Howdy. I threw the driveshaft out of my '27 "TruckBucket". Turns out the rear pinion bearing went south and wobbled around enough that the driveshaft took leave of the rear yoke and went skittering down the road behind me. I guess the first question that might come to one's mind is how in the hell I didn't notice the noise of something going very wrong beforehand. Truth is that the car is relatively new to me, and it is loud...open megaphone headers loud. I did notice a whine, but I couldn't figure out if it was the fatty tires or what. When I noticed that loading and unloading the driveline made it come and go, I began to think that something was amiss, about that time the whole thing went south. So, I have to get a new driveshaft made and a new set of gears. Now (finally) comes my quandary: it looks to me like the axle assembly is tilted upward at an odd angle. I'm wondering if the pinion bearings were starved for oil which caused the failure. It that's the case, I have no idea what to do since the spring brackets and hairpin brackets are welded in that configuration. I don't want to pay to have my punkin' redone only to have it fail again due to (what may be) a fatal street-rod design flaw. You can kind of see from the picture the angle of the differential as compared to the frame. I should've taken I wider pic to show the tranny output shaft. I will do that tomorrow. Thoughts? BTW, it's a Tri-Five 3.70 open diff.
The angle isn't what caused the bearing failure...there are channels in there that direct oil to the bearing, and the oil is flying around pretty good when you drive down the road. but the pinion angle like that could be part of the problem. The engine doesn't have that much "nose up", does it?
It sure looks to my old tired eyes that those hairpins were seriously twisted up by some type of juvenile delinquent behavior. And I'm all for it,,
I wonder if that rear axle angle happened when the driveshaft flew out, look at how bent the hairpin is in the pic from under the car
once you straighten the hairpins it may be a good idea to weld in some trusswork for reinforcement View attachment 6411985
I'm with Moriarty, looks to me driveshaft caught the hairpin, if not the driveshaft something surely did. As bent as the lower bar on the hairpin there is no choice but the pinion to be super high. Time to pull the hairpins ( both sides) and see if straightening is an option or time to buy or build a new set..... Once that's done THEN I'd worry about pinion angle but only then.... ...
3 to 6 degrees max difference between the trans and yoke on the rearend . More or less degrees will cause this.
Nice car, the hairpin looks somewhat distorted in this pic. Does the rear suspension work as it should or does it bind if one wheel is lifted? Dan
The hair pin pictured is screwed up, if the other one matches the bends on this one, that would be why your pinion angle is off. The bearing could have failed if the drive shaft was smacking it or binding the U joint with every revolution, or the bearing could have just wore out. Once the driveshaft took exit, its going to be pretty tough to find out what failed first. Were I guessing, I might think the hair pin(s) failed an acceleration test and bent, causing the other issues. I don't like the open hair pins on a vehicle with power and traction. Not the first time I've seen them bent. The picture showing your bent hairpin also shows that it has an adjustable heim joint on at least the bottom connection of the hair pin, that is where you would fine tune the adjustment of the pinion angle, but with the bend in the lower part of the hairpin, there isn't enough adjustment there to accommodate the dramatic pinion angle.
Check your transmission for a cracked tailshaft housing too. I'm guessing the flexing/bending hairpins led to the failure of the pinion.
The hairpins are both bent like that, and it was that way when I got it. They are equally shaped that way. As this is my first street rod, I didn't give it any thought, I just figured that's the way these particular hairpins were designed.
Just eyeballing I can tell there are more than 3 to 6 degrees of difference between the yoke and trans.
There are heim joints on all three connections, which, after reading some posts on here, doesn't seem advisable at least from a ride standpoint -- and it does ride rough.
the picture above that shows the whole car does not have bent hairpins, the picture from under the car clearly shows where the driveshaft contacted it and bent it
I am guessing the "ladder bars" bent prior to them being contacted by the wayward driveshaft. On hard launches the torque of the rear end will put the bottom element in compression and the top element in tension. The compressive forces exceeded the column buckling strength capabilities of that element and it bowed, twisting the pinion upward and initiating the failure process of the eventual driveshaft failure. The upper element also shows signs of being bent upward (near the front bend) which would also occur with abrupt bending. You will need stronger ladder bars (or tinyer rear tires LOL). It would be a good idea to add a stiffening rib, plate, or tube somewhere midpoint of the length of bars to increase their rigidity. Even better - though somewhat less traditional - would be to use a 4-bar link at the rear by adding a second pivot point at the front. That will also eliminate the stresses put on the housing mounting brackets that happen when one wheel hits a bump and wants to rotate the axle housing wrt to the chassis centerline.
