Duramax Diesels Forum Truck of the Week
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Old 06-28-2019, 08:52 PM
fl0w3n fl0w3n is offline
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Default Considering DD'ing 350k mile LB7?

I'm looking on input on things to consider, I don't want to be stuck on the side of the road late to work or get out in the morning and not make it. I'm not fully sold on the idea yet.



For the first time in 7 or so years I have found myself at a job that does not provide a truck. So, I'm looking into my options for a daily. Commute is only 50 miles round trip, and I'll likely only be doing it for 1-1.5 years before I have a company truck again.



I'd rather not have a payment, but if I did it would be for a small amount and I'd get a GMT800 1/2 ton.



Then I was thinking... I've got my 350k mile LB7 project sitting idle... why not just dump some money into that and DD it? I bought it for a project, only put maybe 1200 miles on it, and only 20 or less since the stuff below.



It's an 02 LB7 ZF6 manual window/doors/rubber floor truck, I've already put in:
Reman trans
NewSouthbend dual disk organic clutch
New NP271 t-case
Rebuilt and shortened the two piece drive shaft (no front shaft yet)
New AC delco motor mounts/trans mount
New AC Delco FPR
New Optima Yellow Tops
New AC Delco water pump, thermostats, and harmonic balancer
Newer better condition seats, dash panels, and steering wheel




I'm thinking I could do:
SAC00's
Kennedy pump

DmaxStore Stg 2 steering kit w/ idler pivot
New 35's (on 17 steelies I have sitting)
Maybe head studs and head gaskets while I'm there
Get rid of the cali egr
4" exhaust

Maybe a new AC Delco radiator, window tint, and an 03+ grill and bumper?


Sounds like maybe $6k in parts to get this thing back on the road?


I'm not as worried about the chassis as I am the lb7 and electrical part. I'll pull the rear diff cover and check the front wheel bearings.
How do I check if the turbo is bad?

I think before starting anything I'd do a compression check to see if I've got blow by and the short block needed work.

Should I be worried about the engine wiring harness? When I did the FPR I noticed some of the loom wrap and raceways are broken so wires are a bit free'er than they should be.
What else am I missing that is likely to shut me down on an old ass LB7?
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Old 06-28-2019, 10:18 PM
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The big things on the LB7 are injectors, head gaskets if coolant hasn't been changed on time (and sometimes they go just because), and CP3 (just due to miles they get weak). The electronics are pretty reliable in my experience.

While you are in doing injectors, just get some friction tape and patch up the harness. Just be extra careful with all the connectors as you undo them, after 17 years of heat cycling, they get brittle. It helps to undo them on a warm/hot day in my experience. Less likely to just snap off.

As a matter of personal preference, I'd keep the 2002 front end. IMO they look better than the 2003+, though they have less options for aftermarket lights and such.

If you do pull the heads for head gaskets, expect the heads to need a decent amount of machine work to be 100%. You can just bolt them back on and see how it goes, but they are often way out of true after this long. Avoid the temptation to do any porting while they're off, there's not a lot of wall thickness and you can spring coolant leaks pretty easily.

I have 330k miles on my LB7 now, my Suburban's motor has 200k, and my brother's truck is around 200k too. The LB7 can go the distance, especially with the SAC injectors now.
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Old 06-29-2019, 12:00 AM
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Can buy yourself a nice used half ton or colorado for 6k
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Old 06-29-2019, 05:15 AM
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I’d finish my project but do it with original plans not settle for half way
If you can’t afford to finish it right now just drop 2k on a cheap ride
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Old 06-29-2019, 06:13 AM
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Quote:
Originally Posted by hondarider552 View Post
Can buy yourself a nice used half ton or colorado for 6k

This^^^
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Old 06-29-2019, 09:11 AM
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Do you need all that work? Why do 35s and have to beef everything up? Why go with the crazy strong front end stuff? Are your injectors bad? I wish I had my 02 back. I’d drive it just as much as I would my lbz. And it had more miles. Just seems you may be going overkill for a work truck. Rebuild the front end with stock parts and sleeves. 285s or 265s will help mpg and keep you from having to crank putting unneeded stress on the front end. Kennedy pump is good cheap insurance. If your heads are already off have them checked and stud it. If not save your money. Get rid of the egr. If it needs injectors go with SAC 45s IMO. Room to grow after it’s retired as a work truck and I’d say mpg won’t be affected. Personally would go with a magnaflow 5” exhaust with resonator like mine. Very cheap. Deep rumble and no cab noise when driving if your tail pipe is in place.

As far as the front end, you’ll need hood, fenders, grill, bumper, brackets, and I’m not sure about core support. However I’d be willing to trade if it’s in good shape possibly because I want an 02 front end on my lbz.
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Old 06-29-2019, 09:53 AM
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All good points.

I hadn’t thought about the CP3. I don’t have a scanner or monitor to check pressures right now so I wouldn’t know what condition it’s in.

The only thing it “needs” is injectors I guess, the rest is just my desire to have things as close to perfect as I can. I think back to my LBZ and how I sold it for more than base price I bought it for (but not including all the money I put into it) and I like to think that’s because I like to do things “right”. This LB7 lived life plowing fields and getting farm repairs, nothing wrong with that it obviously kept it going this long, I just prefer different standards.

It might be overkill doing the studs and gaskets, but I figured if I have to be in there anyways for the injectors I might as well. I haven’t driven it enough to know if it has coolant issues. Should I just skip head gaskets?


