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406 Spring rates

4240 Views 12 Replies 6 Participants Last post by  MogMountain
I was driving through town yesterday and for the first time in a long time I saw a 406 drive by and I followed him for a bit and I was noticing that his suspension was actually moving some on his empty flat bed truck. I was trying to see his coil springs to see what they looked like and they looked possibly smaller than mine and it got me thinking. My truck is a Schmidt cab 406 that originally came with a snow blower. I found a web site one time that told how to calculate spring rates by measuring the diameter of the spring, the number of coils and the thickness of the coils. When I did this my front springs are 1740 LBS and my rear springs are 860 LBS. I'm now thinking that my truck may have way stiffer springs in it because of the heavy blower and the diesel motor that used to be mounted in the bed of truck. I'm really curious now as to what a normal 406 has for springs. I don't mind the rear springs as I usually go wheeling into the Rubicon with a couple thousand pounds and it rides nice going in but the trip out empty is not as nice at all. To get rid of some of the harsh ride out I am now running 41 x 14.50 IROC radials and beadlocks with about 9 psi and I have new shocks which made a huge difference but now I am wondering about different 406 front springs. Does anyone now if 406's came with different springs depending how it was equipped? And if they did does anyone have some softer springs that they want to get rid of, sell or trade???? Years ago when I got the mog before I wheeled it I was planing all kinds of mods to make it wheel better including different springs but then I took it wheeling and realized the German engineers that built it knew what they were doing and to my surprise it wheeled amazingly well. Beadlocks, shocks and tires is all I have done.
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Looking in my parts manual, there are two front springs to choose from: a 31 mm coil & a 25.4 mm coil.
Might this help? Here's a collection of spring info from historical forum and email:

"Group, Does any know the part number of the 406/416 front springs described below?
"The optional "heavier" spring has 6.5 coils of 24.5 mm diameter wire. These
have an unloaded height of 300 ± 5 mm, and a loaded height is 126 mm. The
coils are the same nominal 175 mm diameter. This is the spring you will most
often, but not always, find on the CASE MB4/94 as they were normally sold."

"Like everything else with Unimogs, there's more than one. <G>
404 321 01 04, 21.0 + 0.2 mm diameter wire, 6 coils, height unloaded
282.0 mm ± 5.0mm, spring rate 80 N/mm, the common version, or

404 321 00 04, 23.3 ± 0.2 mm diameter wire, 5.75 coils, height unloaded
255.0 mm ± 5.0mm, spring rate 146 N/mm

this is the normal rear spring, used with or without an inner helper spring. It was a special version option for use in the front.

Jack Russell "
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After reading Jack's quotes went back and re-read my parts manual. It does say 25.4 and 31, but next to the two it says parenthetically the 31 mm is 7/8 " and the 25.4 mm is 1". I'd say the 31 mm is another Case misprint and the 25.4 is the heavier spring!!!
I have the light coils all round on my 416, and unloaded, the ride is nice and soft
Ok, I just went out and looked at my springs and the front ones are 1 inch thick, 6 1/2 in in outer diameter 8 1/2 tall installed and have 6 coils. The rear coils are 15/16 thick, 8 inches in diameter, 13 inches tall installed and have 4 big coils with one small coil on the top and one small coil on the bottom so they can mount for a total 6 coils I suppose. I'm not good with the metric conversions so I'm not sure at all as to what I have here. The stuff that came from Jack Russel's historic forum has me confused on how many different springs there were available for the front and the rear and if some used the same on all four corners. My rears are taller and bigger in diameter.Any body have a clue what springs I have. I do have the over loads inside the rear coils and this truck is not a case. It was brought over from Germany by Bill Harrah in 1970. Thanks for any help on figuring this out.
The Schmidt equipped snowblowers that I have seen have a larger, stiffer spring that the heavy duty 406 spring (406 321 00 04). They also have limiting straps at all 4 corners that makes the ride very stiff when the blower and rear engine are removed. I have a chart that another mogger put together showing 13 different front spring options (there may be more) for various models of Unimogs. The dimension you gave of 6.5" (165.1mm) diameter and 6 coils doesn't match any of them.

You are right about the limit straps on all four corners. That was another question i was going to ask. Did all 406 have those on them? I forgot about them as I took them off the first day I had the truck because the were so short it did not allow hardly any droop. I will see if I can take a picture of the front springs and post. They are much smaller then the rears in diameter and the coils are very close together in space unlike the rears which have large spaces between the coils. At the very least it sounds like my theory about my front springs being really stiff may be right. Does anyone have any softer ones I can put in????
Well I took pictures but they are too big to post and I'm not sure how to make them smaller. I will try again tomorrow with different settings on the camera and see if that will work.
Well I took pictures but they are too big to post and I'm not sure how to make them smaller. I will try again tomorrow with different settings on the camera and see if that will work.
save them as JPG (jpeg) and it will compress the size in MB.

If they are already jpg use a photo program to shrink them. Think there is links to this in the ulimate sticky on top of this forum
Thanks Coach, after reading the sticky I figured out I have a program called acdsee and I think I have this figured out. The first picture is the left front spring. Second is the front right and the last picture is the left rear to show the difference between the two. You can see the holes where the limit straps were bolted.


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So what seems to be the general consensus, Since I have no 406's to look at, are everyone's springs different front to rear and do most people have the lighter versions or the heavy ones? Which leads me back to the picture I took of my front springs - do these look like heavier springs than everyone else has? If these turn out to be the stiffer springs on mine I would really like to find some that are softer. If anyone has some or knows were to get some let me know. Also if anyone needs stiffer ones for a heavy implement let me know and hopefully these springs will be available. Thanks for your help. -Jeff-
Jeff - I would suggest you get/borrow a caliper and measure the diameter. Very hard, if not impossible to make an accurate determination as to size otherwise.
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