Rear end " refreshing "

[That Guy]

I am resurrecting this because it’s a continuation and an update.

Just before Christmas I had the Ford Performance rear differential rebuild kit and decided to just bring the car and the parts to a shop. Figured it was a good time to do it and they just charged me labor. While the car was in the shop, the mechanic called me. He said he had it apart and asked if I wanted to look at it, so I did. The pinion bearing had some discoloration and didn’t look great. The ring gear had some scale on it. I assume it may have been rust, but it didn’t look that bad. The mechanic said we could change the gears out (and id like to go to 3:73), or run it and see how it went. He put it back together and the issue persists. He suggest it may be the scale on the gears or could be the carrier bearing on the driveshaft. I decided to drive it through a couple tanks of gas to see if it got better or worse (while also saving pennies for an upgrade). The issue is still there. It makes a rotations whir-whir-whir under low speeds and acceleration. As speed increases, the whirs become one rushing sound. The mechanic doing the work is a real mechanic. He speaks knowledgeably about differentials and is pretty much a gear head. He said the pattern and backlash were checked and good when he put it back together. I feel confident in him.

Tonight I put the car up on my lift, started it and put it in gear. I used a mechanics stethoscope to listen to the carrier bearing, different areas of the differential, the wheel bearings, and various other things just because. The carrier bearing sounds smooth. There is a little play in it, but I don’t hear a whooshing sound as it rotates (I’ll try to attach a video). I do however hear the whooshing sound right where the pinion bearing would be (see attached pic, area circled in red).

So, here are my thoughts, that little build up on the ring gear could be an issue, I could redo the fix with new (more fun) gears. I could go to a 1 piece driveshaft and see if that fixes it (gets expensive to throw parts at it). One other thing that came to mind is that the car is lowered (by previous owner). I know from my Jeeps, the pinion angle matters. I think my car is lowered 1-1.5”. I’ve read that 1.5” lowered may cause pinion angle issues. I suppose that could possibly be it, and I could get an adjustable upper control arm and work on the angle.

I welcome anyone’s thoughts and advice. I’ll keep working through it.

I couldn’t get the video to upload here of the play in driveshaft. I uploaded a short to YouTube. Here is the link. I hope that’s acceptable.

Thanks,
Erik

 

[GriffX]

I had the same, a whoop-whoop at 5 mph and later a more and more grinding noise at high speed. The big pinon bearing had an uneven wear to an oval shape in the bearing race. I changed it - gone.
To the driveshaft middle bearing, I started a thread to this "driveshaft balancing" or so. I made it also better, will do something about it again in this winter.

 

[brasil]

hi Erik. For me .. the center bearing support of your driveshaft is gone .. so I think it is time for a one piece DS

 

[GriffX]

There are different versions of the support bearing out there. Mine is on the right and it has also a big play like in the video.

 

[That Guy]

Thanks for the replies. I appreciate the insight. I’ll keep working through it and post back what I find.
As far as my carrier bearing in the DS, I figured that could be it, but with my mechanic stethoscope, it really sounds uniform. The whoosh whoosh sound is prominent in the front pinion bearing area. With that being said, I bought new gears (because I wanted 3:73 anyway), bearings, carriers and the whole kit. Now I need to find time to tackle it, or money to pay someone.

Erik

 

[Broncin491]

Mine is making the same whir whir whir noise when slowing down, and grinding when going faster. It’s definitely coming from the rear end from what I can tell. Also, whenever I go to slow down or I’m coasting with my foot off the gas, at around 30 or lower sometimes you hear a light tap tap tap sound every now and then, and it sounds like it’s coming from the rear end also. Please keep me updated whenever you fix yours, and figure out what’s going on. I think I’m just gonna end up having to rebuild my whole rear end also.

 

[That Guy]

Here’s an update (kind of). I finally have all the parts I need to change bearing and gears to 3:73. After we went to a car show this weekend I decided to put the car on the lift and play with it. I disconnected the driveshaft at the rear and then moved it out of the way. I then had my son spin the wheel as fast as he could while I listened to the pinion bearing (where I heard the noise before). It was smooth. So then I hooked the driveshaft back up and had him spin the wheel as fast as he could so the driveshaft would spin too. He couldn’t spin it as fast, but with the DS hooked up, I could hear a slight whir-whir-whir. I had my son listen too and he agreed it made the faint sound when the DS is hooked up.

