Checking out my options: '04 Avalanche Z71 Build?

[Sinfuzz]

Hey Everyone,

I've spent a good amount of time over the past couple days reading through several threads on this forum pertaining to different GM Builds. I'm currently considering building my Avy into an overland vehicle for me and my wife.

I do have an '07 JK Sahara. I love my Jeep, but it does have some limitations for us.
1 - One of these is getting sold. I own my Avy outright, the Jeep I'm making payments on.
2 - SWB is awesome for a couple things I do, and not ideal for other things - winter driving and sand dunes are a couple.
3 - The idea of adding a RTT to my 2 door Jeep makes me just slightly uneasy, especially if anything else ended up getting packed up there.

I know I'll have to put some pretty good money into my Avy to get it up to snuff for some of the trails I do and plan to do.

I am wondering, any of you with similar builds - Do you still have the GM 8.25" Front? Does that need beefing up in any way? What can be done to make it more stout?

I'm already planning on getting the full Rear Suspension kit from Spohn, Rare Parts Front End and HD Tie Rod Ends, maybe RCV Front Driveshafts and there are some other parts I'm thinking about as well.

What are the priority things to upgrade for better reliability out on the trails?

 

[rayra]

You seek Yoda, er @Stryder106. He has all your answers. And he probably even has some useful parts for you, as he's gone thru several iterations of mods.
http://forum.expeditionportal.com/threads/158253-My-02-Avalanche-NFE

And a roster of the GMT800 series folks around here -
https://www.expeditionportal.com/fo...uburban-yukon-etc.155266/page-21#post-2302987

@Burb One for some good trail mods and 'next level' mods. And read @CrazyDrei build topic for what breaks and why.

You don't have a location or intended play area, but I'll recommend an upgraded trans cooler right off the bat. 4L60E tends to die at 275F+.
Rest is pretty ok as is. Depends on your driving style, if you mash the pedal or like having your tires out of contact with the earth. Ball joints, beefier upper control arms, better shocks, refresh your suspension stops and bushings.

/and rejoice that my ban's expired, so someone can give you a comprehensive GMT800 series reply

 

[Sinfuzz]

You seek Yoda, er @Stryder106. He has all your answers. And he probably even has some useful parts for you, as he's gone thru several iterations of mods.
http://forum.expeditionportal.com/threads/158253-My-02-Avalanche-NFE

And a roster of the GMT800 series folks around here -
https://www.expeditionportal.com/fo...uburban-yukon-etc.155266/page-21#post-2302987

@Burb One for some good trail mods and 'next level' mods. And read @CrazyDrei build topic for what breaks and why.

You don't have a location or intended play area, but I'll recommend an upgraded trans cooler right off the bat. 4L60E tends to die at 275F+.
Rest is pretty ok as is. Depends on your driving style, if you mash the pedal or like having your tires out of contact with the earth. Ball joints, beefier upper control arms, better shocks, refresh your suspension stops and bushings.

/and rejoice that my ban's expired, so someone can give you a comprehensive GMT800 series reply

Thank you for the quick references! I think I might have missed one of these. One I definitely did not miss was Stryder's thread. Really hoping to learn more from him!

Common/repeat play areas are Sand Dunes (I live not far from Silver Lake, MI) and trails that include some steps at Drummond Island. I'm also hoping to explore a lot of the upper peninsula after seeing how much ORV trail we have up there. The primary use for this truck is going to be camping though as well as staying a daily driver. Eventually it would be cool to add an RTT but for now, I think we could sleep in the truck with the midgate down.

Beyond that, my wife and I have wanted to take a cross-country road trip since we got married. I'd like to hit some trails at places like Moab and other places throughout the SW and PNW. Plan on keeping the difficulty of trails fairly mild, at least at first. Would be cool to have the capability for more though.

 

[XJLI]

A full-size truck on 33s will do 90% of the great trails across the country. My beef with Chevy (and I own an 05 1500) is they are LOW. If I keep my truck long enough, it’s getting a 12 bolt rear with 4.10s and I’m going to 35s.

