Bolt sizes

[mr_s]

Hi,

Does anyone know what sizes (diameter, thread and length) the leaf spring bolts and lower shock bolts are for a '75 K5 Blazer? I need to order some (had to cut all mine off due to being seized and me fitting a 6" lift). It's running standard 6-stud axles and original springs/shackles as far as I know...

I've not got any proper measuring gear and want to get it right, over here in the UK, these bolts seem damned expensive!! A cursory glance would have me guessing that they are 9/16 UNF and between 4 and 5 inches long for the leaf spring bolts, does that sound right? And 5/8 UNF for the lower shock bolts, 2 1/4" long?

Any help would be appreciated!

Cheers, Martin

 

[diesel4me]

The spring bushing bolts are 9/16" and about 5" long,the shock bolts I'm pretty sure are 1/2" and about 3-1/2" long,I'm not sure on the length,but a bit too long can be used with a few washers,ones too short wont work...someone here will probably know the exact lengths..

U-bolts are the hardest to determine,every application is different due to number of leafs,size of the axle tubes,spring plate hole sizes,etc...

 

[mr_s]

Thanks for that dude, I've got the u-bolts (came with the 2nd hand but hardly used skyjacker kit).

Now I know they are definitely 9/16 (I'm used to metric over here in the UK...!), I'll get searching for some HT bolts somewhere...!

 

[diesel4me]

I'd get at least grade 5's ,grade 8 would be even better...the grade 5's have 3 lines on the bolt head, grade 8 has 6 lines...maybe a online source like Mcmaster-Carr would be easier than looking for them locally??...probably costly either way?..you may want to wait till someone else here verifies my measurements before getting any...or measure the ones on the truck just in case yours differs from mine..

 

[mr_s]

Yeah, I was planning on going for Grade 8s, I figured that the entire sprung weight of the truck will be acting as a shear force on these 8 bolts, so they'd better be pretty tough!

I've seen that RockAuto sell the front leaf spring bolts for a reasonable price (and they ship quickly to the UK too - bought a load of stuff for my old Lexus there a year or two back, was cheaper than in the UK!!), so I'm gonna go out to my garage/workshop tonight and do some measuring, see if they're long enough to fit the rears too...

 

[mr_s]

Actually turns out I'm a dumbass... In the box of spare bits, I had the rear bolts (9/16 x 4 inches) and the front ones are still in the springs. Not measured them as I've only just fitted the rear springs tonight, I'll post the front sizes when I've measured them, just so anyone searching for this information in the future can find it!!

 

[1BEATK5]

the shackle bolts on the front springs are only 7/16" unless you upgrade the bushings and hanger

 

[diesel4me]

Yeah,they are,and how the heck they dont snap with a 6.2 or 454 and a heavy 8 foot Fisher plow hanging off the front is beyond me!.....the front spindle bolts are only 3/8" and its amazing to me only six of them on each side can hold the weight of the truck and a plow without just snapping off too..I suppose the tight fit between the spindle and axle housing does bear most of the load though,and the bolts just keep them clamped together...

The sizes I listed were for the rear leaf springs...I'm not sure in the front spring's front eye bolts are also 9/16" too,or maybe 5/8"?...been quite a few years since I took one out now..did rears on my pickup last summer so I am pretty sure the sizes I gave were close to stock bolts..

 

[1BEATK5]

all the other spring bolts are 9/16" , and those shackle bolts break. I have broken several.

 

[diesel4me]

I'm surprised none of mine broke really,but I dont go off road or get my truck airborne too often (well,maybe a few times in mall parking lots over speed bumps with the plow on it!)..some trucks I've taken apart had those 7/16" bolts almost sawed in half from the shackle links rubbing on them,GM should have used thicker ones with more wear surface and bigger diameter bolts..never understood why they just didn't stick with a 9/16" bolt there and a shackle more like the rear ones are there..