So, it may be the driveshaft. It has 160K miles on it. Today I ordered a one-piece DS. It should be here later this week, but I am out of the state until next Monday. I figure the rear end bearings were done at the end of November at a reputable shop. It is easy for me to change out the DS. I figure if the DS fixes it, I’ll be happy, and I can install gears when I get to it. If it still has the whir, I’ll change gears and bearings sooner and see.

On a side note. I know drive train vibrations can resonate and sound like they are in different areas. My carrier bearing sounds fine when I put the stethoscope on it. There must be a joint of some sort at the rear that allows the shaft to wobble. Maybe that is the culprit? It’s the joint circled in my attached pic. Hard to listen to that joint with a stethoscope while shaft is spinning. I also like to stay clear of spinning driveshafts

 

[JC SSP]

Those stock two piece DS are known to have issues. Put in the one piece DS and see if that take care of the issue.

Which DS did you go with?

 

[That Guy]

Those stock two piece DS are known to have issues. Put in the one piece DS and see if that take care of the issue.

Which DS did you go with?

Ordered the Ford Performance aluminum. Will see what kind of difference it makes.

I’ve heard the two piece are notorious for noise. Read a lot on the topic. Seems odd that Ford would go two piece on a car like this. It’s heavier, more maintenance, and it has to be more expensive to make and maintain. I do see the benefits in a lifted truck or a longer vehicle. I suppose a two piece is more forgiving on the pinion angle. My carrier bearing sounds is lowered about an inch or inch and a half. I’ve read that’s not enough to upset the pinion angle, but we will see. I’ll post back my results some time next week when I am back in town.

 

[That Guy]

***Double post. Sorry

 

[GriffX]

There must be a reason for two piece DS, because all cars I know use them. But the carrier bushing design from Ford is awful. Never seen this strange rubber mesh stuff. Usually they are rubber bellows.
One benefit I see is that the joint in the middle dampens force peaks from the transmission. You will see the wheels will breake lose much easier with the one piece.

 

[That Guy]

There must be a reason for two piece DS, because all cars I know use them. But the carrier bushing design from Ford is awful. Never seen this strange rubber mesh stuff. Usually they are rubber bellows.
One benefit I see is that the joint in the middle dampens force peaks from the transmission. You will see the wheels will breake lose much easier with the one piece.

I have not removed the driveshaft entirely yet. When I do, I want to take it apart and see what it looks like. See what is worn. If it turns out the DS is the source of the noise, I’d like to try to identify the point of failure.

 

[asdrew]

.. Hard to listen to that joint with a stethoscope while shaft is spinning. I also like to stay clear of spinning driveshafts

lol, wise decision

 

[That Guy]

lol, wise decision

Had a buddy get caught in the PTO of a tractor in HS. He lived, but got mangled. Best to learn from other people’s mishaps in my opinion.

 

[GriffX]

I have not removed the driveshaft entirely yet. When I do, I want to take it apart and see what it looks like. See what is worn. If it turns out the DS is the source of the noise, I’d like to try to identify the point of failure.

I remember that some had a CV joint failure, it is changeable, but don't know if you need special tools for it.

 

[That Guy]

I remember that some had a CV joint failure, it is changeable, but don't know if you need special tools for it.

With 165K miles on it, I am just going to change it out. It's easy enough to do.

 

[brasil]

The 2 piece design was made for a quiet ride and probably for higher speeds. The 4.0 has a one piece DS .. but is limited to 110 mls .
The older Stangs , all had one piece DS

So for me a one piece DS is ok .

 

[Broncin491]

Well please keep this post updated at any point if you figure it out! I’m at 170k miles myself, we could be having the same problem. I have just ordered the ring and pinion,and all bearings. Everything just short of a new differential carrier. May as well do everything if I’m going to do it. But if it turned out to just be my drive shaft, I would be so angry after rebuilding the whole entire rear end! But mine and your problem sounds very similar. I haven’t even been driving mine at all because I’m worried it’s gonna crap out on me at any moment lol