The long plan for this truck is a 4x4 adventure mobile, so all the motor work is in the grand plan anyways. The steering stuff is not, I plan to SAS the truck. 4” exhaust is more for clearance concerns, that NP271 is a big’un. 35s wouldn’t be the final tire either so I guess that’s also just an intermediary step... unnecessary.

So I guess I can condense that list down to the bare minimum to get it back on the road, injectors, lift pump, and exhaust (currently only has half an exhaust). Oh I forgot I need to rebuild the filter head too, and the rubber fuel lines at the FPR/CP3. I have the parts just need to do it.

And I agree, I’ve found some decent 1500s ... or I could do a rear main on my 2500 Suburban and some work to that, but I hate driving that thing lol
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Old 06-29-2019, 10:56 AM
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I’d skip the filter head rebuild and buy a new one. They’re too hit or miss. Or, get you two cheap Napa filter heads and mount them in front of your Kennedy pump in the frame rail with a water separator and a filter and delete the head altogether. Ive rebuilt three. I lucked up and two stayed together but one started again after about a month.
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Old 06-29-2019, 11:22 AM
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I wouldn’t worry about it breaking down on you. If it has 1 mile or 300,000 something can Always break.
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Old 06-29-2019, 12:33 PM
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I would keep it simple. If you need injectors, then sac00 or sac45. Maybe a cp3 if it is original. If you want to stud it, maybe you can keep the heads on and do one stud at a time. I would add a lift pump and then see if you need a new filter housing after

265 tires net the best mpg on my lb7.
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Old 06-29-2019, 06:42 PM
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It's not the motor that will fail you.. it's the supporting crap... like the steering box, rear end, electrical, brake lines if it ever saw salt. I'm not selling mine but it's a love hate kind of thing..

Sent from my SM-J337A using Tapatalk
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Old 07-01-2019, 12:43 PM
fl0w3n fl0w3n is offline
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Quote:
Originally Posted by ironmax View Post
It's not the motor that will fail you.. it's the supporting crap... like the steering box, rear end, electrical, brake lines if it ever saw salt. I'm not selling mine but it's a love hate kind of thing..

Sent from my SM-J337A using Tapatalk
Well thatís kind of good to hear, because itís not so much the chassis that Iím worried about. Iíve rebuilt enough of these front ends that I know how to ďbullet proofĒ them now basically, and itís a California truck so hopefully no rust to worry about. The electrical on the other hand is a concern, but since itís basically only got an ECM the chances of an issue should be minimized
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Old 07-01-2019, 12:52 PM
fl0w3n fl0w3n is offline
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Also, if it makes any difference, the plan for this truck performance wise isn’t a whole lot.

I’d like to crank it up to maybe 450hp 750tq, give or take 50. Basically just enough to “hang” with the new stuff.
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2002 LB7/ZF6 CCSB Sierra 4x4
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Old 07-01-2019, 01:07 PM
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Quote:
Originally Posted by fl0w3n View Post
Also, if it makes any difference, the plan for this truck performance wise isnít a whole lot.

Iíd like to crank it up to maybe 450hp 750tq, give or take 50. Basically just enough to ďhangĒ with the new stuff.
You can achieve your goal really easily on a LB7. This tune, lift pump, boost increase valve, and EGR blocker plate (or it might blow the valve open) did 425 HP / 748 lb-ft at the tires, which is more HP at the tires than the new trucks make at the crank.

I run that tune in my Suburban and my brother's truck (well, slightly modified for his SAC45 injectors), and ran it in my truck until I upgraded the turbo.
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Old 07-01-2019, 01:33 PM
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Quote:
Originally Posted by zakkb787 View Post
Do you need all that work? Why do 35s and have to beef everything up? Why go with the crazy strong front end stuff? Are your injectors bad? I wish I had my 02 back. I’d drive it just as much as I would my lbz. And it had more miles. Just seems you may be going overkill for a work truck. Rebuild the front end with stock parts and sleeves. 285s or 265s will help mpg and keep you from having to crank putting unneeded stress on the front end. Kennedy pump is good cheap insurance. If your heads are already off have them checked and stud it. If not save your money. Get rid of the egr. If it needs injectors go with SAC 45s IMO. Room to grow after it’s retired as a work truck and I’d say mpg won’t be affected. Personally would go with a magnaflow 5” exhaust with resonator like mine. Very cheap. Deep rumble and no cab noise when driving if your tail pipe is in place.

As far as the front end, you’ll need hood, fenders, grill, bumper, brackets, and I’m not sure about core support. However I’d be willing to trade if it’s in good shape possibly because I want an 02 front end on my lbz.
^My truck loves 285/75R16 tires and also got great economy with 265/75R16 tires. Empty I am getting ~18.5-20.5mpg on the freeway @ 80mph and 10-12mpg grossing 24k pulling my LLY around with my weights etc.


Quote:
Originally Posted by 2004LB7 View Post
I would keep it simple. If you need injectors, then sac00 or sac45. Maybe a cp3 if it is original. If you want to stud it, maybe you can keep the heads on and do one stud at a time. I would add a lift pump and then see if you need a new filter housing after

265 tires net the best mpg on my lb7.
^ This. When my LB7 needs injectors again (just put in NEW bosch VCOs ~10k ago) I will go to SAC45 because I would like to run compounds for towing my LLY around and they seem to be the best compromise between performance and economy as well as having awesome life.


I personally would replace the CP3 if the budget allowed and skip the head studs unless you're going to pull the heads and do the job completely. Its not the factory bolt that fails, its a design flaw in the gasket where the layers separate and leak. By just changing the studs one-at-a-time you're not fixing the real problem.
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