help me diagnose a severe vibration

for several months now I've been working on this and only making marginal improvements each time.

2001 Tacoma double cab 4x4 stock height . currently with 265/75R16 that are half worn.

vibration is coming from the rear and feels like the reared is hopping or bouncing from the road. vibration begins at 50 and is worse at 55 to 60. shocks are about 2 years old. bilstein 4600s. stock springs. vibration is same with and without shell. happened with my old set of street tires as well.

i have:
replaced rear u joint and greased the other zerks. made a minor improvement.

replaced center support bearing. minor improvement.

rebalanced my tires myself. they were pretty cupped when i had them put back on my wheels recently and since have rounded out. (took them off before i rebuilt the front end. now the cupped ones are on rear). this made an improvement as well but the bouncing is still there at around 60mph.

what else could it be? i know transmission mount can be bad but it doesn't seem bad based on my inspection though it has 325k and 20 years on it.
I've heard pinion bearings?

i picked up some new wheels and i plan to put on a street set of tires that hopefully are balanced better. i know these mud tires are taking like 8 ounces sometimes to balance.
thanks for reading all this and any insight you may have

 

Have you measured the angles of both the shafts, pinion flange, and Tcase flange? That may be informative and is really straightforward to do. Also when is the last time you had it aligned?

 

AXLE WRAP

Overall, the Toyota Tacoma is an excellent, reliable, and well-built machine. But like many other leaf spring equipped vehicles, it suffers from a problem known as axle wrap. The rear axle is only held in place by the leaf springs, which is fine for a while. But over time, as the springs soften and wear out, they lose their ability to hold the rear axle in place. The rear axle begins to move around, and pinion angle changes. And eventually, things like yokes and driveshafts begin to break.

Axle wrap is a problem that plagues leaf sprung vehicles with soft springs, particularly those that are set up SOA (Spring Over Axle). ... Wheel hop is when anaxle on your 4x4 rapidly hops up and down. Axle wrap is unwanted suspension movement that allows the pinion angle to change.

I am not a mechanic, and depend on experienced Toyota techs, that know what they are doing. For several years, thru used and new Tacoma and new 4Runner purchases, in most, I have had vibration, especially in the front ends. Always use Michelin tires. I buy tires at a tire dealer that has the proper equipment, (Road Force), and one step further, a Haweka 6 pin adapter. I am not sure, cone centric or lug centric on these models. Attached is the adapter, find a dealer, Toyota or independent tire retailer, that has this equipment.
Most important, is the tech on the machine, plus has the knowledge to index all four wheels in the balance process.

Hope this helps.
Crank

 

Bent rear drive shaft.
Have a real driveshaft shop check and balance it.
I reccomend six states if you are near one.

 

drive shaft angles look good but maybe slightly less than 0 degrees due to spring sag.

does axle wrap happen at freeway speed? I've noticed that the vibration is slightly worse when not on the gas, just coasting. honestly new springs is one of my planned projects since this really sag with the shell on.

how can the drive shaft get bent? that's usually an off road thing and i haven't been off road in many years.

I'm thinking about sticking a go pro under there and see if i can identify a problem.

 

There are videos showing what you are talking about. Click below, google axle wrap
https://youtu.be/54_6GaYJvWI

 

actually now that i look at the pinion angle again it looks pretty bad. what do you think?

 

Check Carrier bearing?

 

already replaced.

 

Pinion should ideally point directly at the DC joint if you have one. World is not ideal however, so maybe .5 to .75 degrees under the DC joint at rest will allow for near perfect
alignment under cruise conditions(the pinion rotates upward as you accelerate/drive forward). You just have to allow for some axle wrap because it does occur! Goal would be perfect alignment at cruise. That is what helped me.
Good luck!

 

If you have a Double Cardon joint, your U joints could be worn out. I had to replace mine and they were Extremely hard to source. There is also a ball in there that I couldn’t source , so hopefully that isn’t your issue.

 

A few things to check:
Rear spring shackles/bushings loose,worn or binding
Driveshaft bent and/or unbalanced
Broken spring leaf and /or missing clamps
Bad or broken shock,mount, or bushings
Structurally bad tire (tires) (not balance related)
Bad transmission mount as mentioned
Bad (worn) wheel lug holes and/or wrong lug nuts not centering wheel properly on axle axis.
Bent wheels, loose wheels

It's an 18 year old truck with high miles. Any combination of the above is possible. Good luck.

 

i inspected those when i replaced the rear ujoint. thankfully they still seemed good so i lubed them up. good thinking though.

i think I made some progress today. i bought some new wheels last week so i mounted some tires that i had that are street tires and way better condition and lighter than these older mud tires. i only had 2 but i threw them on the rear rear and hit the freeway. way smoother up past 65 but now I'm noticing the vibration from the front. so i guess it's my tires(but could still be my old wheels) one of the mud tires took like over 8 ounces to balance.

im going to get some street tires for this second set of wheels for daily driving. ill throw the mud tires on when i want to use them.

 

In my case when I bought my truck it had some crappy tires on it so I bough some tires off of CL. 31" GOODYEAR authorities. 15x10 steel wheels -40 offset. Truck looked cool as hell but vibrated at hi speeds. That lasted for about a yr. And same thing replaced. U joint, carrier barring, greased, shocks, add a leaf, balanced tires 3 times and still vibration was there. Until....... I bought some OEM Toyota trd wheels and slapped some Goodyear duratracks. Completely different. Felt like a new truck. No more vibration and a hell of a lot smoother ride. Maybe one of ur wheels is not true on a bad tire.

 

i just remembered that when i went to replace rear ujoint, the drive shaft splines where really stiff and i couldn't get it apart to lube it. i know the zerk only fills the cavity. could a tight slip joint cause bouncing in the cab? also how does out get removed for lubing?

 

Love that exhaust.

 

Ouch! If it were me, I would try to pump some extra grease into the spline zerk 1st, then set the rear half of the DL, (the part behind the center bearing) upside down on the floor with the spline end facing up. Now shoot, pour or dribble your favorite penetrating oil (like PB Blaster) all around the seam and gently tap on that area all around the shaft with a plastic mallet to try and get the lube down into the splines. If they are stuck together, there must be rust, which isn't good, but once you get it apart, you can likely give it a thorough cleaning and assess the damage. Unless it is severe, you should be able to properly lube it up and re-use it. If you have any concerns about the condition, I'd sure consult a local drive line shop to be certain. I really tight slip joint can wreak havoc on ujoints, pinion bearings and just isn't a great thing in general...HTH!

 

I had the exact same problem. Checked everything twice. Finally bought new wheels to replace old steel wheels. That did it. As far as axle wraps should buy new leaf packs

 

How much lift do you have on your truck?

 

update. i solved the last of the vibration when my new tires came in from Amazon today. i mounted them to my 4 runner limited wheels and balanced them though they needed almost nothing. and tested it on the freeway. smooth as silk as fast as i went which was 70. thanks all for your help.