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C 10 trailing arm placement

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Have a 1957 Buick Century...
Have a question, picked up C10  trailing arms.....brought them home and put them under the frame to look .

Now my understand is that these arms replace the torque tube and need to be at the steepest angle possible..from the furthest outside part of the axle to the closest point at the intersection of the X without impending the channel for the driveshaft.
That being said.....my axle has the shock mounts on the front of them...and are located near the brake hub, next to them going towards the pumpkin is the spring cup. So the closest place I could mount the trailing arms is after the spring cups..which is about half way to the pumpkin. That would not be a good angle...almost straight.
1. Could I remove lower-shock mount and reposition inward and keep upper mount where it is...changes shock compression angle.
2. Remove shock and coil all together and get coil-overs
other issue...attachment up front, from what I can tell ...do not think the frame as it sits will work for mounting... using the picture as a guide I think that might be the best way to go....cutting the X frame, putting a brace all the way across to each outside channel, rewelding the X onto the brace and affix the arm brackets to the brace...
A little bit of work but I think it would work.any other ideas...except go 4 link, go bags,etc..need help with this set up...not go with another one.
Have a Merry Christmas 
Jimmi V.

Sent from my iPad





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John, yes exactly....just concerned about the placement of the trailing arms...do they need to be as close to the brake hubs as possible to get a decent angle for rigidity for the rear...or can I mount then on the open spot inward of the spring cups.



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Can't answer your question. Usually this modification is done using an open rear axle, not a torque tube axle. 

I do have another question or two. Are you keeping the original engine and transmission?

And if so, what are you trying to accomplish here?

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That's going too be  nice combo. How do you plan to switch the spline drive on the rear axle to a universal?


Of course, what I am driving at is that for the work you propose, wouldn't it be easier and less costly to work with an axle that is already an open driveshaft set up?


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1 hour ago, JohnD1956 said:

That's going too be  nice combo. How do you plan to switch the spline drive on the rear axle to a universal?


Of course, what I am driving at is that for the work you propose, wouldn't it be easier and less costly to work with an axle that is already an open driveshaft set up?



Yes, my question, too........ as I understand, if you find a Buick differential from a 61 or 62...

(open drive lines) it will bolt right in to your housing.


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I don't believe they were way out by the backing plates on the C-10.


C-10 trailing arms were made at least 2 different ways. 1960-62 trailing arms are more angled, and mount out closer to the backing plates. 1963-1972 mount further in toward the center. Which do you have?


I don't know about the rigidity, but I would be inclined to mount the trailing arms at the same spacing they were in the C-10. Assuming the more common 1963-72 C-10 trailing arms, that will be further in toward the center than the rods Buick used. Is the Buick axle housing rigid enough? I don't know. I wouldn't use it anyway without a torque tube for the reason Beemon mentioned (lack of parts), and a whole bunch of other reasons. More on that in a minute. IMHO if you want to use that axle, run a torque tube.


If you don't know what the distance is between the trailing arms is, I could get a fairly close measurement. I have an old C-10 (later-style arms) that drives straight. Post back if you need me to measure.


One thing to consider is pinion angle. On a Hotchkiss drive car (open driveline) the universal joints need some angle. To be specific, the angles of the 2 universal joints need to be equal and opposite. Yoke-and-cross u-joints do not have a constant speed as they rotate. The more angle the joints have, the more the driveshaft speed varies as they turn. If the angles are equal and opposite the speed variations cancel. If not, they manifest as driveline vibration


If an open driveline runs perfectly straight, it will be smooth when first assembled, but the needle bearings will never roll, and they will pound little needle-bearing shaped dents in their races in the cross and caps. You will go through a lot of u-joints.


The panhard rod should be level at normal ride height too, to minimize unwanted steering as the suspension moves. Axle should also be centered.


