I need help fixing this irritating drivetrain noise in my 95 4Runner I just purchased as a work truck.

It makes a constant whinning noise or groan noise in the rear of the truck probably in the axle and gets louder as I go faster. It sounds like I am driving constantly over road grates!

Its definitely not the tire to road noise.

The sound almost goes away when I push the clutch pedal in. I am assuming its because it takes the load/power off of the axle which causes it to be quieter. I noticed the groan also on the down shift as well.

Any help in diagnosing what it is and how to fix it would be greatly appreciated!

Thanks,
Mike

 

check the oil in the rear end

if it doesn't look like honey it needs to be changed.

EDIT: it takes 2 1/2 quarts if i remember correctly....

 

rear diff is singing a song to ya it sounds like. Check oil in it. Is it leaking? Also is your truck a manual? If so it may be gear winning... not a good thing either oil in trans may be low and leaking...

 

You either have a bad pinion bearing or axle bearings.

 

good point. if it goes away when you press the clutch in, it very well could be the tranny.

i think the tranny takes 3 1/2 quarts of GL-4.... not GL-5....

 

I'd also check your U-joints for movement/play.

Dropping the rear driveshaft is an easy job. Make match marks on either end so that you can put it back on exactly as you took it off, take off 8 bolts and drive it in 4WD (front wheel drive now). If the noise goes away, replace both U-joints. Still have noise? Then it's your rear diff or axle.

 

Hey Gang,
Thanks for your advise on my differential problem. I was able to get the fill plug (impact) and drain plug off and very little oil came out. Put 2 quarts of oil into the diff. still groans but not as bad.
NOW THE BAD NEWS! I need a new 3rd member its flat worn out. Found chunks of metal on the drain plug and pinion gears had major wear. I will be posting a WTB 8" 4.300 4-pinion 3rd member.
Thanks,
Mike

 

Well at least now you know what was wrong. You might want to consider lower gearing since you're having to buy a new third anyways. You'd have to do the front too, but those aren't too expensive if bought used.

 

He doesn't have to do the front yet. He just wouldn't be able to stick it in 4wd until he got it done, assuming it's a 4wd.

 

Ok I am a little bit new at all of this.
So your saying I can go with lower gearing? What would be the benefit? What ratio should I get and why? Is my current 4.300 too high or is there a better ratio for gas mileage, light towing, etc?
Since I dont really 4-wheel, but say if I wanted to, if I put in a lower ratio in the rear, then your saying I need lower ratio in the front as well? So would I just need to swap out the ring and pinion only or buy a "front version" 3rd member?
Thanks for your help in advance.
Regards,
Mike
Note: I really only use my 4runner to carry my home repair business tools around town I would like to get a little better gas mileage and acceleration possibly?

 

Sounds like you don't really have a need for lower gearing. The main reason people install lower gears (numerically higher) is because they have put larger tires on. For example, my pickup came with 4.10 gears and roughly 28" tires. I upgraded to 33" tires, so also regeared to 4.88s in order to maintain the ratio close to stock.

If you are certain you won't be getting bigger tires, then don't regear. Toyota engineers set you up with 4.30 for a reason. Just a quick warning though: if you spend much time on this site, you'll inevitably want to get bigger tires.

If you do decide to regear, then yes you can either buy a complete third, or swap the ring and pinion. Buying a used complete third would be cheaper, since you can remove and replace the third yourself, whereas the ring & pinion install will likely require a professional.

 

1 - awesome that you found the problem; make sure you fill it to the bottom of the fill plug (appx 2.6qts according to the manual)

1.1 - Kudos to all those who responded, each and every response was helpful (and i learned like 4 tricks to diagnosing other problems which could occur (clutch in, driveshaft out, U joint/tranny issues etc..)

2 - excuse my noobness, but "3rd member" ? i'm guessing it's the ring in the diff case?.

3 - regearing is a worthy option, even if you go down (up numerically) just a notch, it'll help in accelaration, though your rpm's will raise, so win/loss for daily driving...

4 - also, you'd want a lower ratio (well, matching ratio) front and rear, because if it's in 4x4 high or low, you want the front/rear wheels spinning at the same speed...

Thanks!