2000 Suburban K1500 budget low lift with 37"s

[rayra]

Looks like too much tire to me, especially if you have to chop the crap out of your fender wells to stuff them in there. I wouldn't go bigger than 35s on our sort of setup. And that's not even getting into CV angles. Get a proper suspension lift, do it right. Especially in the front. A setup that drops the front brace and axle down. Then there's the whole gear ratio thing and a 4L60E closer to the end of its life cycle.

Weird numbers on your heights, too. 2" spacers and aftermarket keys on my Z-71, otherwise same vehicle, the top of my well openings are at ~39" right now. I just turned my fronts down another rotation. Ride got a lot better after I properly lubed everything, that includes soaking all the bushings with silicone lubricant spray too. Don't have a better or comparison pic right now, other than those posted in my 'Hey Vortec Guys' topic. Just finished the front tie rod sleeves and other work, still need to go get an alignment.

 

[ExplorerTom]

Edit: be weary of those wheelspacers, they are not hubcentric

Hub centric does not do what you think it does. For a wheel to be centered 100% by a flange on the hub and a recess in the wheel, you'd have to press on that wheel to achieve that level of alignment. Any slop in that interface would show up as massive vibrations at speed.

Instead, look at the shape of the lug nut. See how they are tapered and fit in a tapered seat? That's what centers your wheel. That's why you are supposed to torque lug nuts in a criss-cross fashion with as little weight on the wheel as possible.

Does that flange carry load? You better hope not. A steel flange interfacing in an aluminum recess taking load- guess what wouldn't be circular after a drive down the street: that aluminum recess in the wheel. Instead, load is carried through the clamping force generated between the hub and the wheel when the lug nuts are torqued properly.

I've talked this over with my engineering professors, my stress analyst at work and a friend who works in the suspension group at Joe Gibbs Racing.

 

[Ivan]

Ivan,

Original top of fender height was 35" front, 36" rear. With the 3" level kit it came up to 37" front, 38.5" rear, no ground clearance gained under rear diff. After the 37"s 40.5" front, and 41.5" rear. So the bottom of the rear diff sits 2.5" higher than where I started with the 32"s. I'll get some action shots once I trim the fenders and get wheel spacers.

Andrei

I'm excited to see where you go from here. I'm thinking about making the same jump in tire size. After all, the difference between a "true" 35 and a "true" 37 is in some cases less than an inch (BFG KM2's 37x12.50r17 comes to mind).

 

[Stryder106]

Agree with most folks on here. On my 02 Av (1500) - I have: 35" Grabber x3 tires, 4.88, ARB air locker, Rare Parts 1.5" tie rods, 0 offset wheels, completely aftermarket 4L60E and torque converter, Tru-Cool trans cooler, Hypertech tuner, leveled with CST keys, Eibach Pro Truck Sport shocks, Thorley headers, Rerouted exhaust (to avoid damage), Custom tube track bar, Z-Power rotors, Cognito UCAs, Spohn rear upper and lower arms on the way. I did NOT lift my Av, I did however do some serious cutting. I'm only mentioning those items I put on my Av as they were all to address the known weak points in a 1500 GM truck/SUV.

I'm stubborn - I love my Av and I like being the only one out there in one.

Good luck with your project.

 

[mccustomize]

Don't let the naysayers discourage you. Most have never done what they are saying can't be done.

I ran 37s on my Silverado for a few years with no problems, wheeled it as well. Only broke 1 CV at a hardcore offroad park in sticky clay. I was running keys and a 3" body lift. It cleared the fenders fine and would have cleared a stock bumper with trimming.

I also ran 2" rear spacers for 5 years with zero issues as well. Get some tie rod sleeves while you are in there.

I was running 4.56 gears and later went to 4.88s with 37s so don't fear the gear, keep an eye out on craigslist, guys are always upgrading.

