2001 F-150 4x4 5-speed. When I first go to take off in reverse, I get some strange noises. Sometimes it's like a harmonic vibration / metallic noise, combined with a light popping, and sometimes I get a fairly high-pitched metallic "squeek-squeek-squeek". It only does this for the first 6 - 8 feet or so, then nothing. I have pulled onto a steep hill and let it roll backwards and it doesn't make any noise at all. I have also tried holding the brake on while attempting to reverse, and it doesn't make the noise. It won't do it in forward gears either, only in reverse for the first few feet, like just before I have time to get all the way off the clutch. It does it regardless of clutch position though, as far as I can tell.

Over the last two weekends, I have tried to get rid of the noise by replacing my tranny fluid with Royal Purple MaxATF, as well as the transfer case. I then did the front differential with Royal Purple Max-Gear 75-90, and rear with 75-145. I also replaced the two rear driveshaft u-joints with AC Delco Super Strength greasables. The sound persists. HELP!!!

 

Could it possibly be the rear brake pads? I know they are about due for replacing. (48K mi. on the stockers) It sort of sounds like it could be the feeler on the rotor making the squeek, and the slack in the pad / caliper making the harmonic vibration...???

 

I was going to say u-joints untill I read further. I can't imagine anything inside the transmission would make sounds like the ones you discribe. I don't know about the front diff. I have a 4x2. I guess the breaks would be a good next step.

 

it could be inside the rear axle, but i wouldnt worry about, IF IT AINT BROKE, DONT FIX IT!!!

 

Was the fluid you got out of the transmission clean? Usually when something goes wrong in a manual transmission the fluid shows it.(or the chunks on the magnet)

 

Fluid was grey but not terrible IMO, however it was my first rear-end job so I'm not familar with what normal fluid looks like. No chunks on the magnet...???

 

rear end job? i thought this was in the transmission. which fluid was grey, the tranny or the rear end?

 

Oh, derp...yeah, rear-end was grey, tranny fluid has always been alright.

 

gray fluid in the rear end is to be expected. your truck is fine

 

try adding a synthetic additive to your transmission and reply back. make sure the additive is safe

 

A synthetic additive? In addition to the Royal Purple? What is it?

 

WTF?

Please specify the additive you are referring to? I never believed in synthetic oils let alone synthetic additives. I have no clue what additive you would put in a manual transmission. I run Gm syncromesh in my m50d and it is fully synthetic,but I was just tired of burning up the thin atf every 15k.
Alan

 

i think you should put in some type smooth shifting additive. i am not sure if it is full synthetic, but use something that says on the bottle "smooth shift"

 

Can you get us a part number and location?

 

U-joints