I have a 2000 F-150 4x4 with the 9.75 inch 3.55 rear end. Truck has 87,000 miles on it. Coming home from a long trip about 150 miles from home I started hearing a whinning coming from the rear. I got home and no leaks. Took the rear cover off and the oil looked fine draining. No metal flakes or sparkles. So I backed it into the garage and took the brakes and rotors off. Put it in gear with the diff cover off and pin pointed the sound to the pinion area. I looked at my rear u-joint(which I replaced to to see if it helped) it's good. I checked my pinion an no play what so ever. I spun it as fast as I could and no noise. So I took the nut and outer bearing off and seen a little bit of scaring on the bearing but the race was good. I looked at my inner bearing the best I could and didn't see anything out of the ordinary. Here is where it gets interesting. I put it back together and tightened the nut until there was no play in the pinion again. Fired it up and put it in drive. Noise was pretty much gone. So I gave it a bit of gas and the noise returned. I am going to order the outer bearing tomorrow and replace it to see if that helps. I was wondering if anyone had any inputs or knows of a problem like this and what they did to fix it. If the outer bearing doesn't work then I guess I will have to rebuild the pinion to change the inner bearing. My other question is that my co worker says if I rebuild the diff or even just the pinion then I might as well buy a new ring and pinion because we will not be able to get the wear pattern dead on again and it will make noise or grove a different pattern. Can someone confirm or deny this? I mean my co worker I know has done a few diffs but the cheapest set I found was 800 bucks. I really don't have that kind of money to spend right now.

I would appreciate any help people can give me. Thanks.
Shawn

 

First of all, if I were you, I would just go ahead and have the whole thing rebuilt. I'm kinda drunk so I may be wrong, but you said that the only gear set you could find was $800?!? The most expensive one should only be around $300-350. You really don't even need a new ring and pinion, although it may not be a bad idea. If you're strapped for cash, get a master install kit and some axle bearings/seals and spend the $300 to have it rebuilt. Your friend is right in that if the new wear pattern doesn't match exactly with the one that's already worn into the gears you may have some noise. However, it will be nothing compared to what you are experienceing now. I would be willing to bet that if you just had it rebuilt with new bearings you would be perfectly happy with it and would probably never have another problem.

 

$800? Geez - I can buy a whole 9.75" 3.55 LS disk axle for about $400 used. Where are you?

 

you may as well change it out. if wanted, i have the stock one out of my 2002 f150 2wd. it's a 9.75 3.55 ring and pinion with no scarring on it. it's got about 30k miles on it. I don't really recommend it, but if you are in a crunch for money, make an offer.

second, get a master install kit. it will have all the bearings, shims, and races that you are going to need.

i switched from a 3.55 to 4.10 gears in my truck and absolutely love them

 

as crash lucky mentioned a master install kit has everything you need, i just wanted to add that they are less than any of those prices you mentioned. you need to consider your ring and pinion are probably fine, you probably just need a new bearing somewhere and it never hurts to replace them all.

also, do you have any way to mic your backlash? i set mine in my truck at 10 thou and my motors book asked for 12-15.

 

Thanks ya'll for the responses. Yeah my buddy has a backlash gauge but we haven't tried it. As far as the prices go. I have found cheaper ring and pinion sets but they are different ratios. I have only found 1 website that has the 3.55 gears and like I said it is almost 800 bucks. I was thinking if I do have to rebuilt it then maybe going with 3.73 gears But th rebuild will have to wait awhile if I do that. I will try the outer bearing today and see what happens.

 

dude, Motive gears.

can get them for $385 delivered for front and rear ring and pinion for a ford 9.75 3.55 gears...

 

Most the time, its the inner pinion bearing bad. I would just get new bearings for the pinion and diff. If you don't see any pits on the bearings than it could possible be the gears. You started your teardown to soon. A wine under load but goes away on coast generally is gears, but could be a bearing that is just starting to go bad. Gears like to wine around 60 to 70 mph also. Badly pitted bearings growl all the time and generally their is glitter in the oil. Carrier bearings change as you turn from side to side kinda like a axle bearing.
If you find small pits on the inner pinion bearing, replace all and put all the shims back where they came from. I have overhauled hundreds and never had a problem with a one.

 

Klitch, trucks backlash is 5 to 10. Cars are 10 to 15 with 12 being the best for a quieter operation. Trucks are tighter, they are not as concerned about the quietness. Also never drive the diff shims in with a hammer, they love to break. If I can't find the correct tool, I use the handle on my hammer as a drift to drive it in while tapping with another hammer. It should be very tight.

 

wonder why my motors manual says 12-15 for a f150 with 8.8 equipped? friggin chiltons bought them out i think!

 

Just looked in the Ford Service manual. On an 9.75 it is 8 to 15. I must been thinking of the bigger rear ends. I generally shoot for 8 to 10 on a pickup and 12 to 15 on grandmoms CV. Mustangs, if driven hard, I do the same as pickups.

 

Thanks everyone. I found my problem. It's the inner bearing on the pinion. We narrowed it to the pinion and I replaced the outer bearing Thursday and the noise hasn't changed.

rdeeno-It seems you have done a couple of these do you think that I should change out my ring and pinion? Or do you think I will be ok just changing bearings and seals? I would rather just buy a master install kit and do that but I also want to do it right the first time and don't want to have to replace it again in 10000 miles. Can I get some opinions on what ya'll would do?

Thanks again for all the help. You guys rock. Shawn

 

If you find a bad bearing, then I would just replace the bearings. Use good ones like Timken (is that right) that is generally what Ford uses. Most the time, the factory shims will still work right. Stay away from the cheap bearings, their fit is sometimes questionable. I always lightly pack all the bearings with grease during installation. LOL