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Discussion Starter · #1 ·
Hey Guys,

I've got a '97 F-250 that I bought about 6 months ago. Been slowly working through repairs on it, getting it back in shape. I've done pretty much all of the normal repairs, and today was supposed to have been the last major repair for a little while, I replaced the rear u-joints and the rear pinion seal. I had taken it to an expert diesel mechanic here in town a while back and he had done a bunch of front end work on it, and he had told me the repairs that needed done on the back end, which are what I just finished.

Well, this is my issue. Before I started the repairs, I had a vibration that would kick in at about 65 mph, felt like it was coming from the rear of the truck, so I figured it was those rear end repairs that needed done. Well, now that I've finished those repairs, it's worse, but different. Now, at just over 50 mph I get a solid vibration from not sure where. But the weird part is, it only vibrates when I'm accelerating. Even if I go up to 65, as soon as I let off the gas and coast, even down a hill, no vibration.

When I replaced the u joints, I made sure they had grease and all that good stuff. All the bolts seem tight. The pinion seal I torqued back down to the exact same spot, and there didn't seem to be any play in the bearings, they seemed good. So I have no idea where this vibration is coming from. Any ideas?? I'm relatively new to this, and although I've done a lot of reading and research, and been able to get some expert advice from time to time, this issue has got me totally stumped. I really need to get this fixed by next week, cause I'm moving out of state with it. So any ideas would be appreciated!!
 

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I have the same
so what all did u replace ?
do you have a lift ?

i will tell u i bought all three u joints and the carrier from ford and after 1 u joint a said f this and dropped the shafts of to get done LOL

my press was leaking the retainers weren't going on correctly and they gave u three sizes WTF LOL
 

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Discussion Starter · #5 ·
Well, today I replace the 3 u-joints and the rear pinion seal. A few weeks ago, I did the rear wheel seal, brakes, and replaced the oil in the rear diff. I had it in the shop about a month ago, and they replaced the front ball joints, tie rod, u-joints, brakes, plus some engine work.

I don't have a lift, and yes, I dropped the whole thing to do it today, but didn't replace the carrier cuz it seemed fine, but it's about the only part i haven't replaced. But what doesn't make sense is why only the vibration on acceleration??
 

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interesting

i actually dropped my shafts off at a drive-line service it was getting to be a pain to press the u joints and then i was going to have to tackle the carrier so for 215$ they did it all and balanced

with no lift I wouldn't expect a angle issue that gets worse on accel and since you dropped it you could see the carrier bearing isolator was ok and the bearing was smooth so ??
 

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Discussion Starter · #7 ·
Yeh, I mean at least in my limited experience the carrier seemed ok. I didn't balance it, just lined it up exactly the way that it came off. Do you think I need to have it re-balanced?
 

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re balance yours ? no not really since it only does this on accell

i just did it because i wanted it checked even though I had it all marked when I dropped it off so I could have skipped that expense

the thing that sucks is you don't know if this is an existing condition on one that just came on all of a sudden

the 2 piece shaft has a set spec for the angles and things like lifts or sagging springs can change it

or of course a differential issue but those usually get worse fast
 

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Discussion Starter · #9 ·
Yeh, that's what I can't figure. Springs are sagging, but I haven't messed with them at all, so I don't see why that would cause the sudden change today. It seems like it has be be related somehow to what I replaced, cuz when I drove it yesterday it was fine.

And I've thought of the diff, and maybe somehow the pinion isn't torqued just right, but the pinion nut is on in just the way it came off
 

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He didn't He used the "count the threads and mark the index " method

it's common and while not by the book it works for most
I think some Ford techs do


but obviously something just done is a problem
 

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Discussion Starter · #12 ·
Well, I torqued the crush sleeve back down to exactly where it was by marking the nut and counting rotations and that whole thing. So do you have to do something else to set backlash? I've never done one of these before so I'm not super familiar with all the terms
 

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Discussion Starter · #14 ·
Oh, I gotcha. I almost did a new crush sleeve, but all the mechanics I talked to said I didn't really have to. Well, I might end up having to take this guy into the dealer to see if they can diagnose tmrw, cause I'm out of ideas
 

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Discussion Starter · #17 ·
Well, took the truck into a drivetrain shop this morning. They told me it was a combination of two u joints on the front I didn't realize hadn't been replaced, the driveshaft being slightly misaligned because the yoke was worn out, and bearings going bad in the differential. Fortunately, the gears are ok. So they are fixing it right now. I'll let ya know what the result is.
 
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