Have you tried draining the diff fluid in the rear end? Look at it for chunks of metal, though I doubt you grenaded your diff from a lift. If you support the whole rear end of the vehicle up in the air and spin the rear tires, do you feel any binding? Hear any noise?

 

No I haven't tried draining it but I guess I could. I checked the level, it's fine. No binding that I can see...but I really don't know what I am looking for This is my post from earlier: "Then I put the runner up in jack stands and put her in gear and at about 50 mph it is really bad. If I leave it in gear, the speedo reads about 30, I put my hand to the diff housing, I can feel a vibration or grinding"

I am almost positive I know that the angles changed in the rear, and the u joints are now at a different axis than before and were probably "set in their ways" thus changing the angle of the u joint to the driveshaft. It happened exactly after I did the rear lift. Even if I do in fact determine it to be an angle problem, after replacing the u joints and the trans mount, I guess I will shim the trans mount at the cross member. If that doesn't work I don't know what else to do. I have been to 2 offroad shops and 1 driveshaft specialist with no luck...it is kind of discouraging.

 

If the truck is on stands, and you rotate the driveshaft by hand, do you feel any binding/resistance? You had the tires spinning at 50 mph while up on jack stands? That sounds scary.....

Still got your old springs? Probably a 20 minute job to put the old springs back in and see if the vibration goes away...

 

Yes I have the old springs...I guess I could try that. I'll be riding down the road like this \ should be cool

Yeah it was a little nerving but I was extremely careful. I will check the binding/resistance tonight.

 

If it's the pinion angle due to the lift another way to check this is to load 400-500 lbs in the back. This should compress the OME springs about 2 inches and get you back to the driveshaft alignment you had with the stock springs. This should also move your panhard bar into pre-lift and your vibration should go away.

 

Stephen, I'm on the same page as you. This vibration/humming sound didn't start until I put the OME stuff on. I can tell you this though, that as soon as I put a load in the back or while I'm towing my boat, the sound goes away or is not as bad. I just find it hard to believe that the u joints or diff went bad at the exact time I put the lift in. I don't know how to fix it other than maybe restoring the proper angle of the axle by fabbing up a drop braket for the front link and another for the sway bar? Like the pan hard drop but for the rest of the linkage. Anyone do this yet? Seems like a good idea to me, but can't seem to find anyone doing it.

Does anyone know if the only difference between the rear end of the 2wd and the 4wd is the drive shaft? Seems like the guys with 4wd don't have this issue. If we could figure out what's different that that should be our part to change. Maybe we need to get a driveshaft from a 4x to fix it. Here's some pics of the linkage for reference.

 

I think you're confused. the slip yoke is the part of the driveshaft that slides into the other part. the shaft shouldn't go into the tranny. it should bolt up to the output shaft flange on the back of the tranny. by compress I mean after bolting the front flange up I have to compress the driveshaft (push the yoke into the front piece of the driveshaft) to get the rear flange to mate up with the companion flange (or pinion flange).

 

Austin,

I did the panhard drop already, but I will try putting some weight back there to test with.

I don't have an output shaft flange in the front near the tranny. The real shiny piece of metal (yoke?) just slips into the tranny housing and I just re-install the 4 bolts at the pinion flange in the rear....must be a 4wd thing? Is your rear driveshaft double cardan?

 

Yes, on a 4WD it is and you might have hit on a good point there.
The double cardan might be taking some of the pressure off the angle when lifted.

 

This is a great idea! I am at the point where I will try anything. I have a new tranny mount and u joints on the way. Then if that doesn't work, I am going to try shimming the trans mount itself upward a bit. If that doesn't work, then I am taking it to a shop to have them look at it. I agree that the contol arms would need to move forward to help correct the pinion angles. Hopefully we'll find a concrete resolution for others who do this...

 

Well now we're getting somewhere

 

Ah, a breath of fresh air! I am having similar symptoms but nobody until now really mentioned the word 'humming'. That makes me happy to see this.

I am also having a nasty humming noise from my rig that started occuring shortly after the OME stuff went in. My humming is more of a moan, and the vibration is there but comes second to the noise.