 

[jeep-N-montero]

I'm interested to see what "Jeep trails" you have in mind that you hope to casually cruise in 2wd without busting the rear axle or burning up the trans while trying to turn those 37's. I am a GM guy and wouldn't even try to fit 37's on our Yukon 2500, a full size rig with a leveling kit running 255/85r16's and proper body armor is all you need for most trails that a burb will even fit on. But best of luck to you.

 

[Burb One]

Hub centric does not do what you think it does. For a wheel to be centered 100% by a flange on the hub and a recess in the wheel, you'd have to press on that wheel to achieve that level of alignment. Any slop in that interface would show up as massive vibrations at speed.

Instead, look at the shape of the lug nut. See how they are tapered and fit in a tapered seat? That's what centers your wheel. That's why you are supposed to torque lug nuts in a criss-cross fashion with as little weight on the wheel as possible.

Does that flange carry load? You better hope not. A steel flange interfacing in an aluminum recess taking load- guess what wouldn't be circular after a drive down the street: that aluminum recess in the wheel. Instead, load is carried through the clamping force generated between the hub and the wheel when the lug nuts are torqued properly.

I've talked this over with my engineering professors, my stress analyst at work and a friend who works in the suspension group at Joe Gibbs Racing.

Yes, you are correct in terms of the load bearing. Thanks for clarifying where I didn't. I would still stand by my statement to not use hubcentric wheels on lugcentric spacers (or hubs) especially when wheel and tire weights are close to 2 times the weight of stock.

I always understood that the hubcentric wheels are centered by the flange and that the lugs then provide the lateral force to mate the wheel to the hub which bears most of the load (vs as you said the lugcentric are centered by the tapered nuts).

With that, hubcentric wheels on a lugcentric spacers or hub will not center properly by the lugs because they were not designed to do so (either machining tolerances and the center of rotation in respect to the lugs, etc.) all of which could cause vibration and wear. This is all exacerbated by then the weight of 37's and the increased distance from the bearing the center of mass the spacer makes for the wheel exacerbating any vibration and forces.

In the past few decades whether it is machining tolerances or because manufactures know mismatch with hub/lug centric is much more common since hubcentric became the standard and along with increased liability, machine their hubcentric wheels to be able to be used in lubcentric circumstances without crazy vibrations, etc., i don't know.

I still for one, on something as safety critical as a wheel/hub, will air on the side of caution, especially with larger and heavier than stock applications, especially when we are talking about loading these rigs to close to above GVWR, especially while lifting a wheel (or two) up off road in remote areas.

Saying that, I can't explain why the lugs are also tapered on these GM trucks other than to provide an interference fit for the lugs themselves. I am assuming maybe these wheels are machined to be able to be used in both applications, or maybe GM engineers figured why not center with both (or maybe the interference fit on the flange is not as much as I think and it is just a guide?). All I know is that the above makes sense to me (not a engineer, but am in Physics) and also that GM decided go through the expense of adding hubcentric designs onto their hubs, so for the extra $30-40 cheap insurance IMO.

 

[Burb One]

Camping gear and 37s have more wear and tear than what this thing is rated to tow?

I would say yes, much more.

In terms of the tranny, off road in my expierience is much harder on it. You spend more time shifting and with an unlocked TC than towing on the open road and, at slower speeds which means everything heats up faster. I tow 6k with mine very often and back when I was on 29's i had very limited problems with heat (going up the Grapevine into LA or up the Sierras into the Reno/Fernley area in the summers at 90degrees+ were the only time i would see 210+ with the stock tow package transmission cooler.) When I moved to 33's on the stock cooler I would see 200 daily without the trailer hooked up at all in 80 degree weather The B&M cooler fixed this (recently moved to an even larger trucool).

In terms breaking the weak 10 bolt. I mean if you're cruising off road on a nice dirt road, maybe not, but then what's the point of 37's? With all the camping ******** we all usually bring, close to GVWR with winches, batteries, fridges etc. and you start lifting a wheel or spinning in the mud, I can guarantee that's harder than towing on pavement in a straight line. If the rear is an open diff, than okay maybe on 37's it can be manageable, but IMO 31's and a locker are more capable than 37's and open in everything but rock crawling, which even then, the 31's will be more capable because rockcrawling with 37's on an 8.25 front end and our tripod CV's will crack the tripod the second you have any wheel spin on a 37 and it touches a rock.

