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crownver 01-17-2010 12:51 PM

advice on shock mounts
Hi all, finally have a little time to work on my F100 short box project. (in between never-ending house renos). I've got the triangulated 4 bar set up tacked in, the spring mounts in, and it's actually temporarily sitting on wheels. I used the old brackets from the donor car that have a shock mount on them for the rear end. The mount is for eye? style shocks, basically a bolt pointing forward. Now I need to do the upper mounts. The donor had the stem style mounts, but I'm thinking of using the same on the upper as the lower. I've tried to find info, but maybe it's a dumb question. With the 4 bar set up there is going to be a bit of roll of the rear end and I'm not sure if the eye can take the lateral movement. Also, should I make the mount point the same way as the bottom, or should it line up side to side at 90 deg. to the bottom. Or should I stay with the stem style mount. Thanks for any and all advice......John

aosborn 01-17-2010 03:04 PM

The best bet is to have the shock mounts on the same plane at each end, and perpendicular to the axle. Mounting them that way will tend to rotate the bushings on suspension movement which will help the bushings survive. The eye mounting will be plenty strong assuming you build the upper mount beefy enough. I like to pierce the upper crossmember with a piece of .187 or thicker wall tubing with the proper ID for the shock mounting bolt, and weld it in on both sides of the crossmember. Install a high quality fine thread bolt through the tubing and the shock eye and secure it with a nylock nut with hardened flat washers under the nut and bolt head and you will be good to go.


crownver 01-17-2010 07:45 PM

Thanks Andy, I'll go that route then. I haven't actually got a X member in the correct location but I'll put in a piece of 2X4X1/8 I have. That should be strong enough.

aosborn 01-17-2010 08:40 PM

That 2x4 will be strong enough for sure, but a length of 1 1/2" x .120 wall or thicker round tubing would work just fine and not take up so much room.


crownver 01-18-2010 12:09 PM

Great, that'll add a little less weight too. Thanks!

trees 01-18-2010 03:13 PM

Crown, A couple of thoughts on shock location/mounting. Since you have a triangulated rear, you have some options that can make your truck handle well. First, get the shocks as far out board as possible. If there is room, consider mounting them on the outside of the frame. Second, if at all possible, mount them vertical ie perpendicular to the axle and no tilt to inside or outside. Your triangulated 4 bar motion for all practical purposes allows the axle to move straight up and down (you are talking 4 inches or less extreme travel). I use the Air Ride Technologies' 4 bar set up and the behind the axle adjustable bracket they offer lets you mount the shock directly to the bottom of the frame


crownver 01-18-2010 04:43 PM

Thanks for the input Trees. The bottom mounts are in already as I used the 4 bar brackets that came with a donor car and they included the shock mounts.

crownver 03-29-2011 08:38 PM

back at the suspension again
2 Attachment(s)
Hi guys, I started this thread early last year. Lot of things going on since then, one of which is my semi-retirement, so now I have more time to work on the truck. I've been working mostly on the pick up bed, and have that pretty much ready for bodywork/filler.

Now I'm back at the suspension so I can put the bed back on and keep it there until the cab is done. (room is an issue) I'm still having trouble with the top shock mount. Done a lot of searching and seem to come up with varying opinions on how much up and down travel the shock should have, from 50/50 to 1/3 up and 2/3 down. Been looking at the Monroe shock dimension chart for sizes that might work. That said, I'm trying to decide if I should put a plate across from the upper bar mount to the coil mount, and use the stem style upper shock, or put another bar across the frame and weld in posts to mount eye style shocks.

All opinions are appreciated! Thanks.....John

ericnova72 03-29-2011 09:26 PM

I don't see any problem with a good triangulated mount off the frame/corner of your spring pocket and using a shock with a bayonet stud type end on the upper end. Some of the ProStreet coil over shock kits come with a shock that is bayonet style on the upper end made to mount through a piece of flat plate.

On your second picture, I would bridge the two sides of your upper link mount at the frame with a small(say 1-3/4" x 3", whatever fits frame to eye and covers the span), to keep it from trying to fold over one way or the other.

crownver 03-29-2011 10:30 PM

Thanks Eric, that was what I was hoping for.

Not sure of what length shock to get though, for compression and extension. I've got about 10" from the frame to the axle housing, a little less with the box on. Up to the spring pocket would be about 18 1/2". So would about 3 1/2" up and 4 1/2" down travel be about right? This truck may get some weight on it.

Also want to get the right bottom mount. The stock Monroe shock for the donor car (I'm not tied to Monroe, they just have a good chart) shows a L1/CP3 lower mount style, which translates to a 5/8" loop mount/1/2" cantilever pin mount. Not sure what this means. Seems like 2 different things. Unless they give you a new mount that's 1/2" with a sleeve? Any thoughts on that? Do you know of any other brands that I can check the individual extended length and travel

Yeah, I know what you mean about bracing the link mount. I'll do that after I get the shock mount done. I also need to brace the link mounts on the differential better. I'll be doing all that once I get the frame stripped down and can flip it to do the bottom welds.

aosborn 03-29-2011 10:35 PM

The basic rule of thumb for shock travel is 2/3 for bump, 1/3 for droop.

I don't see a problem with a plate between the upper trailing arm mount and the upper spring pocket. It will add some strength to the trailing arm mount as well. If the span is too wide, just throw in an additional gusset.

As to shock mounting, either will work fine, I just look for the proper length for what I need. Sometimes when you find a shock that is the right length and correct lower mount bushing size, you may just have to go with whichever top mount it has. You could always put tabs off the bottom of that upper plate to install an eye type mount.


ericnova72 03-29-2011 10:37 PM

Rancho Shocks has specs for every shock they carry, you can look them up by application or by travel, and they list what ends are on them and give a chart for the ends also.

Just go to their site and download the catalog, it is in PDF form. Once you find a shock that fits your needs for travel and mounting style you can look up what application it fits and then go to Monroe if that is your choice.

crownver 03-29-2011 11:09 PM

Thanks Eric and Aosborn. So I'll definitely go with the stem mount upper I think. Monroe at least has a better size selection with that. I'll check out the Rancho shocks site. Not married to Monroe, just couldn't find the info elsewhere.

crownver 03-29-2011 11:10 PM

What plate thickness would you use for the upper mount? Would 1/8" with gussets be heavy enough?

ericnova72 03-29-2011 11:35 PM

I would think so, with the gussets close enough to limit having too much open area at the shock mounting bushing area. It's not like it has a coil over spring against it. 3/16" would definately do it if you are worried about it.

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