Yodaforce

1985
22r (254k original miles) smokes a little. Lol. Runs good. Weber carb.
SHocks are old and terrible (saving up for Bil1500's)
Front lift springs (maybe 4", old, bad bushings)
Stock rear springs (with a stupid 3" lift block, stock shackles, bushings are poo)
35" KM2's on 15x10 steel sawblades (exactly 12oz of airsoft pellets in each)
New single steering stabilizer (made a huge difference!)
MANUAL steering (it SUCKS, but I'm waiting for high steer parts)
Just rebuilt both axles (complete end to end with 5.29's all parts Yukon)
New brakes (I mean everything. EVERYTHING except for the brake lines)
4wd works good, low and high.

OK so here is my situation:
I get a rumbling vibration from 45-55. Not just an annoying low grumble, but more like a "SOmething is about to break and fall off the truck!" rumble.

It's not affected by rpm, gear, braking, or acceleration. It's the same in 2wd, hubs locked or unlocked, and in 4wd (same speed range).

The gear pattern (after about 20 shim adjustments on the press) came out beautiful both front and rear. The bearing preload was perfect, backlash perfect, etc....

The vibration is not felt in the steering wheel, brake pedal, or seat. It's an "all over" bearing failure kind of vibration.

I can only think that the problem COULD be:
1. Tires? (ABout 90% tread, no damages) Anyone else have "Mud tire" issues with KM2's
2. Transmission bearing? (output shaft has no play on case) Ujoints are all tight, no play, plenty lube. I don't think input shaft because it's not rpm related.
3. Bad parts? Maybe a bad pinion or carrier bearing? WHeel bearing still feel tight.
4. Front axle shafts (stock birfs)?


The only other symptom of any problem is when it's locked in 4wd, it gets pretty stiff to turn sharp. I believe I read where I can yank the axles and tack them to prevent them from getting in to the carrier too far and bind at the joint. IF that sounds like a good recommendation?

I came here with this problem because I believe THIS is where the real professional Toyota gurus are, so I appreciate any input and advice. I would like to make it just a little more streetable between dirt roads and trails.

85TurboRunner

I vote bad u-joint. The wiggle by hand test is worthless.

Yodaforce

I pulled both drive shafts when I did the diffs and cleaned them up lubed them. Seals held the grease pretty tight and they have about the same smooth resistance as some new ones I have on the shelf. I may go ahead and install them soon, but I'm not real sure if the problem. Could be, but I will find out soon.

Keep any suggestions or theories coming. I'll happily go through all of them to solve the issue.

Yodaforce

Bump.........my head on a wall. Over and over.

FGZ

That was going to be my vote too. U-Joints or loose splines.

Did this just start, always been there, what changed before this started happening?

Since you have checked your u-joints by hand, can you get your hands on another rear drive shaft for testing? Take the front drive shaft out and see if you still have the vibe, that should rule it out, then you can focus on the rear. Maybe a drive shaft shop can take a look and tell you if it's something as simple as out-of-balance, bad u-joint, etc.

Another thing you can do to rule stuff out: swap tires over to some well balanced street tires.

Did you ever disassemble either of the driveshafts at the splines? If you did, did you put them back together out of phase? Or maybe it is considered "in phase" when you line up the indents, I don't remember, but the front and rear U-joint on each driveshaft are supposed to be 90deg opposite the other.

I have a rear driveline vibe to chase down, but I think it is pretty clearly that my rear pinion isn't pointed at the t-case.

Yodaforce

I have been bringing the truck back to life since I picked it up. The truck was not even road worthy for months and with every new repair (more like restoration) the noises and vibrations go away, except this one. I'm sure it could have always been there but covered up by a worse vibration.
I like the front driveshaft idea. I will remove it and test it out to help eliminate that or confirm it.
I have some new ujoints for the rear shaft. Will replace them as soon as I get the chance. I always mark the shafts when removing them clearly so they went back in the same.
I can try a buddy's new tires if I can talk him into it. Lol. Another good idea.
Would the rear pinion angle (with the stupid blocks on it) cause this type of vibe?
Good points. I will keep working through them.

I sure look forward to the day I can do some miles to get to the good off road parks. Lol

FGZ

A bad rear pinion angle could cause the issue I think. I would think you would also see it at a lower speed though. Mine vibes a little around 25 mph, and I never get over about 40 so I bet it would vibe at a higher speed too.

Here is my homework reading from 4Crawler's mass of info, read through and see what he has to say about proper angles because then you'll be able to measure you own situation and see how far off you are from ideal. CLICKY

Yodaforce

Awesome link. Thanks for that bit of info!

Teuf

I vote driveline angle.
[YOUTUBE] [/YOUTUBE]

Yodaforce

Checked angles today. The rear was only off by .5 degree from output flange and rear input flange. Front diff was at 9 degrees while the case output was -2. Front drive shaft slip shows some play. Pulled the front shaft to rebuild. Test drove, still some vibration without the front in so I will be picking up some new joints for the rear shaft as well. WIll the 1 degree on the rear cause a vibration or is that considered "within spec"? Rear tranny mount has some wear and now I wonder if it's sagging in the rear making for more flange angle on the front output.