NEED INPUT - 02 AV Differential and Suspension Upgrades


Hi Guys,

I'm looking at doing some upgrades, translation: spending money, on my 02 Av. NFE 4WD 1500. Here's what I'm looking to do:

1) Tires - based on what we do, and what we want to do - I really want to go to a 35" tire (General Grabber x3). Current tires size: 285/70-17.
2) Differentials - looking to go to a 4.88 gear (for the 35" tires). I currently have 4.10s and the G80. I'm also looking to upgrade the locker (ARB Air?) and ARB strengthening diff cover (will also be fabbing in a truss)
3) Locker: Is the ARB Air Locker the correct choice for Overlanding? With the price tag on it, comes the price tag of a compressor. If I have to buy a compressor, I might as well get the ARB Twin that can also fill my tires and do multiple other things. You can see where I'm headed with this....................
4) Lift - this is my biggest concern. I have literally done months of research on the various lift kits out there and the one (for my rig) that keeps coming up as the top of the pile from a quality perspective is the BDS kit. Added bonus, this is a high clearance kit with the torsion bars in the stock location and the front diff drop is arched to provide additional clearance down the middle of the rig. It also neutrals the CV angles rather than topping them out - so I get full travel.

HERE'S my concern with the lift: BDS says I MUST use the 6.5" kit to fit 35" tires. (They also have a 4.5" kit available). If I add up 6.5" plus the additional 2" of tire - that's 8.5" inches. Deduct my 2.5" of leveling and 1" bigger than stock tire - and that is 5.5" inches taller than I am now. Is that TOO MUCH? Looking at the pic on their website - the Escalade (6.5" with 35" tires) - looks like it is sky high - but I can't tell if that is simply due to camera angle. What do you guys think? Also, I am willing to do some additional trimming and cutting to make room for the 35"s, but it's chicken and egg: If I buy the lift then the tires - tires fit, but is the lift too high? Or, if I buy the tires first, could I possibly drive it home to trim it and then add whatever lift I need (4.5" or 6.5")? See what I mean?

BDS 1.jpg
BDS 2.jpg

5) Atomic's coil over conversion - would love to consider that - but he has not returned my PM.

Doing all of this is expensive - but I'm trying to only do this once and not skimp on quality that could strand me in the desert somewhere.


Do you load anything on your roof? Do you encounter difficult terrain? If you answer yes to either, more height tends to make you more tippy.

I would stay as low as possible.


Expedition Leader
Nowhere in all that do I see any info about the type of wheeling you do or what necessitates all that added height and expense. You're just asking 'should I spend a bunch of money'.
If you describe the type of terrain or regions you like to go off-roading in, how hard you like to go, you might get some more tailored advice.

As far as SoCal goes, you'd really need to be crawling around in a boulder field or deliberately seeking some technical climbing trails to need any of that. The pictures of your rig look like it can already handle the 'normal' wheelin' around here.


I'd stay right where you are. From what I can tell you aren't going to address anything else that would be helpful on the trail, aka steering upgrades and beefier components to handle the larger tires and loads on it. You're essentially building a SEMA truck to do something you're already capable of.

Don't build a SEMA truck. Go out and enjoy your money in otherways. If I had the money back that I pissed away on stuff like this, I'd be alot farther ahead.


To answer the "how am I using the rig" question: We are new to this, so we are progressively getting more aggressive. Using the Backcountry Adventures rating system - we have done some level 3 and 4. Will get into some level 5 with level 6 a rarity but possible to do some stuff we want to do (Mengel Pass). This is also my daily driver.

To answer the do I get into difficult stuff and load on my roof: Relative on the first - but getting more so (see above). Yes on the roof loading.

Steering upgrades have been done already. Rare Parts 1.5" tie rods, Cognito UCAs, Cognito pitman and idler arm braces. Custom Eibach shocks. Adding an Eibach steering stabilizer. Also upgraded my rotors and pads to cross-drilled, slotted, and zinc plated with ceramic pads.

And no - I am NOT building a SEMA truck. Check my other thread on my build please.

