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T56 Magnum XL

I’ve done some researching on here and am trying to bottom out on my plan.

My MT82 may finally be showing signs of rebuild being needed. After a whole lot of track weekends on my 600rwhp Whipple’d 2011 S197 GT. It’s a dedicated road course car - next to no street driving. I’d like to go the Magnum XL route, as it seems like a solid/reliable path forward. Seems like 2.66 is the tranny to go for, for this application.

Which clutch for this application? Which rear end gear? 3.73 or 4.10? If 4.10, will that require a legit diff cooler? I have a cortex diff cover, but I’m not familiar with what it takes to plumb a new diff cooler into the existing system.

Finally, are all Magnums the same from the common sources? Like JPC, Modern Driveline?

Appreciate any thoughts from folks’ experience!
 

Bill Pemberton

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Not sure whether the Magnums are all the same from common sources ( one would think so but always good to ask ) but I would stay with the 3.73s since you have a Whipple Supercharger on your beast. You already have the power down low and I would think you want the ability to wind out on a road course and the SC will negate some areas where some would question a downshift.
 
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JPC was really good to work with in purchasing my Magnum XL package. Legend Gear and Transmission actually built the transmission. JPC was able to put together an entire package that included a speed calibration box, pigtails, and aluminum driveshaft.

You want the close ratio Magnum with the close ratio overdrives. The ratios would be:

1st: 2.66
2nd: 1.78
3rd: 1.30
4th: 1.00
5th: .80
6th: .63

I would initially stick with your 3.73s. Using gears 2 - 4 with the above ratios will be very close to your existing M82 gearing in 3rd - 5th. I would install differential and transmission coolers. Or at least install temperature sensors to figure out if you need them.

The above requires paying for a swap of the overdrives. For some reason, the off the shelf close ratio has wide spacing on the overdrives. I also suggest paying to upgrade to carbon blocker rings, bronze shift pads, and polished internals. It cost me an additional $1000 for the changes. I would replace the shifter it comes with an MGW. I have been running this with an Exedy Hyper single since 2015 (and over 10K track miles) without any issues.

At your power levels, I would use the Exedy Hyper Twin ($2,500).

The entire swap will probably cost you $8 - $9K.
 
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The above requires paying for a swap of the overdrives. For some reason, the off the shelf close ratio has wide spacing on the overdrives. I also suggest paying to upgrade to carbon blocker rings, bronze shift pads, and polished internals.
Tremec now offers a close ratio with the .80 and .63 overdrives. 100% agree with the carbon blocker rings and bronze shift pads. I wish I would have ordered mine that way - the carbon rings really help with the high RPM shifts on the Coyotes. When you’re talking to the supplier about upgraded internals, I would suggest having 3rd gear changed to a symmetrical tooth design vs the advanced tooth design that Tremec specs on the close ratios. Again, really helps with the high rev shifts that we love with these engines. More details here:

Post in thread 'Tremec Magnum XL Fluid Discussion'
https://trackmustangsonline.com/threads/tremec-magnum-xl-fluid-discussion.16761/post-249418


The only other thing I would add is stick with the recommended Tremec MTF. At the very least, don’t use Royal Purple Synchromax with the factory synchros. I had glazed surfaces on 3 & 4 that lead to gear clash. Again, more details of my experience in the thread linked above.
 
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Finally, are all Magnums the same from the common sources? Like JPC, Modern Driveline?
IN addition to those, I saw on FB I believe that places like Lethal Performance and Hellhorse get their transmissions from Dederichs Motorsport (https://www.dederichsmotorsports.com) , Ben Calimer (https://www.calimertransmissions.com/magnum-xl), or RSG (https://rsgear.com/products/performance-race-transmissions/2007-Present-Tranzilla-Magnum), and Ticks Performance (https://www.tickperformance.com/2005-ford-mustang-gt/)

I just want to say I have no experience with any of them perosnally but its what I've gathered from this forum and FB. Hope it helps.
 
