Rear Diff Help: 5.4L, 4WD
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Rear Diff Help: 5.4L, 4WD
All,
Need some basic questions answered if you could. I have a whine coming from my rear diff. I just replaced my rear wheel bearings and seals so I know it's not that, plus, if I have the rear up on jack stands I can hear the whine coming from the rear diff. So here is my list of questions.
1) my tag says I have a 9.75 rear diff. I replaced my rear diff cover with a 9.75. When I did my rear bearings I went to Autozone and bought the bearings and seals for a 9.75, and they were too big. I had to get the 8.8s. What gives? Just a glitch with their catalog system? Just has me wondering what parts to buy for my truck. I am right with the 9.75 right?
2) my truck has 130K miles on it. I don't see a lot evidence of wear on the ring and pinion, but I'm no expert for sure. What are the chances it is just the bearings and not the ring and pinion? I'd hate to replace the bearings and then find the gear lash is making the noise and then have to buy another set of bearings/seals plus a new ring and pinion. Is there any way for me tell?
Thanks.
Matt
Need some basic questions answered if you could. I have a whine coming from my rear diff. I just replaced my rear wheel bearings and seals so I know it's not that, plus, if I have the rear up on jack stands I can hear the whine coming from the rear diff. So here is my list of questions.
1) my tag says I have a 9.75 rear diff. I replaced my rear diff cover with a 9.75. When I did my rear bearings I went to Autozone and bought the bearings and seals for a 9.75, and they were too big. I had to get the 8.8s. What gives? Just a glitch with their catalog system? Just has me wondering what parts to buy for my truck. I am right with the 9.75 right?
2) my truck has 130K miles on it. I don't see a lot evidence of wear on the ring and pinion, but I'm no expert for sure. What are the chances it is just the bearings and not the ring and pinion? I'd hate to replace the bearings and then find the gear lash is making the noise and then have to buy another set of bearings/seals plus a new ring and pinion. Is there any way for me tell?
Thanks.
Matt
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Gigger,
I think what you are saying is to grab the pinion where it meets the gear ring, right? Does that mean that if there is play in it that the pinion and gear rings are worn and need to be replaced? Otherwise I just do the bearings and seals? Thanks.
I think what you are saying is to grab the pinion where it meets the gear ring, right? Does that mean that if there is play in it that the pinion and gear rings are worn and need to be replaced? Otherwise I just do the bearings and seals? Thanks.
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Got it. So on the pinion yoke side if there is play, then I am assuming the diagnosis is the bearings are bad. If I have no play from that side, then it's got to be worn gears -- either the pinion or the ring gear. Would you buy a kit and replace all the bearings located on the pinion while you have it apart, or just the outer bearing and seal? Hey, this may be a prime opportunity for me to buy a shop press!! 
Slow learner, thanks for the tip. Appreciate you helping the do-it-yourself-er.
Slow learner, thanks for the tip. Appreciate you helping the do-it-yourself-er.
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Nope, it gets softer proportional to the RPMs, sort of like cupped tires would sound. Hope that makes sense. Would what you describe be another indicator of lash, essentially because the gears aren't tight?
For those of you who are like me who want to know more about the rear diff of your F150, check out this YouTube video - it's a great resource --
YouTube - Rear Differential Gear Swap on Ford F-150
For those of you who are like me who want to know more about the rear diff of your F150, check out this YouTube video - it's a great resource --
YouTube - Rear Differential Gear Swap on Ford F-150
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Gigger,
I crawled underneath. In neutral, there is no play up and down. If I have it in neutral or park, there is a little rotational play if I turn it clockwise or counter clockwise, like an eighth of an inch, maybe a little more...but nothing up and down.
Doctor?
I crawled underneath. In neutral, there is no play up and down. If I have it in neutral or park, there is a little rotational play if I turn it clockwise or counter clockwise, like an eighth of an inch, maybe a little more...but nothing up and down.
Doctor?
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If you are sure the tires are fine then I would say pinion bearings, is the pinion seal leaking? Was it ever low on gear lube?
You can run the truck in the air and listen to the rear diff with a stethascope or long screw driver to try & pin point where the noise is coming from.
Sometimes we dont hear the noise in the air with no load on it.
If the noise is not that bad them drive it till you can get another opinon at a local shop.
You can run the truck in the air and listen to the rear diff with a stethascope or long screw driver to try & pin point where the noise is coming from.
Sometimes we dont hear the noise in the air with no load on it.
If the noise is not that bad them drive it till you can get another opinon at a local shop.
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I have put it up on jack stands and run it -- the noise is definately coming from the rear diff and not the tires or the axle bearnings (that I just replaced). I just didn't know if it was the pinion bearings or noise from the pinion and gear ring. It did run low on fluid at one point, I had a leaking seal on the rear passenger side axle. It's not something I noticed right away, but I also don't think I was super low on fluid. Low enough though to cause me problems obviously.
I was hoping it was just the bearings, but from what you are saying I think I need to replace both the gears and bearings -- unless you tell me different. I know it's a little hard from my description.
I was hoping it was just the bearings, but from what you are saying I think I need to replace both the gears and bearings -- unless you tell me different. I know it's a little hard from my description.
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forgot to mention -- I'll try the stethoscope tomorrow and if it's noise toward the yoke I'll go with bearings, but if I can't really point point it, sounds like I need to replace it all. Thanks.
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I still think pinion bearings, usually we dont hear ring gear & pinion gear noise in the air because there is no load on them, if you pull the axles, the drive shaft, diff cover, ring gear with spool then with only the pinion left in there all you feel are the pinion bearings, if it feels rough, there's your problem.
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Makes total sense. One last question. If you noticed my first post, when I went to Autozone and got my timken axle bearings, I got the ones they listed for 9.75, and they were too big. I had to go with the ones they had listed for 8.8. This made no sense, but I'm a little gun-shy.
My tag says 9.75, I have a 2000 5.4, with the off road and tow package. I'm not nuts, right? 9.75 is correct.
Thanks for your help today.
My tag says 9.75, I have a 2000 5.4, with the off road and tow package. I'm not nuts, right? 9.75 is correct.
Thanks for your help today.
FTE Legend
Joined: Mar 2009
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From: North Bay Ont Canada
Yes I did read that, you might take that tag to Ford & they will tell what it is for sure, why would it have the smal axle bearings in there I dont know, its might be an 8.8
If you feel that I have helped you I will accept rep points, its that little red heart on the upper right, thx Gigger
If you feel that I have helped you I will accept rep points, its that little red heart on the upper right, thx Gigger