Rayra - I'm in the IE - so the desert and SBDO mountains are my backyard. We are looking to venture out to other SW states (have done Sedona already). From experience thus far, some additional ground clearance would be useful. I just don't know how much is enough vs how much is too much. There is no difference between the cost of the 4.5" kit and the 6.5" kit.

To be the equivalent of a 2" lift and 33" tires on a Tacoma, I'm closer to a 34"-35" tire and a 4"-6" lift given the wheelbase difference.

I can afford to do this once - but I cannot afford to be wrong in my choices.


FWIW: I parked next to a completely stock 2002 Chevy Avalanche Z66 (on road) yesterday - and I just so happened to have a tape measure with me in my rig. Measuring ground to the bottom of my fenderwells at the center point above my tire: Front: 39.5" Rear: 39.5" (My front is leveled up). The stock Z66 measurements: Front: 37.5" Rear: 39.5". Essentially - other than my nose being raised to level my truck - my rig currently has the exact same ground clearance as a stock 2WD on road edition Avalanche. Does that influence anyone's opinion?

Burb One

My final take from the other thread and this post:

1. Tires- 35's with your upgrades will work. Just be careful with throttle management, and just carry an extra CV. If you arent stupid and don't have huge angles the front IFS isn't that bad. 35 MPG isn't THAT bad, but it will take a hit.

2. Reading a little more, maybe the 4.88 aren't such a bad idea? IDK , I checked for you and I am around 2150 rpm at 75mph with 4.10's and 33's. IF I went to 35's this would make it ~2000 rpm which is a sweet spot IMO at 75mph. Idk how much off road vs on road you do, but if I need more grunt I always have 4LO..... 4.88 seems too low for me.

3. With you talking about fabbing a truss, I would seriously look into the 14 bolt. With the expense and/or time of getting a truss for a 10 bolt, mine as well go to a big boy axle and do a truss on it later, In these trucks a truss isn't an not an upfront mod because that not the weak point of these axles. The crappy 10 bolt internals (especially g80) are. If you need a truss it means your doing some serious terrain. The 10 bolt internally, is just not going to be as reliable as a 14 bolt, and with the 14 bolt the truss and stuff can come later. If you need a truss, then the discussion between 4" and 6" on this truck should be an easy answer as well because where a truss is needed a lot more ground clearance is needed... 14 bolt will be more than stock power, or NA power COULD EVER break. I would find a 14 bolt with G80, see how you like it and then later on upgrade to an ARB if you feel you need it (Maybe do the compressor now for tires, and then youa lready have it if you do ever go there to spread out costs). That's been my plan (exacpt I want an E locker, but honestly with the 14 bolt g80 I havent felt a need yet. For diff covers, I am really happy with my BTF (Blue torch fabworks) seems to be the best deal (I think it was $150), and is a serious piece of metal(3/8" ring and 1/4" cover) without costing the $400 some of the covers are.

4. You sound very similar to me. I started out by "just wanting to get there" (IE camping/ beautiful outdoor spots). I started on a 2" lift (level) went to 33's. This was great, but there were places I would have to turn around just because of my clearance. I don't rock crawl or go out of my way to do more intense 4x4 in this truck, but I always wanted "to be able to get there if I needed". In these long wheel base trucks,IMO you MUST have more ground clearance if you want to get there on any trail you can fit on. For me, I slowly evolved into the 6" and staying on settling 33's (MPG). If you can only spend once, go for the 6 inch. You will not be disappointed and it really isn't that tall. My 6 inch with 33's is MAYBE 2" taller total than a 2500 it seems. Worst comes to worst, just put slightly smaller coils or spacers in the rear and turn down the torsion bars (or coilovers) and you'll get even better CV angles with only 5" of lift on a 6" kit. Again, you will always be wanting that 2" more in these trucks, that need overcomes any trouble with CG or aero mpg's.

Also remember, when you start loading expedition and camping crap in the back, you end up really only getting ~5" because all the weight compresses the suspension. Apples to oranges comparison between an unloaded stock truck height and a loaded expo height.