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With an NA engine, will the factory 3:73’s work or will I need 4:11’s ???
I would try the 3.73’s first and see how it works on the tracks you drive. I’m running 4.10’s and most tracks are turned in 3rd & 4th gears. AutoClub Roval is the only track where 5th gear is used. 3.73’s will be predominantly 2nd & 3rd gear for most tracks. Personally I like shifting between 3rd and 4th because it’s a back and forth motion in the same gate. The other thing to consider is the mechanical advantage of the lower ratios - with 4.10’s and less power, my car will hang with and occasionally pull on higher horsepower cars coming out of corners.
 

TMSBOSS

Spending my pension on car parts and track fees.
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I would try the 3.73’s first and see how it works on the tracks you drive. I’m running 4.10’s and most tracks are turned in 3rd & 4th gears. AutoClub Roval is the only track where 5th gear is used. 3.73’s will be predominantly 2nd & 3rd gear for most tracks. Personally I like shifting between 3rd and 4th because it’s a back and forth motion in the same gate. The other thing to consider is the mechanical advantage of the lower ratios - with 4.10’s and less power, my car will hang with and occasionally pull on higher horsepower cars coming out of corners.
Great. Thanks. I will run what I brung and see how that goes. A rear gear change is a small cost compared to the XL upgrade.
 
With an NA engine, will the factory 3:73’s work or will I need 4:11’s ???
When I had my Boss I ran the 2.97 gear set with 4.10s in the rear. I felt this gave me a similar gear ratio as the MT-82 but taller 4th gear since it's 1:1. Defiantly saved time since I was only shifting between 3 and 4. I did have full exhaust, intake, E85 and tune, so a little more power over stock.
 
Thanks very much for the input, everyone. It’s interesting that many recommend the Exedy clutches. Is a McLeod RST or RXT not a preferred option for a road course car?

Also I’ve been talking to one supplier, who says the 2.66 tranny available to them have the .74/.50 overdrives, not the .80/.63 overdrives. No good, right?

They’re also recommending a tweaked version of the tranny that has a mechanical pump inside. We’re talking ~$10k for the full package (though it includes other revisions/upgrades). Do I need all that?? I know folks here have recommended e.g. bronze shift pads and carbon bits, but I’m trying to figure out how far I really need to go here beyond a factory stock Magnum XL. We’re talking real $$ here and I want to make sure it’s well spent :)
 
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You want the close ratio box and overdrives and at least the carbon blocker rings. I would still do the other stuff I mentioned, but that’s budget dependent.

The McLeod RST/RXT don‘t hold up to high RPMs. Amongst my small group of track friend, we found cracked pressure plates on at least half of the installs after a couple of years. These are track only cars.

The Exedy is a bullet proof road race clutch. But, the disks are too thin for a regular street car.
 
I am not a huge fan of my RST. Autocross only so I probably won't crack the PP (I hope) and the light pedal effort is nice, but it is crazy noisy at idle. The flywheel it comes with is also not balanced so you have to have that done.

DaveW
 
You want the close ratio box and overdrives and at least the carbon blocker rings. I would still do the other stuff I mentioned, but that’s budget dependent.

The McLeod RST/RXT don‘t hold up to high RPMs. Amongst my small group of track friend, we found cracked pressure plates on at least half of the installs after a couple of years. These are track only cars.

The Exedy is a bullet proof road race clutch. But, the disks are too thin for a regular street car.


Got it - and this all applies to an HPDE car that’s run for 20-25 minute sessions? I didn’t clarify that above.

Interestingly, my original MT82 lasted a really, really long time. And despite the power level, I’ve been running a factory Boss clutch which also has lasted a really long time. No shifting issues.

That’s in part why I’m sitting here thinking “sheesh does all-mighty Magnum really need all this to perform in my application?” But I appreciate that I shouldn’t half-a** it!
 
Got it - and this all applies to an HPDE car that’s run for 20-25 minute sessions? I didn’t clarify that above.

Interestingly, my original MT82 lasted a really, really long time. And despite the power level, I’ve been running a factory Boss clutch which also has lasted a really long time. No shifting issues.

That’s in part why I’m sitting here thinking “sheesh does all-mighty Magnum really need all this to perform in my application?” But I appreciate that I shouldn’t half-a** it!
Its a slippery slope, you'll need a new clutch with the magnum since it is a different input shaft spline.

The ratios work way better for me and that was the main reason I made the switch, *but* a side benefit was the shifting. We don't shift a ton in autocross, the ratio change of the Magnum was designed to eliminate even more shifting but the even compared to my MGW equipped MT-82, the shifting action on the magnum is 11 billion times better. It is almost hard to explain.

