New memeber, 99 OBS Suburban 4x4 build to date and Plans

**branpowell606** · 05-11-2022

Good Day All, New member Here.
I have a 99 OBS 5.7L suburban I have plans to build and mod. Owned since 143k Miles, at 163k now. So far I have swapped in a k2500 6 lug 14 bolt rear end, put 1" lift blocks in the read, Rebuilt the engine, Mild Cam swapped in, New upgraded spider injectors. Just finished my 0411 PCM swap, so I'll make a post of that with my tune and pinout.
Planned mods:
Swap in Manual transfer case and shifter.
Add in Tow Mode button for my 0411 setup.
Re-gear to 4.11
Manual/Permanent front diff lock
Mercruiser MPFI intake
Remove all parasitic drains, EGR, AC, Water pump Fan, etc.
Exhaust
Add electric fans
Extra Trans cooler
k2500 Suburban rear leaf swap
Vette solenoid in the 4l60e, probably will just build a stage 1 to swap in at some point
I'd love to throw on a junkyard diesel turbo after the intake swap, just to run 6-9lbs for extra towing power.
There's more, but I can't think of it all right now, lol.

**1project2many** · 05-12-2022

Hello from a fellow Suburban owner.

There are some cams that can improve low end and possibly reduce the need to swap to 4.11 gears. If you're looking for strong braking I was able to switch to 2003 Astrovan spindle and caliper plus 2015 Silverado rotors plus 1979 Camaro master cylinder to create an extremely capable braking system. I've been watching for a set of turbo exhaust manifolds that I like but so far I haven't had much luck.

**branpowell606** · 05-13-2022

When I rebuilt the engine, I did put in a mild "Tow Cam." Dr. Bumpstick I hyd roller .465/.470 lift with 209/.215 duration at 50. I just pulled a car trailer for 4200 Miles with it. It does pull decent, but I'll love it to pull a little closer to effortless, lol. When I swapped in the 14 bolt I did upgrade the wheel cylinders from a 8600+ GVWR one ton truck, even though the 14 bolt 6 lug still runs the stock size brake pads, and that did help. I already have the largest 11" drums on the bake I can get without a 8lug swap, and I'm not super interested in rear disk conversion right now. I really like the idea of upgrading the front brakes with stock parts, but didn't know there were options beyond the Police Tahoe front stuff. The Astro Spindle knuckle would need Astro Hubs also, yes? Looks like a two piston caliper on those, Nice! did you upgrade the spindles and Master cylinder together or separate? Just curious how much improvement each makes on its own.

**MO LS Noobie** · 05-13-2022

Regarding the brake issue - I have a 99 OBS Denali, and I fought a low brake pedal for years. Stainless brake lines and hoses, multiple different compounds of brake pads, considered changing it over to Hydra boost. Finally read about changing it over to a 02 Silverado master cylinder, only requires one adapter for one of the brake lines. Worked like magic, great feeling brake pedal and brake performance. BTW just finished swapping in a 6.0 LQ9 LS, three times the horsepower and 30% better fuel mileage, you gotta love technology.

**1project2many** · 05-16-2022

I already have the largest 11" drums on the bake I can get without a 8lug swap, and I'm not super interested in rear disk conversion right now. I really like the idea of upgrading the front brakes with stock parts, but didn't know there were options beyond the Police Tahoe front stuff. The Astro Spindle knuckle would need Astro Hubs also, yes? Looks like a two piston caliper on those, Nice! did you upgrade the spindles and Master cylinder together or separate? Just curious how much improvement each makes on its own.

I would use those same rear brakes if I stumbled on the right axle. Folks love to recommend switching to rear disc brakes but they don't always seem to think about how the vehicle is used. I frequently tow a car trailer. Loading and unloading the trailer also involves removing a *bunch* of weight from the rear axle of the truck for a short time. I set my park brake when loading / unloading and I want all the brake I can get at the rear wheels. I am not interested in replacing a large park brake with the smaller brake found in most rear disc designs. Truth is, I don't need more rear braking, either. When towing the trailer I have two additional axles with electric brakes to help slow the vehicle. When driving without the trailer the truck is unloaded and the rear brakes are not likely to overheat.

