The Stovebolt Site Forums The Shop Area Driveline 1947-55 Shock Recommendations

I'm converting my 1940 Chev 1/2 ton to tube shock using 47-55 mountings. I have mono-leaf front springs so it sits quite a bit lower than stock. Any recommendations on shocks? I have some leeway in placing the upper mount. Can someone give me a shock length measurement at rest so I can factor that in?

Dennis

You'll probably need to consult a shock manufacturer's dimensions to determine what shock travel you need. We can't measure your truck for you. You'll need to find a shock that has compressed and extended lengths that straddle your truck height fully loaded (engine and all sheet metal in place.) FYI, tube shocks first were installed on 1950 trucks, before that, they were lever action.

I purchased a conversion kit from Chevy of the 40s and it came with Monroe shocks. Kit no instructions had to figure out location of on frame supports. I published an installation on Stovebolt.
Sorry in don’t know how to give you the link

Here's TexasA&M48Truck's Post with excellent pictures.
Be advised that he converted from 1948 lever shocks to the later tube style. Your Truck will be somewhat different with the single leaf springs and lower stance. But it may help you figure it out.

Those are very useful pictures. Thanks. What I figure is that if I know what the stock resting length of the shock is then I could manipulate where I mount the upper to get it more where it is designed to be. Does that make sense?

Dennis

Here are the ones I installed on Ol' Roy 4 years ago. In combination with the correct wheels and tires, the truck went from being nearly undriveable to a dream. No wandering, no bouncing all over on bumps and potholes at low speed or highway speed, etc. (stock steering and suspension)

Monroe OE Spectrum 5826 Front

Monroe Monroe-Matic Plus 33049 Rear

Yes, but you still need to be sure that your ride height and mount location is within the working range of the shock absorber.
Otto's truck has stock suspension so his ride height is likely very different that yours.

Here's a link to measurements for Monroe shocks. What you don't want is for the compressed length to be less than the movement of your suspension at full compression. Measure from the axle to the bump stop on the frame to get that minimum length. Max extension is with the axle hanging free, plus a little more for overshoot if you catch air. But that's not as big an issue as over-compressing the shock because there's only the weight of the suspension pulling against the shock. On full compression, you'd be applying the dynamic weight of the truck chassis against the fully compressed shock if the bump stop isn't reached. That would likely damage the mounts or the shock.

The biggest improvement I made to drive-ability was to switch to radial tires. Before radials, I couldn't bring a cup of coffee to work with me. Splish splash. After radials, I could.

Thanks Wally. I'm planning on going with Monroe OE Spectrum 5826 like Otto has. If someone would humor me, I would still appreciate the measurement.

Dennis

Dennis.
I have a drop axle on my truck Posie Super Slide Springs.
Rears shocks are #5847 fronts are #5758. I believe they are Monroe spectrums . My truck is dropped five inches front and rear. Hope this helps. I can give you resting measurements tomorrow if you need them.
I called Sid at Sids Drop Axle. Which is who did the axle for me. Without hesitation he told me what shocks I need. They work great and it rides good.

Thanks Jeff. Man, that's low! My mono-leaf is probably 2" lower. I didn't take a measure before changing. Thanks for the part numbers. I'll contemplate that one. Our setups are probably too different for the measurements to mean anything for me. Thanks for offering to measure though.

Dennis

If your going to install the top mount. My measurements would probably work for you. My mounts are in original locations. Provided you used the shocks I have. Did you say yours is two inches lower than mine?. Is yours bagged?

This is a before and after picture when I lowered it.

No, I'm guessing I'm 2" from stock. Stock axle with mono-leaf only.

If you give me the part number and vendor of your shock mount kits, I will give you my 2 cents on chosing a shock if you are still unsure,

Mount to mount is approximately 12inches on the front. Both mounts are in original location. Two leaf on the springs.

The rear are approximately 17inch from center of the bottom bolt to bottom of top mount. Rear springs are 8 leaf. But are drastically re arched from stock. As are the front springs.

Bartamos, I am just using stock replacements for 41-55 shock mounts from The Filling Station. I got the mono-leaf from Patrick's several years ago.

Jeff, those shocks would fit better. I'm just guessing at the angle right now since I don't have the lower mounts yet. Measurements between the frame and rubber bumper is 1 1/2" at rest and 2 3/4" with frame on jack stands.

Dennis

OK, I thought part numbers would be easier for me because you said 47-55 and then said 41-55 and said "kit". All I saw was 47-54 pieces, not a kit and not the years mentioned. I think I see the pieces you are using and you have not received all the pieces yet. Some of what I'm going to say may be obvious and some has been said.

