Driveline vibration problem

[snipescastle2]

Hello all! Happy Thanksgiving!
I've been having a strange driveline vibration in my truck lately. It starts at 65 mph and gets worse at 80 mph. I had my driveshaft balanced the other day and that didn't do it. When I let off the accelerator it stops, get back on the gas it comes back. I'm going to re-balance my tires again and see if that helps, the engine was totally balanced before I put it together, and I have the correct flexplate. Could a bad torque converter cause this vibration? It could be I through a weight off my tire/tires or maybe even a bad tire. Just looking for suggestions. One note, I did notice a lot more backlash on my pinion yoke when I re installed the driveshaft, I'm starting to wonder if I have the right crush on my pinion crush sleeve after I rebuilt my differential? Could the pinion bearing be causing the vibration? I recently changed the gear oil in the rear end and added the posi additive and I didn't see any weird wear marks on the gear teeth.
Perhaps I should buy another crush sleeve/ pinion bearing/seal and re torque it again? Let me know what you think.
Have a great turkey day!
Ben

[vdawg1973]

I had the same issue after getting a driveshaft built by pick-a-parts...big no no. I ended up taking my DS to the pro's and they were able to rebuild it with a new slip yoke, spicer u-joints on both ends and a new brass sleeve that sits inside of the transmission tail shaft and of course rebalancing. All fixed. That cost me around $280 here in socal.

[snipescastle2]

I'm hoping the balancing of the tires does the trick, but it could be my pinion of my diff. Reason I say that, when I come up to a stop, I hear what sounds like the driveshaft ringing like too much play in the ring and pinion, it could be both....
Ben

[Bigdav160]

Torque converter would be RPM related and not speed related.

The key is the frequency. Thump, thump, thump is tire speed related and usually is only felt at highway speeds.

Driveshaft is much more buzzy and can be felt at lower (35 mph) and then again higher (80 mph) speeds depending on gear ratio/tire diameter etc.

I'm starting to wonder if I have the right crush on my pinion crush sleeve after I rebuilt my differential? Could the pinion bearing be causing the vibration?

This could be key. A pinion that is able to move forward and backwards can give you the accell/decel vibration

[LongBox]

I had a similar problem with another vehicle after having some rear-end work done (ratio change). The shop put a pinion-to-driveshaft flange on the rear that was not absolutely straight.

I changed it out for a known good one, and the problem magically disappeared. Just a thought for you.

[hamjet]

if it stops when letting off throttle, its not tires. it would still vibrate even if you slipped in neutral if it were tires. since you had ds balanced I agree with it possibly being bad pinion loose or pinion bearing. do things like revving the engine it up to 3000 rpm's, if no vibration its not the engine.. you'll find it I'm sure...

[snipescastle2]

Yeah, my money is on the pinion bearing/crush sleeve guess I better round up a new crush sleeve/seal maybe even new bearings just in case.
Thanks for the replies.
Ben

[geezer#99]

Possibly pinion angle!
Under acceleration the pinion climbs up, under deceleration it drops down.
Is your pinion angle set up right?

[snipescastle2]

The rear end is from a 1964 C 10, identicle in most every detail with the exception of the track bar mount ( I removed it it was a funky sheet metal bracket off to the side of the carrier) and this differential has a 12 Bolt posi (Dana) I'm thinking the crush sleeve wasn't correct, as it calls for a much shorter crush sleeve (5/8" -vs. 2.350") I'm gonna have to investigate this as I can't remember which one it has in it.
Have a good one!
Ben

[kwmech]

Can you throw up a picture of the drive shaft? 1 piece? 2 piece?

[Leftlane]

Pinion might be likely, but I'd recheck the drive line angles and double check the condition of your u-joints.

[snipescastle2]

The drive shaft is a one piece, I had a reputable shop in Kansas City
Shorten it for the 700R4, computer balanced it with new u joints.
Today I retorqued the pinion nut and most of the driveline vibration
Is gone, but I can still feel some at 80mph. Not that I should be driving
that fast I'm thinking my backlash might be too excessive, something
I'll check next weekend.
I got my exhaust fixed today and sprayed some undercoating on the bottom side of the cab since I had it on a lift.
Thanks for the input guys!
Ben

[DANTIP]

I'm guessing it's tire-related.

[snipescastle2]

I balanced the tires again, but somebody mentioned earlier that if it were tire balance related,it would be at most any speed, the vibes I'm encountering are at
75-80 Mph. Also, when I come to a stop, and the trans downshifts, I can here distinctive clang or ring of the driveshaft, which leads me to believe I have excessive backlash in my ring and pinion. Probably going to require shims to fix, a weekend job for sure. Better get it done before the weather goes to crap.
Have a good one!
Ben

[CastIron]

That could be driveshaft angle. Watch this to see why:
https://www.youtube.com/watch?v=DDmz0tibVGM

[snipescastle2]

Well, I'm certainly going to check my driveline angles as well, I've heard lowering these trucks does alter the driveline angles, especially major drops.
The rear end I am running came out of a 1964 C10 and bolted right in, but unsure of the pinion angle for that application.
Thanks for sharing!
Ben

[demian5]

Please report back and not go into the black hole of "solved but not reported"...

