Chasing VIBRATION - please help !! (1 Viewer)

[Splash]

1973 FJ40
302 V8
C4 Auto (rebuilt 6 months ago)
Orion T-Case (rebuilt last week)
New drive lines front and rear (last week)
SOA w/front spring reversal
New leaf springs and new bushings
High steer
Four wheel disc brakes
New Longfields
New front drive line
37" BFG Mud Terrains recently balanced

I have a vibration that starts at about 40 mph and gets worse. You feel it in the steering wheel and gear shift nob. Not a wicked bad vibration but very annoying. The steering wheel does not go left and right at all you just feel the vibration.

If you shift between 2nd and 3rd the vibration appears to remain constant eliminating the engine as the cause.

I have done everything I can think of to eliminate the vibration.

I am hoping someone will have a new idea to try.

Thanks in advance and enjoy the pictures.

 

[ibinazbass]

have the driveshaft balanced... sometimes they need to be properly aligned too

 

[Splash]

The driveshaft was balanced last week. We still had the vibration so the driveling shop took it to their sister shop to double check and it was fine. It doed feel like a driveshaft issue but that seems to have been eliminated.

 

[mudnyreye]

Motor Mounts???

 

[batcon]

Are you sure its not the tires- wheels? Nice pics! Good Luck.

 

[MtnTrucker]

It looks like you have done a lot of work to this thing recently all at once. A few questions: You say you are SOA, did the vibration exist before the SOA conversion? Did you rotate the rear axle pinion up to point toward the output shaft of the TC as part of the SOA? If not, you may be getting a vibration due to the extreme angle on the u joint. If yes, did the new DS you installed include a double cardan CV joint at the top? If not, you may be feeling the vibration caused by the top u joint running at a different velocity than the bottom one.

You also just rebuilt your TC. Make sure the bearing preload on the output shaft was set correctly and the yoke itself is tight. Just a little loosness in the output yoke will cause vibration.

I'm assuming you can unlock your hubs and put the TC in 2wd to eliminate the front DS being the problem?

 

[BrianSanDiego]

Pull one driveshaft at a time to eliminate either front or rear shaft as the cause?
B.

 

[Splash]

Thanks for the input.

It has been SOA for a few years and it is a new vibration issue. The rear axle was cut and turned. I am not familiar with the double cardan CV joint and will research that.

The front is unlocked and I even pulled the front driveshaft and went for a test to make sure it was not the problem.

TC was built by Georg at Valley Highbrids so I believe it is proper.

 

[Splash]

Pull one driveshaft at a time to eliminate either front or rear shaft as the cause?
B.

I have done this with the front and will try the rear. TX

 

[ranger]

Rear axle cut and turn?

Check front hubs for loose bearings, also check trunion bearings.
Motor mounts, tranny mounts, loose or broken.

 

[dargreg]

I had a bad vibration in my 82 bj SOA installed rebuilt cardan joint from 83 mini truck end of problem

 

[Splash]

Thanks for the info. I have a CV joint now. Can anyone tell if removing the e-brake from the back of the t-case will extend the driveline enough to help the angle?

Secondly can anyone tell me if a cardan CV joint is different than a traditional CV joint?

 

[splib]

Can you swap the tires/wheels to eliminate them as the culprit?

Need more pics......

 

[F-junker]

Boooobs.... Your a scholar and a gentleman. I've gone through adding a CV or D.C.joint. It was a great addition and eliminated my driveline vibration. I would not that it works best with the tail shaft of the pumpkin pointed directly at the output shaft of the transfer case. If your currently set up like that running a pair of u-joints then that is your vibration problem.
Adding the double cardan joint on my 78 FJ-40 required me to remove a small section of the crossmember a fillet if you will. you can weld it shut if you so choose, the other method would be turning the x-member or deleting the brake drum. I would keep the drum unless you have a rear ebrake on the back calipers.
good luck. also I had my shaft made up by Tom woods and that joint may have been a little larger than a mini-truck dcjoint, you might not need to trim that x-member with a smaller joint.

