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  #1 (permalink)  
Old 04-09-2019, 01:29 PM
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Leaf spring

I have a 1937 Pontiac Deluxe 6 4 dr sedan. It is eguipped with a mid 70's Camaro rear axle.
The axle is mounted on a 1 1/2" block above what I believe are Camaro leaf springs. The springs are mounted to the stock rear shackle, and I believe the front eye mount has been moved on the frame. With the weight on the wheels the rear shackle moves all the way back up to contact the frame rails. 70 psi in air shocks keeps it from constantly riding on the frame.
When I jack the car up to remove a tire, the axle drops 9-10 " and the rear shackle is then vertical.
My thought is these springs are too long and too weak.
How do I go about measuring for a replacement spring?
I can get the eye to eye distance with the rear shackle vertical and the approximate distance the down axle should sit in relation to a straight line between those measurements, as well as the axle center from that same straight line. I know the spring will need more arch than what I can get from these measurements.



I have sent this info request to Eaton Detroit springs, waiting for their reply. Their measurement form has you measure a spring removed from the vehicle.
I just heard from Eaton Detroit, they want me to disassemble a spring following their measurement chart. Not sure this will give me the correct spring.
I guess the question is, how much arch do you allow for movement to get the rear axle height correct?
Does anyone have a mid 70's Camaro? If you do could you measure the leaf spring distance eye to eye in a straight line, and also along the arch? Also how many leafs? Thanks.
I guess I need a rear axle weight for my car, and then find a similar weight rated car with a close spring size.
Probably time to head for the junkyard......

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Last edited by Bob37pont; 04-09-2019 at 01:57 PM. Reason: More thoughts!
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Old 04-09-2019, 01:55 PM
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I had about the same problem with the '39 and enough blocks to put the U-bolt ends to close to the ground. What I did was to switch to air bag rear suspension so when people climb in the back it's just a push of the button to level the ride again. Other times I used a local truck spring shop to re-arch the springs and they were spot on. Might consider adding a leaf if necessary.
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Old 04-09-2019, 02:08 PM
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Quote:
Originally Posted by 39 master View Post
I had about the same problem with the '39 and enough blocks to put the U-bolt ends to close to the ground. What I did was to switch to air bag rear suspension so when people climb in the back it's just a push of the button to level the ride again. Other times I used a local truck spring shop to re-arch the springs and they were spot on. Might consider adding a leaf if necessary.
Don't you need to go with a 4-link to use airbags?
I'll have to ask around for a local spring shop.
If I get these springs stiffened & re-arched to where the rear shackle is off the frame the body will be raised up a bunch!
This is how the rear shackle sits now, I put the rubber in the frame to keep it from squealing!
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Old 04-09-2019, 03:23 PM
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Have you considered adding a leaf, or two ?

Have a look at this site get more info, options.

POSIES Rods and Customs – Super Slide Springs – Street Rod Parts – Hot Rod Parts – Truck Parts – Ford and Chevy Suspensions and Chassis Parts

Here is a neat trick for a leaf spring shackle

https://www.speedwaymotors.com/Speed...ider,5817.html
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Old 04-09-2019, 03:23 PM
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Rear springs

Yes, I went with triangle 4 bar. Could not get the car down with leafs and it's still a bit high with bags but couldn't go lower without cutting into the back seat. Step one would be to find a local spring shop. Where I lived in Fla we had an excellent one that worked springs with ease.
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Old 04-09-2019, 04:25 PM
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Shackle angle in the photo doesn't look that bad, looks more like the use of possibly the original frame bushing hole combined with the short Camaro shackle is a lot of your problem.
Have you considered just making a longer shackle?? You can buy longer shackle kits too, been used since forever to raise cars for bigger tire clearance.

If you decide you are going to replace the spring, the very FIRST thing t=you need to do is go to somewhere they have a vehicle scale, like a truckstop or Agriseed/Farm lot and weigh the car....weigh just the front tires on the scale, the whole car, and just the rear tires so you know the weight on each axle and the total weight.
Can't choose a new spring without knowing how much weight it carries so you can use the spring rate to calculate how far it will flatten out.

Stock 70's Camaro/Firebird is typically 4 or 5 leaves depending on standard or sport/Z28/Trans Am and very close to 160(standard) to 175 lbs/in.
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Old 04-09-2019, 06:17 PM
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Quote:
Originally Posted by rip-tide View Post
Have you considered adding a leaf, or two ?

Have a look at this site get more info, options.

POSIES Rods and Customs – Super Slide Springs – Street Rod Parts – Hot Rod Parts – Truck Parts – Ford and Chevy Suspensions and Chassis Parts


Here is a neat trick for a leaf spring shackle

https://www.speedwaymotors.com/Speed...ider,5817.html
The Posies stuff is neat, also $$! I'd have to call to see if the '37 Chev stuff will work on my Pontiac. I like that it incorporates a 3" drop, wonder if that is with the axle above the spring.
I had seen these sliders earlier, might be an easy fix without raising the car.
There are some Camaro springs of different weights listed on the speedway site as well, I'll have to take some measurements and do the weight calculation Eric mentioned.

Quote:
Originally Posted by 39 master View Post
Yes, I went with triangle 4 bar. Could not get the car down with leafs and it's still a bit high with bags but couldn't go lower without cutting into the back seat. Step one would be to find a local spring shop. Where I lived in Fla we had an excellent one that worked springs with ease.
Working on finding one.

Quote:
Originally Posted by ericnova72 View Post
Shackle angle in the photo doesn't look that bad, looks more like the use of possibly the original frame bushing hole combined with the short Camaro shackle is a lot of your problem.
Have you considered just making a longer shackle?? You can buy longer shackle kits too, been used since forever to raise cars for bigger tire clearance.

