Torsen Diff Upgrade

[Ken R]

I am planning on upgrading the diff to a Torsen over winter and am slowly building towards NASA Spec Iron which allows two diffs, either the Boss 302 (2.7:1 bias) or the FR500S (4:1 bias), both are Torsen.
Does anyone have any insight on how the different biases would perform? Has anyone ran both and had one that did better with lap times, heat management, were there any design changes from Torsen, etc? They are priced about the same so no edge to either there.
Car is currently stock motor and trans, getting a aluminum drive shaft this weekend and I am running 315's with 200TW rubber but will eventually switch to 275 slicks per SI rules
Thank you in advance

 

[RodS197]

I ran the FR500S Torsen in my 2006 Mustang GT for many years. Now I run a BOSS 302 unit in my 2014 Mustang GT for the last 2 years. I have not noticed any difference between the two on track.

The Boss unit is engineered for more HP (400+) whereas the T2R (FR500S) (300+) unit is not supposed to be used for hard launches. I would imagine the Boss unit is slightly heavier.

Both have worked great for me. If you don't have plans to add a bunch of HP to the car, go with the T2R, or the one you can get for less money.

 

[Ken R]

I ran the FR500S Torsen in my 2006 Mustang GT for many years. Now I run a BOSS 302 unit in my 2014 Mustang GT for the last 2 years. I have not noticed any difference between the two on track.

The Boss unit is engineered for more HP (400+) whereas the T2R (FR500S) (300+) unit is not supposed to be used for hard launches. I would imagine the Boss unit is slightly heavier.

Both have worked great for me. If you don't have plans to add a bunch of HP to the car, go with the T2R, or the one you can get for less money.

Appreciate the insight, yeah the rules call for like 315hp max and no plans for hard launches. It's seeming like the T2R is the way to go which I think is the cheaper one but only by a few bucks

 

[TA28]

Actually the t2r unit is the race unit. These were std in the fr500c, fr500s, boss 302s .it is tough unit and will handle more hp than the t2 unit. Neither unit is recommended for drag racing.
Torsen has good web site. They are made in Rochester ny. Only draw back is it's not rebuildable.
Only parts you can get is screw and block which holds axle c clips in.

 

[JDee]

The Torsen in my '16 used to overheat regularly. That stopped when I switched to redline diff lube. But the damage was already done and the diff totally died. That was after 5 seasons of pretty hard lapping, so it was not unreasonable for how hard the car was used.
For sure any track car that is driven hard needs a diff cooler, torsen or not.

 

[Ken R]

Actually the t2r unit is the race unit. These were std in the fr500c, fr500s, boss 302s .it is tough unit and will handle more hp than the t2 unit. Neither unit is recommended for drag racing.
Torsen has good web site. They are made in Rochester ny. Only draw back is it's not rebuildable.
Only parts you can get is screw and block which holds axle c clips in.

Interesting, I didn't know it was in the 302S as well.
From what I've been seeing it sounds like they'll last plenty long enough that a replacement can be justified over a rebuild

 

[Ken R]

The Torsen in my '16 used to overheat regularly. That stopped when I switched to redline diff lube. But the damage was already done and the diff totally died. That was after 5 seasons of pretty hard lapping, so it was not unreasonable for how hard the car was used.
For sure any track car that is driven hard needs a diff cooler, torsen or not.

Yeah I had the same overheating experience in my '17. I do want to add a diff temp sensor/cooler, I think the cover has a spot for a temp sensor but I need to see where it goes

 

[TA28]

when you compare torsen to Detroit locker and the torsen rear being unrebuildable and the locker can be rebuilt. 1k every 5 yrs???
I have 4 rears with t2r in them but leaning towards a locker. Jbs ran lockers in there fr500c and boss R cars in imsa.

 

[EF1]

when you compare torsen to Detroit locker and the torsen rear being unrebuildable and the locker can be rebuilt. 1k every 5 yrs???
I have 4 rears with t2r in them but leaning towards a locker. Jbs ran lockers in there fr500c and boss R cars in imsa.

I am using a Detroit TruTrac myself, but the OP is building to a NASA spec class rules and has to choose between 2 Torsen differentials. Given the choices he has I would choose the one with more bias for his application.

 

[Ken R]

I am using a Detroit TruTrac myself, but the OP is building to a NASA spec class rules and has to choose between 2 Torsen differentials. Given the choices he has I would choose the one with more bias for his application.

Yeah I'm kinda glad there are only two allowed otherwise I'd be in a much deeper rabbit hole ha