Any rear end experts in the house?

[TripleDigitRide]

I'm talking about a vehicle, you sicko!

 

2002 F-150 

Two-wheel drive

5.4 V8

157,000 miles - I've had it for the last 60,000 miles

 

A couple months ago, I noticed a slight chatter/vibration (not wheel hop) when turning. I've only noticed this when started to turn from a stop. I don't think I've ever noticed it when making a turn where I was already in motion. It started happening once or twice a week, but is now happening much more frequently. When it happens, it last only a second or so. I do not notice it when going straight from a  stop

 

Today, I was hanging out with my mechanic buddy while he was installing an alignment kit, calipers and brake pads on my truck. When he got to the back wheels, he was surprised to realize my truck has positraction, as was I. Who knew?

 

He informed me that the chatter/vibration I was feeling and hearing could possibly be coming from the differential. He suggested I change the fluid and see what happens. I've put about 40 miles on it since then, and the same chatter/vibration is still there.

 

At this point, I have no idea if this vibration/chatter is definitely coming from the differential, but it does seem like the most logical culprit at the moment. 

 

What say you?

 

I am slightly hesitant to take it to a shop at the moment, because I just know they will convince me I need to spend $775,736,474.99 on a new rear end, only to find out that wasn't the problem. I drive 30 miles to my mechanic for a reason. Unfortunately, he doesn't specialize in rear end.

[Guest mrstaylor0602]

Add some friction modifier, do some figure 8's and report the results.

Edited February 22, 2014 by mrstaylor0602

[TrickyNicky]

[sigmtnman]

False advertising!!!!

 

I consider myself a rear end expert but only of the feminine kind.

 

"LA face with an Oakland booty"  :woohoo:

Edited February 22, 2014 by sigmtnman

[TripleDigitRide]

Add some friction modifier, do some figure 8's and report the results.

Will I need to drain some of the new fluid I just put in, or add the additive to it?

[sigmtnman]

Friction modifiers and rear ends.  huhuhuhuhuh

[Guest mrstaylor0602]

Just add it in.  It'll only be a few ounces.

[frankmako]

u-joints on the drive shaft sometime will make a sound and give a vibration.  check the u-joints and drive shaft.   rear ends do grinding/humming sounds when going bad.    

[Murgatroy]

Do you feel it in the steering wheel, the floorboards or your seat?

 

If the wheel, it could be front end related.

 

If it is the floorboards or seat it will be drive train related.

[Luke E.]

 Poss rear ends will chatter a bit when making slow moving sharp turns especially on pavement. It's either that or it chirps the inside tire.

[Luke E.]

 I've built a few front/rear diffs before but unless I know for sure what's in the rear end I can't say for sure. Any plans towards Murfreesboro in the truck?

[TripleDigitRide]

Do you feel it in the steering wheel, the floorboards or your seat?

 

If the wheel, it could be front end related.

 

If it is the floorboards or seat it will be drive train related.

Is "all of the above" an option? I swear I do.

[TripleDigitRide]

 Poss rear ends will chatter a bit when making slow moving sharp turns especially on pavement. It's either that or it chirps the inside tire.

It just weird that I never noticed this happening for the first 55,000 miles of owning the truck.  :shrug: 

[TripleDigitRide]

 I've built a few front/rear diffs before but unless I know for sure what's in the rear end I can't say for sure. Any plans towards Murfreesboro in the truck?

Not at the moment, but one can be planned. I think I'm going to try the friction modifier, and if that doesn't work, I'll go from there. I'd rather not have something break and/or lock up on while driving, so if I can get it figured out before that happens, that would be great. 

[Luke E.]

It just weird that I never noticed this happening for the first 55,000 miles of owning the truck.  :shrug: 

 

 As things wear they can start acting differently but like I said I really can't say for sure without seeing it in person. Also my buddy owns an offroad shop here in town and does a fair bit of differential work, i'd trust him not to take advantage. If you're not going to be down this way i'll call next time i'm up your way if you don't have it fixed by then.

[Luke E.]

Not at the moment, but one can be planned. I think I'm going to try the friction modifier, and if that doesn't work, I'll go from there. I'd rather not have something break and/or lock up on while driving, so if I can get it figured out before that happens, that would be great. 

10-4 just let me know if I can help

[Guest RebelCowboySnB]

I just cant see driving a truck that many miles without knowing if it has an open dif or positrack. I also would not expect a posi rear in a 2 wheel drive F-150 but they did make them.

 

Why do you think that it is?

 

Also had you gotten stuck sometime before this started.

 

Have you drove around on a spare?

[Mike.357]

I dunno crap about much as you all know.

 

But I nominate this for best thread title ever.

[Guest theconstitutionrocks]

Man you really opened the interpretation door on that one didn't ya?  :rofl:

[Dolomite_supafly]

When you are under the truck read the tag, or take a picture, that is on the back cover. It will let you know if it is posi and what gear it has. The tag should look something like this:

If the ratio says something like this "3.00" then it is an open differential and should not be chirping at all. If the ratio says "3L.00" then it is a locker and may require the friction modifier. The numbers are the gear ratio so it may say "3.00", "3.55", "3.73" or even higher. If it is missing the "L" in the ratio then it is an open differential and should not be acting like a locker. The "L" in the ratio is the indicator for a locking rear end.

 

The chirping is because the two axles are locked together now. Normally there is a friction setup that locks them together under high load situations but lets the outer wheel spin faster when turning. But because they are locked together now the inner wheel chirps as it tries to keep up with the outer wheel.

 

The friction modifier is actually supposed to let the differential slip some. Without the friction modifier the wheels will act like they are locked together. I would say to try adding the friction modifier and then turn a few circles in both directions. Do not try to do donuts because the axles will just lock up under load.

[Tempest455]

You never said for sure this was coming from the front or rear end for sure? There are a plethora of things that can make vibrations.

 

That should be an 8.8", same as Mustang and many other trucks. That's an extremely plentiful rear end. So if you do have a problem w/ carrier, personally, I would get a complete rear and swap. Find a low mileage truck that been wrecked. That's what I would do (if it needs replacing).

[Johnny Rotten]

You need this

http://www.amazon.com/Ford-XL-3-Friction-Modifier-Additive/dp/B000NU5LP6

[TMF]

 

Ha, I was thinking the same thing.  If I were to concur I would be telling the truth, because I have no other option.

[No_0ne]

I have many decades of careful observations of finely-crafted rear ends functioning as designed ...

[TripleDigitRide]

I just cant see driving a truck that many miles without knowing if it has an open dif or positrack. I also would not expect a posi rear in a 2 wheel drive F-150 but they did make them.

 

I never noticed. I don't do any off-road stuff, and I don't make a habit of spinning the tires. Now I know.

 

Why do you think that it is?

 

I'm sure they had good reason.

 

Also had you gotten stuck sometime before this started.

Nope, never been stuck.

 

Have you drove around on a spare?

Nope, no driving on the spare.