Too Much Pinion?

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JRod01

JRod01

Jesus is my Savior!
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Recently had the 8 3/4 rebuilt and upgraded to a 1350 size yoke (Yukon Brand). The driveshaft remained 7290 so I installed a 7290/1350 hybrid U-joint. Everything went together fine and during the startup/check, the wheels have a very noticeable hop once every rotation. Is there something I've missed during the install? I realize that's hard to determine since you have only one picture to go by. But changing the size of the yoke shouldn't have changed anything else. Your input is always much appreciated, thank you!!

64928734243__BC4DBE55-50B9-43C3-91A8-F2514CA1A723.jpg
 
Is there a chance of binding between the new, bigger yoke and the driveshaft? As above, load the suspension; then rotate the shaft. If you still don't see it, disconnect the driveshaft and see if you can "feel" it in the diff, as you rotate the yoke.
 
make sure your car rear suspension is loaded with the weight of the car before you mess with anything all measurements must be made with the weight of the car on the rear axle. this website should give you the required info you need to fix the problem, from the pic you posted your diff angle seems way to low the angle of the diff upward and the angle of the transmission downward must be equal and opposite (example if the trans is 3 degrees down then the diff should be 3 degrees up so both u joints are spinning on the same plane so as not to bind)

I am no expert on drivelines but this basic info should be able to get you started

Spicer Driveline Operating Angle Calculator
 
Watching this thread.

That angle looks very poor to me to start with! I just looked under the car on jack stands as a reference.

Factory spring mounts on the tubes?
 
I’m running a 3 inch drive line with 1350’s on both sides in my Duster. Have had both a 742 and 489 cases in. (different ratios in each) both with adjustable snubbers and no issues.

Even with the rear drooping, you should be able to spin the tires and axle smoothly.

What else did you change while having the pig rebuilt? You change axel bearings? Brake job?

As the other guys said, check the pinion angle.
 
Others are right about one thing.......you need to get the weight on the axle housing

ARE YOU SURE the slip yoke is not bottoming into the transmission/ trans shaft? Hell there could be a BIG ROCK that somehow got down into the slip splines
 
royslead said:
Is there a chance of binding between the new, bigger yoke and the driveshaft? As above, load the suspension; then rotate the shaft. If you still don't see it, disconnect the driveshaft and see if you can "feel" it in the diff, as you rotate the yoke.
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Super quick update:

when i turn the tire by hand, 3/4 of the rotation of the yoke is smooth, then come to a hard stop. If I really push the tire/yoke will complete the rotation. It could be a cap in the yoke? Nothing is physically binding and I don’t think the pinion angle is wrong, it’s something with the u joint. Thank you for all the help and o”pinions”!
 
Well remove the shaft and move the joints around................You'll soon feel them. And like I said, make darn sure the yoke is not bottomed at the trans
 
JRod01 said:
Super quick update:

when i turn the tire by hand, 3/4 of the rotation of the yoke is smooth, then come to a hard stop. If I really push the tire/yoke will complete the rotation. It could be a cap in the yoke? Nothing is physically binding and I don’t think the pinion angle is wrong, it’s something with the u joint. Thank you for all the help and o”pinions”!
Click to expand...

What kind of U joints? Serviceable or non-serviceable?

Pull the drive line off the yolk and move the u joint by hand. Should be very smooth and somewhat tight. Do the same on the slip yolk side and look in the tube as @67Dart273 said. Something is out of sort..
 
You can tell just by looking at it that the driveshaft is coming in at too steep of an angle, and the larger U-Joint is exaggerating the problem.

Screenshot_20210729-222132_Gallery.jpg
 
If an automatic trans car, then you are turning the output shaft and the planetaries and dragging the band , AND slipping the over-running clutch. So; how can you know which is doing what?
Best advice was to split the driveshaft off, then check it again.
 
oldkimmer said:
So the info once again falls on deaf ears. Asked for help. Got it. Ignored it. Touche’
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Right. The stupidness never ends. I'm not even going to give my 2 cents. A dollar's worth has been given and ignored.
 
oldkimmer said:
So the info once again falls on deaf ears. Asked for help. Got it. Ignored it. Touche’
Click to expand...
I didn’t ignore any of the help. I haven’t had a chance to work on the car again yet. I always appreciate the input given here.
 
