I am hearing a clunking sound in my truck when I go from park to drive or drive to reverse, or park to reverse. So first thing I did was to check the u-joints and they all seemed ok.
Next point was the rear end, possibly low on fluid. I pulled out the only plug and the end had a silver/grey grease on that was more like a graphite type then what I expected to see. there were also metal shavings on the plug end as well. When I stuck my finger inside to feel for oil, what I found was a watery like substance that looked like old 3 in 1 oil, that dripped off my finger as I pulled it out.

I called my local ford dealer and he said it sounded like water had gotten inside of the rear end and caused the oil to seperate. In turn causing the clunking sound.

So far I am ok with this. Now the next part has me questioning him. He told me that I need a 75-140 weight synthetic oil, at $22.00 a qt, and I will need three of those. Plus if there is a clutch pack I may need to do something special for that, didn't quiet catch it, but he did say something about an additive for another $8.00. Then the recommended silicone to seal it back up was another $22.00 And then brake parts cleaner to cleanout the rear end once the fluid drained out. Telling me that I am looking at between $100-$150.00 in materials just to change the fluid in the rear end.

Now, this seemed awefully expensive to me so I went to the zone online and shopped out the marterials and the first thing I noticed was that I couldn't even find a 75-140 weight oil. Second the prices ranged from 4.99 a qt to 15.99 a qt. and the additive was another 4.99.

I guess my question is, does this special synthetic oil exsist and what is the cost of it? Or can I use another oil with a similar weight to it to accomplish the same thing? I know I may need an additive, so I'm ok with that one. Same with the brake parts cleaner I am ok with using that to clean everything up.

But $22.00 for silicone? I think I can use the generic one for like $5.00 right?

Does the cover plate need to come off any special way? And is there anything else I may need to know about when I am changing this?

I am doing it in my driveway and wont be able to run out for materials once I start so want everything in place prior.

This is for my 01 F-150 extended cab 4*4 with a towing package. with 130K on her.

Thanks for your help

 

75-140 does exist and is reccomended for most F-150s 97 & up. Any auto parts store should be able to get you some and if not, the dealer in no way should charge you 22/quart. The clutches and additive he spoke of are if you have a limited slip differential. The additive is reccomended. RTV silicone is all the same, get some high temp stuff for 5 bucks and your good to go. The cover pops off just like any other, take out the bolts and pry it off.

Now don't forget to fix the leaky seals or bad vent tube or however the water got in there in the first place.

 

ok I went to wal-mart and found the diff fluid for 10.97 a qt, the additive at advance for 5 and had a tube of rtv laying around from another project.

I got the fluid drained, and noticed that there didn't seem to be any water in the diff, no milky goo nothing. So I put it all back together and started it up and you guessed it still clunking. As I was finishing up a friend of mine stopped in with his ram 1500, and listened to it. Then we compared trucks, his has to be 10X's worse then mine, he said that is how trucks get, and to drive it and not worry about it. I'll admit I have heard this in alot of trucks, and when I opened up the diff, there didn't seem to be a high amount of wear on anything it all still looked really good in there.

But I did start hauling a boat with it, my first year, and was told that is prob what caused the noise/water problem. By launching the boat and water getting in through the breather.

So I guess I will just assume that it is ok, until it gets worse then look at having the slop taken out of it. I dont know much about differentials other than if you dont know what you are doing you can really mess them up, with the spacers, shims clutches and angles.

 

I'm thinking maybe a u joint still.......even if there is no slop in them or wiggle they can still get in a bind and clunk try soaking them down with some pb blaster or wd a couple times and see if that clears it up. Hey it can;t hurt to try

 

No your right as long as the PB doesnt eat its way through a seal it should be good.

Also cant remember if those had zerc fittings on them I will have to check tomorrow.

 

quite often the clunk is the splines on the drive shaft yoke. when you change directions or put in gear you get wrapup of the sahft and takout any loosness. no problem as you said. you did good with the Wal Mart 75-w140 thats what i used. Didnt really belive the water story from the beginning. Possible, but not likely. The gear lube is thin, the crud on the plug is wear particles mixed with a little oil and stuck to the magnetic plug. its a good idea to change out the gear lube every 75k miles to get any crud out.

 

it could be your u-joints still i'm just offering advice if you do go to change the fluid. don't pry off the diff cover, you don't want to bend it or it will be harder to seal back up when you go to apply rtv sealant to it. loosen and take out all the bolts and the diff cover will still be stuck to the rear pig. with a razor knife or box cutter cut the old rtv as deep as you can until the diff cover can easily be removed from the pig.

it's a rather simple job if all you're doing is replacing fluid. but start with u-joints, they are cheaper.

 

Binding Ujoints usually cause vibration at highway speeds, not clunking. Loose Ujoints cause clunking.

Did you see clutch packs in your diff? If they're in there it's a limited slip and when it's worn out it will clunk from time to time.

 

Whether it's your rear-end clunking or u-joints watery looking gear lube in your rear-end is not good. The manual says that it shouldn't be changed unless it was submerged in water. I changed mine and it was never submerged in water and it had water in the oil and it wasn't a pretty site to see it come out of the rear-end.

 

I noticed my truck makes this noise but only when parked on a hill. My 1996 f150 did this all the time.

 

My drive way has a pretty steep grade to it, so after two years of parknig on it, i guess that loosed things up some.

But, everytime I drive the truck it does appear to be getting a little more quiet and strangely enough it seems to be driving smoother too. Almost like there was drag before, that I am not feeling now. At one point prior to changing the fluid, I backed out of a driveway and when I went to take off I had to hit the gas, it wouldn't take off on its own. That was the decieding factor for me to start looking into this prob.