Some rear end issuess.

[StevenJ]

Okay, let me describe the situation. If I accelerate quickly from a standstill to around 65+ and come to a stop rather quickly a few times in a row or retain 70+ for at least 50+ miles and go to city speeds I get a fair amount of moaning from the rear end. I'm 99% sure it isn't the air suspension making that noise. I have put on about 5k miles since I had 4.10s installed. I am not necessiarly knocking the person whom I had install the gears. It may have been my fault from driving it a bit harder than I should have in the break in period. Again, I have 4.10s and the stock aluminum driveshaft. Maybe it is the whip from the driveshaft that is causing the rear gears to grind a little. Either way, the noise goes away after about thirty seconds to a minute. It isn't anywhere near deafenning. It's noticeable though, sometimes more than others. Does anyone else have any troubles like this? It sounds like a HMMMMMMM kind of grinding like. It only seems to be bad if I come to a stop and leave it in D. If it is neutral, I can't hear it. Again, it doesn't seem to happen all the time, only once in a while.

[fastblackmerc]

Check the rear end fluid, make sure there is enough. Also did your installer use the correct fluid?

[StevenJ]

Check the rear end fluid, make sure there is enough. Also did your installer use the correct fluid?

Yeah, I don't want to say who it was that installed it to give them a bad name or anything but he is a Ford Master Tech and the Ford motorcraft fluid was used.

[DEFYANT]

Did you try going back to him to get it fixed or checked out?

[StevenJ]

Did you try going back to him to get it fixed or checked out?

Not yet, it was done on the side with no warranty. I may have to though. I want to further examine it however.

[Drock96Marquis]

About the only thing you can check is the fluid level, back the car on ramps, open up the fill plug ad make sure it is right up there. He should have used 75w-140, but may have used 80w-90, this shouldn't cause any noise, though.

It sounds like the backlash wasn't set right, there are many fine tune adjsutments that need to be made when setting up a new set of gears. Backlash, pinion depth, runout, we are talking adjustments in the .001" range here.

Also, did you break in the gears properly? There is a great how-to in TCCOA's tech section. I followed that procedure following my RAR swap and the gears are perfectly silent, I plan to follow the same procedure foy the 3.55 swap soon.

[StevenJ]

I probably drove it harder than I should have. I didn't floor it at all during the first 100 miles but I did drive it a bit hard and at varying speeds. It was really bad, the moan at times during the first 100 miles but it went away.

According to TCCOA's website


First time you drive the car, only drive it about 15 minutes or so; DON'T accelerate hard or drive exremely fast
Stop the car and let the gears cool off for about 2-3 hours, unless its very cold outside then matbe a little less
Then Drive again for about 30 minutes or so, no hard acceleration or fast driving speeds, and let the gears cool off again
Then the last time drive the car about 45 minutes or so, no hard acceleration or fast driving, you get the picture, then for the last time let the gears cool. I broke the first rule, I accelerated hard for the first fifteen minutes, not a full throttle but still fairly hard. I gave it about 10-20 minutes to cool off and back on the highway. On the way home I drove it normal and not too hard at all for about 40-50 minutes. I probably drove it a good bit harder than I should have.

[Drock96Marquis]

Even though you were a bit rough on them, I think it was an installation issue. The fact that you said it WAS moaning VERY badly for the first 100 miles makes me strongly feel it is an installation issue.

If you want, you can pop off the diff cover and take a peek in. Get yourself some gear marking paint and take a look at the wear pattern. Of course this doesn't tell you everything, if something is way off you will be able to tell. I can get you a pic of the desired wear pattern if you want to do this.

[ScottB]

Could be the preload on the carrier bearings is not tight enough. That will make backlash vary. It took me several gearsets to learn how to do this with the old bearings. But I would think a Ford tech would have done this a million times, so who knows? It never hurts to ask them to check it out. Offer to buy some new fluid if he needs to open it; that is fair.

[ScottB]

He should have used 75w-140, but may have used 80w-90

Why is that? I've used both in the 8.8, but lost an axle bearing in the heavy stuff so never went back (could have been unrelated). Never have heard a good argument either way is why I ask.