5. I don't think atomic comes here very often. I PM'd you his email...
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Arizona Native

New member
I would love to have the differential and the other upgrades.
As for the lift and height, I guess I'll just tell you how I feel about my vehicle since its fairly similar in size, and since I thought about the same kind of lift before.

I just got back from the trail to the sunflower mine (and bloody basin road before that), and there is no way I would want to be any higher or any wider. Roads that the Suburban barely fit on with 1,500 foot drop offs. I used to want the 6 inch lift myself, but once I started going on trails I wanted to go on, I started to be very content with what I had.

Now, there was a point where I did stop on the Sunflower Mine trail, not only did it get narrower, it got very rocky.
It wasn't really because the Suburban couldn't make it, I could have easily continued, I just would have to spend time building rock ramps (planning on buying ramps maybe soon), and would be checking to make sure I wasn't going to roll over every 2 minutes (which a lift would not help with). I was lazy and didn't want to spend time to do that, and chose to hike to the mine instead, since it was only a mile away.

On top of that a side note of course, I'm carrying around a family (which I know you probably are not), so I have to ask myself, is it worth the time and safety risk going any further. So far the Suburban has gone everywhere we wanted it to go otherwise, and is probably capable of even more.

I'm looking at pictures of Mengel Pass, and see a few lower height suvs taking that trail. Which tells me, going slow and taking your time, I should be fine (of course, I've learned, you never really know until you get there). But you could get away with a higher vehicle and feel ok on that trail, since it does not have 1,500 foot drop offs on the side (from what I can tell).

Honestly, I feel like I need several different vehicles geared up depending on what trails you want to go on. That's what I'm telling my wife at least :p.


Appreciate the input. I want to be clear on this point: I do NOT want to go higher than I have to to fit the bigger tire, but I do know that I would like some additional ground clearance for my frame rails (breakover angle) - take a look under your rig - that stuff was not intended to be drug over rough ground. I do have skid plates - but that doesn't help everything.

I hear you on the higher CG - hence trying to not go as high as that picture indicates. When I put a tape measure against my truck - and then look at that pic - I cannot relate the two. It just doesn't seem like 5" should be that much higher - but again that pic is causing me some serious concern. I do NOT want my rig to look like that. I like the lower bigger tire look - but it does need to come up at least some.

As for Mengel pass - that has some sections on it that you had better have some additional ground clearance.

For my rearend and truss - I have a buddy who is really good with Fab - I'm actually thinking of the truss not out of complete need for what I'm doing, but the combination of: what I'm doing, with the extra weight of overlanding, and the piece of mind of just giving it that much more strength.

I am now considering the E-Locker. I carry a 10# C02 bottle so I'm not without ability to air up and down.

PM received - thanks much.

Arizona Native

New member
If directed toward me, well, I mostly do my own mechanic work, so I do know whats underneath there :p.

I understand what your doing, all I'm saying, is that I haven't had to spend any money on bigger tires, or anymore lift, and mine has been fine. If I'm in a place I'm going to hit, I'll try to build a ramp.
I feel that we already are at the right balance between rock crawler and stock condition. I know you measured the other vehicle, but that's the thing, mine is at the exact same height now, if you don't need it, you don't need it. If you want it, go for it. I totally wanted 35s myself, but not having them hasn't stopped me from going anywhere I wanted to.

The other thing I would say, if you haven't already been on Mengel pass (or any of the other planned trails), why not try part of Mengel pass and the other difficult trails, and see how far you can get? It looks like there are quite a few places to turn around on Mengel pass if it doesn't work out. That's kind of a way to 'troubleshoot' for what you need, still have some fun, and not spend loads of money if you don't have to.

I've felt the same way about trails, thinking it was going to require more gear, only to try it and find out it was doable.

That's all I have to say, I'm sure you'll have fun either way.