But all you need is a torsion bar crank for a level and some beefy rear springs in the back, and some bigger tires. If you have 3.73s or 4.10s, go right to a 285/75-17. Only reason I went with 285/70 is because I have 3.42s. If you have the G80 even better.

The front end is fine, carry a spare CV shaft on the trail bc that’s your fuse, with RCVs you’ll just blow the diff up. But to be honest unless you’re rock crawling and beating the truck up you won’t have an issue. I wouldn’t waste my money on the $500 tie rods, just get the sleeves and carry a spare for each side which comes out to like $70 bucks. I’d swap a bigger rear end in (bolt in from an Escalade) before worrying about the front. Corvette shift servo is an AWESOME and cheap trans upgrade as well.

 

[Sinfuzz]

A full-size truck on 33s will do 90% of the great trails across the country. My beef with Chevy (and I own an 05 1500) is they are LOW. If I keep my truck long enough, it’s getting a 12 bolt rear with 4.10s and I’m going to 35s.

But all you need is a torsion bar crank for a level and some beefy rear springs in the back, and some bigger tires. If you have 3.73s or 4.10s, go right to a 285/75-17. Only reason I went with 285/70 is because I have 3.42s. If you have the G80 even better.

Awesome, I do have 3.73 gears and the G80. When I upgrade the tires I'm going back and forth between 285/75-17 (Yoko G003) and 255/80-17 (Cooper ST Maxx). I figure 255s are closer to stock width and I would like to use my stock 17s if possible. Between those 2 specific choices is there anything that should tip the scales one way or another?

The front end is fine, carry a spare CV shaft on the trail bc that’s your fuse, with RCVs you’ll just blow the diff up. But to be honest unless you’re rock crawling and beating the truck up you won’t have an issue. I wouldn’t waste my money on the $500 tie rods, just get the sleeves and carry a spare for each side which comes out to like $70 bucks. I’d swap a bigger rear end in (bolt in from an Escalade) before worrying about the front. Corvette shift servo is an AWESOME and cheap trans upgrade as well.

I'll revise my initial parts list a bit. Definitely holding off on the RCVs as well, I had a suspicion that would just hasten the destruction of my 8.25.

The Avy in question IS getting up there in miles, I think it's at around 230k. The Rare Parts HD Tie Rod Assembly is in the $3XXs, I do really want to swap out as much of that stuff as I can. I know almost all of the truck's history and I don't think it's had any steering or suspension maintenance in the past 6 or 7 years. In fact, I just recently blew out a rear brake line. My step 1 is going to be replacing all the brake lines and possibly a couple calipers if I have to.

Thank you for all the info! Really appreciate it.

 

[rayra]

You'll want the wider tires for sand and crawling around on big rocks.
I've done the keys and spacers and I've got just over 14" of clearance at the frame. And my stock tire size is 265/70-17.
A 285 will get you another 5/16" of ground clearance for $800. Not worth it IMAO, unless you have to buy a new set of tires anyway. Anything bigger than 285 will require cutting fender openings or much costlier lift kits or both.
GM wheel well openings are big and square but their bottom corners really crowd larger tires.

Take a look at the Powerstop GMT900 front brake and rotor replacement. Was a bolt-in upgrade for me, with 17" rims, but I think it will work with 16" rims. I'd have to measure. It's a good affordable upgrade. But if you want a stock set of front calipers, the ones I've pulled off are just sitting bagged up in boxes in my garage. They're yours for a low price + shipping. I'll have to check, can't recall off the top of my head, but I think near-new pads are in with them.

If you like straddling hard ruts and intend Moab, you do need to do something about the spindly front tie rod ends. They're 1/2" dia. I did the inexpensive sleeves and they are working fine for me in high desert / river wash crawls.

Go to rockauto.com, they've got real good prices on several tiers of replacement parts. You could do a factory refresh of all your suspension and driveline components for the price of just one fancy name brand off-road component purchase. And that would go a long way to improving your daily ride.

 

[Sinfuzz]

You'll want the wider tires for sand and crawling around on big rocks.
I've done the keys and spacers and I've got just over 14" of clearance at the frame. And my stock tire size is 265/70-17.
A 285 will get you another 5/16" of ground clearance for $800. Not worth it IMAO, unless you have to buy a new set of tires anyway. Anything bigger than 285 will require cutting fender openings or much costlier lift kits or both.
GM wheel well openings are big and square but their bottom corners really crowd larger tires.

