Thoughts & Guidance

mars2878

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Hello GMT400 family,

Here is where I'm @, my 99 Suburban k1500 needs full brakes, lines & rear axle u-bolts (phase 1), 1 cv axle (torn boot), front sway bar, front shocks & maybe a LCA (heavy scale, metal might be soft) (phase 2).

I was offered a k2500 Suburban rear axle w/ relatively new leaf springs for stupid cheap. This axle has a 4.10 ratio. My Burban is 3.42 ratio.

I need to do the rear brakes & lines anyways. So I'm thinking swapping the k2500 axle in.

Here is what I'm not sure of.
A: Is there a 4.10 8lug IFS front that I can swap in?
If not, I'd be willing to SAS it.

B: My T. Case is the 4button Auto 4x4, either way I'd like to swap out to a NP21.

C: If I SAS it, I'm thinking of using a 90ish 10bolt (does come w/ a 4.10) along w/ a 90-91 np21 (vss). Both pass side drop.

I'm not looking to crazy off-roading w/ it. I want it to very streetable, but be better able to handle some light to mild trails. Camp out of the back when I feel like it.

I am currently running 285/75R16. I want to stay w/ a 16in rim (currently running 00 Tahoe Z71 rims, plan on going w/ steelies) & not go much bigger in tire diameter because I don't want to trim the body or bumper.




So does this sound solid?
If possible, what do I need for an 8lug IFS 4.10 swap (yr & model of donor)?
If SAS, what do I need besides the axle, f. driveshaft, t. case, f. leaf springs?
what is a good donor for the leaf springs?
I hear that off-road design is good, thoughts?
Any factory brake upgrades for the 10-bolt?


Before it's asked, why not use a d60 or even a d44.
A: cost
B: availability
C: I have better access to the 10bolt donors & it's less expensive.


Oh & before I forget, I also have the Hydroboost setup that I removed from a 98 k3500 ccsb that I plan on installing & I already deleted the ABS module.


Thoughts? Ideas? Useful help?

TIA,
Mike
 

Bloke

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Are you sure you want or need 4.10s. I got them on my truck and i would rather switch back to my original 3.73s. I run 305/70/16s and with the 4.10s. 2400 [email protected] with and about 200 miles per tank full vs 3.73 2000 [email protected] maybe 230 or 240 miles per tank full. Less rpms means better mileage and less engine wear at least for myself. I rarely tow and I don't believe i have too big of a tire that warrants a 4.10 for me. Sure i get a quicker start at the line but really who am i racing that i am going to beat with the old 5.7 v8 rated at 255 hp?
 

mars2878

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Are you sure you want or need 4.10s. I got them on my truck and i would rather switch back to my original 3.73s. I run 305/70/16s and with the 4.10s. 2400 [email protected] with and about 200 miles per tank full vs 3.73 2000 [email protected] maybe 230 or 240 miles per tank full. Less rpms means better mileage and less engine wear at least for myself. I rarely tow and I don't believe i have too big of a tire that warrants a 4.10 for me. Sure i get a quicker start at the line but really who am i racing that i am going to beat with the old 5.7 v8 rated at 255 hp?


Bloke, thank you for your input.

It's not that I need or want 4.10s, that just what happens to be in the k2500 Suburban rearend that I can get dirt cheap.
I never learned or messed w/ ratios, so I dont fully know the consequences.
Hence why I asked for others experiences & input.
I do know that tire size & tread type effect things.

I'm just @ the stage that I either keep it stock as is & fix the faults or sas & fix faults. SAS route would be more time consuming & more money, but this vehicle is not a dd, but still needs to be reliable for its monthly trip.
 

Bloke

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Think of it this way like you said you have a better rear end that you could get cheap and it has all good parts just swap it out. Not sure if you are getting bigger rear brakes but that could be a plus. You can try the 4.10s if you don't like it you could always go back in and switch it out to your original 3.42 ratio. Just depends on how much time and money you want to spend. Good luck on this.
 

letitsnow

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I would stick with stock replacement parts. The ride and drag of the 3/4 or 1 ton stuff takes a bit of the fun out of it for just lighter duty stuff. The stock 1/2 ton parts are less expensive and easy to find.

If you planned to tow big stuff or pull stumps out, different story.
 

alpinecrick

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Your K1500 Suburban came equipped to handle light to moderate trails. Simply replacing wore out parts with quality parts will probably be more of an upgrade than we imagine.

