Nope all the manuals call for it. No you won't hurt it.

 

So would you still think that this vibration could be related to the differential fluid? assuming that jiffy lube did screw me over, and didn't service it properly, would it make sense to still re-do the fluid myslef by dropping the cover?

 

Iduno, if I was absolutely positive, but your left in a position of not knowing. You could have a bad gear, something wrong inside. Again, without knowing what they did, how are you to know or anyone for that matter ?

 

So you're still inclined to think the problem is coming from the differential? Have you heard of people having this vibration with the conventional differential too? I'm kind of inclined to think that whatever jiffy lube did... if anything, didn't really make any difference... I don't know anymore...Maybe it is a tire...I didn't really notice any of this until new tires... but I kind of thought i ruled that out with the rotation. Its really wierd... not sure if I mentioned it before but it does seem a little less loud of a rumble on asphalt, rather than concrete freeways, but that could just be that the sound bouces off the concete more. And I noticed today that the rumble/vibration isn't quite as intense when I coast down through 65, than it is as I accelerate up through it. Its really very weird... if you guys have any other ideas please let me know... I'm gonna go and take a good look at the tires if I get home from work in the daylight tomorrow to see if I see any strange wear patterns as I have driven it a couple hunded miles over the weekend. Thanks again for everything.

 

Well, it's certainly not limited slip clutch chatter. You used the right fluid, but you didn't have to use the modifier.

 

well, I've got a couple things I'm gonna try this week if I have time. Gonna try to rule out tires entirely... found these Ideas on the web. read that tire manufacturers put dots (red or yellow) on the heavy spot of a tire and that the heavy spot of a rim is the valve... any truth to this? The site sait that the stem and the dot should be mounted opposite. Also going to drop tire pressure in the back to 25psi and take it for a quick drive see if anything changes. I've got original shocks in the back and I'm wondering if there is just a little something out of whack on the tires if the bad shocks are magnifying it. But still not inclined to think tires. Do you guys know if tire/wheel balance (out of round...etc) will have single speed vibrations or is it somthing that say starts at 45mph and gets worse the faster you go?
Thanks guys

 

well, looked at the tires yesterday. No strange tire wear yet... also, can't see if there were any dots marked on the tires before they were installed... so not sure about if the heavy spots on rim and tire were matched when mounted. Do any of you guys have any experience with a tire out of balance/round, or possibly belt separation? What were the symptoms? Do you guys know if maybe like Discount Tire would be able to look at the tires for a reasonable fee and let me know if they are alright or not? May go talk to them this weekend.

 

take it to a shop and have the tires road force balanced. It is a machine that applies pressure to the tread of the tire to simulate as if you were driving down the road, this will let you know if you have a problem in the tires or rims. Yes there are dots on tires that are supposed to be lined up with the valve stem but it usually doesn't really make a difference.

 

Hey guys...
Thought I'd give you a quick update on the truck. I finally broke down and took it to ford... for 95 bucks they road tested it with the EVA (the vibration computer thing) and had a certified vibration tech take a look at everything. They said from what they saw/felt they had narrowed it down to the driveshaft or possibly the carrier bearing, but they were betting on the driveshaft being out of spec so they sent it off to a driveshaft shop to be ran on a lathe (no extra charge) and they also said that they thought this model was one that they had lots of problems with and may actually be covered by ford...so it might not cost me a dime. So they got the truck until monday... I'll keep you posted.
Also... all the rims and tires checked out OK! So my apologies to the samsclub tire guys.

 

Yea, that's quite a different problem, -one I haven't heard of in these trucks.

Let us know how it turns out. Sounds like you have some real good guys working on her now

 

well got the call from ford yesterday. They said the driveshaft shop said that the driveshaft is slightly out of round. He said he couldn't guarantee that it will fix it but that this is where we should start. Said it will cost $230, I'm going to go down and talk with the service manager and the tech today and find out exactly what they found.. how far out of round...if the shaft will be replaced or balanced, what the odds of it fixing it are... etc...
I'll let you know what happens.

 

For around 350 you can get a new driveshaft made just food for thought and can put it in yourself. Glad you finally found the problem though.

 

Well still kind of at a loss. I went down to talk to the guys at ford today and they seemed really wishy washy on the driveshaft balance. I started asking questions about how far out it was and what the tech thought the chances of this causing the vibrations were. The kind of left it at... the shaft is really just slightly slighty out and that that is just kind of their best guess. but it could be other things, anything from the rear of the tranny to the differential... that's kind of vague... so now I really don't know what to do. The 230 was just to have the shaft rebalanced... seems a bit high to me. I was doing the same thing ford is doing... just guessing around (u joints, wheel bearing, diff fluid... etc) I'm just really disappointed because when I first spoke to the ford guy he went on about the EVA and that he has 4 vibration techs, so it should be no problem... and now I'm really not any further ahead... just down 95 bucks. I didn't get the truck back today because the shaft was still out at the driveshaft shop... the service manager said he'd talk to the tech about some tsb things I brought him (ex. 4.5 inch shaft to a 5inch shaft), but I didn't hear anything back today. I'll give a call tomorrow and see how its going. I just don't feel like shooting in the dark replacing things that might fix it at DEALER PRICES!!!
Also the service manager (not the tech) mentioned maybe the torque converter... but that spins with the engine speed not vehicle speed right? To be honest I really have no idea what the torque converter does or how it works.

 

Alright guys... got more news from ford last week... NOT SURE IF ITS GOOD OR BAD. So they told me they talked to the guy at the driveshaft shop again and he said that with as little as the shaft is out of balance, it shouldn't be causing my problem. So they told me that they would keep working on it. Then I got a call on thursday and the service guy said they had kind of ran out of ideas on the drive line and for kicks they put the truck in park and ran it through different rpm ranges and found a vibration at around 2100rpm. He wanted me to come in and check it out... I didn't have high hopes, because everything I was feeling was speed related... sure as hell, it was the same vibration though...so weird. So I asked him, how in the heck can it be speed vehicle related when the truck is driving, but then engine speed related when its in park... at least he was honest and said "hell if I know". So he said he'd have to have one of his engine techs check it out now... they're still just charging the 95 bucks... but it seems like this guy really wants to know what's going on with the truck. Just off the top of his head he said maybe engine mount or maybe a loose mount on the tranny or something like that... but they'd look into it. I'll probably go there tomorrow, so if you guys have any ideas, please let me know and I'll run it by them.

 

could be something as simple as a slight miss fire bad plug or coil pack