The Stovebolt Site Forums The Shop Area Driveline Spring perch width

I will install a 2004 Colorado rear end into my 54 with 2" wide springs. New spring perches are needed due to the 2" off-center axle position as well as a 1' difference in width. I can find perches for the tube diameter (3 1/4") and length to accommodate the 2" off-center, but they are all for 2 1/2" wide springs. Can I attach 1/4" spacers on the bottom plate to 'hug' the springs?

Instead of flat spacers, I'd suggest using two pieces of 1" steel angle iron on top of the spring perch, spaced to straddle the spring leaves. That would give you a more stable cradle to locate the spring leaves.
Jerry

You need u-bolts to fit the springs, but they won't fit the perch if its wider, so the u-bolts will need to fit the perch. Now you need spacers to keep the springs inline with the u-bolts. So yes, you can add spacers on the sides of the u-bolts. I would use steel with bends on each end so they can't slide out or move around, or as Jerry said above, two pieces of angle iron across the tops, facing down the side part way, just be sure to ease the sharp corner of the angle iron so the u-bolts fit down tight.

Have you checked with Detroit Spring or your local trailer shop for the correct width perches? It's not hard to open up the diameter to fit a bigger axle tube if you could find a 2" width the right length. It has to be welded to the axle tube anyway, so being a little jagged won't hurt. Be sure to replace the u-bolts.

Does the '54 have 2" wide spring hangers?

You should have total weight on the rear axle to set the pinion angle before welding. Most guys just clamp the perches to the housings and finish the build before any welding, you then set the correct pinion angle, tack weld the perches, pull it all apart and do the final welding. Weld a little on each perch so as to not warp the axle tube with too much heat. Jump across and weld a little then jump back to the other side.

On my truck, the axle in it was already set right, so simply measured the perch angle compared to the pinion seal flange area, then transferred that to the new housing.

The angle iron solution is a great idea. The question about 2" spring hangers---the frame is a 53 or older, so this is just one more feature in opposition to it being a true 54. I have never needed to be concerned about pinion angle, but understand its importance. This YT Video shows my exact issue. His practice is to attach the new perches in the same position as the original. Is there a reason why this won't be correct ?

No reason you can't, thats how I changed mine. I set the original housing on stands with the pinion level, then measured the perch angles. I then set the new housing on stands and duplicated the measurements and welded them in place, A little bit on each side till it was all completed.

Your pinion angle should be exactly the same as the yoke on the transmission, in other words the face of them should be parallel to each other.

I have been kicking this can down the road for a while. On my 53 3100 I have a Frankland Quick Change with a Bicknell torque arm. I'm running leaf springs with a light coilover in the rear with a panhard bar. I'm thinking about changing the spring frame mount to a modern style width and using a standard perch and spring. If I go with the old narrow spring I'm pretty much guaranteeing a custom made spring to suit my needs. Miscalculate and eat it. No returns. If I go with modern width springs they already make a wide range of rates. Please keep posting.

I had Detroit Spring make me a set of four, 1 3/4" wide custom springs.

I had to weigh the truck in " as driven condition ", meaning all the weight it's going to have on the tires when going down the road, including fuel, the driver, passenger, and any luggage. I used race car, four wheel digital scales for super accurate measurements. The weight was split 50/50 front to back and only slightly heavier on the left then the right, had I been building a race car I would have been pretty happy with the measurements!

I then put the truck frame on stands and unhooked the rear shackles and shocks so the axle was back on the scales. This weighed the axle, tires, brakes, shocks, half the leaf springs, and half the driveshaft. I then moved to the front and did the same thing. The spring shop needed to know how much weight the springs were holding up and how much was unsprung weight ( everything below the springs). Doing a little math I figured out how much was above and below the springs.

Next I removed one front and one rear spring. I places a small round axle or bar in the ends of each spring, added bearings to the bars so the axle would roll with no drag, think of a skateboard. I had my Toyota truck jacked up in the rear so I could get the springs under the back of it. I placed the spring centered under the trailer hitch of the Toyota. I placed one of the scales between the hitch and the spring, then slowly lowered the truck down till I compressed the leaf spring one inch, measuring off the garage floor, read what the scale showed to see how weight it took for one inch of compression.. This gave me the spring rate of the spring I had been using. I have the numbers wrote down somewhere, but the new spring have a rate about half of what I was using. Factory '37 front springs are something like 490 lbs per 1 inch of compression.

The new springs are much softer, had the same ride height, have teflon buttons on each leaf, and they supplied all the correct attaching hardware. This was quite a while back, 10 years maybe, so cost has likely gone up. My total bill was around $1200 after shipping was added, spring averaged $250 each.

I had two choices, sell the truck and buy something that rides better, or fix what I had. New springs were the cheaper option. I am real happy with how rides now, '37s are short wheelbase and don't weight much, so it rode like a Jeep with heavy springs and shocks ( a lot of front to rear bucking ). It's now much closer to a car than truck, so hauling loads is out, but I never intended to haul gravel anyway. I did add a front sway bar since the truck was now softer riding, it tended to lean more in corners then I liked. The bar helped restore the stability.

No matter what springs you use, you need to know how much weight they are going to hold up. Sprung weight and unsprung weight is a must know item. The guys at Detroit spring were super helpful, ask a lot of questions about what I wanted, then came up with springs that worked. I can always send mine back for service if needed, they keep good records and can replace, repair, or update pretty easy.