redmack

I was hoping that someone could shed some light on a rear end issue that i have . Travelling down the roadway , whenever putting power to the wheels i heard a slight hum . Also when pulling out from a stop and turning either left or right , there's a very noticable scrubbing vibration . This progressively gets worst the further i drive . I hauled the cover off the rear end but there's nothing visably wrong , no metal filings or anything . Any input would be appreciated . By the way , my truck has 230,000 kms on it .

ranken

Your limited slip differential may be grabbing, mine got so bad at one point that you could feel the rear wheel hop if you turned short. Had the transmission fluid changed and friction modifer added, and everything was fine.

kookookachew

Don't you mean differential fluid?

biscuit141

How much friction modifier did you add? I need to do this service to mine and I wasn't sure.

ranken

[quote=biscuit141;391413]

How much friction modifier did you add? I need to do this service to mine and I wasn't sure.

I don't know for sure how much to add, I just had the truck serviced at a garage. You could probably ask your ford service dept and they would get you lined up with what you need. Probably a good idea to do it soon if your rearend looks o.k.. When they pulled the cover off of mine there were metal shavings in it; but as I said, mine was bad enough to have wheel hop. Oh, I had the differential serviced and not the transmission as stated in the previous post.

02Screw

About 6 months ago I thought that i had a rear end problem myself. You could hear a hum coming from the rear end when you take off from a light or turn or bascially whenever you let off the brakes. Well turns out that my caliper was froze up in the rear. If you have disc brakes in the rear it is something to look at. You will know that it is frozen if when you take a c clamp to the piston to compress it (like you normally do on a brake job) and it doesnt move.

biscuit141

Thanks. I did the brakes when I first got the truck and everything checked out. The way its acting, I'm 99% sure its the diff. from what i've read.

camstng66

Uhhhh, what is the original post date???? ranken, do you work at the cemetery??? You seem to like pulling threads back up from the dead...

redmack

Thanks for the reply. I was getting ready for a rebuild in the spring and the kit is very expensive so I'll definitely give the modifier a try within the next couple of days Thanks again!!

brorip

I have the same problem with my F150 7700 with 150k miles. The positraction clutches in the rear are slipping so I had Goodyear Tires replace the fluid with fully synthetic about a year ago, but the problem did not change and has since gotten worse. I went back a couple days ago after reading about the friction modifier and they didn't know if they put some in but they gave me a tube to put in myself. I'll take out some fluid and try the additive and go from there. Many threads post that this has solved their problem.

As far as the whining from the rear end, that is your ring and pinion. It's not an immediate problem (mine is doing it too), but eventually you may need to rebuild the rear diff which can cost up to $1,600 with bearings, posi-clutches replaced and ring and pinion. Hope this helps.