Rear Diff, Pinion Gears. And what will hold.

[Ashtar]

Hello All,

I am looking for some input. I currently have a 2015 GT PP, that makes around 800 hp. The MT82 is being replaced with a T-56 Mag XL. The current rear is a 3.55, and the clutch is being changed up to support the HP, as is the drive shaft. The haft shafts will be done with the rear gear. Here is the problem.
The T-56 has a 2.97 first gear the MT82 has a 3.66. So the old setup yelds a (3.66x3.55)=12.993. Great take off's, when I could get the tires to hook.
The new setup (2.97x3.55)=10.543. While I'll be able to hit 62 mph, in first. Not sure I'm going to like that. And with the 2 OD gears 5th and 6th. Now I maybe getting a head of myself. It should be done by this coming weekend. I hope. (gotta hate time..) So, I have yet to even test drive it. To get back to the numbers I'm used to, I have two choices. 4.11's will take me to a (2.97x4.11)=12.2, and the 4.56 will take me too a (2.97x4.11)=13.5 (some how I fear that this one will just make 1st gear not really usable.)
Here is the question. 4.11's or 4.56's Will the (traction-lok) limited slip differential work, and will it hold? What am I missing?

Thanks in advance.
Dave

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[whatsup62]

Hey Dave,
I have a 2015 PP car as well. Put a TR6060 in 3 years ago and it has the 2.97 first gear.
I ran one Summer with the 3.73 stock Torsen. although it held up just fine, i felt the gear was just not enough.
I ended up buying a cheap center section and putting in 4.09s with a Wav-trac Torsen. Kept the 3.73 for a spare. The 4.09 is a match made in heaven with that trans gear ratio.
I am into the mid 800hp range....you will love it!

 

[Ashtar]

Hey Dave,
I have a 2015 PP car as well. Put a TR6060 in 3 years ago and it has the 2.97 first gear.
I ran one Summer with the 3.73 stock Torsen. although it held up just fine, i felt the gear was just not enough.
I ended up buying a cheap center section and putting in 4.09s with a Wav-trac Torsen. Kept the 3.73 for a spare. The 4.09 is a match made in heaven with that trans gear ratio.
I am into the mid 800hp range....you will love it!

@whatsup62 Thank you for the info and input. Looks like I'll be going with the 4.09's as well.

Dave

 

[Nutones]

I have a similar problem. Just had installed a magnum xl with a 2.66 1st gear and my rear gears are 3.55. I have a whipple stage 2 Gen 3 generating at the wheels 720 horsepower and 551 lbs ft torque. Sluggish off the line due to the tall gearing. Should I go with a 4.10 rear gear setup at the very least without overheating the differential?

 

[whatsup62]

I have a similar problem. Just had installed a magnum xl with a 2.66 1st gear and my rear gears are 3.55. I have a whipple stage 2 Gen 3 generating at the wheels 720 horsepower and 551 lbs ft torque. Sluggish off the line due to the tall gearing. Should I go with a 4.10 rear gear setup at the very least without overheating the differential?

How are you going to know if you overheat the rear?
I have been running the 4.09s for three years and have had no issue - now I don't drive 120 everyday but I do drive some distance at 80mph - plus roll race and dig race - still going strong. Use a good synthetic lube. I assume yours is a traction loc rear and not a Torsen. If that is the case you will still need to add the Ford friction modifier to the lube.

 

[Nutones]

Whatsup62: Honestly I wouldn't know. Probably just overeacting for no good reason. I'll contact my shoppe about swapping the rear gears for the 4.10s. I miss the low end torque I had with the MT82 but unfortunately that transmission didn't last thanks to the RXT clutch I ran. Switched out that clutch for the mantic twin disc sprung hub cerametallic unit. So far no noise or chatter. Thanks.

How are you going to know if you overheat the rear?
I have been running the 4.09s for three years and have had no issue - now I don't drive 120 everyday but I do drive some distance at 80mph - plus roll race and dig race - still going strong. Use a good synthetic lube. I assume yours is a traction loc rear and not a Torsen. If that is the case you will still need to add the Ford friction modifier to the lube.

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