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99 Suburban 6.5 to 5.9 Cummins Swap

usanumber1

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Pulled it apart, this is the main cylinder/bore seal. I think this is the culprit. I put a new one back in, but I blew out the seal I just replaced. Nailed it. New booster it is.
 

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usanumber1

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Installed new booster last night, went to install (after store was closed), pedal was kicking back, pulled out of shop slowly into empty parking lot, no brakes. Oh good. Removed master cyl, looked in booster, there was no spring, rod, or spider retainer. Oh. Good. Luckily I got to o’reilly just now, they let me get the old one. Installed, now I brakes, but the pedal is soft. Regardless, it stops and doesn’t lock up.

now I need to find out why my damn rear seat heater hose is leaking. I hate coolant. Gets everywhere. Makes the biggest messes.
 

usanumber1

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Lots of good news. Got brakes working, spent $100 on brass fittings for my heater lines, and had my exhaust finished. Still loud, but not like a dump truck.
 

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usanumber1

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Ok, brake experts. I moved out of town, and left the truck at a Cummins shop to give it an general mechanical inspection before I drove it to my new home out of state.

brake system specs:
GM Hydroboost booster
GM PS lines
GM Hydroboost pump
Wilwood MC
Wilwood prop valve
All new brake hardlines
Basically new soft lines at knuckles
All new Ford D60 brake assembly parts


They’ve been addressing the brakes, and it’s still locking up, but only the fronts. The prop valve is set at approx 60F/40R. The tech was saying that he doesn’t think it’s the booster because if it was the booster, all of the brakes would eventually lock up, I agree with that assessment. Ideas?


9137E453-737C-474E-8C1B-6F0F10F37AA0.jpeg7017C9B3-B695-47B9-8774-C414DFDE8659.jpeg
 

Will L.

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Do they lock up and any pdeal pulse or does pedal drop when it occurs?

The booster, master, prop valve, and caliper shoe disk set up is all a moot point. You should be able to have no rear axle brakes and the fronts still not lock.
The abs unit reads the tone ring teeth via the sensors and when it locks up, the tooth count is off from the formula and should cycle abs. iirc it is a 3 point system where each front is controlled and the rear axle controlled. But the 2 fronts feed info and one bad sensor can tell the module to do both the same to avoid pulling to one side.

Guessing you already threw a couple new front sensors at it. Next is plugging in the ol computer to read what is happening with the sensors when it occurs. Make sure the signal of what is happening is actually getting to yonder software to decide when to cycle and a what rate. ABS parts cannon is common even in dealerships back then. It was bad enough that AM General using most all gm stuff in hummers went to land rover for the abs. Not any better btw, just different problems. Anyways, the fastest solution in shops was parts swap. Countless people got new abs units and a reflash only to return in a few weeks.
 

FellowTraveler

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Did I read correctly, FORD frt ABS rings are installed? If so, then it is doubtful the ABS controller in a GMT415 can be calibrated for "brake to tire size". If I remember right (old dustbin memory) that feature was only available on GMT425 and higher truck models "but" that Burb had a 6.5td maybe it can be calibrated. My Burb has this feature and I had accessed it through the device controller in the CAR CODE ODB2 software and adjusted to the 295/75/16 tires and perhaps TEC2 but I am thinking the TEC2 had a cutoff for larger tire sizes.
 
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