Scody21 said:
What kind of U joints? Serviceable or non-serviceable?

Pull the drive line off the yolk and move the u joint by hand. Should be very smooth and somewhat tight. Do the same on the slip yolk side and look in the tube as @67Dart273 said. Something is out of sort..
Click to expand...
They are serviceable. It’s all brand new. I’ll get back at it this weekend. Thanks for everyone’s help and patience.
 
JRod01 said:
Thank you very much for that!! Anxious to find the problem. Haven’t driven the car in 9 months so when this happened it was pretty defeating.
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Yeah, our car projects often are a "slow motion" deal. We put a lot of time & money into them and sometimes we need to take a step or two back and regroup. It's all part of the show!
 
A lot of times people get on here askin for help and then say something like "the car's not here right now" or "I caint get to it till next week" or some such.....and it's all good, but I think sometimes when that happens, we kinda get antsy. Everybody wants instant gratification. lol
In my opinion, somehow you've ended up with the pinion angle WAY low and that's puttin at least that rear u-joint into a bind. The pinion and transmission output shaft center lines are supposed to be parallel and I cannot see anyway in the world how the transmission output shaft can be parallel with the pinion. It's just too far down.

Good luck with it and keep us posted.
 
JRod01 said:
Super quick update:

when i turn the tire by hand, 3/4 of the rotation of the yoke is smooth, then come to a hard stop. If I really push the tire/yoke will complete the rotation. It could be a cap in the yoke? Nothing is physically binding and I don’t think the pinion angle is wrong, it’s something with the u joint. Thank you for all the help and o”pinions”!
Click to expand...

well there is something to overnighting the u-joint caps, most u-joints tightening specifications is a lot less than you would think. AND IF you find that the pinon angle is too low no need to worry they sell angled shims to correct for improper pinon angle so no need to cut and weld new spring/axle perches.
 
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devilchicken said:
well there is something to overnighting the u-joint caps, most u-joints tightening specifications is a lot less than you would think. AND IF you find that the pinon angle is too low no need to worry they sell angled shims to correct for improper pinon angle so no need to cut and weld new spring/axle perches.
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Step 1. Pull the driveshaft, and check the rearend. Its probably fine, but.....
Next, check both ends of the shaft for bad joints.
If its the pinion angle binding, angled shims is a quick and easy solution. Mine are installed to get the pinion down more, i suspect yours will need to be installed opposite. (Installed in a low 11 sec, 122 mph car). Sbims available from two to six degrees.

20191124_100112.jpg
 
JRod01 said:
Super quick update:

when i turn the tire by hand, 3/4 of the rotation of the yoke is smooth, then come to a hard stop. If I really push the tire/yoke will complete the rotation. It could be a cap in the yoke? Nothing is physically binding and I don’t think the pinion angle is wrong, it’s something with the u joint. Thank you for all the help and o”pinions”!
Click to expand...

You need to back up here, think about this.

If it was a U-Joint problem it would get tight on the yoke at 1/2 rotation, not 3/4 rotation, like you are saying.

Leading you to the ring gear on your freshly rebuilt 8 3/4 chunk that is not seated squarely on the differential housing, probably a steel burr under on edge if it, or it was torqued unevenly. This should have been caught on the ring gear backlash setup, probably did not do the full rotation check of the backlash.

Like putting all the bolts in the ring gear, then starting at 12:00 o'clock with the impact wrench and going around the clock till they are all tight, instead of tightening in an X pattern in increments as you bring up the torque going around it multiple times.

Next step, pull the driveshaft off and rotate the yoke by hand 360° multiple times and make sure it is rotating freely with no binding.

Could even be some debris in the new carrier bearings slowing the roll.

Once the chunk checks out then move forward. Making sure the new driveshaft length is not bottoming out in the transmission. Rotate the driveshaft by hand with the transmission in neutral to make sure that is turning free on full revolutions before bolting the driveshaft up to the yoke at the rear end.
 
JRod01 said:
They are serviceable. It’s all brand new. I’ll get back at it this weekend. Thanks for everyone’s help and patience.
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An FYI. Non serviceable U joints are what is wanted if your running a motor that is more than stock. The serviceable ones have a built in weak spot right where the zerk fitting hole was drilled..
 
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