Projects 1955 Buick Truck Arm Suspension Help and Advice

Here is my current project. It's a 1955 Buick century sedan, I am in the process of putting in a trailing arm set up and need some help and suggestions on locating the rear axle so that I can start welding up the cross member brace and hopefully get this project rolling. I am planning on using the stock springs in the stock location for the time being, then upgrading to bags later down the road. Also going to use the factory panhandle bar. Any suggestions would be appreciated. Thank you.






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Do you have the original rear axle assembly? Did you take any reference measurements prior to disassembly?

If not, then there are ways to get it right. First, start with the factory wheelbase. My reference says 122" for Special and Century models.

I would begin by establishing a centerline for the front wheels/spindles. Put a chalkline or other durable marking on the floor, making sure it is perpendicular to the centerline of the frame. Use triangular measurements to accomplish that.

Then you can measure 122" back from that line and establish the rear axle centerline.
That, too, needs to be perpendicular to the frame centerline and verified with triangular measurements. You can use plumb bobs or similar to layout lines on the floor or transfer lines on the floor to the elevated axle.

Once you have everything exactly where it's supposed to be, you can design and fabricate the needed forward brackets for the trailing arms and spring seats on the axle. If you still have the original rear axle, I would attempt to use the brackets from it and transfer them to your new axle. If not, you can fabricate what you need. It wouldn't hurt anuthing to make the front trailing arm attach brackets adjustable in so manner...i.e. a provision for shims so that any unintended small fore/aft misalignment could be corrected easily.

 

Thanks for the advice, it is very helpful.

I do have the factory rear end assembly, one complete and one taken apart. Unfortunately I didnt take measurements prior to taking it out. I will follow your suggestion and measure out the 122" from the center lines of the front wheel/spindles and work my way back.

Thank you.

 

I think I would back up a bit, reinstall the original suspension with the tires you intend to use attached but without the springs, drop the whole shebang down on a level floor and set the frame to your intended ride height front and rear.

Do X checks to verify the frame + suspension is as square as possible and, if it is square, I would tack the original rear axle to the frame using square tube spacers and ensuring the tubes are clear of the truck arm to axle mounting areas.
Then I would remove all the old suspension arms etc, leaving the original axle attached to the frame by the square tube brackets.
This will ensure you have the axle in the correct place for truck arm installation. Mock the arms up to the OEM axle and make your mounts etc off that axle BEFORE you install the new rearend.

You're still gonna need lots of measuring etc but at least you will have all your current positioning verified off the original positioning so the wheelbase will be dead on and any frame clearance issues from the truck arm conversion will be obvious at the driving height of the vehicle.

For me, it just seems like it would make things easier to work off of solid things instead of building and designing components separately, with the hope everything fits exactly as you want once you get to actual assembly.

 

Given that a Buick with torque tube drive locates the rear axle via it's connection with the transmission, and the original transmission does not appear to be in this car, I respectfully disagree with reinstalling the original rear end.

I certainly do agree with getting the chassis and axle at ride height to insure adequate clearance of all components. Even temporarily welding the axle to the frame to maintain it's position, once situated. Locating the axle assembly accurately is not voodoo magic, just plain 'ol geometry and careful measuring.

To insure 'squareness', the axle should first be accurately centered side to side and at the correct wheelbase point. Then you can measure from the exact same point at the outer ends of the axle to a center point of the chassis up around the transmission mount area. When those two diagonal measurements are equal the axle is perpendicular to the chassis.

I use a tape measure for this onto which I have attached a small wire hook at the end. I have found the wire hook locates more accurately than the blunt end typical of most tape measures. You just have to be careful to consider whatever extra length the hook adds to the measurement.

 

I already have a different transmission in place, so I'd prefer not putting the original back in. I think I'm just going to go with the measuring 5 times route. Thanks for the advice.

 

Ohhh...didn't realize that Buick used a torque tube till then! Guess I'm a bit biased toward Chevy! LoL
Time to get good with a measuring tape I guess!

 

Here is how it is progressing so far. All suggestions and critisms are welcome.

 

As a suggestion I would ensure that the:-

• Forward mounting of the rear trailing arm pivots are double sheered solidly as there quite a load on the pivots when driving;
  
• Rear panhard bar is the correct length at ride height as the rear end won't be centred once body and weight is on ground, wheels will be offset to one side. Maybe an adjustable bushing threaded into one end after drilling and tapping tube;
• Upper and lower shock mounts are parallel so as bushing don't wear prematurely or unevenly;
  
• Pinion angle is up 3 degrees at ride height to compliment the 3 degrees downward angle of the engine / transmission assembly; and
  
• Axle flanges are equidistant from chassis rails at ride height.

Those housing saddles are critical and shouldn't be welded until housing and trailing arms are centred and geometry is set at ride height. I used a trammel bar to check lengths and diagonals when I did a rear axle swap in my friends 42 Chevy PU using a 46 Olds X-member with trailing arm suspension, upgrading to a 9" with coilovers. Housing is isolated to arms and not solid mounted like truck arms. Don't finish weld anything until everything else has been done correctly beforehand. Measure twice, cut once. Still need to add panhard bar

 

Thanks for the great suggestions and the picture of your set up.

 

I'll be doing the same for my 49 Super. Watching for info.

 

What year Chevy trucks have this type of suitable set-up? I am about to undertake a 55 Roadmaster conversion.

 

I used a "Wishbone" assembly to center my truck arm suspension in my 54 Stude.
That way, there is NO side to side movement with different ride heights...as the car drives down the street.

Mike

 

Missysdad did a 55 buick a few years ago, went with a set up similar to yours. Look him and his thread up with the search function. He built a very nice car.

 

Chev half ton pickups 1967 - 72. They were made in the shape of an I beam out of 2 stamped channels rivetted together. This was so they could twist. If you hit a bump and one side of the axle goes up and the other goes down they need to twist.

Another way to get at the same thing would be to use 1 1/2 or 2" square tubing but with the rubber mount at the front oriented the other way, like a Ford twin I beam rear mount.

 

Chevy trucks used the trailing arm setup from 1960-72