Yet another GMC build

[Rickysnickers]

Very well done!

[daveshilling]

Originally Posted by OKGMC4

Engine bay assembled

Sweet mother of GOD what is this wizardry?! That's your freaking INTAKE? Leave some ladies for the rest of us man, and don't come near my wife.

[OKGMC4]

First time in the sun for 2 years. Got gas and so far so good. Need to adjust one coil over for height, an alignment, a dyno tune, and charge the AC.

[daveshilling]

Originally Posted by OKGMC4

First time in the sun for 2 years. Got gas and so far so good. Need to adjust one coil over for height, an alignment, a dyno tune, and charge the AC.

Big Day!! Excited for you, and excited to do the same thing one day.

[dsraven]

AND it was sunny, nice. must feel good to start it up and drive it outside in the sun.

[6DoF]

that bed box is MONEY!

and congrats on the sunshine!

[Rickysnickers]

Awesome job!!!

[mongocanfly]

Nicely done...

[oldman3]

Looks great...Jim

[Kevin_C]

looks great!

[OKGMC4]

My rack started leaking from both bellows and I’m not really sure why. It was rebuilt in 2011 but maybe the seals didn’t like sitting so long or maybe it wasn’t a good rebuild to begin with? Unsure. Anyhoo, it looks like C4 racks are getting rare because they are going for $300-$400 on ebay, parts stores can’t get them anymore, Turn One in Michigan can rebuild one but that starts at $375 with a minimum 2 week lead time. I thought I’d try my hand at a $30 seal kit but when I got to reassembly I could not get the short shaft back in without destroying the 4 square nylon rings on it. Believe it will take special tools to do properly. Plus no way to test it first and still don’t know why it failed. I found that a company called Lares in Minnesota produces new c4 racks with a lifetime warranty. Summit has them for $450. I hate to spend that much but might be the best option since used is so much. When it came time to choose between Flatout Engineering or Progressive Automotive for a crossmember I went with the one that fit my corvette rack. Since seeing you can get a tbird rack for $100, wondering if I made the right choice.

[OKGMC4]

Got about 200 miles before trouble. Slipped in 1st gear once, temps started climbing, then it started shaking, then the converter started grinding. That was all in a 3 mile trip. Wasn’t even getting on it. Snout on the converter chewed up, front seal came out in pieces, front pump loose. Tranny shop said since I pulled it all out of a truck hit HARD in the front, it probably allowed the converter to smack the pump and crack it. He quoted $1500 to rebuild. Looks like I get to learn how to rebuild a 4L80E!

[dsraven]

these are pretty good manuals.
https://atsgbookstore.com/4l80e_dl/?...QaAtXEEALw_wcB

[dsraven]

start with a good power wash.
also, before installation, flush out the cooler lines and replace the cooler.all that stuff is stuck in that old cooler. some will put a filter inline but I am not on that side of the fence, personally. I have seen a hydraulic shop flush new lines and then blow a plug down the line with compressed air to clear any solvent from the line and see if the plug comes out clean or if the line needs more flushing. they use what looks like a roll up ear plug.

[dsraven]

I have also seen a cut away of a previously flushed plate style trans cooler. it still had lots of debris in the plates. a new cooler is cheap insurance.

[dsraven]

you're gonna be soooo tired of ATF soon.

[OKGMC4]

Took the trans apart and all the frictions and steels looked perfect so put them back in. The only damage found was a chewed up converter snout, the stator bushing was banged up, and the front seal came out in little pieces. I replaced the bad parts and put it back in and it’s been driving perfect for almost 200 miles now. Not really sure why it blew the front seal out in the first place. The bad news is I’m not 100 percent thrilled with the 5.3 power. Seems to have about what my cammed 6.0 had naturally aspirated. Not bad, but I ain’t scared yet. Thinking of gapping the 6.0 rings and swapping it. More cubes, little more compression, more cam, and more boost should thoroughly scare / thrill me.

[OKGMC4]

I pulled the heads off the 6.0 and regapped the rings. I changed the Texas Speed 224R out for a mild custom turbo grind from Cam motion. I changed the wastegate springs for 12lbs. Pulled the 5.3 and pushed in the 6.0. The idle needed raised from 650 to 750 and I think I need to lean the idle out a little below 13.6 where the tuner set it. But the power so far is ridiculous. I only pushed it to half throttle and it’s walking sideways while still accelerating and shifting. I believe I finally have the scary power I’ve always wanted. Need to look into wider stickier tires now.

[6DoF]

[Kevin_C]

Looking great! I saw this video the other day and thought of your truck. I was a bit surprised by his current brake and suspension set up.

https://www.youtube.com/watch?v=nf1MItkMMKM

[OKGMC4]

Originally Posted by Kevin_C

Looking great! I saw this video the other day and thought of your truck. I was a bit surprised by his current brake and suspension set up.

https://www.youtube.com/watch?v=nf1MItkMMKM

Man that thing is a beast!

[OKGMC4]

Really wanted to make sure my tune was safe for the engine so I had it dyno tuned this morning. The verdict…
605 hp
656 ft lbs.
I think it has more than enough power now. My poor 275/40zr18 tires agree. I had backed down to 10lb wastegate springs because I was afraid to lean out up top. I’d rather give up some power than burn it up at 12lbs boost.

[6DoF]

haha, yeah, the makings of a tire smoke show

[OKGMC4]

I thought my brakes were ok. Good at low and medium pedal, but hard at panic stop levels. Truck would slow down but not like it should. I only had 14 inches of vacuum at idle. And also not much vacuum being made under boost. I took out my 30 year old 4th gen f body vacuum booster and installed a new universal hydro boost, using the firewall bracket off the vacuum booster. I can now lock all four tires up and slide if need be. Pedal feels strange, never had hydro boost before.

[OKGMC4]

Also never posted a video before so will try here. I have the first dyno pull after the turbo 6.0 install. Don't know why I didn't record them all, just didn't. Since then, I have extended the tailpipe all the way to the rear and swapped the bullet muffler for a Dynomax 3.5" Ultraflow muffler. I would not say the truck is quiet, but it is twice as quiet in the cab now.

https://www.youtube.com/watch?v=XfJldrXsr6g


Hopefully this link works?