Vibration diagnosis- Took off rear DS, noise gone. Questions.

[exrsa1]

A few days ago, my 62 suddenly developed a vibration/rumble strip noise at speeds above 50 mph.

The whole car does NOT shake, its just a deep vibration that is very loud- sounds like you are driving over a rumble strip constantly. Most of the noise goes away if I take my foot off the gas driving at freeway speeds, but comes back instantly if I start to accelerate again.

Today I changed the transfer case oil- was pretty low and filled mostly with ATF which I guess had seeped in from the tranny. Drained this out and put gear oil back in. Cleaned drain plug magnet which was coated with a layer of very fine material (dust like) then underneath that a thin layer of small metal shavings.

Got back on the interstate and vibration did not change.

Took the rear driveshaft off, and running it front wheel drive, the vibration disappeared.

The u-joints on the rear shaft seem very solid with no movement that I could tell. The transfer case rear output bearing has very small amount of play in all directions. The x-fer case front output bearing has some play in all directions, noticeably more than the rear.

Does taking the rear shaft off isolate the problem to one of the u joints on the rear shaft / the shaft itself OR could the transfer case still be the cause of the vibration?

Also, do I need to cover the wholes left where the read DS connected to the differential or t-case? Can water get in there? I am going to be backing a boat down a ramp tomorrow, and the rear differential will be likely submerged. With the DS off, will this be an issue??

I've been following this post since I have something similar going on, but have aproached it differently. I just purhased an 88 FJ62 and at highway speeds, and a slight hill is encountered, it starts vibrating as you describe. After reading your post, I tried a few things and I realized that when I shift it out of D and into 3rd, the vibration goes away. Have you tried that? I felt around the drive shaft and the flanges and nothing seems out of the ordinary loose. I currently have the transmission open to clean the strainer and do a flush, since I thought it might be the tranny that was slipping, and the clean and flush could fix the symptom. If perhaps you have time, could you check to see if yours does the same, meaning the vibration goes away if you shifted from D to 3rd.

Thanks
Ex

 

[Bomar]

Bryan,

Let me know if you need some help.

Bomar

 

[Cruiserdrew]

Really think this is the problem? How much is too much play in the rear output bearing? I have maybe 1/16 inch play

I know my t-case is due for a rebuild, but I was hoping to get some more miles out of it. Planned on replacing the fubard t-case and transmission with rebuilt transfer case and h55f sometime down the road. Wanted the t-case to last at least as long as the automatic trans... maybe like you say, its time is up and I should rebuild the case. If its the cause of the rumble/vibration im getting, I guess I have to. Also, it leaks from pretty much every gasket...If i could hold off not rebuilding it just yet, that would be great tho..

Any methods for narrowing it down to the rear output bearing without tearing the transfer case apart? Tape a garden hose somewhere and listen through it?

That's probably the answer because the proper amount of play is ZERO. If there is play, it implies the preload on the pinion bearing is ZERO, which means it can dance around on the race. Rebuilding a split case is not hard. If I can do it, you can too, but no-you can't get the output bearing out without disassembling the case.(I know you were gonna ask!)

Since this is an FJ62, also consider the t-case input gear. TrickyT had a vibration at speed that turned out to be the worn spline problem on the transmission output shaft that he solved with a McNamara gear. Do you have a big clunk when going from forward to reverse? Do a search on McNamara gear for loads of info on this common FJ62 problem. You could also PM TrickyT-he's a good guy and I'm sure would share his experience.

Definitely eliminate the easy stuff like a U-joint, but if you found slop where none should be, you know where to concentrate your forces.

Good luck.

 

[rover67]

swap driveshafts with Bomar and see if it goes away..

My pinion and output flanges on my truck have a tad bit of wiggle and they don't cause any vibration... I realize that they are not perfect, but I'm just sayin..

 

[meatsauce]

That's probably the answer because the proper amount of play is ZERO. If there is play, it implies the preload on the pinion bearing is ZERO, which means it can dance around on the race. Rebuilding a split case is not hard. If I can do it, you can too, but no-you can't get the output bearing out without disassembling the case.(I know you were gonna ask!)

