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GapRider

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Mustang GT MT82 to T56 Magnum XL swap - info to fill in the gaps.
I did run into some things that the kit did not address and the info was not abundantly available so I wanted to document it to help others doing the same swap.
Apparently many people have done this swap and weren't aware of any issues but following manufacturer recommendations, including various checks and measurements is always the right thing to do to ensure maximum reliability and performance. People have had blown throwout bearings because they didn't check proper clearance and over stroked the slave cylinder, others had repeated issues with starter engagement because the bellhousing plate starter hole was over sized and relied on starter bolts to align the starter. Some things do matter.
1-The wiring for the tranny -> see pic below
Speedo hook up - you get a 6" pigtail that plugs into the T56 speedo sensor, the user has to figure out how to wire up
You also get an Abbot electronic speed conversion box with four leads coming out of it and some printed instructions about setting ratio options in the unit.
I had to call JPC racing and ask for a wiring diagram to hook this up.
I had to search online to piece together what you need to know for this to work​

The MT82 has a 3 wire speedo sensor output (OSS) that produces a digital (square wave) output which the PCM reads. The three leads are +12v, Signal, Ground

The T56 has a 2 wire speedo sensor output (VSS) which is an analog pulse (not square wave), I don’t know it's voltage peak so I didn't want to wire that straight to the Mustang for fear of damaging the PCM input. The two leads are Signal and Ground and polarity doesn't matter - either one can connect to Signal, the other to Ground.​

There are three ways people do this
WITH the Abbot electronic box: (the box converts the T56 signal to digital square wave which is safest for the Mustang PCM)
1-Use the Abbot box as set (2.75:1 pulse rate) and leave the Mustang PCM speedo parameters alone. Play with dip switch settings in the Abbot box to make speedo adjustments.

2-Set the Abbot box for 1:1 pulse ratio and adjust the Mustang PCM parameters in the tune, this is what I did because I wanted all the conversion to be in one place and be able to adjust it anytime using HPTuners
The primary parameter in the tune is the #pulses / output shaft revolution. This is 34.0058 for the MT82 and needs to be changed to 12 for the T56 (borrowing info from a GT500 tune which apparently uses TREMEC transmission)
WITHOUT the Abbot electronic box: (Some have done this but you are feeding an analog pulse to the PCM instead of the digital square wave it is expecting.)
3-Wire the T56 sensor to the Mustang harness (omitting the +12v wire) and then adjust PCM speedo parameters in the tune.
IN THE TUNE:
a-SPEEDO SECTION/VSS P. / Rev - Trans (#pulses / output shaft revolution). This is 34.0058 for the MT82 and needs to be changed to 12 for the T56 (borrowing info from a GT500 tune which apparently uses TREMEC transmission)
b-TRANS SECTION/SHIFT GENERAL/GEAR RATIO - enter the T56 Gear ratios for 1 - 6
c-TRANS SECTION/SHIFT GENERAL/MANUAL - enter the T56 Gear ratios for 1 - 6 and Reverse. Here you also enter the min and max values for the ratios (I used excel to do this, calculating from the MT82 values in the tune) - it's about + and - 2%
d-SPEEDO SECTION/N / V Base (RPM / MPH in 1:1 gear) - this is 5th on the MT82, 4th with the T56. Drive the car in 4th gear at any nominal MPH and note the RPM. You could also log those values for more accuracy. Divide the RPM by the MPH.
For example 4th gear, 60 MPH, you read 2950 RPM on the tach
2950/60 = 49.167


Reverse lockout solenoid
The MT82 doesn't have this so you have to be creative.
You receive a 6" pigtail that hooks to the T56 reverse lock out solenoid and that's it, there were no instructions/wiring diagram provided by JPC.

One way to do this:
Get a momentary contact switch at your local auto parts store, rated for atleast 10amps
Use the factory wires feeding the accessory jack in the console to provide +12v and ground for the reverse solenoid circuit.
Backup light
There is a 2 pin plug on the T56 and a 2 pin plug in the Mustang harness, they do not match, you will have to decide which style you want, order that one and replace the original, either T56 or Mustang, whichever you chose.
I chose to cut the pigtail off the MT82, cut the plug from the T56 and solder the MT82 pigtail to the T56 backup light wires.