Now about that Buick rear axle... at the very least you will have to weld the perches for the torque arms to it. If the pinion angle is different or panhard rod position is wrong, you might have to cut everything off and reweld. Either way, it screws up the wheel alignment because the axle housing warps from the welding. You can fix this on an alignment rack (with all weight on, so ride height is normal) by heating the axle housing out near the ends with a rosebud torch, and watching the alignment on the machine. You are shooting for zero camber and zero toe on both sides, and zero thrust angle. It is best to have it mocked up with no seals or oil, as that is all probably going to get ruined. Keep a fire extinguisher handy.


If you don't have access to such equipment it might make more sense to have Moser or Currie or whoever build you an axle housing (with shafts if needed) that is square with everything already welded on. If it were me, I would stay with a dropout style axle, because if you need to work on it, you can set it up on the bench instead of under the car. The Ford 9 inch is a good choice because parts, including any gear ratio you might want, are readily available. It has higher drag than some other axles, but is bulletproof. The old late 50s to early 60s Pontiac/Olds axle is another good possibility. Lower drag than the Ford, but more expensive and less choices for gear ratios. Mopar 8-3/4 is another possibility (my favorite), but tends to be really expensive, and never came with the same wheel bolt pattern as the Buick, so there is no possibility of off-the-shelf axle shafts.

EDIT: One final thought, never assume anything taken off of an old C-10 is within any sort of reasonable tolerance. Don't attach the front mounts for the trailing arms to your frame until you have verified that the rear axle will be in perfectly straight (with normal ride height and the panhard rod level!). You may need to fudge the mount locations a little.

Edited by Bloo (see edit history)
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Bloo, thanks for all the info....a lot to chew on

I am going to put the torque tube back on for angle alignment....believe it should be 3* negative...and motor will be 3* positive

  (or visa versa)... can’t remember at this exact moment...

Being the torque tube was an important part of the rear end ...taking it out means we need to replace it with something to take on that responsibility ..for me I chose the C10 trailing arms...from my understanding they need to creat an angle to offset the forces...like a 4 link would do...

I have my frame on stands and it is level forward and back,right and left.....how do I get it to ride height to make the panhard bar straight...as it sits now..it is no way near level...and when attaching the front part..again..how do I attain ride height when it’s on a jack stand?

also, want to keep axle if all possible...I can’t be the first person to do this....

here is a pick of my rearend..and a picture that was sent to me...

thanks for all the help...learning as I go....

Jimmi V.





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If you go with the 61 open driveline (if you can find it), you will not be able to replace the carrier bearings because they do not exist. At that point, there is no reason to replace any of the bearings in the carrier unless absolutely necessary. If your ring and pinion is good, great. If not, you're SOL unless you pay a hefty amount for a brand new set. Depending on the carrier bearings, there will always be axle noise, too. It would be easier to find an axle with similar wheel width and weld on coil pads and shock mounts by comparing to your current differential, then you can have all new parts. The nice thing about the truck arms is that you can probably get away with using U bars over the axle like exhaust fasteners. That's how they did it in your second photo. 


What is compelling you to go this route? New transmission? 


The only way to stimulate axle load is to put the body back on the frame. Unless you have a friend or know someone close to you in a local Buick club with the same car and they are willing to weigh the car with scales under each wheel. Once you know what the loaded weight on each tire is, all you would have to do is load the coil mount on top of the frame with the same weight on each side. You will have to load the front, too.


Lastly, do not cut the x-frame like your third reference photo. It is a structural support member and is designed that way for a reason. Do what they did in the second photo and weld a mounting flange to the x frame without butchering it. 

Edited by Beemon (see edit history)
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Yes, putting a 700R4 in paired with the 1966 401 nailhead....

Trying to find a 61 differential to switch out my stock one.( bolt in )

then get  driveline made.

my question is where exactly do I attach the trailing arms on the axle to get the most benefit for securing the rearend...from what I understand I do not want them straight...I am not drag racing,want them at an angle for cornering support, and front to back support, the panhard bar is for side to side.

if I go wide..need to remove lower shock mounts...where would be the best place to put them...just pivot bottom of shock inward and remount bracket? Remove entire shock and remount someplace else?  Remove coil and shock and replace with coil overs?...


also, very confused on ride height...if the body is on and the car is on the ground...how do I work and line up the rear end or do anything when it’s 4 inches off the ground?

if the frame is straight and level....on jacks, why can’t I adjust everything?


no challenging you...I really don’t know....




