Rear Diff Upgrade 3.55 / Truetrac question

[thedude]

Looking for a second set of eyes from guys who have done gears on S197s (especially 3.55 + Truetrac setups).

The car is my 2009 Mustang GT with New 3.55 Ford Performance gears new Eaton Truetrac New bearings throughout Raytech Solid pinion spacer (no crush sleeve).

From what I can tell, it looks like a good, usable pattern its just not "perfectly centered" heel-to-toe. I've heard Ford Performance gears can look like this and settle in after break-in.

Setup details:
Pinion preload: ~17–18 in-lb (new bearings and I'm running on the low side for road racing)
Backlash: right at .009 (checked in multiple spots, consistent)
Raytec solid pinion spacer


Pattern:
Slight bias toward the toe on both drive and coast
Centered vertically (not deep in root or running off face)
Good contact length across the tooth
Not sharp or edge-loaded


Main questions:

1. Would you run this as-is for street + road course /track use?
2. Does the slight toe bias concern you at all given the backlash is .009?
3. Anyone running a similar setup (3.55 + Truetrac) seen patterns like this and how did it behave long-term (noise/wear)?

Appreciate any experienced input, I'm at the "button it up or chase it" decision point.

 

[whitmanink]

the contact patch is within spec , id send it ,

the second and third pick you can see you have the right amount of center and up down on the gear meshing .. on the lower end you are close but by no means out of spec,

send it

 

[GriffX]

That's my 3.73 set-up. It makes a bit gear noise, but I noise dampened the rear quarter panel



PS: I had to drag out the axles with c-clamps to insert the spacer in the Truetrac which feels not right, but it was.

 

[thedude]

Thanks That’s what I was thinking I’m literally chasing .001 at this point and I think it’s good enough that it will be ok. It’s just been a while since I did a full rebuild so I’m being a little bitch about it.

 

[whitmanink]

That's my 3.73 set-up. It makes a bit gear noise, but I noise dampened the rear quarter panel

View attachment 114913

PS: I had to drag out the axles with c-clamps to insert the spacer in the Truetrac which feels not right, but it was.

yea yours is definitely on the low side and i can see why it whines,,
there is a tolerance and its a pretty forgiving window ,, but the whine tells me one or more of the contact points are yelling HELP lol

 

[whitmanink]

Thanks That’s what I was thinking I’m literally chasing .001 at this point and I think it’s good enough that it will be ok. It’s just been a while since I did a full rebuild so I’m being a little bitch about it.

yea your overthinking it and dont wanna have to rip it all apart again..

you are golden and it wont make noise you are within spec for sure

 

[GriffX]

yea yours is definitely on the low side and i can see why it whines,,
there is a tolerance and its a pretty forgiving window ,, but the whine tells me one or more of the contact points are yelling HELP lol

Whine is a too strong word, it is making more noise than the 3.55 that's all, not annoying at all. The gear set was used so it was more difficult to see the contact patch. None of my friends would notice something.

 

[86GT351]

Looks good. To re-do for .001 is not worth the effort.

 

[brasil]

Looks good. To re-do for .001 is not worth the effort.

...and we have to think about the calibration of the micrometer... also 0.008/9 is a good number
specs are0.008 -0.012. if I remember right

 

[whitmanink]

i aimed for .10 to have a buffer just for that..
and that is a great thing to bring up., same can be said for torq wrenches and pretty much any measuring tool .
tolerance stacking kills engine builds

 

[whitmanink]

Whine is a too strong word, it is making more noise than the 3.55 that's all, not annoying at all. The gear set was used so it was more difficult to see the contact patch. None of my friends would notice something.

my 4.10 are as quiet as the stock gears .. and i think thats how it should be if done correctly

thats using ford gears ,, not another brand , as thats a whole new rabbit hole to run down

 

[GriffX]

my 4.10 are as quiet as the stock gears .. and i think thats how it should be if done correctly

thats using ford gears ,, not another brand , as thats a whole new rabbit hole to run down

There are tons of threads for 3.73 gear noise. It is really not an issue with my set-up. The Ford install kit used Ratech shims, which were bad to handle and of no good quality.
(I also had that install problem Glasstop described here https://www.s197forum.com/threads/f...process-differences-that-affect-setup.139760/)

 

[whitmanink]

There are tons of threads for 3.73 gear noise. It is really not an issue with my set-up. The Ford install kit used Ratech shims, which were bad to handle and of no good quality.
(I also had that install problem Glasstop described here https://www.s197forum.com/threads/f...process-differences-that-affect-setup.139760/)

yes and unfortunately the noise is due to install error

and if you do not use ford gears and set them up like ford gears ,,you will get whine..
if all the driveline and axle parts are good and not worn out or damaged and the gears are ford gears ,, they will not make noise ,,