If you decide you are going to replace the spring, the very FIRST thing t=you need to do is go to somewhere they have a vehicle scale, like a truckstop or Agriseed/Farm lot and weigh the car....weigh just the front tires on the scale, the whole car, and just the rear tires so you know the weight on each axle and the total weight.
Can't choose a new spring without knowing how much weight it carries so you can use the spring rate to calculate how far it will flatten out.

Stock 70's Camaro/Firebird is typically 4 or 5 leaves depending on standard or sport/Z28/Trans Am and very close to 160(standard) to 175 lbs/in.
The pics are deceiving, the spring eye is laying on the rubber pad on the frame rail.
The slider Rip mentioned looks like a decent option, I really don't want to raise the car.
I have an truck scale available locally, plan to weigh the car as you described. Speedway also lists some Camaro springs with different weight ratings, up to 225#.
What's the formula for calculating the spring rate with the axle weight?
I'm going to measure my springs length from front to the centering button to see if they will match what Speedway lists.
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Old 04-09-2019, 10:43 PM
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I'm using the sliders, like them very well, good way to get low.

Only suggesting Posies as a resource of knowledge it is always good to know what all is out there ......
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Old 04-10-2019, 05:29 AM
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Quote:
Originally Posted by rip-tide View Post
I'm using the sliders, like them very well, good way to get low.

Only suggesting Posies as a resource of knowledge it is always good to know what all is out there ......
Knowledge is king!
Better to learn by asking questions than throwing $$ at an issue without research!
Not to say I won't throw $$ at it, just hope to do it once!
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Old 04-10-2019, 08:27 AM
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Originally Posted by Bob37pont View Post
Knowledge is king!
Better to learn by asking questions than throwing $$ at an issue without research!
Not to say I won't throw $$ at it, just hope to do it once!

Heard that ........ ! and wise
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Old 04-10-2019, 08:27 AM
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add a leaf

WE have 36 an 37 Pontiac's. I have never had the 37 project up on the hoist. the 36 has springs that are narrower and more leaves than the camaro parts on the racks. some 4 X4 forums tell what bone yard springs will swap. I reversed the arch (reversed eyes) in my Model T front main leaf using a Hf tubing bender. chalk the shape then gradually work along the spring enough times. I don't know id the camaro springs would fit thru a HF tubing roller to do it faster. The 36 is stock straight 8, the 37 had a SBC and chevy pickup rear with the Pontiac wheel lug pattern
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Old 04-10-2019, 11:44 AM
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Quote:
Originally Posted by timothale View Post
WE have 36 an 37 Pontiac's. I have never had the 37 project up on the hoist. the 36 has springs that are narrower and more leaves than the camaro parts on the racks. some 4 X4 forums tell what bone yard springs will swap. I reversed the arch (reversed eyes) in my Model T front main leaf using a Hf tubing bender. chalk the shape then gradually work along the spring enough times. I don't know id the camaro springs would fit thru a HF tubing roller to do it faster. The 36 is stock straight 8, the 37 had a SBC and chevy pickup rear with the Pontiac wheel lug pattern
Adding a leaf along with the sliders may be the answer.
Next question where does one get a single leaf to add, a pair of junkyard to disassemble?
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Old 04-10-2019, 03:09 PM
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This afternoon I pulled a wheel to get some better pics & info. The wheel/axle drops 6" when the car is jacked up until it is off the ground.
Measuring the spring eye to center pin confirms they are Camaro, 24" from the front, 30" from the rear. Speedway offers a good selection in different weight ratings.
I still have to get the car weighed so I can calculate the correct spring rate.
It's apparent to me the front spring eye mount has been replaced, while the rear shackle is mounted in the stock frame hole.
The pics show the spring both weighted and hanging free, I did let the air out of the air shocks.
When there is weight on the axle the leaf spring is almost flat, with the rear shackle pushed back tight against the frame.
I normally run the air shocks ~ 75 lbs, this gives me about 1/2" clearance between the rear eye and the frame. Sliders might allow the spring to move a bit more.
I'm tempted to get the sliders and install them with the current springs to see how that works.
All of the speedway listed springs are described as having 6 1/2" true arch. Does this mean that is how the spring sits unloaded?
Once I get the weight I can better figure out what weight spring I need. From what Eric mentioned standard Camaro springs were either 160 or 175, I betting these are 160.
First pics show the spring loaded, axle on a jack stand.
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Old 04-10-2019, 03:13 PM
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These pics show the springs unloaded, axle hanging, rear shackle is vertical.
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Old 04-10-2019, 04:25 PM
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first thing I have to comment on is the very last picture.....holy unsafe, Batman - no u-bolts around the axle tube!. The way the spring is clamped in the perch with just regular bolts is a very poor way to do it. Even when the factory started to cheap out and do this in the 1970's on Camaro/firebird and Nova they always used 1 u-bolt per side and just 2 regular bolts.

Second thing is that rear shackle angle when spring is unloaded....it should not be vertical like that, it should be straining forward almost to the point of the spring eye touching the frame(the reverse of what your dealing with when it is loaded).
My guess is the use of the convenient original bushing hole in the frame created this problem....correct use of that original frame hole would have meant the front spring hanger would have to be moved forward 3" or so, and that would mess up wheel centering in the wheel well. Correct fix here with the Camaro spring is to correctly locate a new rear bushing mount hole. Slider might be the easiest way to fix that.
The standard Camaro leaf pack is well known for going flat and sagging out, so they probably do need replaced...but to fit and function as they should you really need to do something about that rear shackle location problem.
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