At the time I was un aware of different master cylinders. I just looked at Oreilly. They have 2 different numbers listed. It looks like they have different thread sizes so I probably have the right one.
Peruse RockAuto. You need to dig deeper to get parts that are for the heavier 2500/3500 trucks.
Look for an MC for a C2500, pick 1998 for example, and look for one listed for "8,600#" or "JB7". More on this later.
Ditto for the calipers.
If you read through the GMT400 threads you'll find some parts numbers referenced. I'll also provide some, below.
Here are some MCs that you can use, there are certainly others. Look for an MC used with the 2500/3500 trucks, 8,400# GVW brakes or 10,000# GVW brakes
ACDelco 18M712
Centric 13066030
Notice that these are both 1.25" bore MCs. You can also see that they are non-quick-take-up MCs by looking at their picture; the body of the MC shows no "step" along its length.
If you compare pictures of the MCs, you'll see that some have an odd looking taper near one end of the body; that's where the "quick-take-up" piston lives. You Don't Want That. From what I've seen on RockAuto, most (all?) of the quick-take-up MCs are listed as having 1.125" bore, and are listed for use with JB5/JB6 brakes.
ACDELCO 18R741 and ACDELCO 18FR742 appear to be 80mm piston calipers, from their specs. Further below I give numbers for the 86mm calipers.
Read this thread, and make note of any discussion regarding fitment of pads when using the larger piston brake calipers.
Thread 'Upgrade Front Brake Calipers'
https://www.gmt400.com/threads/upgrade-front-brake-calipers.58795/
370 and 369 are common pad numbers, 369 is the pad number for the smaller piston calipers and 370 is the pad for the larger piston calipers. They can be interchanged to some degree, that’s discussed in this thread (above), among other things…
Too, as you may have read, the 369 pads (which you already have on your brakes now) can be fitted on the larger-piston calipers, as noted in this post:
https://www.gmt400.com/threads/upgrade-front-brake-calipers.58795/post-1254484
Why use one pad or the other? Neither is optimal b/c of the mish-mash of
rotors (yours being smaller in this case) with the
calipers (which were designed for a slightly larger-diameter rotor). The 370 pads, which fit the larger 80mm/86mm calipers, are slightly bigger than the 369 pads which fit the smaller 76mm calipers (76mm is what you already have).
I used the 370 pads, which were designed for the 80mm calipers I bought. They fit the calipers fine but, since the pads are larger than those normally used on my truck, they interfere slightly with the rotor (see the post here
https://www.gmt400.com/threads/upgrade-front-brake-calipers.58795/post-1251888 )
Another guy, in another post (I gave the link above), used the smaller 369 pads on the larger caliper. In his case, the pads don't fit perfectly on the calipers (but the fitment is manageable, and not a safety concern AFAIK) but they fit nicely on the rotors (there's no interference like I mentioned in the previous paragraph).
My recommendation: If you have a grinder, get the 370 pads and the 80mm or 86mm calipers. Fit everything to the vehicle and check for interference b/t the pads and the hub of your rotor.
- If there's no interference, you're done.
- If the interference can be managed by grinding / clearancing the pads a bit like I discussed in my post (link above), then do so
- If the interference cannot be managed, attempt to fit the 369 pads (you already have) onto the calipers, and re-attempt fitting them to the vehicle.
Is all this clear as mud?
Trust me, this pad "issue" is the only issue with this entire process. It's very much plug-n-play, otherwise.
Here are a couple part numbers which RockAuto's specs show as being 86mm piston calipers, although there are certainly others:
NUGEON 9717271A - front right
NUGEON 9717271B - front left
POWER STOP L4347 - front right
POWER STOP L4348 - front left
FYI, for reference, I've included an image from the factory service manual for 1998 (below).
The caliper sizes aren't mentioned, neither is the MC bore or whether the brakes are "low-drag" / "quick-take-up".
The rear brake information is more illustrative, as is the brake assist method used (vacuum / hydraulic)
You must be registered for see images attach
