Can anyone help, PLEASE!
I have a vibration/ shutter in the seat of my pants when I accelerate from a stop when turning left or right. I say shutter because it feels like it would if the tires were breaking loose and hopping to get traction. They are not breaking loose though. I have tried doing it with my foot on the break and it still does the same thing. It started about 800 miles ago and is continuing to get worse. I have a 97 F-1 4x4 with a 4.6 auto. 3.55LS with 91000 miles. At 87000 I changed my front and rear differentials as well as the transfer case with Amsoil synthetic. At the same time I had the rear drum shoes replaced and new 275/75/16 tires installed. The truck was running perfect up to that point and for 3000+ miles after the changes. I took the truck to the dealer and they want to tear the rear end down just to look. Sound expensive and no guarantee that is the problem. Any suggestions would be great. Thanks in advance.

 

ucred,
that sounds like mine acted a couple of years ago. turned out it was the tranny fluid. dealer changed to mercon5 & it's been ok since. it was ok for 34K before this started.

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97 Lariet-sc-4.6-4x off road-auto-3.55 LS-
superchip-K&N-3"
pvc air box mod-Granetelli MAF

 

red lariet;
What is the pvc airbox mod?

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'99 F-150 Lariat
Flowmaster Exhaust
K&N in stock airbox
Polaris Sport 400 ATV highly modified and lightened for 300' sand drags. 0-60 in less than 300 yards, under 5 seconds.
You only live once; so ride hard!

 

remove the rubber fitting going from the air cleaner housing to the inner fender-cut the end of the air cleaner box to accept a piece of 3" pvc thinwall pipe & run that through the inner fender hole. There is a post with pictures by the guy who came up with this somewhere on here.

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97 Lariet-sc-4.6-4x off road-auto-3.55 LS-
superchip-K&N-3"
pvc air box mod-Granetelli MAF

 

redlariet,
Thanks for the info. I am due for a trany flush about now away. I just thought if it was the trany I would have a vibration at all start outs, including straight. It needs done so at least I am not throwing my money away like in the case of a rear diff tear down. I'll let you know if it works. I certainly hope that it does.

 

When you changed Diff fluid, did you add a friction modifier, if not, thats your problem, the friction modifier keeps the clutch discs in your LS rear end from grabbing, Don't worry though, there shouldn't be any damage done, just change it again, and this time add the friction modifier

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BigBunnell

98 F150 4X4 XLT flareside V6 5sp K&N Flowmaster and some other goodies

 

BigBunnell,
I was told that the Amsoil did not require an additive. How ever after the shutter started I contacted Amsoil and they said that it would not hurt anything if I added some, so I did. No change at all. I had a Chevy Z-28 when I was a kid and use gear lube that was not Chevy stuff. I had all kinds of problems. I took it to the dealer and they switched it out to Chevy lube and everything went away. I wonder if this could be the same thing. Maybe the diff doesn't like the Amsoil. Maybe I should just change it out to the ford lube. At $40 a quart it seems like an expensive trail and error process. What do you think?

 

Now that I think more about it, it could well be the rear end not releasing. I'd look into that before a trans fluid change. You're supposed to add all the little bottle of friction modifier you get at Ford.

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97 Lariet-sc-4.6-4x off road-auto-3.55 LS-
superchip-K&N-3"
pvc air box mod-Granetelli MAF