Time to rebuild the differential...

[Anthony@HTM]

So I had a pretty good day at Buttonwillow Raceway, knock on wood this car has been very solid. I was even able to set a new PR.

However since I did poly diff bushings and Delrin cradle bushings I have noticed more noise at slower speeds, especially during shifting.

I jacked the car up in between sessions and it seems that there's a lot more slop now in the pinion to ring connection. So I plan on going to 3.73 gears and rebuilding it.

Has anyone in the HPDE scene noticed this?

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[Simmons-Racing]

I will have some 3.73 with 7,000 miles on them for sale real soon.

I am switching to either 3.55 or 3.31

Simmons

 

[wildcatgoal]

Mine is essentially like that (I think) and I've never been on a track...

 

[Whiskey11]

I will have some 3.73 with 7,000 miles on them for sale real soon.

I am switching to either 3.55 or 3.31

Simmons

I'm legitimately surprised you still have this car! I'm glad you are sticking with it and hope you continue to stay with it!

As for the diff noise, looks normal to me. When I rebuilt my S197's rear axle with the minimum backlash spec it had about that much play in it when on the car. I haven't checked this car (no reason to since nothing back there has been touched) but It wouldn't surprise me if it was the same. Keep in mind that .008" of backlash at the R&P is going to be a decent sweep at the pinion gear and driveshaft.

 

[Anthony@HTM]

I'm legitimately surprised you still have this car! I'm glad you are sticking with it and hope you continue to stay with it!

As for the diff noise, looks normal to me. When I rebuilt my S197's rear axle with the minimum backlash spec it had about that much play in it when on the car. I haven't checked this car (no reason to since nothing back there has been touched) but It wouldn't surprise me if it was the same. Keep in mind that .008" of backlash at the R&P is going to be a decent sweep at the pinion gear and driveshaft.

Good to know.

My concern is something breaking due to the pinion and gear slam into each other when there are quick speed changes.

 

[gsxr1300]

Anthony is that a traclok or torsen diff?

 

[Competition Orange]

So I plan on going to 3.73 gears and rebuilding it.

Anthony is that a traclok or torsen diff?

The above would lead me to believe traclok.

 

[esacteksab]

Not as bad as phunk's. I thought he also mentioned this occurred after bushings were installed. I wonder if the factor bushings allow enough deflection to not tear things up?

 

[CoastHighway]

My 2015 GT PP has 6 HPDE days on it so far. Mine had a bit of play in the driveshaft, and the dealer voluntarily swapped in a new driveshaft. The diff seems solid still.

I'm NorCal also, and I think 3.73 gears don't match Laguna and Thunderhill well. Annoying, but not enough to take the fun out of it.

 

[Optimum Performance]

Anthony,

I'll check mine tomorrow but these differentials run real hot so I think Ford dialed in extra backlash. Hard load and coast down "wear" typically won't change dimensions a ton but there is a reason the '16's have a temp. warning in them. We are at about 9K hard miles, third fluid change but it had a lot of play since day one. I'll see if I downloaded the specs. We should have our plug-n-play oil cooler kit for the axle out this summer. You get a good price on oil ;) start sampling and changing to see if you can see if it's temp related.

 

[Anthony@HTM]

The above would lead me to believe traclok.

Yup just the basic 3.55 LSD

 

[Anthony@HTM]

Not as bad as phunk's. I thought he also mentioned this occurred after bushings were installed. I wonder if the factor bushings allow enough deflection to not tear things up?

Well I had nothing noticeable until I did poly diff bushings and Delrin cradle bushings. That's when I noticed it at first.

The OEM bushings seem to really take up a lot of slack

 

[Anthony@HTM]

My 2015 GT PP has 6 HPDE days on it so far. Mine had a bit of play in the driveshaft, and the dealer voluntarily swapped in a new driveshaft. The diff seems solid still.

I'm NorCal also, and I think 3.73 gears don't match Laguna and Thunderhill well. Annoying, but not enough to take the fun out of it.

Interesting as in going up to a 4.09 option?

 

[Anthony@HTM]

Anthony,

I'll check mine tomorrow but these differentials run real hot so I think Ford dialed in extra backlash. Hard load and coast down "wear" typically won't change dimensions a ton but there is a reason the '16's have a temp. warning in them. We are at about 9K hard miles, third fluid change but it had a lot of play since day one. I'll see if I downloaded the specs. We should have our plug-n-play oil cooler kit for the axle out this summer. You get a good price on oil ;) start sampling and changing to see if you can see if it's temp related.

I came right off of the track and the infrared said 206 degrees, so they are indeed hot.

I certainly have been considering cooling options for it, I heard that the GT350 had cooling fins on its diff cover but apparently that's not really the case.

My results have been really good for oil, trans and diff fluid thus far and have just broke the 9k mark as well.

 

[Norm Peterson]

Well I had nothing noticeable until I did poly diff bushings and Delrin cradle bushings. That's when I noticed it at first.

The OEM bushings seem to really take up a lot of slack

The slack between the ring teeth and the pinion teeth was basically always there. The OE bushings just filtered out most of the noise so you tended to not notice it. Not saying you shouldn't consider rebuilding the diff, just that what you mainly noticed was the difference in NVH transmitted up into the cabin.

FWIW, the stiffer bushings will at least theoretically increase the impact loading a little every time that the gear tooth clearance is suddenly taken up. The whole diff and its support system became more rigid.


Norm

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