What is that (rrrrrrrrrrrrrrrr) noise in the rear end that I hear when I take off from a dead start and at the same time I'm turning,(only). I think it's the clutches slipping, but is that normal to hear it? It's also about 26deg. out when I hear it. My truck has 5K on it. I don't know if it's bad or normal, has anybody had this noise. I heard about this ant-friction lube, but should'nt the rear end have it in it already???? Never heard it in my 01 s-crew.

 

It doesn't sound normal. You might want to run by your dealer and have them go for a ride.

 

That's not normal, you better take it in---neither is the 26 deg you were talking about---burrrrrrr

 

The only problem is, it only happens when I go to work at 5:00 am and sometimes when I get off work. I can make an apt. but I have a feeling I won't be able to duplicate the sound on a given time. Thanks for the the reply. I have read a few post in the Diff dept. and some people said they had added MORE ant-friction lube ??????? I don't know. I don't want to touch it due to warranty, but don't want to wait and mess up vital parts.

 

That’s always how it is; you can’t recreate the sound for the mechanic. I’d take it in anyway. Tell them what you wrote above; maybe they already know what it is.

 

Thats true Rusty1 and I am going to take it in. Thanks for the reply.

 

Little update: Instead of a rrrrrrrrrrrr noise it's more like a shuddering when I turn and accelerate hard, but there is no chattering. Talked to shop foreman at Ford dealer, he said sounds like I need a little more modifier to free it up some. What do you think, sounds right, but is it???? How about you racerguy, what do you think about what the shop foreman said, have you come across an issue like this? Thanks in advance. Rich

 

Modifier----what's that?
I'd like to hear what “racerguy” or "lxman1" has to say. As for me, I’m not sure I understand what that guy’s telling you. I was hoping the dealer would know what to do but…
I know from watching “Trucks TV” that rear-ends are very intricate using shims and calipers to put it all together. I think your having a problem with the proper shimming and the gears are binding up.

 

Modifier is the anti-friction additive that goes in the diff w/ the gear lube. The modifier is for your clutches to slip while turning, in a limited slip diff.I know I don't have any gears binding, also the noise does not happen after the truck has been ran. Like I said it's when it is cold and it's when I leave to work in th AM. Thanks for the reply Rusty1

 

Yup I would add another bottle of friction modifier to the diff and see what happens. Better yet would be to change the oil in the diff and add 2 bottles of friction modifier to it.

 

Mine does it. It is quite normal for a good tight LS unit. I only with the one in my Mustang was as tight.
You can probably get rid of it by changing the fluid and adding extra modifier. Me personally, I like it. It lets me know that it is working.
Jimmy

 

Thanks Racerguy and lxman1 that is good to know. Like I said I don't think there is anything wrong with it, just want to get familiar with the way it works. When your not used to hering certain sounds and noises it's good to know if it's a good sound or bad sound. You all have a GREAT HOLIDAY!!!!!!!

 

My '98 F150 4WD started doing the same thing (shuddering when turning corners) when I started towing my boat - 6000lbs inc trailer. I also got a flashing overdrive light sometime along the way. I brought it in to a local chain auto garage to check the diff oil level and for codes for the flashing overdrive light, but the oil was full and there were no codes for the flashing overdrive light. They told me, "Oh, you have to have these oils (trans, transfer?, andd diff changed on a regular basis." Well, I've never had oil changed in my diff before, and the trans oil only once in my '89 Mustang in my 30 years of driving of all the cars I've had, so anybody have any further input?

 

ford trucks with limited slip rear ends MUST have good rear end oil andthe LS fritcion modifier. I would definity go to mechanic, drain the rear end, add two quarts of new gear lube, preferably synthetic, and 7 ounces of the addative. you con do yourself and get at AutoZone if you are qualified. IF THIS HAPPENS ONLY WHEN YOU ARE TURNING___ it is the addative.-- change the oil also.

 

run that purple oil or what ever for the rear end... you dont have to add stuff to it... Well thats what it says on the bottle... realy good oil they say... cost alot tho...

havent got it in my truck but thats because I kinda distoryed my rearend and now have a trac-lock