 

[ExplorerTom]

or maybe GM engineers figured why not center with both (or maybe the interference fit on the flange is not as much as I think and it is just a guide?).

It's not an interference fit. It's a clearance fit. To be an interference fit, tightening the lug nuts down would effectively press the wheel down onto the flange. But the proper way to press something together is not by applying the compressing load off to one side (like a lug nut would do). Applying the compressing force to one side would cause that steel flange to wallow out that soft aluminum bore in the wheel. And pressing a steel flange into cast aluminum wheels.....

Best I can tell, the reason for the steel flange is so the wheel can rest on that instead of the threads of the lugs before you can get the lug nuts seated. Next time you have your wheels off, push the wheel so it's up against the hub face like it would be if the lug nuts were tight, then slide the wheel along that hub surface. It won't slide far because the lug studs and that flange, but it will slide. Imagine if you were to tighten the wheel down at one extent or the other of that motion. Imagine the vibrations it would create.

Also, next time you are putting the lug nuts on, put the first lug nut on that's on the side (like the 9 or 3 o'clock position). Seat it so it's tight but not to final torque. This will allow the wheel to rotate about that lug and rest against something (probably the steel flange). Notice the position of the other lug nuts in their holes- they won't be quite centered. As you tighten the next lug nut, watch as the wheel moves slightly as the lug nut seats into the wheel. Now the remaining lug nuts should be pretty close to center in their holes.

 

[TwinDuro]

Cool build CrazyDrei, I like your low-budget approach!

While 37 inch tires are indeed a lot of tire for 8.25" IFS front differential (or any 8-1/4" differential come to think of it) and CVs, my humble advice and an option that I haven't seen anyone mention is "carry a spare CV axle" and have the tools, supplies, knowledge and practice to do a trail swap-out if needed. The chance of having a complete CV failure to the point of making your rig no longer drive-able would be pretty small, and you'll probably never have to do it (it would be a PIA out on the trail), but if it comes down to it, its definetly an option.

Now if your front differential fails completely (I've never seen a documented example for the 8.25," pictures anyone?), that becomes a slightly more interesting problem, but it's still possible to get off the trail in 2wd if a little ingenuity (E.G.: trail hackery) is used...

I think the key with a tire this big on a rig this heavy, is be gentle with the go-pedal. Treat it like a sensitive friend that doesn't take criticism well.

For a rear axle that is better capable of handling those big meats (it would be more difficult to find then a replacement 8.5 ten-bolt, especially for a reasonable price, but they are out there) you might considering looking for a 6-lug 9.5" semi-floater 14-bolt out of a similar-year Suburban, Escalade or GMC Yukon, but make sure it has 4:10s and don't fall for the rear axle from a 1500HD pickup because it's setup for leaf-springs and not coils. Here's a link to an individual that did this: http://z71tahoe-suburban.com/iboard/index.php?showtopic=34465 These rear axle assemblies are notoriously hard to find, but a great upgrade, as the ring-gear is one inch larger and the axles are 1.37 inches in diameter. Not quite a 14-bolt full-floater, but much better then the stock 10-bolt you currently have. You'll need a conversion u-joint to work with your stock driveshaft when installing this axle.

Another option, and one that would be worth considering, is the more commonly available rear axle from a Hummer H2... Supposedly, because of the H2s weird hybrid frame design which is some parts 1500 and 2500 if I understand correctly, the rear 5-link 14-bolt 9.5" axle will bolt into your Suburban, but please investigate this if you consider it because I've never personally done this particular swap. These axles came from the factory with 4.10:1 gears and a factory Eaton e-locker (electric locking differential) and can be had online for $600-$800 with free shipping. The problem with this swap is that it's 8-lug and the width of the axle is 3-4 inches wider then your current axle. The width isn't a problem, since it would allow you to just not run wheel spacers on the rear, but the lug-pattern is, because then you'd have to carry two-spares with you. Not a deal breaker, but annoying, especially for a matched set of wheels. They do make 6-to-8 lug conversion wheel spacers that are 2 inches wide that would work for the front if you wanted to run 8-lug wheels all-around, but being that those are 2-piece spacers, and that your running 37" tires, that would personally make me very nervous.

