Hey guys o have an 04 f150 4x4 with 80,000 miles. my rear end has been chattering and vibrating when pulling my boat. i know this has to do with the ls clutch packs. after researching the web and talking to a local mech. i changed oil in my rear end. i used mobil1 75w-140 oil and used the friction modifier. after a few figure 8's and 10 miles or so there was no significant change. is there a break in period i should be aware of or should i see some relults pretty quickly. thank for any help.

 

i had the same problem...i got it rebulit at my local stealership

 

When is it chattering?

I mean ... is it when going generaly straight down the road ... or on sharp turns ... or when pulling up the ramp and one wants to spin?

 

further to tbear853's response, do you have any difference in tire size from side to side on the rear (wear or inflation), how many bottles of modifier did you use (2 required for the 9.75" and it should smell like rotten fish if it's the right modifier). Keep in mind that most after market LSD manufacturers do not recommend the use of synthetic oils with their products because synthetic oils reduce the effectiveness of the friction modifier and increase the likleyhood of chattering. Heat is also a factor. The hotter the operating temperature, the more likely it is to chatter.

 

My 05 has a grinding noise and I was told it was a ring and pinion, also had a tsb on it. I think that is what my problem is. I was also told after the r&p is replaced the problem might return in time. I think I'm going to research a after market kit.

 

If you have to replace it I would suggest the Eaton Detroit Truetrac differential set that does not have clutches. It is a gear set up in the chunk that does work.

 

no difference in tire size. i used one 7 oz. bottle of modifier. i talked to a local mech and he said to switch to a synthetic oil. and i cant really tell any difference when the truck is hot or cold the chattering is equally annoying

 

even when pulling straight down the road if the road has any incline it will vibrate. when turning the wheels and pulling off from a stop it vibrates and pulling a boat will increase the vibration in all situations. it will quit vibrating after say 12 mph. after that the truck is smooth as butter.

 

Shiver,

The response from the fluid change should be fairly immediate. If the fluid change were going to fix the problem you should know within a mile or so of driving. One more little thing might be worth a try... You wrote that you added 7 oz of the friction modifier which, I believe is one tube. Lets assume that you got in most of the first tube. I believe the specs call for 8 to 10 oz so, before you step into a costly repair, you might pick up another tube and add about half of it. I don't think it will make a difference with the grinding but the price and time is not much so it's worth a shot.

I was getting some of the same grinding during low speed turns so I opened up the housing, drained out all the old fluid, flushed it good with brake parts cleaner, buttoned it up and added the synthetic 75W140 (what is spec'd for this truck) and a tube and a half (give or take) of the friction modifier. Completely fixed my grinding/chattering.

 

yeah thats is the exact procedure i did on my rear end but like i said i only put 7oz of modifier i will pick up another bottle and add a little more and see if that helps. do u have any idea on possible prices of replacing the clutch packs. thanks in advance

 

No. I don't know the cost for replacement. Once mine became quiet again, I didn't look into more expensive teardown/repair. Like I wrote, I don't think a little more friction modifier will make any difference but, who knows unless you try. Good luck with it!!!

 

The reason I asked is because going down the roadway, both rear tires rotate at the same speed and the two little side gears on the ends of the axles inside the differential then also turn at the same speed, there is then no "differential" speed in the two axles.

If your rear tires are the same size and properly inflated, and if you are going down the roadway in a straight line, or even nearly straight, and you are still feeling or hearing a chattering in the rear ... it ain't the clutches.

Is there any chance that any part of the exhaust system is coming in contact with either the rear axle housing or driveshaft or frame? Check insulators, look along at close points for signs of contact.

Could also be a u-joint, maybe a pinion bearing, maybe a ring & pinion problem. Doesn't sound like a wheel bearing.

My opinion as a car nut of 50 years anyway ...
... Definately not the LS clutches. The clutches don't transmit motive power, they just apply extra pressure to the spinning wheel under load. If they wear completely out, the truck will still go, it just don't have LS anymore.

 

shiver3, My clutch pack, ring and pinion were replaced under Ford warranty @ 35,000. It had the same symptoms that you decribed. The warranty ticket had a price of $1600 on it. There should be a powertrain shop that could do it for less, around $1000 or so.

 

tbear brought up a good suggestion about the u-joint. Your truck has non- greaseable u-joints and you mentioned that you had a boat. Check your u-joints in the rear driveshaft for any amount of play and inspect the seals at each leg of the cross. Look for signs of rust around the seals. If you find either one of these symptoms, then I would remove the driveshaft so that the u-joints can be checked for free movement. A u-joint in the early stages of failure will give the symptom that you are describing (vibrating at low speed and high torque).

 

Yes sir, it will ... and it won't get better.

I suggested checking exhaust system first because it so easy, but u-joint is my guess. They'll agrevate you no end.