BEST DIFFERENTIAL FOR OPEN TRACK/OCCASSION DRAG

KanzenShelby

New Member
Established Member
Joined
Sep 1, 2018
Messages
20
Location
Washington
Hey guys, I'm new to the mustang world. Owner of a 2013 Shelby GT500. I need your personal experience and input on the best differential I can put on my car. I already ordered the 3.73 gears for it.
I want to do more open track racing and occasional drag racing. I want a diff that will hold up to the abuse. My power will be approximately 750 RWHP on ethanol. I also drive this to and from work on sunny days. Also want rear end noise to be as close as to stock as possible. I dont want to spend a fortune on a new diff. maybe around the $500-800 range.
Please let me know what you think. Any advice would be greatly appreciated.!!!
Thank you!
 
Last edited:

Coz

Active Member
Established Member
Premium Member
Joined
Feb 25, 2017
Messages
429
Location
Philly Metro Area
Is yours a Performance Package car? If so, you have the strongest Torsen made and will be great for the track and will stand up to occasional drag strip use.

If you have a base GT500 then upgrade to the Torsen. It is normally available as Ford Racing upgrade under P/N M-4204-MB and runs for about $900.00. However, the exact same differential is available as a replacement part under part number CR3Z-4026-A, also known internally as Torsen 409000-2170. The carrier is cast with #CR3W-4026-AB on it. This is available for about $750.

Before you go with the 3.73 gears you may want to check the road course track(s) you will most likely attend with your current 3.31s and see what gears you will be in during various portions of the track and how often you will be shifting. Also, what gear/rpm you're in at the end of the longest straight. A track app to record your speeds and rpms would be very helpful here.

Then see how that would translate if you had the 3.73 gears. You want to avoid having to go above 4th gear at wide open throttle. With 28" tires you're looking at 6700 rpm @ 150mph. This is above the normal redline for your GT500.
 

KanzenShelby

New Member
Established Member
Joined
Sep 1, 2018
Messages
20
Location
Washington
Is yours a Performance Package car? If so, you have the strongest Torsen made and will be great for the track and will stand up to occasional drag strip use.

If you have a base GT500 then upgrade to the Torsen. It is normally available as Ford Racing upgrade under P/N M-4204-MB and runs for about $900.00. However, the exact same differential is available as a replacement part under part number CR3Z-4026-A, also known internally as Torsen 409000-2170. The carrier is cast with #CR3W-4026-AB on it. This is available for about $750.

Before you go with the 3.73 gears you may want to check the road course track(s) you will most likely attend with your current 3.31s and see what gears you will be in during various portions of the track and how often you will be shifting. Also, what gear/rpm you're in at the end of the longest straight. A track app to record your speeds and rpms would be very helpful here.

Then see how that would translate if you had the 3.73 gears. You want to avoid having to go above 4th gear at wide open throttle. With 28" tires you're looking at 6700 rpm @ 150mph. This is above the normal redline for your GT500.


First off, thank you for your reply. I never thought of it that way. I appreciate your advice on taking it to the track to see what gear I will be at before I install the 3.73. From doing the research on here. Seem like every one that drag on weekends and daily drive it. Love that option. So I will try a few events locally here first before I jump into installing it.

I do have the Performance Package with the Torsen setup. So if I heard you correct. It is good enough for the drag strip on occassion right? Thanks for your input. Much appreciated!
 

Coz

Active Member
Established Member
Premium Member
Joined
Feb 25, 2017
Messages
429
Location
Philly Metro Area
If you were just driving on the street and going to the dragstrip then even a 4.10 would work. But a 4.10 on the rosd course would not work too well. Plus, with all your torque plus 4.10's I would suspect it would get squirley powering out of a turn. 3.73's may be a handful too. When you go to the track with your 3.31's take note of how it handles in the turns. Assuming you have fecede tires, If your ass end kicks out a lot on you then 3.73s are probably going to make it worse.

If the road course has a lot of long straights, you will run out of RPM in 4th gear.

Conversely, if it has a lot of tight turns, all your torque may work against you with respect to maintaining traction.

Your Torsen is ok for an occasional stint at the strip but, the stress on the Torsen will also be affected by the tires you run. Radial slicks will be the toughest. Bias ply with softer sidewalls will be easier. Drag radials will be tougher than max or extreme summer tires.

A clutch-based Ford Trac-Lok diff can handle more abuse than a Torsen and can be rebuilt. But you definitely don't want that on a road course with 700+ HP!

Some people speak highly of the Eaton Tru-Trac differential but I don't have ant experience with it.

Forgot to mention that stock GT500s have been known to heat soak on a road course. Running E85 may help mitigate that problem. Bring extra fuel since i don't know too many road course tracks that sell E85. You may only get two 20-minute sessions on a tank of E85.

Everything has it's tradeoffs...
 

KanzenShelby

New Member
Established Member
Joined
Sep 1, 2018
Messages
20
Location
Washington
Great info and advice Coz.... Thanks again.

So what you’re saying is I can’t have my cake and eat it too??... lol
 

MarcSpaz

Resident Trouble Maker
Established Member
Joined
Nov 29, 2016
Messages
2,760
Location
Location: Location:
Did you decide what gear you are going to go with? Your tire is going to have a big impact on what you do. Diameter and traction both play in.

I had a car with a TR6060 and 650+ lbft of torque. I ended up with a 2.63:1 gear ratio on 28" tires for the track. I have 3.73 in my GT350 and I can't go WOT off the apex with a 29" 300 tread wear tire. I am thinking about dropping to a 3.08/3.09 and a 28" Cup 2 for better traction and less likely to blow the tires off in a curve at 85+ mph.
 

Users who are viewing this thread



Top