Of course, with any of these swaps, you'd need to find a matching 8.25" front diff (option code "GT5" for 4.10:1 gears on the RPO code sheet in the glove box) in the wrecking yard as well.

Lots of options to consider, some of which are affordable and some of which aren't, but at least there's options. :sombrero:

 

[CrazyDrei]

While I am very weary of 37's on the 1500 running gear and would highly recommend against it, as stated the 10 bolt is not going to like the 37's at all, much the less the 8.25 front end... All of this adds up to anywhere you actually needed 37's for, will just blow up your running gear and get more than stuck but broke (pun intended)

With that caveat, I am interested to see it done! At the least, ignoring the above, you need to get a much, much larger transmission cooler. Even the tow package one won't be enough. There is a medium sized B&M all said and done for $60-80 if you do a search, but I would recommend a tru-cool (see my thread for details). They run around 110 bucks. If you don't, with 37's and camping stuff in it that 4l60e is going to maybe last 5k miles. I wouldn't be surprised if you hit 220 degrees on a cool day at 70mph...

Edit: be weary of those wheelspacers, they are not hubcentric which the GMT800 wheels and hubs were designed to be. I would say don't worry about it if you were on 33's maybe 35's but with 37's and the stress involved I don't know.... I'm the first to say wheel spacers are okay if well and properly designed (id doesn't effect the stress much than the same backspaced wheel) but those are not the proper design....

geronracing,

I appreciate your concern regarding running 37s with the 8.25 up front especially with 3.73 gears until I find a good deal on 4.10 or 4.56, however this is a negative hypothetical armchair philosopher stance with no real world examples to back the claims. I used to have a 1988 Isuzu Trooper 2, I put 3" lugcentric wheel spacers and 35x12.5s on the stock 15x5" rims, ran that setup for 115k miles with absolutely no issues, and I beat that truck up on 4x4 trails every weekend for over three years. Suburban drivetrain is much stronger (all parts are visually larger/thicker) and will have absolutely no problems with the 37s.

4L60e is a terrible transmission on paper and the towing package on the Sub sux too, especially since it's only rated to 8,200#, however I have pulled a 12,300# boat (no electrical or surge brakes) from Vegas to LA 8-10 times a year for the last two years in 115 degree heat with 6 people in the truck and AC running at 55-65mph and the thermostat never read above 195.

I am concerned about blowing up my tranny, diffs, axles, u-joints, drive shaft however I can not find any actual numbers of the shearing or torsional values that support these claims.

So to stay on the positive side of the build, 1,000 miles with the rear spacers and no wobble or problems, front spacers are going on in a couple days, so I'll put the pics up in a week or two.

Stay tuned for more shenanigans.

 

[CrazyDrei]

Looks like too much tire to me, especially if you have to chop the crap out of your fender wells to stuff them in there. I wouldn't go bigger than 35s on our sort of setup. And that's not even getting into CV angles. Get a proper suspension lift, do it right. Especially in the front. A setup that drops the front brace and axle down. Then there's the whole gear ratio thing and a 4L60E closer to the end of its life cycle.

Weird numbers on your heights, too. 2" spacers and aftermarket keys on my Z-71, otherwise same vehicle, the top of my well openings are at ~39" right now. I just turned my fronts down another rotation. Ride got a lot better after I properly lubed everything, that includes soaking all the bushings with silicone lubricant spray too. Don't have a better or comparison pic right now, other than those posted in my 'Hey Vortec Guys' topic. Just finished the front tie rod sleeves and other work, still need to go get an alignment.

rayra,

Glad to hear of others building their Suburbans for fun adventures. My keys are at no turns for the same reason as you, to keep the ride better. Tow package has the same springs as the Z71, I think your truck sits higher because your springs have not had to deal with the same abuse I put mine through. I regularly haul 2-3,000 pounds in the truck for 500-1,000 miles at a time, and that beats up the suspension pretty bad. What size tire are you running?