My observations:
1.Your truck is earlier than the fellows that have done it. I don't know much about a 1940 frame or suspension. I believe you are converting from knee shocks.
2. It seems like the lower shock mounts are fixed by how they mount. It seem they set up the angle of the shock.
3. I would measure and record the necessary dimensions and a bunch of other reference dimensions. You do mention bump stop already. Seems like the suspension "travel" is 4.25, plus or minus allowances.
You want to do measurements after all new or original springs, spring hangers, bushings and any other suspension components are installed, lubed and torqued.
4. You don't say if bump stop dimensions are at rear or front. I assume rubber is on the axle not on the frame? You are saying at ride height it's only 1 1/2 to frame?...and only drops 1 1/4 ?

My "Too Sense":
5. I would mount the lowers and the clamp the uppers to a temporary position that clears everything and allows at least 3 holes to be drilled thru frame, later on.
6. There is a math (trig) calculation that could be done to determine the actual shock travel at it's angle vs the vertical travel of the suspension. This would be a bit difficult. An interpolation of that can be done knowing that the angled shock travel will be less than the 4.25 vertical travel.
7. "At rest", meaning truck sitting on tires on the ground. (Ride height)
8. Shocks should be pre loaded to about 1/3 travel when mounted at ride height. This plays into your selection of a shock.
9. After choosing the shock(s), bolt them onto the mounts tight while uppers are still clamped. Adjust upper for proper bolting, preload, angle and perpendicular to brackets.
10. When all is good, mark at least three holes using the mounted/clamped upper as a drill template. Bolt up bracket with Gr 5 hardware. 5/16 or 3/8. UNC.

This is just a rough idea for though, without being there. This is a custom situation and takes some planning and thought as you know. Maybe copying newer conversions and parts will work OK, maybe not.

1 - My '40 originally had the knee shocks but otherwise is very similiar to 47-55.
2 - Yes
3 - Axle can go up 1 1/2" and down at least 1 1/4". So 2 3/4" travel?
4 - Bump stop is on the spring. It's is fixed to the u-bolt fixture. Yes 1 1/2" at ride height and only drops 1 1/4".

Yes 2 3/4 travel. My 4.25 number is wrong. Seems like the rear brackets do not set up an angle but the front lower does.

Got it. When the lower bracket arrives, I'll bolt a length of all-thread to see where it wants the upper mount to go. How much off angle is acceptable?

Question on your mention of setting it up for 1/3 travel at ride height. It may be more like 1/2 travel given the midpoint of the Monroe 5758 like Crummy has is 12.08".

AI and serching many many sites says:

1. 30 degrees is good, A liitle less is OK. More is not. Zero is optimal for the shock but not for the ride.

2. The shock is supposed to be set up to be compressed at about 30% of the shocks travel numberl. Some sources seem to say 1". You need to have some preload to keep it from rattling.

Pleae search and come up with your own decisions.

I see you are trying to work with a shock you already have and trying to make it work. That's OK'

My approach was to select a shock after mocking up the brackets. On a custom install or conversion, that seemed like a better way than trying to make a certain shock meet all the various parameters. Whatever they are determined to be by filtering member suggestions and trusted internet advice. Noting there were no instructions that I know of. I have done a few "custom" shock installs. 55-59 and 60-66.

I haven't bought the shocks yet. Just looking at the specs from Monroe that Kevin so kindly linked for me. You guys have given me a lot to consider. Thanks. I may be back with more questions.

I have run Monroe super 500 in the old days, like 40 years ago, some modern Monroe equivalents and KYB Gas-a-Just (Not sure how they designate it). The KYBs are by far the best but by no means the cheapest. I used a Ford Mustang application that also fits other fords with studs on both ends. Your application would be different but KYB probably has you covered. The catalog will tell all. They're listed by length, travel and mount type, among other specs.

Good idea tommy. I'll take a look.

Dennis

Found a couple KYB shock with similiar dimensions. I'll wait 'till I get all the parts for mock-up before ordering. Looked loser at the mounting area on the frame today. The upper mount will be behind the crossmember which means hard to get at. Buggers. I'm thinking rivnuts may be the way to go.

Dennis

Crummy, I was just about to make a post asking for some of the information you provided in this thread. Thanks for the info and part #'s on the shocks you used. I am considering using the '47-54 front shock mounts on my '36, but didn't know if there were shorter shocks available that would work. I also have a Sid's dropped axle and Posies springs.

