Broken axle

[Boondox]

Ethan, our green 57 Dodge truck, has a broken rear axle. Looks like he was driven over a large rock at some point. Lots of superficial damage underneath, with a bent and poorly repaired driveshaft. And of course that lack of balance was transmitted to the rear and led eventually to the axle breaking.

I have the rear end of a 70 Dart (8 3/4) I'd like to swap out, but the mounts where the leaf springs are fastened are 5/8" further apart than stock. Is it difficult to move these in a bit and reweld them? Never done that sort of thing before, and am not even sure it's possible. But I hope so...I sure would like that gearing! [img]/forums/images/icons/crazy.gif[/img]

Pete

[egon]

Pete.
Are you talking about the leaf spring attachment to the frame or the rear end attachment to the leaf springs?

Egon

[Boondox]

</font><blockquote><font class="small">In reply to:</font><hr />
Are you talking about the leaf spring attachment to the frame or the rear end attachment to the leaf springs?

[/ QUOTE ]

I mean the bracket on the rear axle housing where the center of the leaf springs is attached with a couple of U-shaped shackles. If I don't move those brackets toward the center about 1/4" on each side, the brackets and leaf springs won't mate up properly. Make sense? Not sure if my description cuts it. Should I send a picture?

Pete

[robertn]

It's really easy to remove the spring pads, and weld new ones on where you need them. You must make sure they are positioned properly of course.

You need to make sure the pinion angle is set properly. If it is not, you can get bad drive line vibration. If the angle is too much, it will eat up u-joints.

For lift kits on 4x4's, they supply wedges a lot of times. If you lift the frame of the vehicles vs the axle, it change the angle of the drive lines and pinion. Too get around that, they put the wedges in.

I don't know though, where you would look for the proper driveline and pinion angle.

[s1120]

<font color="red">I don't know though, where you would look for the proper driveline and pinion angle </font color>

Easy. Go right to the horses mouth. Measure the pinion, to spring perch angle from the old rearend out of the truck. Use either the newer perch, or if it will not fit the truck springs, use the old perches. Measure the with of the old setup, and making sure everything is centered, tack them on. Now if I am not mistaken, the 8 ¾ rear has a removable center section. If so I would remove it, and the axles, before you finish weld. Don't want to risk hurting those bearings, or seals. While we are on the subject of welding, unless you are a REAL good welder, I would take your gutted housing, with tacked on perches in the right place, to a pro. You don't want to warp the housing, or have them perches falling off. That would be a BIG problem.

[chevdog]

What Paul said ...
We do this pretty regularly around here since most of my pals race - and break stuff.

You can buy an inexpensive angle indicator dial from Sears, Harbor Frieght, or similar. Here's what I do:
Remove the old axle and support it upside down so the spring perches are on top. The heavy part (yoke) will want to swing down - tilt it up and support it solidly so that it is dead level (0 degrees). Now measure the angle of the spring perches and write that down - it will be duplicated for the perches on the new axle. If they are each a little different, take the middle number between the two readings - the axle may be a little twisted.

Get the new axle and support it in the same manner, then set the new perches on it in the correct width location. Rotate the new perches so they duplicate the original spring perch angle reading and clamp 'em down securely. Check everything twice. Add a tack weld at the 4 corners of each perch, then check everything again. Go get a Coke and come back and check once more. Now you are ready to weld.

If you TIG weld in sections and keep a cool cloth on the tubes, you should be OK, but it's always possible you can melt a housing seal. The best is to have the axles out. You want the center section in place so you can get the yoke level to measure the spring perch angle.

If you are within a degree or two of the initial readings you should be OK, but be sure to get the driveshaft re-done and balanced- not expensive to do this. For cars that see a lot of strip time, we usually add 1-3 degrees of downward pinion angle since the rear yoke/pinion will want to go up -hard - as the car leaves the line. You will be OK duplicating the original angle. Don't forget to check the tranny and engine mounts while you're at it. I would suggest new perches from Moser, Currie, Tom's Differentials, Randy's Ring &amp; Pinion or similar unless yours are difficult to obtain. For sure use new Grade 5 u-bolts and remember that they will stretch so check the torque again after that first drive. I don't know what axle tube diameter is on your truck, but let me know if you can't find them locally - we carry them for 3" and 3 1/4"axle tubes but this is no advertisement, just some help.

[s1120]

I forgot about the drive shaft problem. If it has been bent before, and badly stratend, I would just scrap it and get a new one. There are a lot of mail order drive shaft places out there. Now before you get a new one, you want the new rearend in the truck. If you are keeping the stock motor, and trans, make sure the mounts are good.[you don't want the motor/trans sitting to low, or at the wrong angle] You dont want to mesure the old shaft, the new rearend will probably be a bit shorter, or longer then the old one. Who ever you get the new shaft from, will tell you how they want you to mesure for the new shaft. Good luck.

[egon]

Pete:
You have sure gotten some great advice here. I'll stop asking silly questions.

Egon

[Boondox]

Got some great advice here! I unbolted the 8 3/4 rear from the 55 parts truck then used the tractor to lift the truck up in the air (every backyard mechanic should have a Kubota/JD/NH in his toolbox!). With the rear ends side by side it was obvious I had measured wrong. Plate to plate and perch to perch measurements were right on! Even the angles were the same!

So right now I have the two driveshafts (70 Dart and 57 truck) at a machine shop being combined into one, with the tranny end of the damaged unit being attached to the newer undamaged shaft and shortened by an inch or so.

Found a replacement exhaust manifold at a junk yard in Arizona (gotta love the Internet!), new shocks in Boston, and parts for the bed in Ohio. The fuel pump is rebuilt, and the carb is about ready to go back together. The fuel tank is up in Canada being repaired and lined.

Thanks for all your advice and encouragement!
[img]/forums/images/icons/grin.gif[/img] [img]/forums/images/icons/grin.gif[/img]
Pete

[CJDave]

Boonie, is that the polyspherical V8 Mopar engine? I just cannot for the life of me remember the cubic inches, was it 315 in the pickups? [img]/forums/images/icons/crazy.gif[/img]