.... correct LOL
 
#18 ·
Thanks alot! Gonna have to give this a try. Does anyone make a 5" downpipe, or is 4 the biggest we can go on LLYs.
 
#20 ·
huthuthut;2008184; said:
Thanks alot! Gonna have to give this a try. Does anyone make a 5" downpipe, or is 4 the biggest we can go on LLYs.
this down pipe is about 3" if I remember..maybe 3.5"...if you go any larger you hit the firewall and probably have to modify your tranny dipstick. Don't quote me on that, but it seems that is where it would go.

You maybe referring to the front pipe...in which case they do make a 4 and 5"
 
#21 ·
Great write up! What size is the stock pipe?
 
#22 ·
Ok... so basically this is as big as we can get with the downpipe, even if we have 5" all the rest of the way back? (Front pipe back).
 
#23 ·
huthuthut;2008402; said:
Ok... so basically this is as big as we can get with the downpipe, even if we have 5" all the rest of the way back? (Front pipe back).

as far as I know yes, but don't quote me on that. You might check out TTS, they have one and I think it's larger than this one here. there isn't much room back there due to the firewall. If the turbo was mounted on the side or something then you could come out of that housing with a larger pipe.
 
#24 ·
How long did it take you? I know a lot of times with these projects it seems simple and quick once it is written up but that is because the guy that did the write up already did all the suffering and we don't hear about that. If you have a rough time estimate and maybe how high your blood pressure got or how many times you threw things and screamed obscenities that would give me a good idea if I want to attemp this or not. (I am not the only one that does that when working on my truck am I)?
 
#25 ·
So is it worth the money? Lowered EGT's? Did the tone change at all?
 
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