Forum Discussion

Octaneforce's avatar
Octaneforce
Explorer
Nov 06, 2022

P30 Disc brake vs drum brake ball joints

https://ibb.co/hmHLG0S



Ive had issues with the ball joints on my p30 since ive owned it. Ive had shops replace them twice in my ownership, and the rest of the time they told me the ball joints are fine.

Well i developed a new clunk in my front end and determined it was my lower ball joints because the castle nut would not longer stay “snugged” down and i was cranking on them at every gas stop during my last trip.

I decided to replace all the ball joints myself and put this problem to rest. I did a ton of research and bought the proper part numbers for my disc brake model p30 and even purchased a few different brands to compare them. Worked until about 8pm last night taking my time and confirming i have no other issues. The lower ball joints practically fell out of the truck when i loosened all the hardware.

As you can see in the picture above, the truck had the WRONG lower ball joints in it, despite my attempts to explain to the recent shop that did it that there are 2 kinds. I suspect that it had the wrong ball joints the first time i had them replaced as well.

Pictured: left joint is the existing drum brake style ball joint. The shaft is shorter and every so slightly narrower, which explains why it became so loose

Right joint is a new old stock parts master disc brake style ball joint i bought on ebay for this comparison.

Ive installed moog all around. Sorry for the winded post but my mind is blown that this has gone on for so long. P30’s honestly shouldnt be on the road due to lack of repair knowledge in the industry but ive got so much invested into this thing that it needs to get me another few years.
Class A
  • Octaneforce's avatar
    Octaneforce
    Explorer
    Nov 16, 2022
    Brian in Michigan wrote:
    It seems that theres often 4 options for lower ball joints when you look for them;

    Motorhome/stripped chassis with rear disc (part number 6511) *this is the correct one*

    P30 standard van with rear disc (part number 6175)

    P30 with rear drum (part number 6129)

    F44 heavy duty chassis (part number 6117) *im not sure what truck these are for*



    OK what would be the difference between the stripped chassis and the P-30 with rear disc?


    Im not sure, its different part numbers so id have to assume chevy did something to change the front end for each application.

    I assume the p30 with rear disc means a regular bread truck, and the stripped chassis got some minor change when they built them for rv manufacturers.

    To be clear i only did this research as it applies to my 1993 model year, however it seems to be the same confusion for most of the 90’s
  • BrianinMichigan's avatar
    BrianinMichigan
    Explorer
    Nov 13, 2022
    It seems that theres often 4 options for lower ball joints when you look for them;

    Motorhome/stripped chassis with rear disc (part number 6511) *this is the correct one*

    P30 standard van with rear disc (part number 6175)

    P30 with rear drum (part number 6129)

    F44 heavy duty chassis (part number 6117) *im not sure what truck these are for*



    OK what would be the difference between the stripped chassis and the P-30 with rear disc?
  • Gjac's avatar
    Gjac
    Explorer III
    Nov 13, 2022
    Octaneforce wrote:
    Gjac wrote:
    This is a very serious issue. I had two failures due to a shop installing the wrong ball joints. The first failure was entering an interstate in Ohio rounding a corner at 20 mph and the left ball joint failed and the whole front end dropped. After it was fixed the shop back in Ct had to do additional work and replaced the correct ball joints with the undersized ones. The second failure was rounding a corner in Montana at 60 mph and the RH ball joint failed, I thought the MH was going to flip over but I managed to stop it safely. The was no warning sounds of clunking just a sudden failure and the whole front end just dropped. The lighter P-30's have drum brakes in the rear, the heavier ones have disc brakes in the rear. After much research I had the shop in MT. replace the ball joint with Moog parts. The confusion for the person who orders the parts is the ball joints listed under the rear drum brakes say HD so they think it is stronger not realizing the ball joint is undersize. The difference is P-30's with rear drum brakes get one part number and P30's with rear disc brakes get another part number.


