I just got my 06 shorty crew 4x4 back from being serviced today. One of the things I had them do was check the differential as I just noticed the rear end would stutter as I gave it gas turning right or left mostly from a stop or near stop. I have owned this truck for about 3 weeks and it is my first Ford. I read about the woes of not adding the modifier after changing the diffy oil from this site. They said the clutches looked good and a flush, new fluid and modifier would be all I would need. Well it still gives a rumble. not quite as bad but not like it was when I bought it. I basically picked up the truck from the shop and drove straight home. Does this modifier have to work in and loosen things up for a bit or do I have other issues?? The shop closed for the weekend as I left so I have to wait till monday to call. Any ideas???

Thanks!

 

Give it a few days. It does take time for the modifier to work into the clutches. Verify that they used 75w140 full synthetic fluid, and find out what brand fluid and what brand and how much modifier they used.

 

Thanks for the input. I am quite sure they used whatever Ford recommends. They changed the plugs and I know they were going to use Motocraft and non other as they said " whatever Ford recommends". I will check in with them on Monday. I'll get some miles on her this weekend now that I know that it needs time.

 

I'm having this same problem. Shuttering while turning off a start. I changed the fluid in the rear diff and added the friction mod. Is it possible that it has all burnt up, or is gone? Should I do another fluid change?

 

Same questions apply to you - fluid weight and brand, modifier quantity and brand.

 

GLC Thanks for the input so far. I will find out tommorrow on what they used. How much modifier should go in? I have been driving for about 120 kilometers mostly highway but drove around a bunch of shopping centers this morning. It is the worst when I back up, then turn left or right then drive forward. Thats when it almost shakes the truck. I can crank the wheel to the left or right and do a 360 with little or no vibration. It vibrates a bit from a stop then left or right only about 60% of the time but the worst is reverse, stop then forward withthe wheel turned. They said the clutches were ok. It doesnt vibrate when I go to reverse then back out of a parking stall. Have I gave it enough time to soak in? What else other than the diff could it be?.

Thanks

 

GLC I have the same problem,is there a friction modifier that you would recommend ? have you noticed a difference from brand to brand? thanks

 

I have read the Ford friction modifier is the best. I have also seen guys running it in their Chebby's. In an 8.8 or 9.75 diff one bottle is all that is normally used if you have a stock cover but I have read that some who still have the shudder have added another to fix the problem. I have two in mine with my Mag-Hytech cover.

 

Hello!

Straight from the OWNERS manual - 4 oz of Motorcraft XL-3 in a 9.75" LS diff.

==>http://www.fcsdchemicalsandlubricant...ransaxle Fluid

Cheers!


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