swap/upgrades to front calipers

[DixieWASP]

No problem. For me, the biggest important I make, for brake pedal feel, was to do the MC swap. I got my MC off of a 2002 Tahoe, I found at pull-a-part. Been going strong for ,IDK, 7 or 8 years. There is a write up on here about doing the swap, if your interested. If you click on the first pic, it will enlarge, and you can zoom in, on the MC.

I have a 1989 1500 and the brakes are mushy. I plan on installing new brake lines, calipers, and related hardware. I plan on bleeding the rear ABS unit. What exactly did the 2002 Tahoe master cylinder do for your brake feel? Did the pedal get hard or .....?

 

[kennythewelder]

I have a 1989 1500 and the brakes are mushy. I plan on installing new brake lines, calipers, and related hardware. I plan on bleeding the rear ABS unit. What exactly did the 2002 Tahoe master cylinder do for your brake feel? Did the pedal get hard or .....?

Yes. The pedal feel a lot more solid. On the 96-99 GMT 400s, they have that KS brake system. Your 89, doesn't have that. The whole thing about the MS swap, is the size of the plunger piston, inside the MC, is larger on the GMT 800 trucks. Some people on here, say, they don't like the swap, for me, it was a big improvement over the OE,,,,MC. I got mine at pull-a-part. That way, if I didn't like it, I wasn't out much money. It's been on my truck for IDK 8 years are so.

 

[DixieWASP]

Yes. The pedal feel a lot more solid. On the 96-99 GMT 400s, they have that KS brake system. Your 89, doesn't have that. The whole thing about the MS swap, is the size of the plunger piston, inside the MC, is larger on the GMT 800 trucks. Some people on here, say, they don't like the swap, for me, it was a big improvement over the OE,,,,MC. I got mine at pull-a-part. That way, if I didn't like it, I wasn't out much money. It's been on my truck for IDK 8 years are so.

Thank you for asnwering my question!

 

[kennythewelder]

Thank you for asnwering my question!

My best advice is, be sure to bleed the hell, out of everything, after installing your new parts. Also be sure to get the back brakes adjusted, as snug as you can.

 

[Schurkey]

If you still have the low-drag JN/JB3, 5, or 6 front calipers, the GMT800 master cylinder is NOT an appropriate "upgrade".

The low-drag calipers should be used with a step-bore (3-chamber) Quick Take-Up master cylinder. The small-piston JN3 calipers would be used with a 1" main bore Quick Take-Up master cylinder. Larger-piston JN/JB5 or 6 would use the 1 1/8" main bore QTU master cylinder, along with a bigger power booster than the JN/JB3 brake systems got.

The bigger bore of the master cylinder requires more "power" from the booster.

Photo 1. 3-chamber QTU master cylinder with huge rear piston to supply the gush of low-pressure, high-volume fluid the low-drag calipers require.

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Photo 2. Larger JN/JB5 and 6 booster compared to JN/JB3 booster.

As kennythewelder has said...rear brake adjustment is critical, and almost always out-of-adjustment on the 254mm (10") leading-trailing shoe rear brakes. The 11.x Duo-Servo drums are MUCH better.

 

[L31MaxExpress]

I actually just spent ~5 hours swapping out a set of parts store reman 1-ton calipers for a set of AC Delco remans. Also swapped on an AC Delco reman hydroboost for a 2006 3500 van with a new master cylinder for said van. Bleed the heck out of it with fresh DOT4 from a sealed container. I also changed the steering gear box as well. It steers and stops very nicely now.

Unlike the NBS master on the vacuum boost setup I tried years ago the newer van master and matching hydroboost make enough pressure to have adequate panic stop like braking with moderate to heavy pedal pressure. Kicked the ABS in at about 50 mph.

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[Camuchi]

Have you bled the ABS module using a GM Tech 2 or equivalent scan tool? If not that would be my first recommendation before you start swapping parts out. It can make a huge difference in pedal feel/travel.

i dont have a scan tool that does that but can get or find one. i am diy only so where do i find one?

 

[df2x4]

i dont have a scan tool that does that but can get or find one. i am diy only so where do i find one?

You used to be able to find Chinese Tech 2 clones on eBay and Amazon for a few hundred dollars, but they seem to be much harder to find and more expensive now. If you search "GM Tech 2" on eBay you can still find some for $3-400.

Alternatively you could look for a used Snap-On scan tool, but I'm not sure which models will do the ABS bleed on a '96+. On that subject, there is the "GMT400 Community Scan Tool" that you could get on the list to borrow for free, but I'm not sure if it will do the ABS bleed.

https://www.gmt400.com/threads/gmt400-community-scan-tool.60565/