[Rob Petrie E395]

We own a bunch of K3500 trucks as well as a few dozen that I see in my shop as customers. The first thing I would do is disable the ABS system and take it out on a wet or gravel road and make sure it will lock up all four tires without the ABS on (at 15-20 MPH it should lock them up with ease). If you dont have the equiptment to do it you can unplug a front wheel speed sensor which will set a code and disable the ABS. When you plug it back in and drive it a few miles it will reset itself and reactivate the ABS so dont worry about not having a scan tool to reset it when you are done. You need to have the ABS disabled or you cant tell if its not locking them up because the abs is kicking in or because you are not making the pressure needed to lock them. Anyways if it is only locking one or the other rear wheel 9 times out of 10 you have a stuck wheel cyl (alot of times even though it only has brakes working on one rear wheel it wont pull it just does not seem to want to stop when loaded). I see this mostly on trucks that rarely pull a trailer and were bought before gas prices got high because it was "cool" to have a crew cab dually for a daily driver. If it does not seem like it wants to lock them at all or has weak braking capibilities 9 times out of 10 they have a bad hydroboost. You still need to check it over good to make sure there is not another problem but I have seen more weak hydroboost units than anything else where weak breaking is concerned. The biggest problem I see on these trucks are the front rotors warp if you try and pull heavy trailers with no trailer brakes (I see this on farm trucks all the time). My personal truck (98 k3500) pulled a 44' Haulmark untill last year and I never had a problem stopping. If you want to make sure its the hydro before spending the money you can get a gauge from Strange Engeneering for about 40 bucks that screws into where the bleeder screw goes to check pressures instead of the high dollar Kent Moore stuff.