Since this is an FJ62, also consider the t-case input gear. TrickyT had a vibration at speed that turned out to be the worn spline problem on the transmission output shaft that he solved with a McNamara gear. Do you have a big clunk when going from forward to reverse? Do a search on McNamara gear for loads of info on this common FJ62 problem. You could also PM TrickyT-he's a good guy and I'm sure would share his experience.

Definitely eliminate the easy stuff like a U-joint, but if you found slop where none should be, you know where to concentrate your forces.

Good luck.

what does the big clunk mean? mine does do that some times and post lift i have a vibration i believe to be either under the console between the seats or in the rear somewhere. the vib is not at highway speeds. starts just over 20 mph. i haven't gone past 45 and its still there but not as noticeable.

 

[Cruiserdrew]

what does the big clunk mean? mine does do that some times and post lift i have a vibration i believe to be either under the console between the seats or in the rear somewhere. the vib is not at highway speeds. starts just over 20 mph. i haven't gone past 45 and its still there but not as noticeable.

The clunk means that the input shaft (the tailshaft of the transmission) is worn and the splines have partially worn away. It happens because the input gear only engages a short section of the splined shaft. The McNamara gear replaces the input gear and has splines that run the full length of the gear. That lets it engage more of the input shaft spines including ones that are not worn. That eliminates the clunk. Tom said he eventually got a vibration at speed that was the gear vibrating on the worn splines.

Check this out:Jack McNamara - Differential Specialists

Just for the record, my 117k FJ62 does not clunk or vibrate, but it's bone stock and has no lift at all.

 

[Bryan062087]

Yeah, I have the big clunk/ worn input shaft.

As far the rear u-joints being starved of grease- I greased everything up really well before I took the driveshaft off, but that was my first time greasing it so who knows...

I was busy all day to day, I will have some more info tomorrow. Did fine driving in FWD though.

 

[TBIFJ40]

I dont buy the worn-splines-clunk-theory. Anytime youve got gears, theres going to be some slop resulting in a clunk. The splines could certainly cause a clunk, but thats not the only reason.

 

[doctorjj]

Start with the simple stuff. All this talk of rebuilding your rear end and T-case when you still haven't ruled out the driveshaft???

I went through heck trying to get my vibration solved and it sort of came out of nowhere. I tried a couple of aftermarket u-joints and finally just got both new Toyota u-joints from C-dan and had them professionally installed and had the driveshaft balanced. It was smooth as silk after that.

 

[FJ60Cam]

From my limited experience...

when I had bad ujoint(s), it only made a rumble at highway speeds. When I installed a bad used diff, it made lots of noise at all speeds.

Hopefully it's just your driveshaft.

 

[dwillmo]

Bad u-joint

Do the easy stuff first. Bet you'll find its the u-joint. Pinion can have tremendous amount of slop. I was replacing u-joint on my Jeep Cherokee wiggled the pinion shaft and was so bad I took it to the dealer when I got it back together. They said that it was within factory specs.

I've always marked the shaft too when I removed it so I could get it back like it was, but then, I've ran some shafts that had been repaired which had some big honking welds --no way they were dynamically balanced--and they didn't vibrate.

The bigger the shaft is, the harder it is to diagnose bad u-joints just by getting under there and trying to jerk things around. You just can't feel any slop. I had a big International Cab-over years ago. I was ready to get the rear drive axle replaced ($15,000 then) and a driver on the road told me to change the u-joint first. I did it on the road at a truck stop with limited tools. I've had a lot more trouble with smaller vehicles. But anyway, that was it, even though you could not feel any looseness with the shaft installed.

 

[Bryan062087]

I should know by tomorrow if its the u-joint/driveshaft or something else. I'll update on what i find.

 

[Bryan062087]

Bad rear u-joint!!

Ordering two new u-joints and going to balance driveshaft..

 

[rover67]

sweet, way to go. Truck Parts Specialists is where I got mine balanced. Quick turnaround. Just let them do everything.. it's not worth your trouble to mess with the joints. And Dan has the best deal on the joints themselves.

 

[doctorjj]

I hate to say I told you so, but....

Seriously though, I'm just glad it wasn't anything major. It will seem SOOOO smooth once you get the new u-joints and a balance. You won't realize how bad it had gotten.