what Proportion valve to use

[Ray Parker]

The more-important question is why you'd convert to rear discs in the first place.

A rear-disc conversion is a whole mess of troubles; aftermarket conversions are generally horrible due to lack of caliper support from the cheap, flat brackets. And then there's the issues with the parking brake.

Better/simpler/cheaper to use upgraded rear drum brakes--dumping the "10 inch" leading/trailing shoe design for the bigger Duo-Servo system makes a nice and SIMPLE improvement, for example.

Can I ask about the upgraded rear drum brakes...This is all new to me.. I have a 1998 GMC c1500 2wd and I would like to upgrade my rear drums with that bigger duo- Servo system .where would I find out all of the information on this.
Thanks in advance.. Ray

 

[GoToGuy]

2500 , six lug wheels with 14 bolt semi float axle 9.5 inch ring, some 1500's have 14 bolt axles also.

 

[Schurkey]

Yup, the 2WD are a more-involved conversion than 4WD, because most of the desirable axles will have 6-lug axle shafts. You'd either buy 5-lug axle shafts to fit the 9.5" semi-float "14 bolt" axle, or you convert to 6-lug wheels. The 4WD 1500s already have 6-lug wheels, so they've got it easy.

You'd need a C2500 6-lug axle, the K2500 6-lugs are a different width. Of course, it needs to have the right gear ratio--either the same as what you have, or a deliberate change with recalibration as needed.

You'll need four U-bolts and nuts, and a conversion U-joint. Plus whatever repairs are needed on the axle you select--brake job, fresh gear lube, maybe axle seals...maybe bearings, maybe gears. Choose your "new-to-you" axle assembly wisely.