Strange Butt Massage

Yes, the title is correct. I am getting a strange butt massage when I put the truck under load at speed. 2" shock leveling kit (F and R) with 35" KO2 A/T tires.

To further clarify. Tires have been balanced and rotated twice (little bit of cupping but that's because both L and R LCA front and rear bushings are shot, next repair) so it's not a tire shimmy. At speed (anything above 5ish mph) without throttle, no massage. At speed with cruising throttle (light pedal), no massage. At speed giving some go go juice, definitely a butt massage.

Replaced the throwout bearing with a brand new Toyota OEM part. I'm not 100% sure, but I believe it started after. Could be a possible bad bearing/rubber bond?

Have drive shaft out and down at the drive shaft shop. Was thinking maybe a u-joint was bad or even that weird wobbly doohicky that joins the two shafts. Turns out everything is pretty solid. Just waiting to hear back about the balance.

Last thing I can think of is maybe the rear diff is shifting (up or down) under load and acceleration causing a weird angle on the u-joint causing a wobble in the drive shaft?

Anyone have experience with this or any other ideas?

 

On other vehicles I've had torque vibration in the body, (what it sounds like your describing) from in-board, CV joint wear. (assuming you have a 4WD truck)

This would be my first guess after U joints.

 

Yes, it's 4WD. Vibration occurs with 4WD both engaged/disengaged. Not sure if that'd make a difference with this issue but I'll give them a check. The driver side CV is new after my diff rebuilds but the vibration happened way after the rebuild. At least 5k miles now.

 

Does the vibration continue when you let off the gas pedal?

Does the vibration increase/decrease to match speed?

When was the last time you greased the entire driveline, including all yokes, shafts, etc.?

When was the last time you adjusted your rear brakes?

 

It does not. As soon as I put a med to heavy load it it comes back. At a cruising load (just a wee bit of pedal) it is not there.

I don't know that I've actually paid attention to this part. I will find out later tonight on my drive home.

I just had the entire drive shaft out and down at the shop. All ujoints, yolk, and weird Toyota wobbly joint all checked out fine. They were greased up and the entire drive shaft was balanced with carrier bearing. Need a little weight up front (2 washer stack) and 1 in the rear. Vibration is still there bit not nearly as bad.

Ya I probably need to do this. Just recently started a squeal but think it might just be brake dust. Need to pull the wheel and verify though.

The drive shaft shop guy said that the rear diff could be articulating up and down thus causing a bad angle on the ujoint and thus creating a wobbling of the drive shaft. Was thinking of mounting my go pro under there to see but haven't had a chance to do that yet.

 

That's a pretty classic symptom, hence why I ask. I tend to get this backwards sometimes, but IIRC, loss of vibration when letting off the pedal at speed is usually indicative of u-joint or carrier bearing problem. General logic is, and why I'm remembering it this way (my memory sucks), when you let off the gas, the driveshaft is putting near-zero realtime load on the bearings/joints. The moment you re-engage and apply enough load, you're engaging the faulty bearing assembly, and vibration returns.

I know the shop told you your carrier bearing and u-joints are fine, but I'd be skeptical just because of that one symptom. IMO, u-joints are easy enough to DIY replace with needlenose, hammer, and a socket or dowel. I prefer Dana, Spicer, or Moog if I'm replacing. I prefer u-joints with zerks, personally.

Note that other people have found similar symptoms because the carrier bearing housing wasn't fully secured, wrong bearing was installed, was installed backwards, or because they didn't clock the driveshafts correctly when replacing the bearing. YMMV. But that's my take on it.

 

I appreciate the reply Shifty. I will most likely end up doing the ujoints sooner than later. Apparently the wobbly shaft connector is replaceable as well so I'll look into that. My other option that I started research was just doing a 1 piece but that's a long drive shaft and may cause more problems.

Carrier bearing is a brand new oem from Toyota. I was worried that maybe I had a faulty one but not sure how to even test that. So said it appeared to be good

 

This helped me get mine back together when i didnt mark the alignment.

 

When you said "wobbly shaft connector" I thought you were talking about the carrier bearing. Got a pic of the part you're talking about?

 

i'm guessing the double cardan.

 

I've seen posts noting the alignment of the joints as well. I'm certainly not an expert, good thing we have Shifty!

 

Before you just go fixing stuff willy nilly, you know some people pay a lot of money for strange butt massages right? (I mean, that's what I hear)

 

Thanks for posting this! I always mark drive shafts before I pull them but this will help me to double check.

 

Yes that's what I meant! Couldn't remember the name of it lol

 

Lmao. Pretty sure with the price of gas, this would have been up there with the expensive ones (seeing how it was only happening under acceleration)!

 

Pardon my ignorance if this doesn't apply to a 1GT or if I missed it, but did you do a carrier bearing drop after the lift? On my Turd Gen I had a small lift and slightly larger tires put on, and I needed a carrier bearing drop to address a little vibration under load. As soon as that was in the vibration was gone.

 

I did not do a carrier bearing drop. I dropped the front diff with spacers but not the carrier. Should I have done that? Read a bunch of post about leveling kits and lifts but hadn't read anything on the bearing.

 

I can't say for certain because my truck was a 2019, but I didn't do a diff drop. Just a carrier bearing drop from Coachbuilder. Without it I had a bit of vibration.

 

On the 1st gens most folks don't need to do much of anything except extended swaybar links (up front though) unless you go over 3". No diff drop, no carrier bearing drop. After 3 - 3.5" I'd be scrutinizing angles, myself, but you got plenty of guys on here at 3" who have neither dropped. I bought diff drop for my lift, but won't bother installing it. At $35, it was more of a "just in case". I wouldn't recommend installing one unless immediately after lifting you found symptoms indicative of an issue.

 

Am I the only one wondering "....as opposed to a familiar butt massage?"

 

Mine doesn't have one, the angle isn't severe. It ain't dead nuts straight but I don't believe it's caused.me any vibration from down yonder to the extent in this post. I'm thinking if we can get some pictures of the OP's drive line someone may be able to tell of the carrier etc has actually been replaced/ greased like previously mentioned

 

I did the replacement myself a few months back with an OEM one from the dealership. Had an autoparts store one on for a few years and seemed to be replacing it every 1-1.5 years. Figured they were just sh*t quality. But never had any vibrations. Drive shaft shop said the same and that the drive shaft wasn't actually too far off. The rebalanced shaft did reduce the vibration a bit but not completely. I'm pulling the rear ties and drums tomorrow to adjust the brakes as shifty mentioned.

I can't recall any one thing that might have started the shimmy, it just kind of started. Only major things I absolutely still need to do are replace both LCA and steering rack. Maybe the LCAs being fugged up (both sides, front and rear bushings) is causing a general truck vibration under acceleration but I'm not sure.

 

I try to be as entertaining as possible in my descriptions of things!

 

I just skimmed the thread. Has anyone mentioned the needle bearing? Are you getting any noises or just the butt massage?

 

I don't think so, have you done that on yours yet? I'll probably do mine when I collect the parts to do the boots and what not. Boots arent ripped but I do sling some grease.

 

Yes I did mine and replaced it with the ECGS part. This is the way. @FrenchToasty will loan you his special tool if you send him good vibes and a beer.

 

It doesn't look like that bad of a job or technical at all more messy than anything. I'll look up that thread I've read it several times, actually probably in 1 of my 51 tabs currently.