The pictures you provided are also helpful. If I could ask a favor, when you get time, would you mind giving me some dimensions on the upper front shock mount? Mainly what I need is the distance from the top bolt holts (rivets on yours) to the top hole on the bracket where the shock mounts. This would enable me take some measurements from my axle to frame so I can figure out if these mounts would work for me. Also, if you have an angle finder, it would be helpful to know what angle Chevy put these mounts at.

Also, it looks like the top right hole on yours is above the frame and does not have a rivet? Or maybe it just looks that way in the picture.

Thanks!
Ron

Ron, I'm doing the same on my '40. Probably more similiar to your '36, but I know nothing about those. Maybe the pictures can help a bit. On mine, the green painted sheet metal is about 5/16 over the frame. I don't want to reshape or cut that so I'm going to use a 3/8" steel plate and weld the top mount to that, then bolt the 3/8" to the frame. I can also raise it some rather than bolting to the frame. One picture shows the top mount giving about 11 1/4" between mountings. I don't think that is enough. I haven't decided where to mount it yet. I got KYB KG5514 shocks. Specs on that are compressed 8.74, Extended 13.86. The Monroe 5758 is 9.38" and 14.63. I didn't take into account this style shock needs the rubber bushes. Each are about 3/4". It would be easier with a shorter shock. The selection is limited with the S1 style ends. Still haven't decided to keep these shocks yet. Have gardening duty for another couple days then I'll get back to it.

Forgot to add I bolted the all-thread to the bottom mount to see what angle it wanted.

Dennis

Ronald and Dennis ,

I look at thing better tomorrow and get some more information compiled for you. I'm unfortunately tied up today.

Take your time, Jeff. I appreciate it!

Dennis, thanks a lot for the information! I'm going to look at everything you posted in more detail tonight. In the meantime, did you check the Monroe 5751? It's shorter than the 5758. 13.44/8.5 extended/compressed. Maybe that would work better for you? Just thought I'd mention it.

Monroe 5751

EDITED to say the 5741 is close to the KYB's you already have.

Ok finally got a second to take some pictures and measurements for you. You are correct that the top rear rivets hole is just at a half above the frame. These are consistent from side to side . As is the 9inch measurement from the center of the front shackle mount on the frame to the lowest rivet. With the wheel off and the axle set on a block to simulate ride height. The axle is almost dead nuts with the 4 degree shim under springs and on top of the axle pad. My floor is level as well. So using a framing square rested on the level and butted up to the axle the angle looks to be about 50 degree from level. This makes sense in my mind. Hope it works for you
Honestly if you bolted the lower shock mount on the underside of the spring ,bolted up a shock to that, the angle of the lower mount will get you in the ball park of where you need to be angle wise. My upper mounts appear to me to be original location. And I base that solely on the fact that the rivets are still in place. And again are consistent from one side to the other. I hope this helps you locate them. If you use the shocks that I indicated you should be good.
The mounts are roughly 12 inches apart outside to outside.

After taking some measurements and wrapping my head around this a bit. My bump stop is about 1/4" less than the travel of my shock. Thus hitting the stop before bottom the shock out. To date I have not bottomed it out. But I'm also very cautious of rough roads and try to avoid them when I can.

One more picture for reference.

Hey Crummy would you mind taking a few measurements of the rear as well? Im curious as to what the mount to mount distance is with posies springs and the distance between the axle and bump stop? Did you keep the rear uppers in the original location? I have posies as well but have moved or am moving the shock mounts to the interior of the frame for clearance issues I also have the posies lower shock mounts which can slightly move the lower mount higher or lower. I figure if you have been happy with the ride of the Monroes 5847, I can set mine up to match the mount distance you have. Thanks for the help.

Dongray,
I just saw your post. I am out of town until next Monday. When I get home I will get you those measurements.
Also my upper mounts are in the original location as is the lowers. Both to the outside of the frame.
I drive the truck often and to date have not bottomed it out. Front or rear. I have however graded off some driveways as my drop axle is very close to the road.

Thanks I appreciate you checking it out for me. I was wondering did you buy the Posies that center the axle in the fender or the stock version that keeps the axle slightly forward?

Dongray,
The rear shocks are 17 inches from center of the lower mount to the top mount bracket edge. To my knowledge mine are the stock version. I got my drop axle and the springs from Sids Drop Axle out of Oklahoma. I met him at Hershey show 2 yrs ago. He took my stock axle and steering as cores. If you happen to be going to Hershey next month the Poises is just up the road in Hummelstown.

If you purchased them there could save you shipping. Hummelstown is 10 minutes from Hershey

The bump stop is 2.5 inches from the rear.