Ducky's Dad

FWIW, I ran 35" BFGs for years and years on my '98 K1500 on a stock suspension with no lift and no leveling kit and no problems, other than having the rear diff rebuilt at about 100M. Front diff is still original, despite its reputation for being fragile. I don't think you need an extreme lift. I don't think you need 4.88s, either. G80 is OK, ARB locker is better. One key to running 35s successfully on stock (or close to stock) suspension is careful wheel selection. Mine is on a set of OEM 17s from a later GMC truck. Don't get carried away with unnecessary mods. IF you are willing to spend big bucks on a lift, get the tires and wheels first and see what you MIGHT actually need. The only mod I made on my K1500 was to stretch the rear inner fender liners with a BFH. If you expect to need snow chains, you may need to be a bit more careful.


What about spring rates?

Are you taller AND softer to get the articulation?

Taller is bad.

Softer is bad.

Taller AND softer is HORRIBLE!

Burb One

FWIW, I ran 35" BFGs for years and years on my '98 K1500 on a stock suspension with no lift and no leveling kit and no problems, other than having the rear diff rebuilt at about 100M. Front diff is still original, despite its reputation for being fragile. I don't think you need an extreme lift. I don't think you need 4.88s, either. G80 is OK, ARB locker is better. One key to running 35s successfully on stock (or close to stock) suspension is careful wheel selection. Mine is on a set of OEM 17s from a later GMC truck. Don't get carried away with unnecessary mods. IF you are willing to spend big bucks on a lift, get the tires and wheels first and see what you MIGHT actually need. The only mod I made on my K1500 was to stretch the rear inner fender liners with a BFH. If you expect to need snow chains, you may need to be a bit more careful.
I think this is the best advice as well, keep thinking about what you actually need, by just getting out the on the trails you are going to be going on.

Saying that, from your other thread and your other posts it looks like you have thought about it, and I personally think from what you've said as "permanent these lifts are" both in time and cost and the trails and terrain you have been talking about, you will be disappointed with the 4" and will want the 6" eventually for how long these trucks are and that's going to cost $$ over again. Id wait on the gears, etc until after you get the lift and tire size figured out. Your'e on 4.10's so it's not going to be undriveable (and in my opinion will be ideal gearing) Plus, you can think about the axle at that point. The g80 is a bomb, so maybe that will need to be sooner than later however...

Edit: Also looking at that avalanche photo, that thing must be cranked to the moon, look at where the diff sits and where the wheel hub is. I bet that thing doesn't have a pound in the back, and they cranked the front all the way for the picture(in addition to the low angle)
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Wiffleball Batter
WRT Mengel Pass, how bad is it these days? I crossed Mengel in a stock 1999 4runner with 31.5" tires (265/70/16) in 2011 and I don't recall it being that bad. Has it gotten worse since then?

There were a couple of pretty much bone-stock extended cab Ford Rangers in our group, too (125" wheelbase on those, just 5" shorter than your Avalanche.) They may have been running 33's but that's it.


ArizonaNative - that was not a dig at you - just a comment in general about longer wheelbase and some of the stuff I have run across thus far. I do actually use my rig quite regularly and am not waiting for anything - but it gets to be a: If you want to do this, then you must do that............sort of scenario.

Mengel Pass - rated a 4 in BCA so yes - very doable. I did see some pics of a Tacoma with 285/70-17 (my size - and shorter wheelbase) over a rocky section of Mengel Pass Trail scraping pretty good and getting a little damage. Wheel placement looked good in the pic. I haven't done it yet - but plan to within the year (a Death Valley traverse trip).

I'm seriously tempted to buy the tires and by the time I get to my buddy's should know exactly where to beat, bang, cut, and fold. My concern is what happens if I put the tires on it and then can't actually drive it - I'm stuck. I have to do the tires at 4WP because they are doing warranty swap on my existing Pro comp tires (ick) so - once the new tires are mounted - I own them whether they fit or not, and whether I can drive away or not. That's just a little scary - ya know?

What keeps getting to me is the comments from BDS that I MUST use the 6.5" kit. Their 4.5" and 6.5" are the same price - so they wouldn't get any benefit in putting me in or the other. But they are telling me that because of the shape of my fenderwell - I must do this. On the flipside is my fabricating buddy, who's opinion is buy the tires and we'll just cut the hell out of it if we have to.

UGH...............................this is making my head hurt.