Mikronized

So, here is what's going on...
I'm driving on the freeway this morning at about 70mph, and when I take my foot off the gas and coast I can hear a grinding noise from the rear/middle of the truck... but then when I gas it again then the noise goes away.

any ideas? it could be my driveline, but who knows

4runner4ever

Most likely the pinion bearings or something elso in the diff. Check if there is any play on the diff flange.

sidfactor

I heard this same noise in the same situation right before I blew my rear end.
I had nailed my rear diff along some trail and I guess it had leaked quite a bit. When I noticed the noise I took it to my mechanic. He showed me how my gears were sort of welding themselves together. He was shocked that they hadn't locked up on me yet. It was the perfect time to upgrade to 5.29's.
I would at least check your diff fluid right away.

Mikronized

thanks guys for the input... I'll check my fluid once I go home tonight

The Rusty Gear

Also check your U-joints and make sure your driveshaft is firmly bolted on both ends. I had a similar problem where I heard a grinding sound while coasting. Turned out one U-joint was worn beyond recognition, and the driveshaft was barely hanging on (the bolts on the front driveshaft flange were either missing or loose)

805specr

My truck is making the same noise as well. How much does something like this cost to repair? I hope it's not too much.

Mikronized

ok.... so I checked the fluids in both diffs, lubed both drivelines and checked to make sure they were tight.. the noise is still there...

sucky, I guess I'll take it to the shop tomorrow

blackrunner91

hey man, it's your pinion angle. I have the same problem. I also have the Superlift kit just like you do. The angle at the differential end is the problem. I bought a Tom Woods custom driveshaft with a dual cv joint and long travel slip-yoke. That new driveshaft still didn't fix my problem though. That only helps the angle on the t-case end of your drivshaft. Is what you'll need to do is either cut your upper links in half and lengthen them about an inch(i think). I'd have a good welding shop do the welding though. You don't want one of those suckers to snap for sure. If you don't want to go through that trouble, you could spend $250 at Downey Offroad or All-Pro Offroad and get some adjustable upper links with heims on each end. I just bought some from a member here pretty cheap with a bunch of other stuff. I hope to have them by the end of next week. I hope this helps.
,Louis

anthony1

iTrader: (1)

I heard that before......
After I SAS the truck, I used AllPro links and OME860 coils in the rear. I adjusted the pinion angle with the AP upper links. I was getting the same grinding noise. Marlin said I needed a pre 86 front D-shaft and lengthen it. The part cost me 75 bucks at the junk yard and another 150 to lengthen and balanced.

Mikronized

so is it the pinion angle or the driveline length or both?

blackrunner91

it's the pinion angle, but the reason that he had the shaft lengthened is b/c it was a front d-shaft from a pre-86 truck. The reason that he used that shaft is b/c it already has the dual cv joint.

Mikronized

ok... so once I buy new upper links I need to adjust them to push the top of the axle back right?

I drew a little diagram of what I think is going on, let me know if i'm right... he he he

blackrunner91

hey man, that's exactly what I was saying. Oh, and nice drawing dude, let me know how you solve your problem.

Toyo_Master

I had the same noises when I first bought my truck a couple of months ago. Mine has a 4" lift and the pinion angle was pretty steep. I pulled the driveshaft and found the center support bearing was trashed so I replaced it and the front and rear U joints. When I re-installed I spaced the CSB down as far as I could to reduce the pinion angle. Now the only time I hear any noise at all is above 65 MPH and I have to work at to get it to make noise. Most of the time now it's very quiet and I can live with the small amount of noise it makes.

Toyo Master

deathrunner

I understand that this coudl be the pinion angle. I am expereincing the same problems but I think it is in the diff. Is this entirely ruled out?

I just had my dshaft rebuilt so I know the joints are good. I am running minimal lift (Maybe 2.5"). And my pinion has loosened up in the past. But I don't recall any noises when it loosened up.

If it is the pinion angle, why is it only above 60mph? and why only make that noise in the brief moment of engaging or releasing throttle?

Dr.Feelgood

Sound a lot like a worn pinion bearing. The reason for the noise when is the release of the driveline pressure when you're off the gas or in neutral and there's play from the worn bearing. Getting back on the gas applies the pressure back onto driveline and the bearing. I had this happen on my Mazda truck (never fixed it). After a 4-5 mile drive you could feel the heat generated near the flange of the differential. Now it's beginning on my Toy too. Not so hard to change on the Toy's though. No suspension lift on either truck.

dirtypuke

yep i agree with toy-yoda. i just had my rear end rebuilt because of the same problem. the shop i took mine to said that someone over torqued the nut that pulls the assembly together and it messed up the front pinon bearing, it looked pitted. i had the shop replace all the bearings and all the seals while they had it apart and it cost $550.

AW1090

Hey mikronized....it's the pinion angle...I've had the problem ever since I did my lift and it's roughly the same lift you got on your 4runner. Coasting on the highways it just has a bad vibration/noise coming from the rear or middle of the runner. I checked into the upper links, but was waiting until I skin the underside to really do anything about it cause I'll have to lengthen the d-shaft then anyways..

modlite

Question, I'm looking at rebuilding mine, but someone told me that my ring and gear could be bad too at this point? I have horrible slop in my pinon, do you think it killed my ring and gear too?

904_runner

One question. How is pinion angle going to cause noise? Make sure it is full of oil. If it is low it's not lubing the bearings enough and can cause noise. Did it just start doing this?