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The panhard does not control side to side, it is only used to locate the body centered over the axle. This is why you need to load the axles. Small body Oldsmobiles used a rear sway bar, you could try to adapt it if you find a parts car. 


Like I said you can figure out what the axle load is by weighing a similar car and then attaching weights to the axles that are equivalent. You can do this on jack stands. But you have to weigh it at all four tires so you get a proper weight distribution over each axle. The front loading will be much different than the rear. Once the suspension is compressed, you can attach the truck arms and see where it sits. 


I agree with you a 61 to 62 center section will work best. Do you have one lined up? 

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  • 6 months later...
  • 3 weeks later...
  • 3 weeks later...
On 12/22/2018 at 4:46 PM, Build4#2 said:

Section7-13 of the service manual has dimensions you need for ride height. You will have to figure out how to compress your springs. Bruce

One suggestion is to replace your srings with treaded rod(ready bolt) so you can ajust things up and down without "fighting" spring pressure. Once youve got things sort contact Detroit Spring or equivilent for a pair of correctly engineered springs. Inexpensive and accurate!

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  • 10 months later...

Im doing the same thing to my 1949 super 50series .was wondering how it worked out and if you had any more pics or tips .Im going to run the c10 cross brace from side frame with added length and then box the center x im doing this with body still on frame as I have a lift in garage .folks say I m to old for this but 63 years old but 21 at heart lol Im using the 12 bolt rear and making spring perches out of cab brackets  to sit over ubolts 

Edited by Al Deal
more info (see edit history)
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  • 3 weeks later...

@Jimmi VI know that I'm kind of late posting here, but I think that the original Chevy coil spring sat on the trailing arm.  Check out a build by No Limit Engineering and see what they did with the spring mounts, panhard bar, and shocks on one of their builds. (They sell a relocation kit.) I'm posting one picture from  their build. They are using the panhard bar for lateral stability.  



Edited by RivNut (see edit history)
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  • 3 years later...

I have a very nice unmolested 38 Spl, actual mileage is 37k.. When I say unmolested that is a fact. It was a one owner car, a woman in Kansas City that bough new. The owner prior to me was more interested in keeping the car original so he never fixed any thing. Car ran well but left a trail of fluids every where it went.

I put the car away for two years, kept it running and did a lot of checking for parts, options, etc.

The '38 is not my first Buick, I have a '40 Super and a 52 Spl Riviera HT, both of which are projects.

I had a friend for many years that was a real wiz with vintage Buick's. Following my friends advise I gathered up a set of C10 trailing arms, a '63 Riviera rear end (same tread width as the '40) a ST400 trans and a 401 nailhead punched out to about 413. All of which have been rebuilt for the 40.

A couple of months ago I put the '38 on the hoist and started taking things apart to heal up the oil oil/fluid leaks. Every seal, gasket, hose, etc was a total waste, Removing the trans we found the the clutch was 'Goo' sticky from oil. When we pulled the the drums brake parts fell out. broken springs oil soaked brake lining. Every portion of the suspension needed a total rebuild.

I had to rethink the project, I like old cars, however, I like them to be safe and reliable.  So many of the parts for vintage vehicles are unobtainable, which have better well convinced me to up-grade the power-train under the '38.

The 440 gearing and torque tube are a potential problem, I know the C10 trailing arms and Riviera rear end will bolt right into the 38., my friend did that to his '38 Century cpe many years ago. Trans is a problem. I have found a company in Los Angeles that will build a T-5 trans and adapter for the '38, the rear end gearing presents a problem. I need 3.90/4.10 for the overdrive T5, nobody has gearing for the 63 rear end.  Wm

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