    I cant beleive these ball joints didnt fail like you described. They were clunking for over a year and nobody believed me. It appears that the lower ball joint can be pretty bad and still hold together thru gravity, but the upper ball joint would allow the control arms to seperate and be more catastrophic. That whole front end on these is under built.
    To be precise, the first failure started with clunking, I went to a shop out west that deals with front ends, and they told me the noise was caused by the coil spring being misaligned, they supposedly reseated the spring charged me $400 and I was on my way to a ball joint failure. The second failure there was no warning at all.
  • Octaneforce's avatar
    Octaneforce
    Explorer
    Nov 12, 2022
    enblethen wrote:
    The ball joints for disc brake P-30 are shorter and fatter than those listed in most cases. The C-30 uses the same ones.


    Its strange, chevy used the c-30 name for the pickups and the vans at different times.

    As far as my 1993 motorhome p30 goes, no other truck that year shares the same lower ball joint part number. I looked into the other pickups and bans of older years and they all seem to use the drum brake part number for the lower ball joint. I didnt look into the uppers. Its all very fugazi
  • Octaneforce's avatar
    Octaneforce
    Explorer
    Nov 12, 2022
    enblethen wrote:
    The ball joints for disc brake P-30 are shorter and fatter than those listed in most cases. The C-30 uses the same ones.


    It seems that theres often 4 options for lower ball joints when you look for them;

    Motorhome/stripped chassis with rear disc (part number 6511) *this is the correct one*

    P30 standard van with rear disc (part number 6175)

    P30 with rear drum (part number 6129)

    F44 heavy duty chassis (part number 6117) *im not sure what truck these are for*
  • Octaneforce's avatar
    Octaneforce
    Explorer
    Nov 12, 2022
    Gjac wrote:
    This is a very serious issue. I had two failures due to a shop installing the wrong ball joints. The first failure was entering an interstate in Ohio rounding a corner at 20 mph and the left ball joint failed and the whole front end dropped. After it was fixed the shop back in Ct had to do additional work and replaced the correct ball joints with the undersized ones. The second failure was rounding a corner in Montana at 60 mph and the RH ball joint failed, I thought the MH was going to flip over but I managed to stop it safely. The was no warning sounds of clunking just a sudden failure and the whole front end just dropped. The lighter P-30's have drum brakes in the rear, the heavier ones have disc brakes in the rear. After much research I had the shop in MT. replace the ball joint with Moog parts. The confusion for the person who orders the parts is the ball joints listed under the rear drum brakes say HD so they think it is stronger not realizing the ball joint is undersize. The difference is P-30's with rear drum brakes get one part number and P30's with rear disc brakes get another part number.


    I cant beleive these ball joints didnt fail like you described. They were clunking for over a year and nobody believed me. It appears that the lower ball joint can be pretty bad and still hold together thru gravity, but the upper ball joint would allow the control arms to seperate and be more catastrophic. That whole front end on these is under built.
  • Gjac's avatar
    Gjac
    Explorer III
    Nov 11, 2022
    This is a very serious issue. I had two failures due to a shop installing the wrong ball joints. The first failure was entering an interstate in Ohio rounding a corner at 20 mph and the left ball joint failed and the whole front end dropped. After it was fixed the shop back in Ct had to do additional work and replaced the correct ball joints with the undersized ones. The second failure was rounding a corner in Montana at 60 mph and the RH ball joint failed, I thought the MH was going to flip over but I managed to stop it safely. The was no warning sounds of clunking just a sudden failure and the whole front end just dropped. The lighter P-30's have drum brakes in the rear, the heavier ones have disc brakes in the rear. After much research I had the shop in MT. replace the ball joint with Moog parts. The confusion for the person who orders the parts is the ball joints listed under the rear drum brakes say HD so they think it is stronger not realizing the ball joint is undersize. The difference is P-30's with rear drum brakes get one part number and P30's with rear disc brakes get another part number.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Nov 06, 2022
    Reminds me of changing a U-Joint on a Dodge Maxi van
    They listed two different joints.
    I said "Give me the more expensive one"

    and that was the one that fit... (The difference was likewise obvious once you saw it.. They showed me both so I knew aright away I got the right one when I pulled the old one).
  • enblethen's avatar
    enblethen
    Nomad
    Nov 06, 2022
    The ball joints for disc brake P-30 are shorter and fatter than those listed in most cases. The C-30 uses the same ones.

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