Confused about brake upgrades for 93 K1500

[1998_K1500_Sub]

get a hydroboost and matching master cylinder from a 2500/3500 truck (use a 1994 k3500 diesel or 454) ... You will have to modify the brake pedal or find one for a hydroboost at a wrecking yard. I would just find a complete system from the wrecking yard.

This ^^^

As noted, the pedals are different for the hydroboost brakes, so consider taking them from a donor.

Too, the hydroboost systems have a tube-and-fin power steering oil cooler mounted in front of the radiator. Grab it, too, otherwise they're easy to find on eBay.

(Edit: Some but not all have the tube and fin cooler.)

 

[Schurkey]

the hydroboost systems have a tube-and-fin power steering oil cooler mounted in front of the radiator. Grab it, too

My '97 K2500 8-lug has Hydroboost, but no tube-and-fin cooler.

GM put a piece of plain tubing (no fins) that made a big loop inside the frame-rail behind the bumper. Tubing wore through on a bolt, so I bypassed the thing. No cooler at all, now. Gonna have to do something about that next summer.

 

[1998_K1500_Sub]

My '97 K2500 8-lug has Hydroboost, but no tube-and-fin cooler.

Thanks for pointing that out. I expect hydroboost necessitates some sort of cooling, though perhaps not the tube and fin cooler.

I’ve corrected my prior post.

My 1998 K1500 Suburban came with NO PS cooler and 3.42 gears. I’ve since added the tube and fin PS cooler in anticipation of adding hydroboost at some later date.

I now remember in previous forum discussions on this “PS cooler” topic that the tube and fin cooler’s use by GM seemed to correlate with rear gear ratio. I believe there was some speculation that, on account of the resulting higher engine and PS pump RPM (e.g., with 4.10 gears) the tube and fin cooler was installed.

 

[nick7269]

Sorry for my slow reply, I need to check my spam box, I missed the replys.

I just looked in the glove box and saw a code that was JB5. I wish I had known to post that in the first post.

I am going to replace the lines with SS lines and I have access to a OBD scan tool to bleed the brakes. I am going to pull a rear wheel off tomorrow and try to see what size drum is back there because I am not sure about that yet.

Now knowing that I have a JB5 brake system, what are your opinions?
thank you
nick

 

[1998_K1500_Sub]

Now knowing that I have a JB5 brake system, what are your opinions?

@Schurkey gave his advice earlier in the thread:

https://www.gmt400.com/threads/confused-about-brake-upgrades-for-93-k1500.59858/post-1272010

All comments in this thread related to the front brakes remain valid.

The JB5 front brakes are the same as the JB6, so when you read about front brake modifications you can think of those RPOs as synonymous.

Here's a matrix of various RPO codes and what the mean. Notice the similarities / differences in the fronts brakes, the rear brakes, and the assist (vacuum or hydraulic) between the different RPO codes (image from 1998 GMT400 service manual, Volume 2, pg. 5-5):

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What the matrix doesn't tell you are the differences between, e.g.,

- calipers: bore diameter and interchangeability
- calipers: whether "low-drag" or not
- master cylinder: piston diameter
- master cylinder: "quick take-up" (used with low-drag calipers) or not
- rear slave pistons: diameter and interchangeability

The various comments in this thread, and in threads linked-to in this thread, help shine some light on these differences.

 

[nick7269]

Awesome, thank you guys!

 

[Schurkey]

I just looked in the glove box and saw a code that was JB5.

I am going to pull a rear wheel off tomorrow and try to see what size drum is back there because I am not sure about that yet.

Now knowing that I have a JB5 brake system, what are your opinions?

JB5 has the 254mm (10") leading-trailing shoe drums. Terrible. They're practically guaranteed to be WAY out of adjustment because nobody uses the park brake, and that's needed for the adjuster to work. Lucky if the park-brake cables aren't seized.

As far as I'm concerned, there's no point in "fixing" the 254mm rear brakes. If the shoes are worn-out, it's time to upgrade to the 11.x Duo-Servo rear brakes; which gives you the equivalent of JB6 brakes.

There's not a thing wrong with the JB5 (or JB6) front brakes, master cylinder, and booster, if they're in good working order. You "can" upgrade them, but it's the rears that make the bigger difference.

If this is a K1500, a rear-axle upgrade to the "Six-Lug" K2500 gets you a better axle (14-bolt semi-float 9.5" ring gear) AND the better brakes. Match the new axle's gear ratio to the front differential of your truck. If this is a C1500, things are tougher because the bigger C2500 axle will come with six-lug axle shafts but your truck has five-lug wheels. The C2500 and K2500 axle widths are different.

 

[1998_K1500_Sub]

JB5 has the 254mm (10") leading-trailing shoe drums. Terrible. They're practically guaranteed to be WAY out of adjustment because nobody uses the park brake, and that's needed for the adjuster to work. Lucky if the park-brake cables aren't seized.

As far as I'm concerned, there's no point in "fixing" the 254mm rear brakes. If the shoes are worn-out, it's time to upgrade to the 11.x Duo-Servo rear brakes; which gives you the equivalent of JB6 brakes.

Regarding the 10" brakes, is it safe to assume that, if their hardware is in good condition, routine adjustment of the brakes is worth the effort?

By "routine adjustment" I mean pulling the rear wheels and drums, and tweaking the adjuster to take up the slack b/t the shoes and drums.

 

[AuroraGirl]

Regarding the 10" brakes, is it safe to assume that, if their hardware is in good condition, routine adjustment of the brakes is worth the effort?

By "routine adjustment" I mean pulling the rear wheels and drums, and tweaking the adjuster to take up the slack b/t the shoes and drums.

Why cant you just use the parking brake mechanism which does that for you

 

[1998_K1500_Sub]

Why cant you just use the parking brake mechanism which does that for you

How well does that work, assuming they're currently "WAY out of adjustment" (as @Schurkey phrased it)?

OP will benefit from the details, if it's doable.

Otherwise, OP could adjust them manually first, and then make a mental note to use the parking brake routinely.

We're assuming the parking brake "stuff" is still usable, which may not be the case.