Re-gear, now got the vibes

1Fine40

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Have a 04' Tacoma ExtraCab 4x4 running 265/75R16 rubber for now. Going to 285's when the 265's wear out. Re-geared the rear diff to 4.88 to get back some pep. Drives real nice around town and such, but at Freeway speeds now getting one heck of a vibration?? Was very careful not to have driveline separate when performing 3rd member swap out, so don't suspect that as an issue...but why would it now vibrate
like gang busters? The replacement 3rd is a rebuilt unit from a very reputable builder so I can't imagine what is making the truck buzz at 3 grand on the tach.. What did I miss? :hmm:

Cheers!
 
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not running dry u-joints anywhere? Been a long time since I dropped my driveshaft. I've heard of people installing driveshafts backwards, rusting off weights etc.

is it the 3k tach that you always get the vibrations or do you have to be going fast as well?
 

1Fine40

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not running dry u-joints anywhere? Been a long time since I dropped my driveshaft. I've heard of people installing driveshafts backwards, rusting off weights etc."
is it the 3k tach that you always get the vibrations or do you have to be going fast as well?
I suppose the shaft could have issues, I will look it over closely, but it was smooth as butter before the 3rd member swap....

You have to be going 65 to 80 for it
to get really bad. 3K on the tach in other gears is per normal.....
 

1Fine40

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Have identified a couple issues. 1st, the DS was not "in-phase"! It was off by one or two splines at the Center bearing flange! That didn't help things, so fixed that but still a buzz at speed. Next, made sure angles were correct with shims and a nice angle finder gauge. Was off a bit, so corrected that. Things much better, but not gone yet. Next up, swapped out old center bearing for new. Some improvement, but not as much as I had hoped for. Hmmmm, going to remove back half of shaft next, and give CV and rear U-joint a closer inspection. Also run truck on front
driveline and see if the vibration goes away. Will report back if anyone cares:meh:..
 

1Fine40

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Did you try to raise the back end on jack stands and see if you can see if tires or driveshaft is causing your issue?
Nope, the tires are not the cause, they are balanced and quite round..after a check on the road force balancer. It is definitely a driveline issue, but where the problem lies exactly is what I am working on now. Going to pull the rear half of the shaft Saturday and see if the front half vibes around much. Wish I had a Go Pro to slap under the rear, but not that well fixed :hillbilly:..
 

1Fine40

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Well, I had a bit of a time gap to try some stuff last night, so WTH, I pulled the back half of the DS, the piece after the CB. Rotating the u-joints through full motion reveals the back joint is not healthy! So that needs replacing when I can source a new matsuba joint. But, I had an idea and gave it a whirl. Put truck in 4th gear and tached it up to 3000 rpm and whatdya know...a nice bit of buzz coming from the unloaded front half
of the DL! :idea: I'll run the truck on the front diff for a few days while I replace the back joint and then I will take the whole thing to a shop for a thorough re-balancing, front to back! Will report back thereafter, but I think I have two issues..out of balance shafts and a carked U-Joint!

:cheers:
 

yotadude520

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Well, I had a bit of a time gap to try some stuff last night, so WTH, I pulled the back half of the DS, the piece after the CB. Rotating the u-joints through full motion reveals the back joint is not healthy! So that needs replacing when I can source a new matsuba joint. But, I had an idea and gave it a whirl. Put truck in 4th gear and tached it up to 3000 rpm and whatdya know...a nice bit of buzz coming from the unloaded front half
of the DL! :idea: I'll run the truck on the front diff for a few days while I replace the back joint and then I will take the whole thing to a shop for a thorough re-balancing, front to back! Will report back thereafter, but I think I have two issues..out of balance shafts and a carked U-Joint!

:cheers:
Look forward to hearing what the verdict is!
 

1Fine40

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The back U-Joint had a nice wear pattern in it from the needle bearings, so yeah, it was time for it to go! New Matsuba joint is pressed into place and off to the shop for a balance and overall wellness check. They say they can run it up to 3K rpm, but I asked them to run it higher if possible and see what "shakes out":hillbilly: We shall soon see if this gits er' done 🔧....
 
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1Fine40

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Got shaft back and in last night, shop told me that the DS was unbalanced a fair bit, but they got it good again. Once installed, I checked angles and everything looks to be just about as good as I can get it. Pinion is about 1 degree below perpendicular to
rear half of DS at rest, so it has room to rotate up a bit under driving conditions:grinpimp:. Checked shaft linearity with a string line and got it set correctly, all straight..and then took it for a drive...:steer: I only got up to about 65 on the highway and things seem to be smooth, so we'll keep our fingers crossed for additional runs at higher rpms! I am cautiously optimistic at this point.
 

1Fine40

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I am pleased to report smooth sailing up to 75mph which by my calculations has the driveshaft spinning at around 3880 rpmo_O!!
Not gonna try going much faster since that would not be productive at this point. However, I now plan in earnest for 33's to replace the current rubber this spring🆒..that should slow the shaft down just a little and be a very good thing!

:cheers:
 
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