Take a look at the Powerstop GMT900 front brake and rotor replacement. Was a bolt-in upgrade for me, with 17" rims, but I think it will work with 16" rims. I'd have to measure. It's a good affordable upgrade. But if you want a stock set of front calipers, the ones I've pulled off are just sitting bagged up in boxes in my garage. They're yours for a low price + shipping. I'll have to check, can't recall off the top of my head, but I think near-new pads are in with them.

If you like straddling hard ruts and intend Moab, you do need to do something about the spindly front tie rod ends. They're 1/2" dia. I did the inexpensive sleeves and they are working fine for me in high desert / river wash crawls.

Go to rockauto.com, they've got real good prices on several tiers of replacement parts. You could do a factory refresh of all your suspension and driveline components for the price of just one fancy name brand off-road component purchase. And that would go a long way to improving your daily ride.

I will let you know as soon as I can on the calipers, thank you for letting me know! I know a couple of my bleeders were frozen pretty bad, that’s why I’d be replacing.

I have some very bald tires on the truck at the moment. That will actually need to be one of my first moves. If I do go larger than 285, I really wouldn’t be sad about modding my fenders. Do wish I could unsee the awesomeness that are the @CrazyDrei and @Stryder106 trucks....

 

[XJLI]

I did 285/70 and just had to trim the plastic inner fenders, but I have aftermarket wheels that stick out just a little more than stock. You shouldn’t need to trim that badly with the 285/75. Only reason I didn’t go that size is gearing. The skinnies are definitely cool, but I’d want a wider for all the weight the truck puts down, but that’s just me.

 

[wirenut]

If you want a stout Avalanche keep in mind they were available in a 2500 series. Some of these even had the 8.1L big block. Good luck finding one, I'm sure they are rare as anything, but if you do it would be awesome.

 

[Sinfuzz]

If you want a stout Avalanche keep in mind they were available in a 2500 series. Some of these even had the 8.1L big block. Good luck finding one, I'm sure they are rare as anything, but if you do it would be awesome.

Definitely aware of the 2500s and their inherent extra durability. They are kind of uncommon, I haven’t seen many for sale within 200 miles of me either.

 

[Stryder106]

Replied to your PM, but just saw this thread. Hi!!!

Correcting something in my PM reply - I said Stop Tech brakes - it's Powerstop - oops sorry. The bigger brake up front makes a big difference. The biggest difference is to circular file your ABS fuse. The other thing is EBC Yellow Pads. I will respectfully disagree with some of what was posted (there are many ways to skin a cat) but there is nothing "wrong" with anything mentioned: MY preference - Tie Rods - Rare Parts. I looked at just doing the ends, and if on a really tight budget that will work. But that beefy end is still threaded onto an undersized rod. I'd rather have the whole thing more bulletproof. CV Axles - I can't tell you how many I went through - not breaking them, just wearing them out and tearing the rubber boots in really rugged terrain. I added up the cost and could have purchased the RCV axles. So I did. Which addressed the axles as a weakpoint. However, there is a downside to the RCV axles - they are what's called a "Wet Joint". Meaning you fill them with grease until it squeezes out - then when you drive it slings out all of the grease it doesn't need - all over everything in your front end. I like mine clean so this irritates me - but it is what it is - and it's that way for a reason - it makes it easier to expel water. Now, there is a case to be made that by having an axle that won't break means you are more likely to break the diff and when out on a trail it is much easier to change an axle a diff. This is very true - BUT - I also am very conscious of what my Avalanche is and isn't. It is an overland-exploration rig - it is NOT a rock crawler. 99% of what I do a rock crawler would call "trail riding". When/if changing gearing, look for something that is hardened. Both G2 and Nitro gear are. I went with the G2 because they are actually manufactured by Richmond (a name I trust for extreme applications). I HIGHLY recommend changing your gearing from 3.73. My Avalanche is an '02 NFE (I'm the original owner) so it came with 4.10 gears. When I went to 33" tires - the 4.10s were still good but I could "feel" the increased strain. So, when I decided to go to 35" tires, I jumped over the recommended 4.56 and went to a 4.88 gear to increase mechanical advantage and reduce the stress on the individual components. That has been a solid choice as the truck gets moving much easier. This allows less strain on the parts involved. Cognito UCAs, Moog PS LCAs, CST 2" lift keys, and fully customized suspension. The other thing I did was put in dual limiting straps to limit the droop. I have plenty of droop, but the Cognito LCAs allow for 2" more droop. I found that that was about 3/4" too much and was putting rotating parts at bad angles so I added the straps.