Swapping in an 8 lug axle and making it work will cost a lot, making the cheap axle kinda' expensive.

If I had my druthers I'd have a manual t-case and hubs, but what is there works, although an electric axle actuator in place of a thermal actuator is a nice option if one takes the time to route the new harness correctly. The "trick" to long lived t-cases is keeping the fluid fresh.

Changing t-cases and going to a solid axle and front driveshaft on the passenger side is a major undertaking and what do you have?........a FrankenTruck that you will be working on every other time you drive it.

Selling the 14 bolt, 8 lug axle that you got cheap and maybe making a profit, and installing good suspension/front end/steering parts is how I'd approach it.
 

badco

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8 lug bolt right up. Leafs also. Front dif is available in 410. Any decent shop could swap gears up to 4.56 maybe 4.88. SAS with a ford Dana 44 or something isn't bad and retain left drop
 

b454rat

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Going with a lower ratio doesnt always mean better mileage. Maybe in Texas down south or Midwest where there’s no hills, it might effect it. But up in the north where there are hills, along with the aerodynamics of a barn suburban, need every lil bit to help. Bigger tires are rolling mass, need to factor that in as well. But a SAS isnt really that hard. But the cost is definitely more than rebuilding the stock crap. But it will last longer than the IFS crap.
 

stutaeng

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Hello GMT400 family,

Here is where I'm @, my 99 Suburban k1500 needs full brakes, lines & rear axle u-bolts (phase 1), 1 cv axle (torn boot), front sway bar, front shocks & maybe a LCA (heavy scale, metal might be soft) (phase 2).

I was offered a k2500 Suburban rear axle w/ relatively new leaf springs for stupid cheap. This axle has a 4.10 ratio. My Burban is 3.42 ratio.

I need to do the rear brakes & lines anyways. So I'm thinking swapping the k2500 axle in.

Here is what I'm not sure of.
A: Is there a 4.10 8lug IFS front that I can swap in?
If not, I'd be willing to SAS it.

The only 2 front differentials made for these trucks where the 8.25" on the 1500 and the 9.25" on anything 8 lug. I don't think the GMT400 K1500s ever came with 4.10s, that I'm aware of. I think 3.73 were the highest on the K1500s. Dunno. There's guys that have done the 8.25" to 9.25" swap, but it's pretty involved.

B: My T. Case is the 4button Auto 4x4, either way I'd like to swap out to a NP21.
NP241? Should be a direct swap, as that was a standard option.

C: If I SAS it, I'm thinking of using a 90ish 10bolt (does come w/ a 4.10) along w/ a 90-91 np21 (vss). Both pass side drop.

Passenger drop? As in the V-series (square body)? Aren't those kinda hard to find?

I'm not looking to crazy off-roading w/ it. I want it to very streetable, but be better able to handle some light to mild trails. Camp out of the back when I feel like it.

I am currently running 285/75R16. I want to stay w/ a 16in rim (currently running 00 Tahoe Z71 rims, plan on going w/ steelies) & not go much bigger in tire diameter because I don't want to trim the body or bumper.




So does this sound solid?
If possible, what do I need for an 8lug IFS 4.10 swap (yr & model of donor)?

I thought you could swap the entire front suspension from an 8 lug to your K1500, but @Schurkey recently posted a pic showing the upper control arms being different (8 lug vs 6 lug 2500,) so I'm not certain on that now...

Another option is a 14 bolt from a 2500 6 lug rear axle. Those came with 3.73s and 4.10s. It sounds like 3.73s or 4.10s will work for you. I favor 4.10s for slight advantage during heavy hauling/towing.

Is your 14 bolt at semi-float? I think you can convert it to a 6 lug with different, stock axles. Look into this, but I seem to recall you need different calipers/rotors? There is no real easy way to convert the 8 lug to 6 lug on the full float axle, unfortunately. Unless you get something custom machined.

If SAS, what do I need besides the axle, f. driveshaft, t. case, f. leaf springs?
what is a good donor for the leaf springs?
I hear that off-road design is good, thoughts?
Any factory brake upgrades for the 10-bolt?


Before it's asked, why not use a d60 or even a d44.
A: cost
B: availability
C: I have better access to the 10bolt donors & it's less expensive.


Oh & before I forget, I also have the Hydroboost setup that I removed from a 98 k3500 ccsb that I plan on installing & I already deleted the ABS module.


Thoughts? Ideas? Useful help?

Yes to Hydroboost.

TIA,
Mike
 
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