Ive been spending all my time working on the she shed so the truck has been neglected a little. I decided to do a little work this weekend. I ordered some parts to refresh the front brakes.
Before starting. Standard 20 something year old GMT400 brakes.
I want to upgrade where possible, but on service items (like brakes) I want stuff readily available in local parts stores. I went with raybestos severe duty truck pads, autozone high carbon steel rotors, and whoever rebuilds autozone's calipers. I didnt do normal replacements for the calipers though, they are K3500 SRW calipers. They are the same footprint, but have a larger piston and are supposed to use a standard piston seal instead of the "low drag" setup in the half tons. The low drag calipers are generally considered the root cause of the terrible pedals GMT400s always have, so I figured it was worth a shot, and even if it doesnt help, I still like the idea of having a larger piston and more fluid at each caliper. I think there is something to it though, because its how GM spec'ed the police tahoes.
New pads vs old pads.
An old timer told me that pads and shoes have a two letter code specifying effectiveness when cold and hot, ranging from A-G. Higher being better. I hadnt heard this but decided to check my pads. Looks like my new pads are a FE. So they should work pretty good and a little better when cold. I didnt have the whole series of numbers and letter for the old pads, looks like they could be BBs or Esomethings. Hopefully they are an improvement.
New caliper vs old caliper. You can see the difference in piston size.
only modification needed was to spread the retainers on the inboard pad a little. I think the 1500 calipers use a 2.94" piston and the K3500 caliper uses a 3.15" piston.
Everything installed.
After that I put some new fluid in the reservoir, bled them real quick, did an ABS bleed, then one more gravity bleed to be sure.
I realized I hadnt changed out the diff fluid yet so I did that next. Rear fluid didnt look crazy, just old.
Front fluid was a little more surprising.
Looks like Ive got some water in there.
I let it all drip out, then ran some fresh stuff through until I wasnt getting discolored fluid anymore.
I put the plug back in and filled it up. I should probably look into how this diff is vented, and replace whatever it is. I havent submerged the diff since Ive owned it, but who knows what happened before. Generally when Ive seen them this bad, they were either recently submerged or have a vent problem.
I poked around under the truck, I have a lot less oil leaking now, so I think the intake and valve covers helped. I cleaned it up a little bit, I may have a small leak from the power steering pump, but I didnt really have a trail or much fluid to track so I just cleaned it. I still have a little oil around the bottom of the engine, maybe the oil pan. I had some on the trans pan, but couldnt tell if it was oil or trans fluid, and neither were low so Ill just monitor them until I can figure out whats leaking.
After that I went to test the new brakes.
They made a huge difference, both in pedal feel and actual stopping power. The pedal has the slightest soft spot, but engages much faster than before and hauls the truck from speed much faster. I also did some work on my dads 91 K1500 Suburban today (which has a new master) and the difference was night and day. I still havent done the rear brakes, or even adjust them, and Im rolling on what appears to be the 23 year old 150K mile master cylinder. I was planning on adjusting the rear brakes today if there was a window in the backing plate, but there wasnt and Im not going to pull the drums off until I have all new parts ready to go on. Probably in the next week or two Ill get all my rear brakes parts, and do the rear overhaul. I think because of the mileage Ill probably do a master preventatively and to finish of the brake overhaul, but with the difference the fronts made Im probably just going to stick with the gmt400 master instead of swapping to the gmt800