If I do a 3" body lift I do not have to touch the fenders to fit the 37s, however I want to keep the center of gravity as low as possible and this is a very low budget build so I'm cutting fenders to fit the 37s. BTW you mentioned CV angles and advised a proper suspension lift, you do realize that my CV angles are 100% stock and will remain in the factory travel range and if I put 53" tires on my truck the CV angles will not change. If I do a lift kit then ALL the angles of all the suspension parts will change and put an increased amount of stress on every suspension part increasing the likelihood of a breakdown.

Stay tuned for more shenanigans.

 

[CrazyDrei]

Hub centric does not do what you think it does. For a wheel to be centered 100% by a flange on the hub and a recess in the wheel, you'd have to press on that wheel to achieve that level of alignment. Any slop in that interface would show up as massive vibrations at speed.

Instead, look at the shape of the lug nut. See how they are tapered and fit in a tapered seat? That's what centers your wheel. That's why you are supposed to torque lug nuts in a criss-cross fashion with as little weight on the wheel as possible.

Does that flange carry load? You better hope not. A steel flange interfacing in an aluminum recess taking load- guess what wouldn't be circular after a drive down the street: that aluminum recess in the wheel. Instead, load is carried through the clamping force generated between the hub and the wheel when the lug nuts are torqued properly.

I've talked this over with my engineering professors, my stress analyst at work and a friend who works in the suspension group at Joe Gibbs Racing.

ExplorerTom,

Thank you for finally turning this thread in a positive direction, I am getting bored of hearing people make stuff up and pretend to be hypothetical experts with absolutely no scientific proof behind their guesses. Your friend who does suspension part stress analysis is absolutely correct that the so called "hubcentric" wheel is held in place by tapered "lugcentric" lugs which must be tightened in a cross pattern to properly seat and center the wheel. My use of spacers is to increase the offset of the wheels because it's a budget build, I can't wait to see the comments I get when I put 3" spacers on the front, LOL.

Thanx for the positive insight.

Stay tuned for more shenanigans.

 

[CrazyDrei]

Agree with most folks on here. On my 02 Av (1500) - I have: 35" Grabber x3 tires, 4.88, ARB air locker, Rare Parts 1.5" tie rods, 0 offset wheels, completely aftermarket 4L60E and torque converter, Tru-Cool trans cooler, Hypertech tuner, leveled with CST keys, Eibach Pro Truck Sport shocks, Thorley headers, Rerouted exhaust (to avoid damage), Custom tube track bar, Z-Power rotors, Cognito UCAs, Spohn rear upper and lower arms on the way. I did NOT lift my Av, I did however do some serious cutting. I'm only mentioning those items I put on my Av as they were all to address the known weak points in a 1500 GM truck/SUV.

I'm stubborn - I love my Av and I like being the only one out there in one.

Good luck with your project.

Stryder106,

Sounds like you have a sexy truck, do you have any pictures? How do you like the hypertech? I always like the look of the Av, but my wife wanted more indoor storage space for traveling with kids. Do you have any pictures of the cutting, specifically the front?

 

[CrazyDrei]

I'm excited to see where you go from here. I'm thinking about making the same jump in tire size. After all, the difference between a "true" 35 and a "true" 37 is in some cases less than an inch (BFG KM2's 37x12.50r17 comes to mind).

Ivan,

I am right there with you on this one, difference between true 35 and true 37 is really one inch or less so the diameter is not an issue. The weight is a slight issue, I'll get the exact weight of 32.5" on 18" rims compared to 37s on the 17" rim. I'll crunch the numbers to see what the payload weight equivalent of the increased rotational mass really is just to silence all the theoretical naysayers. I'm extremely busy right now, however will be trimming fenders in a couple weeks.

Stay tuned for more shenanigans.