As far as the front brake swap, there are a couple of options when using the Astro spindles. Here is a thread which provides one path: https://www.gmt400.com/threads/nbs-a...upgrade.20774/

IIRC that thread ultimately recommends using the 2003+ GMT800 axle shafts and hubs. I did not follow that path but I believe that may be the easiest way to complete the swap. In my case I had already installed new wheel bearings and axles into the '99 GMT400 and I didn't want to throw them out. There are a few details worth noting when going this route: 1) there are no threads in either the spindle or the bearing hub. You will need to use bolts and nuts to attach the bearings. Tractor Supply to the rescue! 2) The Astro hubs move the bearings further from the differential and increase the front track width. The GMT400 bearing and hub appears to move the wheel about .200" outboard of the original Astro wheel location. The hub and spindle together increase front track width noticeably. Using the GMT400 front axles and bearings requires installing axle spacers. I used 1" spacers and have not had issues. Using the GMT400 front bearings with 13" rotors requires moving the brake caliper outboard. Two 9/16" flat washers worked for me. 3) The GMT800 and newer vehicles do not use a seal on the interior side of the wheel bearing. I believe the seal provides some protection from salt and road scum common here in the northeast and helps reduce the tendency for the axle to become seized in the bearing. Liberal use of anti-seize is a good idea if moving to the new design parts. I was able to get creative with an alternative number seal. I believe I also removed the shields from the outer CV joint so the axle could be drawn into the bearing properly. I will do my best to provide pictures and more accurate information if needed.

Ultimately I am very happy with 13" front brakes. I did try using a Bosch master cylinder from a 2015 truck because I'd picked up front spindles complete with rotors, hubs, and calipers, rear axle, and master + booster. The booster hit a number of components on or near the firewall and the master cylinder was not a direct swap onto the GMT400 booster. In order to get the Bosch brake components you need to find a truck with rear drums. I chose to use the Camaro master cylinder as I believe it offered a good compromise between pedal travel and pedal effort while eliminating the "Quick Take Up" system that makes the GMT400 brakes feel so sluggish.

I have tried a number of approaches to cure the "slow apply" brake system on GM vehicles with a Quick Take Up master cylinder. Years ago I switched an S10 Blazer to dual piston front calipers and larger rotors. While this reduced pedal effort it did little to decrease the time required to apply the brakes after beginning to apply the pedal. I then switched to Hydroboost using a QTU master cylinder. That improved things slightly but not like I wanted. In another attempt I switched a 1998 G3500 cutaway with Hydroboost to the 1995 style Hydroboost master cylinder, a non QTU style. While this made it very easy to apply the brakes quickly, it also required slightly more pedal effort and resulted in many complaints about the brakes being too hard to apply compared to other vehicles in our fleet. At one point I convinced a friend to replace the QTU master on his 1995 GMT400 with one from an older truck with the same diameter piston. He absolutely loved how quickly the brakes applied although he felt the pedal apply point was slightly lower. I do not believe he ever swapped back. My current Suburban was purchased last fall and has yet to receive any brake upgrades. I plan to switch the Astro spindles onto this vehicle but for now the brakes actually stop very well. But the QTU master is still present. As I begin to work my way through the project list for this vehicle I will probably swap the Camaro master cylinder from the "old" Suburban. I am extremely confident that change will make stopping feel dramatically better due to 1) elimination of QTU master and 2) increased hydraulic pressure due to smaller diameter pistons.

**branpowell606** · 05-21-2022

I will definitely check out that thread. IDK about the wider width or spacers though, I'll need to sleep on that one, lol. Sorting out some other kinks atm with the 0411 swap and cam, and sorting out my idle/starting. I think I'll probably have to dive into tuning a bit before the brakes get much attention. Squeaky wheel and all that.