Hott Diff 3.73

[wiwaniuk]

Okay guys, here goes my first request for info. My '03 F-250 7.3 has started to exhibit what sounds to me like something metal rubbing together behind or under the cab. I have spun the driveshaft as fast as I could by hand, but I have not been able to recreate it. I have dropped the shaft centering bearing and it appears pretty smooth in its operation. I have felt the universal joints and they appear to be all right. Oh yea, the sound is repetitive and its frequency increases with forward motion of the truck. Tonight I crawled under there to feel for something warm and I believe I found it. The rear differential is hot to the touch (120 degrees or higher) from the pinion back to the rear cover. Is it possible for the clutch pack to slip and make this noise or is this normal? I have never experienced a rear diff this warm before aside from the middle of the summer. I am planning to change the rear diff oil tomorrow so that I can check for water or other foreign material. The truck's diff is the 10.5 limited slip. The truck has 44k miles on it. Any ideas or suggestions? Thanks!

[Rodslinger]

I've never had one too hot to touch that's for sure. You're doing the right thing though by draining it and checking for shavings, or any pieces of metal. If you jack up the rear end, put it in neutral and spin the tires can you re-create the noise? I don't mean fire it up and put it in gear, just manually turn it......unless you have someone you don't particularly like that would be willing to crawl up under there.


Oops! I re-read your post and you did say you spun the drive shaft and it didn't make the noise. Well let us know how it goes after changing the diff fluid and if it's still doing it we'll come up with some other ideas. BTW - what type of diff fluid are you putting back in?

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Last edited by Rodslinger : 11-03-2005 at 03:45 AM.

[wiwaniuk]

I'm going to install Amsoil 75w-140 with 8 oz. of friction modifier. Thanks for the feedback!! I'll keep you posted on the outcome.

[wiwaniuk]

Well, Rodslinger, I changed the gear oil. I have not driven the truck yet as I am waiting the hour for the RTV to dry. The old oil was dark; it also had a foul odor the likes I have never smelled before in a differential. The gears looked really good. The inside of the differential housing was covered with a powder gray-colored substance that wiped off pretty readily. My guess this is from the clutch pack. I do not know if this is normal for 40k worth of use. Any thoughts??

[Rodslinger]

Nah wiwaniuk you're alright. It stinks and the grey is normal - I say normal but I've probably done it 20 times to different vehicles and they've all had it. As long as you didn't see any real metal or worn teeth, etc. you're fine. When the rtv dries and you give her a spin let us know if you still have the noise. Heck if nothing else it didn't HURT to change the diff fluid at least.

[wiwaniuk]

Back at you, Rodslinger. Thank you for your reply. I took the truck for a weekend excursion (no pun intended) towing my travel trailer - went to watch the open-wheel Modifieds race in Concord, NC. The truck was quiet most of the way. Sometimes the noise returned I think when I turned sharply. It was pretty loud just driving around Concord unladen. Once I hooked up the camper again, it got quiet. I am about ready to prop up the rear axle and try to recreate this sound at home (or if I come to my senses in time, take it to a garage with a frame lift). In my heart, I believe it could be the drive shaft centering bearing. Whatever it is, it's most annoying, but does not appear to be affecting the truck's operation right now. The truck was either driven up north or on the beach (rusty scale on unprotected driveline parts has always indicated a corrosive environment such as road salt to me). That is part of the reason I am thinking that way. Any experience with this?

[Rodslinger]

Shoot buddy I wish I could hear it. Is it a 4x4 by chance?

[wiwaniuk]

Yes, it is a 4x4. I have the noise whether I am 2x or 4x. Thanks for your response.

[Rodslinger]

I had a strange noise coming from mine every time I turned after the first time I took my FX offroad. It would make it when I turned mainly. After taking it to the dealer they determined that one of my "auto locking" hubs hadn't unlocked - even though I manually locked and unlocked 'em before I went onto the ranch. They fixed it and it hasn't done it since.