Differential Experience Help PLEASE!

[dcoland70RR]

Hello, So I am by no means a greatly experienced fully experienced mechanic. But, I have done many many things over 20 years to cars. So one thing I have never worked on a vehicle is a rear end. My 1970 roadrunner was leaking at the differential. After some investigating and some info from a mechanic I pulled the axles slightly out and removed that very heavy gear assembly where the cover is attached from the front. I found no gasket, only a small deteriorated amount of silicone there. Cleaned it all up and put a new gasket on and after that big job to re place a 4 dollar gasket, NO LEAKS< Perfect.

This is where I need help. SO while the gear housing assembly was out I twisted the posi unit to the left and right by holding the input area that the drive shaft bolts to. I was able to move the input shaft a small maybe quarter of an inch to the right before the gears would start moving and the same to the left. So I ASSUMED the gears are worn out from being likely original, almost 50 years old. I took the beauty out last weekend on 2 different days for over an hour cruise and after about 40-50 MPH I am getting some odd vibration feeling through the drivetrain that appears to be coming from the back of the car, like the rear end. But not certain. I am thinking since the car has a recently balanced driver shaft with new joints, new leaf springs and shocks. This is most likely the sign that the rear end needs new gears?

If it is most likely I need to rebuild the gears in rear end andy brand recommendations? Do I need new axles too? Or how to check them?

I appreciate the help because I enjoy figuring things out with help here versus paying a mechanic from a shop a small fortune to do this.



Thanks

 

[66Satellite47]

INMO the rear axle/gear will not create a vibration. Your gear play, side to side sounds good. Pull the driveshaft out turn around, see how that works. Seems like a driveshaft orientation issue.

 

[Cranky]

Did you mark the driveshaft and yoke so you could put it back together as it came apart? Did one or both u-joint bearing cups come off at any time? If so, one or more of the needles (needle bearings) could have fallen out. Make sure they are all in the cups. You can tell if they are all in there because there will be NO spaces or gaps. Also, when you pull the axles if ever again, pull them all the way out instead of letting them hang part way out. When you pull them part way out, they are resting on the axles seals and they are not exactly light. Also, make sure the driveshaft is in place like it's supposed to be. And unless you are hearing gear noise...whine or howl, it sounds like they are ok. That little bit of slack is normal and the pinion to ring gear clearance is called back lash.

 

[Frank Mopar]

Not to rain on a parade but its not called a posi. Sure grip or limited slip is proper. The Mopar crowd will appreciate that.

 

[Cranky]

Yup....lol. A buddy of mine still calls them a posi (GM term) after correcting him several times years ago. Thought maybe he was just trying to get under my skin so I quit correcting him but, nothing changed so I call him just another GM flake

 

[beanhead]

Cranky's post is right on (I think he might have done a few of them!) Did you set the axle end-play after putting it back together? It's how you get your proper axle bearing clearance(not causing your vibration problem)but important nonetheless

 

[PurpleBeeper]

INMO the rear axle/gear will not create a vibration. Your gear play, side to side sounds good. Pull the driveshaft out turn around, see how that works. Seems like a driveshaft orientation issue.

Great point 66!

 

[dcoland70RR]

Thanks all, it had that minor vibrate at speeds before taking it out to replace gasket. Just not sure how much play is normal for it or not when turning it by hand. Thanks for the proper learning correction of sure grip or limited slip. Learning is key to Mopar Love

 

[dcoland70RR]

Did you mark the driveshaft and yoke so you could put it back together as it came apart? Did one or both u-joint bearing cups come off at any time? If so, one or more of the needles (needle bearings) could have fallen out. Make sure they are all in the cups. You can tell if they are all in there because there will be NO spaces or gaps. Also, when you pull the axles if ever again, pull them all the way out instead of letting them hang part way out. When you pull them part way out, they are resting on the axles seals and they are not exactly light. Also, make sure the driveshaft is in place like it's supposed to be. And unless you are hearing gear noise...whine or howl, it sounds like they are ok. That little bit of slack is normal and the pinion to ring gear clearance is called back lash.

I did not mark it but all is back together well. When I pulled axles slightly out, first time ever in life, I gently put the ends on jack stands to avoid it from slouching down and to help no damage. No caps fell off the u joints at all. Drive shaft appears exactly where it is suppose to be. On jack stand moves freely easily, I double checked all tightened bolts, etc, and no problems at all found. Not sure exactly what it is but sounds and feels like a vibration at higher speeds. Took it out few hours ago and that vibration feeling coming from back end started to happen at lower speeds now. I believe it is the rear end. I am not a rear end specialist at all but if the teeth on gears were slightly worn out I would assume they would maybe somewhat vibrate at speeds if the gear teeth were almost starting to round out?


Thanks

 

[Cranky]

With gear wear, they will more often whine or howl than cause vibration. The gears in my diesel have been crying at me for years but no vibration but those are not the only times I've had bad gears. I let a 3.91 go dry in a Dart years ago and that thing got loud but wasn't vibrating. I drove it like that for many months before finally parting out the car. The gears would have to be pretty bad off to cause vibration imo. Even gears that are pitted from sitting for too long usually run quiet and do not vibrate. What did they look like when you had it out? Something really worn out will usually be noticeable.