Not sure that justifies the cost if the ratios work for you in the MT-82 and you can shift it.

DaveW
 

Ludachris

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For what it's worth, I came across a company called American PowerTrain, which has a Tremec kit for my old F100. I see that they also have a Magnum XL offering for Mustangs:

I haven't done any research to see if any track rats have worked with them on a Mustang build but it might be worth jumping on the phone and having a discussion with them to see how they compare to the other shops. I might have to see about getting them (or another shop) involved here as a vendor at some point, might be a good fit. If you do call them, be sure to mention this forum. I know I've always thought about putting a Tremec in my GT someday.
 
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Nashville, TN
I’ve done some researching on here and am trying to bottom out on my plan.

My MT82 may finally be showing signs of rebuild being needed. After a whole lot of track weekends on my 600rwhp Whipple’d 2011 S197 GT. It’s a dedicated road course car - next to no street driving. I’d like to go the Magnum XL route, as it seems like a solid/reliable path forward. Seems like 2.66 is the tranny to go for, for this application.

Which clutch for this application? Which rear end gear? 3.73 or 4.10? If 4.10, will that require a legit diff cooler? I have a cortex diff cover, but I’m not familiar with what it takes to plumb a new diff cooler into the existing system.

Finally, are all Magnums the same from the common sources? Like JPC, Modern Driveline?

Appreciate any thoughts from folks’ experience!
I cover this swap extensively in my book, and did a detailed video on the install. A few notes that I learned after doing the video:

1) Any clutch with solid hubs is going to be noisy in neutral and in 4th (and possibly 3rd) gear under 2K rpm. This is because the firing pulses from the engine are transferred directly to the trans, and the unloaded gears rattle around. Get a clutch with sprung hubs. The Centerforce DYAD is a great twin disc option because it uses a common sprung hub for both discs. If you don't care about noise, the Exedy clutch I used is fabulous in every other respect. Smoothest clutch I've ever driven (even OEM clutches).

2) Align your bellhousing using this tool. You cannot indicate off of the center bore of the bell housing because it's not a machined datum surface.

3) The Bowler Transmission module noted in the video is effing awesome. Get one.

4) I've used drive shafts from three companies, and Dynotech is by far the only guys who seem to know what they're doing. Trust me. Make sure your drive shaft is from Dynotech if buying a kit.

5) Get the trans slid all the way to the passenger's side to avoid any shifter boot squeaking in first gear. My boot rubbed a bit on the console, so moving it all the way to the right side of the car made it better. Slotting the trans crossmember more solves the issue.

Holler with any other questions.
 
I cover this swap extensively in my book, and did a detailed video on the install. A few notes that I learned after doing the video:

1) Any clutch with solid hubs is going to be noisy in neutral and in 4th (and possibly 3rd) gear under 2K rpm. This is because the firing pulses from the engine are transferred directly to the trans, and the unloaded gears rattle around. Get a clutch with sprung hubs. The Centerforce DYAD is a great twin disc option because it uses a common sprung hub for both discs. If you don't care about noise, the Exedy clutch I used is fabulous in every other respect. Smoothest clutch I've ever driven (even OEM clutches).

2) Align your bellhousing using this tool. You cannot indicate off of the center bore of the bell housing because it's not a machined datum surface.

3) The Bowler Transmission module noted in the video is effing awesome. Get one.

4) I've used drive shafts from three companies, and Dynotech is by far the only guys who seem to know what they're doing. Trust me. Make sure your drive shaft is from Dynotech if buying a kit.

5) Get the trans slid all the way to the passenger's side to avoid any shifter boot squeaking in first gear. My boot rubbed a bit on the console, so moving it all the way to the right side of the car made it better. Slotting the trans crossmember more solves the issue.

Holler with any other questions.

Thanks very much. Well I had a couple calls with Joe Diederich and placed an order earlier this week - what a nice and knowledgeable guy. Interesting to hear your thoughts/experience, b/c what I’m getting through Joe includes a Driveshaft Shop driveshaft w/ billet yoke, and instead of the Bowler, there are I believe 3 separate harnesses. Also I got an Ace clutch.
 

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