If you are not ready for the expense and commitment of a RTT - I used to have (sold it) the Napier Sportz tent for the Avalanche. That this was pretty great. If you are planning to sleep in the bed - this is how I'd do it - and how I did do it for a few years.They only cost a couple of hundred.

If you are in the market for the Spohn rear trailing arms - hold off on that. I had them and sold them. Nothing wrong with them, but a friend of mine did the custom suspension and when he saw those on my Av he got offended and made different ones. But, I may be changing up again here soon (did I mention that my friend also likes to experiment?). Again, nothing wrong with them, but he has been doing the "What if we did....?" thing again................LOL.

Speaking of suspension - I'm not sure which model Av you have - but if you are looking for shocks - check out the Eibach Pro Truck Sport shocks. My Avalanche was the project truck for those. So, they are designed with your rig and a combination on-road / off-road use in mind. Not very often you can get an off the shelf shock that is actually purpose built for your vehicle.

Getting on my soapbox (but really not meaning to) - here is the approach I use when doing things to my Avalanche or selecting which gear to add/bring: Reliability, Capability, Recoverability, Survivability. Whatever I do has to make an improvement in 1 or more of those areas. If it doesn't, then it's a waste and I don't do it. Example, Thicker tie rods improve the reliability and capability, but also reduce your likelihood of having to be recovered. Reducing your likelihood of having to be recovered also reduces the likelihood of being in a survival situation (not sure how remote you plan on going - I go really remote). A winch will directly impact 3 and 2 and indirectly impact 4. My water filtration system impacts 2 and 4. See what I mean?

I'll add to what Rayra said - feel free to ping me for stuff as I might have some things you want/need and save you some money. I'll send you my cell number via PM so you have it. I'm typically always on that unless I'm in an area that doesn't have signal.

 

[Stryder106]

One other thing - the G80 in the rear diff. Mine was great, but when I was changing my gears I started debating whether or not I should change that out as well. Then came the debate - another G80 or something different? Well, as I mentioned I hadn't had a moment's trouble with mine. I called Eaton to ask their opinion on it. The guy asked my how many miles were on my current G80. When I told him, his reply floored me. He said, "And it still works? I'm shocked. You should change that ASAP as they usually don't live much over 100K miles." So, I put in an ARB locker.

Might as well address the rear diff questions. Chevy 10 bolts are not as fragile as most people will make you think - unless you are extreme rock crawling -then it is wholly inappropriate. Mine: ARB locker, G2 hardened axles (60% stronger than stock Z71 axles), G2 master bearings kit, ARB rear diff cover that spreads the load and reduces deflection, G2 4.88 gears, rear diff has been trussed using mild steel tubing, Eibach anti-sway bar and custom links. I decided to truss mine because of all of the weight I'm carrying.

One final thought (for the moment) - Preventive maintenance is your best friend. Keep stuff fresh.

 

[Martinjmpr]

An Av is basically a Suburban with the back roof cut off so any of the Suburban drivetrain mods should work (lifts, shocks, etc.) Given that you're in Michigan I would think that rust mitigation would be a top priority for you - here in dry Colorado it's not so much of an issue.

 

[CrazyDrei]

Staring off with an 04 Avi Z71, you are already way ahead of the game. Just as XJLI, Rayra and Stryder106 have mentioned there are different things you can do to start beefing up your Avi for the trails. There are several main things to consider: how much $$$ do you want to spend, terrain you will be driving the vehicle on and your driving style.

