Rear diff vibration
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Rear diff vibration
Hi all. New to the site today mainly because i just bought a new-to-me 2004 f150 lariat crew today. Nice truck, very clean and only 43k (28 000 miles).
Problem is I'm noticing some rear end vibration on slow acceleration from a stop and once the truck started to vibrate harshly at about 70 kmh. pulled over because i thought i may have gotten 4 flat tires all at the same time. lol. I did some investigation and discovered the rear end was rebuilt 2000k ago including crown and pinion. I work for a Dealer of a different manufacturer (which I'd rather not mention) and we did the safety on it. While doing the safety we noticed the rear diff cover leaking, opened it up and did a diff service with the proper synthetic ford fluid. My main question is that I'm wondering if there should've been a posi additive put in as well and could this possibly be causing this feeling or is it possible that the dealer who did the diff rebuild screw it up by not getting the preload right or something to that effect?
Thanx in advance for the help.
Problem is I'm noticing some rear end vibration on slow acceleration from a stop and once the truck started to vibrate harshly at about 70 kmh. pulled over because i thought i may have gotten 4 flat tires all at the same time. lol. I did some investigation and discovered the rear end was rebuilt 2000k ago including crown and pinion. I work for a Dealer of a different manufacturer (which I'd rather not mention) and we did the safety on it. While doing the safety we noticed the rear diff cover leaking, opened it up and did a diff service with the proper synthetic ford fluid. My main question is that I'm wondering if there should've been a posi additive put in as well and could this possibly be causing this feeling or is it possible that the dealer who did the diff rebuild screw it up by not getting the preload right or something to that effect?
Thanx in advance for the help.
Fleet Mechanic
Joined: Dec 2004
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From: Ketchikan, AK.
i wonder if they did use the wrong fluid..... does the rear that you have require the friction modifier? possibly they didnt use it. im not the most experienced with the differentials... but, if they didnt get the pre-load of shimming correct on the pinion, then it would whine either on accel or decel.... or could even make worse noises. does it make any noise, or just vibrate and shutter? i have read some posts here also about the clutch packs going out on the rear. just a couple quick thoughts.... and welcome to the site !!!
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Thanx for the welcome. The funny thing is there is no whine at all, and I used to work for Dodge for quite a few years, I know what diff whine sounds like. lol. So i dont think they got the pattern wrong or the pre-load, but the friction modifier is a good question. So back to my original question, does a posi rear end require a specific friction modifier, and does the Lariat come standard with a posi rear end?
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The shudder is the posi clutches slipping and grabbing. You should be able to just use the proper ford fluid and appropriate friction modifier (required), that should take care fo the problem. The same symptoms affected my 04 Scab FX4.
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we redid the fluid at the time of the safety and used the proper ford fluid, but I know we didnt use a friction modifier. Does ford sell this or can i use a generic type? any suggestions on which type to use if generic is available?
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Quick update. Re-did the diff service with the proper Ford fluid and friction modifier. Noticed the difference right away on tight turns, circles etc. Went on a road trip and the vibration is pretty much gone. Another victory for OEM I guess.
Thanx for the help.
Thanx for the help.
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devozoo
Explorer, Sport Trac, Mountaineer & Aviator
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Aug 8, 2012 02:24 PM
