Okay, first off, it's my Father's F150 were dealing with. Yes dealing with. he buys Ford because his sisters husband worked for Ford and gets the Z-plan or A-plan whatever they call it for immediate family members of My Aunt. I'm out of that loop. Good grief. So he gets the best deal everytime with no hassle.

Anyways, I'm in his truck last week and when he was making a turn the rear tires where grabbing and fighting eachother. He gave it gas and the inside tire would chirp instead of slip/bind like it was. Now he just had the rear diff cover replaced and new fluid so I was thinking maybe they forgot to add the friction modifier in...
I pulled the cover to drain the fluid and he has an open differential?? WTF? Why does his rear end chatter like that around turns if it's an open carrier? Could maybe they added friction modifier in and was causing that problem? I've ever come accross this before. He had it done at a reputable garage. The spider gears had minor wear, but nothing unusual for 80kmi in an open diff.
Any help or thoughts or ideas would be appreciated. Ohh, he certainly won't buy a dodge. sorry for those thoughts...lol

 

Come on DOG! MUST we work on a FURD!LOL

 

Well, the problem is I HAVE to work aon a Furd and I have no idea what the malfunction is??? Other than being a Ford...haha

 

'dog, 4 wheel drive? and more importantly, if so, auto-4 wd, push button or stick?

 

yes he has 4wd, but the problem is when he is in 2wd mode and the problem is severly amplified when towing. Lots of bind around turns when he was pulling his dump trailer. Approx loaded weight was under 5,000lbs. It's definately the rear causing the issue. He already had his u-joints replaced and I just stuck the gun to them and they were 95% full. I'm lost here??? Could it be the awesome Ford design of control arms or lack there of and the tires are actually hopping? But how?

 

It's gotta be something with the suspension at this point and not the differential. I would almost think that some of the angles for the pinion to drive shaft and driveshaft at the transfer case could be wrong. They usually make a bunch of noise but Ujoint wear is common with that and you said the Ujoints are good.

 

Yeah, u-joints were the first thoughts even before the diff when we thought it had an lsd. Well, my father told me it was an lsd and Iwas going off that.
It just seems so weird because the tires squeel like they are fighting the outside wheel. All I know is that i was fooled into thinking the truck had an LSD. Picture an LSD that didn't get friction modifier. those are the symptoms except this is an open carrier

 

what would happen if the gears were set too tight? wouldn't the spinders bind?

 

I thought about the fact maybe too thick of gear oil would cause the clearances between the spiders to diminish causing the bind, but the spiders have visible wear which would eliminate tight clearances and the fact it's a stock diff with 81kmi on it. Larger clearances would act as old u-joints would. Clunky and bangy as my Silverado was with a severely worn case of spider gears. not the case here. I was thinking that maybe the friction modifier was causing hotspots and binding the gears but I don't know how relevant that would be?????

 

why not just try changing the oil and see if that does it?