I went the cheapest and least expensive route I possibly could, there are other options, but below is the list of whet I would do the next time I build a Suburban or Avalanche.

Tie rods: Three options increasing in price: tie rod sleeves, rare parts HD tie rods or JD Fab uniball/heim tie rods.
Biggest problem with the tie rods that I encountered on the trail is the actual outer most bolt that goes into the spindle that shears off, so if you plan on driving hard, go all the way to JD Fab tie rods or make your own for 1/4 the price. JD Fabrication GMT800 tie rods

Lift/level kit: what size tires do you plan on running and how much do you want to spend vs do yourself?
33" tires: minimum F150 front torsion bar keys and rear coil spacers. That will bring you 3" up front and rear and fit 33" tires with correct offset rims or spacers. Minor trimming would be necessary to eliminate rubbing.
35" tires: Level kit and 3" body lift for lower budget or 4 or 6" differential drop lift on higher $$$ end. Keep in mind what kind of driving you plan on doing, 4 or 6" differential drop lift and 35" tires will give you less ground clearance with 35" tires than a level kit with 33" tires will.
37" tires and up: I put a lot of time which I had into a level kit and body lift ro fit 37" tires without rubbing, most do not have the time I do. 6" suspension lift and 3" body lift will fit 37" tires without rubbing and 40" tires with lots of trimming and body work.

Pull your rear coil springs out and measure them, if you have towing package or Z71 they need to be at least 17" unloaded flat on the gorund, if they are right at 17" or below, upgrade to the Moog rear coils.

Locking differential. G80 is a fantastic auto-locking rear differential, it is amazing and everyone that doesn't like it is just bummed that you can pick one up on eBaY FOR $100 shipped. It will last 50-100k miles and replacing it takes two hours in your driveway. G80s or GovBombs have a bad reputation for breaking under unnecessarily hard driving. They fail or snap your axles unless you drive extra carefully all the time off road, who wants to do that? I have a Detroit rear locker and absolutely love it, whish I put it in sooner. Your other options are eLocker which I had a terrible experince with and would never ever run it in my rear, but definitely up front. ARB air-locker is great if you want to overcomplicate things and look really cool on the side of the trail as you trouble shoot and fix air lines or electrical wires involved in the air system. I have onboard air and would never run air lockers. OX locker is the most expensive and option but also the most simple and bulletproof. It's a mechanically actuating rear locker. If I plan on crawling win my daily driver I would get the OX, for everything else Detroit.

Rear axles: factory axles are great but our trucks are 14-20 years old, when putting in a new reasr end or regearing get hardened axles.

Gear ratios. 3.73 will turn 35" tires just fine on dirt roads but if you plan on actually having to use 4x4 you need to change your gears.
33" tires 3.73 factory is fine but if you plan on towing get 4.10.
35" tires: 4.10 for everyday driving, 4.56 if you plan on towing or doing really really technical stuff.
37" tires: 4.10 work great under most circumstances but unless you get sub 80# tire 4.56 will be needed.
40" tires: 4.56 if you run a tire that's 80lbs or less 4.88 for all other 40" tires.

Front differential: 8.25 is a great little diff, has been turning my 37" tires just fine other than one incident which was entirely my fault. Keep it. If you do a differential drop 6" lift upgrade to a 9.25" front IFS and find yourself a TrueTrac or eLocker front diff to stuff in there. Keep in mind that 9.25" front diff, new CVs, couple custom parts that need to be machined, new 2500 CV axles, new gears and a front locker will cost more than you paid for your Avalanche, ultimately is it worth it?

Spare tire: factory spare tire area if you chop it to pieces and do a little custom fabricating work will fit a fully inflated 35"x12.5 tire leaving no wiggle room once it's inflated. If you plan on running 35" tires that's a great place to mount a full size spare keeping it out of the way and protected. If you plan on keeping your spare in the bed, thats a great place for a 20-25galon second fuel tank.

Everything else is cosmetic stuff that you can upgrade to beefier looking but other than that serving no practical purposes.

Hope this helps, keep us updated on your rig, post lots of pictures but most importantly get out there and explore!

 

[XJLI]

This thread is great. Lots of information.