Front Differential

[adsinclair]

After crawling around under my new 4Runner getting to know it, I noticed that the front differential seems sloppier than what I expected. After grabbing the inboard CV joints and moving them, they seem to have excessive what I believe is called lateral movement. Not in/out of the diff or twisting, but side-to-side. I checked another Trail and SR5 at the dealership lot and they seemed to be similar to my 700 mile TE. The drivers side had slightly more play than the passenger. Both have a definite sound and is barely visible when moving.

That got me wondering about the internals of the diff. With having the ADD locked and the transfer case unlocked for 4wd, the propeller shaft (which is tight along with all flanges) has about 20 degrees, or 1/2 to 3/4" rotational movement at the flange bolts.

Can anyone verify this slop is normal in their PT 4wd front diffs? To check the input flange rotational play on the front diff: start the car and put it in 4wd (hi or low doesn't matter, I used 4hi), turn off the car and pull the key, rock the 4Runner back and forth while shifting into 2wd. Reach underneath and rotate the front propeller shaft back and forth. This process should lock the ADD but take the transfer case out of the equation.

I know the isn't accurate for backlash or pinion preload, but it seems like a lot of play for the diff gears in their entirety. I have read that lockers can have more play than normal diffs, so I'm wondering if the ADD might be a factor in this.

I apologize I don't have a vid, but it is very similar to this but maybe a little worse... Front diff play - YouTube

Thanks for your feedback in advance!

 

[adsinclair]

I meant to specify, when rotating the front propeller shaft, the twisting force is pretty decent and going back and forth from "clunk to clunk". From "clunk to clunk" I have around the 20 degree total play.

I did check the rear diff, which is a little more difficult without removing the drive shaft. It seemed to have less play, which is weird being it has an electronic locker...

Thanks again!

 

[offroadingatc]

In my experience that's pretty typical, although I havent checked my current 4runner. Chances of the two you checked both being faulty seems pretty small.

 

[adsinclair]

In my experience that's pretty typical, although I havent checked my current 4runner. Chances of the two you checked both being faulty seems pretty small.

I'm not as worried about the front CV joints, as I can find some documentation of people having play. It seems to be normal.

I am more interested in the propeller shaft rotational play at the flange. I would really appreciate someone crawling underneath their SR5 or Trail...

 

[adsinclair]

Bump for the weekend. :thanks:

 

[homeyclaus]

Well, let's see. The differential is mounted to the front subframe assembly, and the CV joints and axles connect to the knuckle that articulates between two A arms. Given that the up/down movement there is substantial, and the angles involved, it would seem logical that there would have to be that kind of play in the shafts.

As far as the looseness of the front diff goes, are you sure the electric hub lock was engaged? This is what connects the diff to the axles, so the whole set of assemblies does not spin when in 2WD. I don't have the FSM in front of me, I forgot what the official name for it is, but there is a solenoid that locks the drivetrain up up front when 4WD is engaged on the PT 4WD models.

 

[adsinclair]

Thanks for the reply!

As far as the front inner CV joints, here is a good video depicting the play: Front diff play - YouTube

I have read multiple threads in Tacoma and FJ forums about this being normal. As long as it isn't eating seals, it is nothing to worry about. Being brand new 4Runners, FJ's and Tacoma's are experiencing it, I'm not as worried about it as now. Just was kind of shocking after comparing it to previous vehicles I've owned and side-by-side with my wife's Acura RDX (which has zero play, granted it's also AWD).

I am sure the front diff ADD is engaged. I'm assuming the light on the dash is one factor in whether 4wd is fully engaged. There is a sensor on the ADD that I'm guessing sensed the fork's position.

When taking the transfer case out of the equation and keeping the ADD locked, it seemed like excessive rotational play in the input flange. I am mostly curious what other people's play averages. I can find rear diff videos and threads and it appears that my rear play is normal (about half of the front's).