Weak/bent hairpin rods caused the pinion angle to aim for the moon. The excessive pinion angle caused the driveshaft to leave the chat and the hairpin damage got worse, as evident in the "after" pic. Check for any excessive play in the pinion gear, if excessive...repair. If within "spec", send it. Straighten the hairpin rods and add a gusset like Moriarity mentioned. Adjust the pinion angle to mirror the transmission angle. Replace driveshaft. Do burnouts.
You don't need to completely change all the brackets on the rear axle, you just need to either reinforce those hairpins as Moriarty mentioned with more support between them, or build new ones. Since the hairpins have heim ends you can easily adjust pinion angles by turning the heim ends in or out to raise the angle. I personally prefer the lower arm of haripins or ladder bars to have an inline adjuster so the hairpins don't need to be totally disconnected to make adjustments, but it can be done with what you have. Just might take numerous times of dropping both sides on the axle ends of your hairpins to get it corrected. Personally I'd probably toss those hairpins after this damage and buy new ones to start fresh with. And if new ones aren't well braced I'd add bracing before painting and installing them.
With heim joints everywhere and the axle acting like a solid anti roll bar any bump action on either side will be stressing everything. It's usually the chassis tabs that prove to be the weakest point but in this case the flimsy, unsupported hairpins provided the weak point. Add some power too and here's the result. I'd be replacing the bars and substituting some bushes with a degree of compliance. Tougher bars on the exisiting mounts and heims and wait for the next failure? Chris
Now this idea is radical and kind of weird, but it popped into my head (probably due to the migraine I currently have). Replace the shocks with solid links, with rubber eyes like shocks have. There will be a tiny bit of give in the rubber bushes, but essentially the rear will be solid mounted, so just like a go cart. Great for dropping the clutch at 6000 rpm, but likely not fun to drive for long… Okay, I’ll get back on my medication. Just ignore that idea
Like others said ,Hair pins , Gussets Needed or heaver tube construction needed, & @ lest a Front drive shaft catch In pic looks to have Buggy spring , Can you push down with Little force ? Being a T bucket , it more likely 1,400 to 1,600 ish pds , maybe 1,300 . Engine & trains 750 ish pnds .. Air in tire's 25-28 psi to help / solve harsh Ride quality
Thanks for all the input. I just assumed the hairpins were designed that way, as they are equal in their arch. Moriarity pointed out that it does appear more bent in the undercarriage shot vs. the whole car shot (both pics show the driver's side). The full pic is from when I first bought the car. Also, the paint that he referenced has been that way for a while, and it's on both hairpins in the same spot; it wasn't caused by the driveshaft hitting it. It's becoming clear to me that what I thought were "rock chips" is actually paint flaking due to stress. And I reckon tear-assing around has bent them even further. I hadn't noticed the difference in the arch before; they've gotten progressively more bent as I've been driving it around. Oooops. Unfortunately I noticed today on further inspection that the trans seal is wallowed out and the tail shaft itself has wobble (Turbo 350). Now I'm in for a transmission rebuild(?) My ignorance has gotten quite expensive. I've added some more pics. You can also see that the spring shackles are wonky as well. Well I have learned a lesson my friends -- the value of which has yet to be fully realized.
My daughter is a metalworker. I'll have her straighten these and weld in some gussets. Replace the front heim joint with a neoprene bushing? The fine folks at Drivetrain Specialists are currently building me a new driveshaft and rebuilding the diff.
As far as rebuilding your trans I don’t think so. Start with a new seal and maybe a tail shaft bushing.
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