I believe we are sharing different symptoms to the same problem.

I was convinced my vibration/noise was coming from the front end somewhere, possibly the tranny. I had the tranny flushed, a triple lube job and tons of other maintenance but the problem remains.

Stephen - those tranny mounts look great to me

 

I think the difference between the 2wd and 4wd driveshafts will make this problem worse for the 2wd guys. I've had the OME lift for 2 years and didn't notice the "vibration/humming" until a gear change from 4.10s to 4.88s. Now at 70mph I'm spinning the driveshaft at the same RPM that would have been 83mph with the 4.10s and I rarely drove that fast. I feel the vibration in the floorboard and it also vibrates my rearview mirror. Dropping the attachment point for the lower control arms should have the same affect as using longer lower control arms but you'll loose ground clearance at that point. Structurally I think your drop bracket would have to be significantly stronger for the lower control arms than the typical panhard bar drop that people are using. I'm working on replacing my upper control arms with arms that are adjustable so I can make them shorter. This should solve the problem but I haven't tested it yet. I also couldn't find any info on someone else doing this for a 3rd gen. 4Runner.

 

Rob, I have taken out the rear driveshaft and driven in 4wd, to isolate the front drive for vibration. I initially thought my problem was in the front.

 

strange. Passengers and I all agree it sounds like its up front, or near the front.

vibrations travel I guess

 

I think you guys need to go back to the original question. " the vibration starts after you lift the rear" .
Couple of things chage when you lift....the d-shaft angle at the trans side, length and the pinion angle.
Being a 2wd, the d-shaft is longer than the 4wd ones. You've mentioned that the 2wd d-shaft is different than the 4wd ones in that there's no flange on the transmision side right? So changing to a double cardan joint is not an option for you unless you can find a flange that will fit the output shaft of the trans.
You can get AllPro adjustable upper links. With that, you can adjust your rear pinion to point the d-shaft toward the trans more.
If you're close to me, I'd lend you mine for you to try it out.....GA to CA is pretty far.

It could very well be that it will go away after a while. When I did my Body lift, the angle of the steering wheel change. There's couble of U-joint like links in there and it took a while for the steering to feel smooth again.

 

Thanks for the offer Anthony...I was just in Manhattan Beach last week but sans my truck. I am having my u joints replaced, a new trans mount (maybe), and the mechainc is going to work with me to try and lower the transmission cross-member. Which I hope in effect will do the same as raising the pinion angle with respect to the transmission. I am trading his work for a wireless netwok installation in his business, so I am hoping to get a in-expensive and most importantly a quality fix. I've seen his work and I feel very comfortable that he will help me get it right. He has been around the auto business since he was 9. I am actually glad I found someone who took the time to look at my problem. He is also the person that welded my panhard bracket. Which looks good btw...thanks Steve!

 

but then he'll be putting a buckle in the coil springs in that the upper and lower seats won't be parallel anymore. not a good thing to do to a spring that's made to compress straight.

 

It's not as bad as you think. I did it on mine and drove and wheeled fine.

 

Just got a 2 inch (advertised) lift that actually put me up just around 3 inches this saturday at Slee Offroad. As I was driving to get an alignment (because the front wheels got thrown WAY off) I noticed the dreaded driveshaft vibration. It started right around 50 mph, and was pretty much a minor irritation, although I think driving long distances might cause the ol' hands to go numb. I could feel it in the steering wheel, feel it in the seats, and hear a little hum. My girlfriend noticed it too.

SO - after getting the alignment done, I went BACK to Slee, and talked to Christo. He said, a) lube the driveshaft, and if that doesn't work, b) wait to see if the springs settling makes it go away, and if that doesn't work, c) bring it back in and we'll see what we can do. He seemed quite certain that a and b would take care of the problem (especially if the d-shaft hadn't been lubed in a long time, which I don't know since I've only had the truck for about a year.)

So anyway - I took it out today, and brought it up to 50 and it APPEARS the vibration is gone. I didn't get to drive at 50 for too long, but it looks to be settled. I figured I'd just add my 2 cents.