LONG: Help diagnose rear diff noise - 1997 Cobra

Is there a change in pitch when you let off of the gas at higher speeds? If the noise changes pitch with heaver throttle it sounds like the pinion bearings. And if you have the rear end already torn down you should also check your backlash on you ring. "shouldnt be more than .010".

My guess is carrier bearings.

Thanks for the replies. I think its pretty much impossible to figure out whether its pinion or carrier, so I am going to replace the whole schmeer to be sure.

New questions:

1) Does a new pinion bearing require a new race? I have always assumed they get installed in pairs.

2) If I get a new pinion bearing, do I need to reset/check pinion depth?

3) (as above) Do new carrier bearing require new races, and if so, do I need to confirm/set backlash with the new bearings/races?

I am all set to replace the outer bear> >

When you replace your carrier and pinion bearing's you always need to replace the race because it has worn to the previous bearing and would either cause scoring or noise. When replacing the pinion bearings you will have to reset pinion depth, but usualy you can reuse the same shims and be pretty close. The carrier is a little more tricky, after you install new bearings and races you need to check your back lash and you are going to need marking compound to see your gear mesh pattern. Is your cobra stock? A taller gear is always a good Idea for modular cars do to the heaver weight, go with 4.10 or 4.30 but you will loose top end. Now if you have boost then I would go with 3.73's

I just discovered the source of that noise in my own '89 5.0 LX Sport. Mine had gotten to the point of being shaky at 90 mph. I kept hearing noise then I noticed clunk clunk as I got on and off of the gas. I thought gearset and bearings but I could find no slop in mine and the patterns were dead on front and back so..... I thought it is just the polygraphite bushings making the noise and 'gear clunk' and high speed vibration more pronounced. I knew that wasn't right and I was getting ill about it. I had even spun the axles up on a lathe to make sure they weren't twisted. Then one night I was adjusting the valve lash on my 1965 11:1 293 (289) CID fuel injected Ford small block that is hooked to this rear end thru a T5 and it came to me. The differential bushing indirectly supports the inside end of the rear axle by directly supporting the side gear. With the side gears and the clutches retained by the spring, it isn't evident that there is any play inside the carrier. I had even taken my clutch pack apart and restacked it still not noticing the slop, in one side in particular, of the side gears because I didn't think to set the side gears in place without the clutches there.

I had already changed my outer rear bearings and checked the axle races for wear and concentricity.

I have allot of nine inch stuff and a big steel table, I was thinking about jigging the table up with the 8.8 and putting nine inch ends on it. The reason for that sudden change of subject was side load. The retainer grooves and ends of my 8.8 axles were blue. There were marks in the gear pin where the axles had briefly touched it at some point before. It seems to me that this side loading of the carrier bearings is just not good. Not to mention the possibility of popping one of those lil buttons off of the end of an axle.

My two Cent. D

____SNIP___

Well you lost me:) The axle is kept in the housing by the pin and the "C" clip. Pin keeps it from going in, "C" clip keeps it from going out, correct? What side loads are you talking about?

Al