What size bolts have you used when replacing the upper ball joints? Reason I ask is that most uppers come with smallish 1/4 screws which fit with some play in the holes of the control arms where the rivets were knocked out. Another kit comes with 5/16" bolts which are just a bit big to fit in the holes and the directions say not to enlarge the holes? I have used the smaller 1/4" before but they make me nervous as I figure the ball joint could shift. I also am considering using the threaded rivet head style screws but the dopes that sell them do not know the size???? All they say is they are OEM. Real good customer service. You would think they could invest in a caliper.
The tensile strength of a 1/4" fine thread grade 5 bolt is over 4000 lbs. Even the shear strrenth will exceed the loads the bolts will be under. Dont worry, use the 1/4 bolts
Jason, Thanks. I did have the 1/4 in my car I changed several years ago but got confused when I saw the 5/16.
The replacement ball joints typically come with Grade 8 bolts also....so you've got more strength there.
Believe it or not I got two different ones from AC Delco. Both had same part number. One came with grade 8 5/16" and the smaller ones in the other box were 1/4" but grade 5(three slashes). I do not think there is much stress on these but I worry about movement due to the holes in the control arm being bigger than the 1/4" screws.
I always use a 5/16 grade 8 and throw those little ones out. I have seen numerous cars with the smaller bolts have the ball joint floating around in the upper control arm, a recipe for disaster. The holes end up elongated and the bolts get wear marks in them. I tried using the 1/4's before and with the bolts in but not tight, you can move the ball joint around...seems to me it would be difficult to get the ball joint in the exact correct location with them.
Steve, that is what I thought but I spoke with Delco Engineer today and he told me design of ball joint allows use of small screws and placement of screws keeps unit from moving.. My older control arms with small screws were used for several years and never moved. I juts forgt about them being small after not having a problem. Now after starting to build a new set the doubt has just risen back to the surface.
I would also not want to drill out the ball joints smaller holes to accept the larger screws. Any warranty would go right out the window in case of an accident. The other unit with the big screws was designed for them to fit. Moog units come with small as well and bigs would not fit.
I know this is old but I just had the similar problem. The AC delco upper ball joints (part number 88911380) I purchased only had 5/16 grade 8 bolts and the size of holes in the ball joints were 5/16" but the holes in my control arms are only 1/4" Is it bad to drill the control arms?
It's not going to hurt anything to drill the control arm out to 5/16th... It's not a big size jump... I would say stay with the grade 8 bolts as well... Don't use lock washers... Get regular washers and grade 8 lock nuts... I've seen way to many lock washers rot out or break and than you have a sloppy fit... I never use lock washers, I only use washers on both sides and lock nuts... He was only worried (by the sounds of it) about the warranty if for some reason he needed to send the control arms back for warranty...