 

[4x4 Station Wagon]

You mentioned at 40 mph so I lean towards tires. I had spacers/adapters on a VW bug back in the day and one cracked. It would start shaking hard at 35 and go away at 45. It is possible you threw a weight on one of the rims. Inspect all the way around the outside and inside of the rim to verify if it looks like a weight is missing..... Or I have had two tires in my life that started to seperate and created a nasty vibration. One was a low profile tire that couldnt take the constant sidewall flex (very noticable bubble in the tread of the tire) and the other was a BFG all terrain that was difficult but you could see it with the naked eye.... Did I say naked?? Your pictures have got my mind in the gutter!

 

[bsevans]

My vibration disapeared after I had a CV installed on the rear drive shaft. If you do this you need to make sure that the rear pinion is pointing at the transfer case output.

 

[slickrock]

check the front shackles. Tighten the way down and go for a drive. IF vibration gone, there you go and need to find a happy medium between too tight shackle bolts or flex.

 

[Jerzfj40]

Caster angle

I had the same problem with the vibration. Have you checked the caster angle since you installed the lift? also if you installed longer shackles that would add to it also . Mine was at 0 degrees and should be at about + 2 degrees so i installed caster shims and it corrected the problem.

 

[Splash]

Interesting. I will check in to the caster angle.

 

[orangefj45]

more info for everybody.

i just did a lot of work on ross' rig, part of which ws in effort to eliminate the vibration. here's some of the history of this rig and recent work completed:

SOA for a while
auto conversion about 6 months ago including a new skid plate and track-bar

ross brought it to the shop for a few updates along with a slight vibration issue and major t-case noise (orion)

this is what i found:
the 40 had a busted engine mount
the t-case had suffered some damage
rear drive-line was slightly out of balance
long travel front driveline had worn out splines

so i had the drivelines redone
rebuilt the orion completely including a NEW main shaft
replaced the engine mountd with a much stronger "captive" design

alongside all of that i also did a rear disc brake conversion and fixed a couple of other items ( these definetly have no bearing on the vibration issue at hand although the disc brakes could ).

i got the rig put back together and took it for a test-drive only to be dis-apointed by the fact that the vibration was now worse. it definetly felt like a drive-shaft so i removed the freshly re-balanced rear shaft and took it back to the driveline shop. they chucked it up in the machine while i was watching and checked it. ran very true and showed to be in spec. actually, it showed better than most. it is a cv style shaft.

so that put me back to square one. i re-installed the driveline and tried a few things to no avail. things i inspected:
shackles, bushings, springs, u-bolts and perches are all in excellent shape
caster is correct
no loose front wheel hubs
no bent rims or axle shafts
nothing grounding out on the body
exhaust clears everything

so i jacked the 40 up and put it on jack stands. then ran it with and without the rear drive-shaft. the vibration was better since there was no load on the drive-train and the only issue i saw was that the e-brake drum wobbled a little. so i put a dial indicator on it and came up with .010" runout. so we tried a different drum and still had the vibration. that left m to believe that the new main shaft might be either bent or mis-manufactured.
so i removed the t-case again, tore it down completely, inspected every part to my best ability and put it all back together with another new main shaft.
i did chuck the "old" new main sgaft un in a lathe as well as the replacement and the old one definetly had some run-out issues.
i thought i had the problem solved. re-installed the t-case in the cruiser, checked the drum for run-out. perfect.
finished putting the rig back together, go for a test-drive and the vibration is much better but it's still there.
at this point i jacked it back up and ran it without the rear tires. still there. so i ran it without the rear discs. still there but getting harder to notice with no weight or load on the running gear.


at that point, ross had to pick u pthe rig from me and we decided to go after a couple of small engine issues and then re-visit the virbtaion problem.

that's it in a nut-shell. i have spent 40 hours or more chasing down this vibration to no avail. i realize that the firmer engine mounts will transmit any vibration a lot moreso than the old rubber mounts.

so my next move will be to build another rear drive-line after we get the tires and wheels re-checked. i did rotate them which seemed to make no difference. the only other culprits i see are:
rear axle shafts ( i am confident that they're not the cause since i did check them)
rear disc brakes ( maybe one of the discs was'nt machined right or is out of balance)
rear wheel spacers ( i checked these more than once also )
e-brake drum ( we've tried 4 different ones so far )

either way, we'll get it fixed. i have had to deal with pl;enty of vibration and drivetrain issues in the past and i'm confident we'll get this one worked out. it's just putting up more of a fight than most...........