[67 chevelle]

tailshaft bushing/bearing , is something else to check

[Coley]

One assembly issue often missed when installing (re-installing) a driveshaft is the end to yoke/U-joint alignment 'phasing'.
The yoke 'phasing' is different than the pinion angle issue.
With respect to the phasing you have to make sure that the driveshaft yokes are directly in line with one another.
They are easy to get out 15°, 30°, 90° etc....and they go together easily so you would never know after assembly that anything was wrong or 'out'.
Regardless, here is a very quick video that references this (albeit relative to a toyota truck driveshaft...but this doesn't matter)
https://www.youtube.com/watch?v=dt69zYAcXME
This issue holds true for all driveshafts....and many guys have assembled these 'out' of phase, thus resulting in driveline vibration.
Worth a check....
All Good
Coley

[snipescastle2]

Ok, I picked up a couple of 2 degree pinion shims that I'm installing later today
hoping this will eliminate my vibration issue.
I still want to verify my backlash, but I forgot to bring home the dial indicator,
guess that will wait for next Saturday. I broke down and bought the correct heater/A/C defroster hose kit, I figured since I had to change out my heater core (I found my passenger floor carpet wet with anti freeze) luckily i had a spare here at the house. Since I have to pull everything out to change the core any way, figured it's easier to do it now. Just want it done before I put her to bed for the winter. Have a good one!
Ben

[snipescastle2]

okay, it's been a while since I posted on my vibration problem, Thought I'd better get back to it and post my findings....

I first took another member's suggestion and downloaded the "Tremec App" on my smart phone, then proceeded to raise the truck up at the same height at all four corners and kept the suspension loaded (as if it were at ride height)
the Tremec App has a few tools for finding tire speed/axle ratio's etc... and a driveline angle finding tool. the first angle you need to find is the crankshaft center line, either using the harmonic balancer or the engines oil pan rail/oil filter boss to get this measurement from, place your phone up against the edge or flat surface. once you have the first measurement, you then click the "Next" button and find the driveshaft angle, placing your phone against the driveshaft, then you click the next button, and finally get the pinion angle reading. you can do this a couple of ways...either un-bolting the rear u-joint from the yoke, or use the machined surface of the rear of the housing to place your phone against to find that angle (it will work with the phone on it's side or standing up) then hit next. if your driveline angles are correct, all the reading will be "Green" in color, if they are not, then the bad reading will be in "Red" on the display.

my first reading was .9 downward, the driveshaft angle was 1.3 downward and my pinion angle was .7 upward so, my driveline angle was like 1.8 degrees, in the red...... from what I have seen posted here on the forum, typically, a 2 degree pinion shim is necessary to correct the driveline angle.
I made two pinion shims from a piece of 2"x 6" rectangular channel, using an industrial band saw, set the table for two degrees and cut out two equal pie shaped pieces. these were long enough to place on the differential mounting pads and the U bolts would help keep them in place until I could impact them tight. once I tightened up everything, I re did the angle measurements and I came up with 1.6 in the green. I had a few other things I needed to check before I tried to drive it and see what the difference was, but I'm convinced this was the culprit of the source of my vibration issues. I had to check my ring gear backlash because it felt excessive and it was, when I first grabbed the ring gear/carrier to turn it, I felt the whole carrier move side to side and well as the backlash, come to find out, the carrier side bearings were not fully seated in the races, so I had to re-shim it and recheck my gear tooth pattern.
it took some shuffling of the shims to get it right, meaning I had to remove a shim on the right and put it on the left -vs. Versa. I ended up with .006" backlash and a near perfect contact pattern, so- good to go. Since I had to remove the axles to re shim the carrier, I replaced the axle bearings and seals while I was at it. end result....no more vibes!!! well worth the trouble......
Ben

[demian5]

Originally Posted by snipescastle2

1.8 degrees, in the red......2 degree pinion shim... I re did the angle measurements... 1.6 in the green.
ring gear backlash... excessive ... had to re-shim it and recheck my gear tooth pattern. I ended up with .006" backlash and a near perfect contact pattern... replaced the axle bearings and seals
end result....no more vibes!!!

So what was the vibration caused by? Did you drive it after the shims?

You did a lot of "possible vibration" related work.

Thanks... trying to get the same vibration fixed on a 3/4 drop with an already new diff and bearings.

[snipescastle2]

The problem was mostly due to the incorrect pinion angle. The addition of two (2) two degree
Pinion shims installed between the differential housing mounting pads and the coil spring
Control arms (pointing the pinion downward) took care of the driveline angle problem, which
Ended up being the source of my vibration at 80 mph.
Ben

Originally Posted by demian5

So what was the vibration caused by? Did you drive it after the shims?

You did a lot of "possible vibration" related work.

Thanks... trying to get the same vibration fixed on a 3/4 drop with an already new diff and bearings.

Posted via Mobile Device

[demian5]

Originally Posted by snipescastle2

The addition of two (2) two degree
Pinion shims installed took care of the driveline angle problemPosted via Mobile Device

To kick the pinion up or point it down?

[snipescastle2]

Originally Posted by demian5

To kick the pinion up or point it down?

It needed to point downwards, as you accelerate, the differential
Wants to torque upwards, so mine needed to point down.
Ben
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