Improper Backlash Symptoms??

[pedalquickly]

I have been battling various noises since I bought my 01 2wd SR5 4runner almost a year ago. I have a low roar that starts around 60 and get worse till about 70. I replaced the u joints and had the drive shaft balanced.. no improvement. I bought another used drive shaft that seemed to help a good bit. But not entirely what I think it should be.

I recently added new Old Man EMU springs and shocks to the rear and Old Man EMU struts and springs to the front. Now the springs did lift the truck both front and rear about 1 1/2" higher than stock.

Now, I have a slight "hum" and light high frequency vibration that seems to be coming from the back portion of my 4runner. I must be on smooth pavement to detect it. The best I can tell it only happens above 30 mph and only when I'm at what I refer to as neutral acceleration. The period just when I suspect the drive shaft and rear end are neither slowing or speeding up.

So, I replaced both u-joints in my drive shaft and the pinion seemed like there was no up/down, side to side, or in and out play and probably 3/8 inch or so of rotational play.

Could the little bit of lift be causing some mis-alignment of the drive shaft, or is the noise a symptom of improper backlash?

Thanks

 

[02SE]

I have been battling various noises since I bought my 01 2wd SR5 4runner almost a year ago. I have a low roar that starts around 60 and get worse till about 70. I replaced the u joints and had the drive shaft balanced.. no improvement. I bought another used drive shaft that seemed to help a good bit. But not entirely what I think it should be.

I recently added new Old Man EMU springs and shocks to the rear and Old Man EMU struts and springs to the front. Now the springs did lift the truck both front and rear about 1 1/2" higher than stock.

Now, I have a slight "hum" and light high frequency vibration that seems to be coming from the back portion of my 4runner. I must be on smooth pavement to detect it. The best I can tell it only happens above 30 mph and only when I'm at what I refer to as neutral acceleration. The period just when I suspect the drive shaft and rear end are neither slowing or speeding up.

So, I replaced both u-joints in my drive shaft and the pinion seemed like there was no up/down, side to side, or in and out play and probably 3/8 inch or so of rotational play.

Could the little bit of lift be causing some mis-alignment of the drive shaft, or is the noise a symptom of improper backlash?

Thanks

The first thing I would look at is the angle of the transmission output, and the angle of the pinion flange. I would also look at the slip-yoke for wear, and also the trans output bushing for wear.

Incompatible angles between each end of the driveshaft, and/or worn slip-yoke and output bushing, can cause a high-frequency vibration.

With the lift, you have effectively moved the slip-yoke further out of the transmission, so any wear in the slip-yoke or trans bushing, will be exaggerated.

 

[Dirtyfingers]

I'd also check the oil of the tranny so make sure there's no metal shavings in it. We had improper backlash on the main reduction gear on our ship, which is basically the transmission of it, and it had metal shavings all up in it...though it's a double helical gear type...ehh may be worth it to check it out.

 

[pedalquickly]

Thanks for the info.. I don't have a slip yoke, just a single drive shaft with a u-joint on each and..

How is the best way to check the tranny to differential angles?

 

[Doc2012]

Thanks for the info.. I don't have a slip yoke, just a single drive shaft with a u-joint on each and..

How is the best way to check the tranny to differential angles?

You DO have a slip yoke.

It's on the axle side of the transmission.

It slides in and out of the drive shaft.

This site does a damn good job explaining.



Driveline 101

 

[pedalquickly]

You DO have a slip yoke.

It's on the axle side of the transmission.

It slides in and out of the drive shaft.

This site does a damn good job explaining.



Driveline 101

I guess i am not clear on exactly what a slip yoke is. I looked at some images online of slip yokes and I don't have anything like it. My trans has a male splined shaft and the drive shaft has a female splined shaft that slides over it. Is this what you're referring to as the slip yoke?

 

[02SE]

You have a 2wd 4Runner, that means you have a slip yoke. The slip yoke is what slides in and out of the tail end of the transmission to allow for up and down movement of the rear axle.

4wd 4Runner's have a slip-joint in the rear driveshaft. This also allows for the up and down movement of the rear axle.

 

[02SE]

My trans has a male splined shaft and the drive shaft has a female splined shaft that slides over it. Is this what you're referring to as the slip yoke?

The female splined shaft is the slip yoke.

A slip joint, which the 4wd 4Runner has, is often erroneously referred to as a slip yoke.

 

[pedalquickly]

Oh Ok, I appreciate the clarification and now i understand.. If it has something to do with misalignment because of the slight lift added, could I not just load the back to cause it to sit about where it was before and test to see if the noise is still there? It is only about 1 1/2" higher than where it was and I was thinking it had sagged at least a half inch of that.