Hey guys i have a big problem. I have a 2002 f150 4x4 with a 9.75 with 3.55 LS gears that seems to be binding up only at low speed turns. I had the rearend re done about a year and a half ago. only difference this time there is an occasional whine. I was told that it could either be the clutches again or maybe a u-joint? Pease help me out here as i need this fixed asap. Thanks for any help.

 

Most likely the clutches. Put a bottle of friction modifier in it and go do some "figure 8's".

It isn't that hard to check the u-joint either. Block the wheels and put it in neutral, crawl under it and grab the D/S and try to wiggle it. Up and down and side to side. Any movement-replace the u-joint.

 

like i said though, they are only about a year and a half old. they shouldnt go out so quickly

 

If they are grabbing then they aren't "going out". At low speed sharp turns they need to slip just a little, that is what the friction modifier lets them do. This is a fairly common issue and the modifier is cheap compared to a new set of clutches.

Do a search for friction modifier and you should get a ton of information to help you understand how it works.

Good luck

 

do what he says, most likely who ever rebuilt the rearend used fluid that didn't have enough fiction modifier in it, i know for a fact that Valvoline 75W140 LS does not have enough in it, baffled the guy that installed my gears.

 

I took the truck up to the shop that i had the cluthches replaced in it. He is trusted by many here in town my father uses him, my boss and several others that i know have recommended him. He said all it shoould need is a good service. Sa I wanted to service this myself what is a ball park estimate on it and how much time would it take or would it be worth it to just take it in and have them service it?

 

put a bottle of friction modifier in it it costs $5 from ford. by "servicing" i'm going to assume he means change the gear lube, about a 1/2hr labor $40-$50 and 3 qts of full synthetic 75W140 another $40-$50. so $80-$100 is what you'd be looking at, put a bottle of modifier in it and save your money.

 

Mine's been doing this too, friction modifier seems to be correcting the problem. It is nowhere near as noticeable as compared to a week ago.

 

It's normal. It's caused by the outer wheel going faster than the inner wheel during a turn. The clutches rub. Add friction modifier to eliminate the jerky feeling.

 

I'm sure with your window down you'll hear a clicking or popping sound, hence a binding in a turn and this is abnormal. By putting in FM (as recommended) will remedy this part of it .

But, the whine has absolutely nothing to do with the binding in the clutch packs.

The whine has everything to do with a problem with the gearset, unfortunately.

 

Sunday I had to pull a trailer loaded with about 1,000 pounds or maybe more of bricks on it. I heard the whine for the first time when i was turning up into my alley and come top think of it, the only time i heard the nasty sound was making a hard left turn into my alley with the loaded trailerand i havent heard it since. Is there a place where i can add some friction modifier to the rear end to see if it helps? i know this is alot of questions but I know almost nothing differentials. All the help that i have gotten is greatly appreciated though, thank you.

 

Yep. In through the fill plug. You have a large diff. there, and it may take more than the usual 4oz bottle from Ford. Check the spec in your manual. You'll find some people will say more can't hurt, and that is true, but it will also lessen the lock-up performance.

 

Don't forget that you may have to suck some of the existing oil out before you add the modifier.

 

Took the truck to the shop(even though I didnt want to) and had the rear diff serviced. They put in new high performance diff oil and a double dose of the friction modifier. It has fixed the problem(knock on wood) and it now drives great.Thanks for all the help guys!