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Buick 1940 weak bouncy rearend


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Hi all. 
 

looks like i have 2 issues on my heavy rear of my sedan. I think that the springs lost a bit of their strenght and the shocks also dont look like they do what they supposed to do. The spring i have new ones from the factory and will arrive next week from america.  The shocks i did refill but maybe with the lower grade oil? I could add quite some oil and see no leaks. But still to weak. Can i use thicker oil?

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Thanks for the links. I used the oil in the picture below. So best to try is a thicker oil. I hope they have ISO with a higher number lets say between 75 and 100. I did notice a large bolt at the bottom of the shock absorber, is that for draining ? I also read about suck the fluids out from the top. Dont want the remove the bottom bolt and some parts will fall out 🙈

 how does one know if your shocks are weak or the springs are weak. When i hit a speed bump with 20mph the rear feels like the body hits the ground and feels soft and does a few extra bounced after. I know my shocks links are shot and does will also arrive from the states soon
 

 

thanks

75405D3A-72F6-4817-A470-7DABA343D0B2.jpeg

Edited by Robby120113 (see edit history)
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Fill plug is correct, I think bottom one has a valve behind it.  I think you just have to turn it upside down and let drain unless you want to do some dis-assembly. 

My .02C on the oil. I have tried 100 on front shocks - too stiff,  22 too light. I settled on #48 on the Chevy.  I would use on front and back but... Iive in a cool climate too.  

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Can anyone confirm this? i dont want to remove the shock for the refill. Or maybe someone know how much is inside?So when i used a vacuum line i can check if i remove most of it.

 

edit: i found below picture. I am wondering how i can get all the oil out, can i remove the static valve stem? Looks like the lowest point.

 

Thanks

rear shock.jpg

Edited by Robby120113 (see edit history)
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4 hours ago, Robby120113 said:

Can anyone confirm this? i dont want to remove the shock for the refill. Or maybe someone know how much is inside?So when i used a vacuum line i can check if i remove most of it.

 

edit: i found below picture. I am wondering how i can get all the oil out, can i remove the static valve stem? Looks like the lowest point.

 

Thanks

rear shock.jpg

 

Just remove the shock. Its easy. Don't risk taking it apart and screwing up the valving just to change the oil. It's bolted to the outside of the brake backing plate and there's a conical stud holding it to the shock link that often just comes apart when you remove the retaining nut, otherwise you can press it apart with a socket and a C-clamp or a pickle fork. I've removed the rear shocks on my Limited, which are hidden inside the frame, several times and it takes about 20 minutes to get them both off, not counting putting it in the air. Remove the fill plug, put the shock upside-down on your drain pan, let it drain for 15 minutes, put it in a bench vise and refill as you gently move the arm up and down through its range of motion to burp out the air. Don't over-fill. Clean it up and reinstall. Easy project on a Saturday afternoon.

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5 hours ago, Matt Harwood said:

 

Just remove the shock. Its easy. Don't risk taking it apart and screwing up the valving just to change the oil. It's bolted to the outside of the brake backing plate and there's a conical stud holding it to the shock link that often just comes apart when you remove the retaining nut, otherwise you can press it apart with a socket and a C-clamp or a pickle fork. I've removed the rear shocks on my Limited, which are hidden inside the frame, several times and it takes about 20 minutes to get them both off, not counting putting it in the air. Remove the fill plug, put the shock upside-down on your drain pan, let it drain for 15 minutes, put it in a bench vise and refill as you gently move the arm up and down through its range of motion to burp out the air. Don't over-fill. Clean it up and reinstall. Easy project on a Saturday afternoon.

 Thanks 🙏🏻 

about the overfill i first did till it came out the filler cap. But ive now also read in the shop manual some air need to be present. Do you look trough the small filler hole to guess the level or is it easy to see?

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I have the shock absorber removed. At least the 2 bolts. The shock link is still connected. But doesnt matter for now. I can turn the shock up side down and empty it. I noticed that the top bolt is not completly tight. And could turn the shock link while the bolt didnt. So maybe i will remove that bolt so the shock link will come down. See if i can make it more tight and with that eliminate the rattle that i had before

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Robbie:

 Thanks for the incentive for me to tackle my changeover. I bought a set of rebuilt shocks at Hershey in 1989. Other things got in the way and I did not begin to get the car back on the road for another 23 years. I did not even think about the shocks until I experienced the "bouncy ride" you described. Overall I think your 1940 shocks are easier to service than the ones on my 1937. My fill hole is on the side. The units are well buried inside the upper frame.

 

The removal and installation of these shocks was a trial at best. I know now why I put it off for over 30 years. The only convenient way to actually fill the shocks in place one would have to have the car on a lift.  My garage is not very deep and already crowded with stuff for the other Buicks. Since we were expecting no rain, I did the job outside in the alley driveway.
 
 Just trying to manipulate the jack inside was going to be a problem. 1937s still have leaf springs.
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In the photo I have yet to add the (2) 5" lifting boxes as this set up still did not allow me enough space and drop on the rear axle to remove the shocks. The shocks have to be snaked out of the frame at the front shackle of the leaf spring. The lever has to be at the perfect angle for the unit to clear the leaf spring at the shackle. 
The stuff I drained out of the "Rebuilt Shocks" I bought in 1989 was the most rank smelling stuff.  Worse than old 600W steam cylinder oil. The smell to me was a combination of raw sewage and dead fish.
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I refilled with the Delco Shock oil I have in a 1939 image copywrite can.
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I was able to source the NOS shock links from a local Buick Parts supplier.
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Cars had the repro links which I ordered. Then they called back to say that it would be not till the end of October till they could get them back in stock. Since the car was sitting outside in the driveway. I was going to reuse the originals temporarily but my friend Skip Boyer came through for me.
Worked the shock levers to "Burp" the unit and topped off. I did this with the unit in the horizontal plane.
The shocks on my car are pitched at about a 10-degree angle, so I figured that should leave enough space. My info in the service manual also states "do not overfill". Of-course with no description on what that means.
Before I put the car back into the storage garage, I did a drive over some streets in town where I remember the rear end of the car being bouncy. MUCH NICER! STABLLITY BETTER!
Edited by dibarlaw
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  • 2 weeks later...
Posted (edited)

I have 2 springs, 2 shock links and 2 shocks on the way. But since i retightend the shocklinks topbolt in the frame rail it is already much quieter. I also refilled the shocks and that was also a huge difference. U fortunately 1 shock i so worn that even the thickest oil doesnt make the shock stiff anymore. When all the parts have arrived i will install them including the air bags from tigerball for extra stability

Edited by Robby120113 (see edit history)
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