2-The bellhousing plate [verify starter hole is correct 3"]
Besides serving as a containment for the bellhousing, it's function for a Ford is to provide accurate starter location to ensure proper starter gear / flywheel ring gear tooth engagement
That starter location hole is sized exactly to fit the starter snout closely, for the 5.0L in our Mustangs, this is 3". The starter bolts and the normal bolt hole clearance can not provide this alignment.
Mine was a little tight on the starter so I sized the hole barely with a sanding drum. Also, I had to drill the starter holes to the next size for a little more clearance to get the screws in easier. This is OK because the screws don't locate the starter, the plate does.
Make sure you verify the starter hole in your plate is 3", the starter hole in the plate I received from JPC racing was much bigger, 3.4" (mix up in packing from the supplier, not JPC), otherwise this won't properly locate your starter and you can have issues with poor gear contact.

3-Slave Cylinder/Throw out bearing spacer
Throwout bearing clearance must be measured anytime an aftermarket clutch, flywheel, bellhousing, transmission or throwout bearing is installed. Failure to get this correct has blown out throwout bearing slave cylinders due to reaching end of stroke if there's too much clearance, or causing interference between the slave cylinder sleeve and the clutch plates if there's not enough clearance.

You can measure this using the below pics as a 'How to' guide. My measurements showed 1 1/6" clearance. I had a 0.580" spacer made. This puts the slave cylinder in the middle of it's operating range, not close to maxing out at the end of travel. I did not use a thicker spacer to achieve 1/4" clearance as the Tick instructions (for GM cars) state because that would have put my slave cylinder sleeve into the clutch disc.
Since a lot (or even most) people have used this kit with no spacer and only a few posts stating they blew slave cylinders, you could buy a spacer from Summit Racing for about $17.99 and should be just fine.

IMPORTANT
Slave cylinder must be fully retracted/compressed to take measurement 'B'

4-Rear end ratio
The MT82 has deep ratios, not reaching 1:1 until 5th gear, most manuals are 1:1 in 4th gear. I wanted the car to be geared the same as stock with the new tranny so I used excel again to calculate overall drive ratios. See the pic below.
The T56 comes with two options for ratio sets 2.66 first gear or 2.97 first gear. I plotted the overall ratios for the MT82 and stock 3.31 gear, and both T56 options with different rear gear ratios. The 4.10 gear provided the closest match to stock. The 2.97 was the closest match to stock but the 2.66 has a closer ratio spread. I chose the 2.97 and there is a noticeable RPM drop between 3rd and 4th gears. In hindsight, the 2.66 gear would be a better option if you like close ratio and more even RPM drop from gear to gear

Thoughts after driving the car:
It shifts like I expect a decent hot rod to shift - all mushy, clunky, notchy, slow shifting and high RPM lockout is gone. It just feels like it should.
I love having a one piece driveshaft, much lighter, simpler, and again is the way it should have been.
The 4.10 gears kept the stock overall drive ratios so no difference there, you can still climb a tree in first gear.
I do notice the larger RPM drop between 3rd and 4th gear and wished I'd picked the 2.66 gear option.
The RST twin disc clutch. I love it because it has light pedal pressure and it's way more clutch than I need so I never had to worry about it. And it's beautiful.
It does engage higher up on the pedal travel as many other people have noticed also.
It does have a little more noise at idle in neutral (I could care less about this)
It does have a tendency to chatter a little at low RPM light throttle engaging it slow but that's because it doesn't have a sprung hub like factory clutches. Again, I don't care, it doesn't have those because it's a race clutch-ish.
Absolutely no difference in starter noise so I believe perfect starter gear engagement.
Cruise control still works (all the speedo parameters in the tune are correct)
There is a noticeable vibration noise at around 1500 RPM in 4th gear lugging but it sounds like rattling, I'm hoping its a heat shield or something. When I find out I'll post up.
Overall, very satisfied after finally doing this swap. Ford should have never put the panel truck style MT82 with remote shifter and two-piece drive shaft in their hot rod. I believe it was budgetary, they over spent on that glorious Coyote motor (best American engine IMO) and the project manager said 'OK great, now we have to cut cost somewhere!' as he looked at the drivetrain engineers. That's just my opinion of what happened.
Thanks to the guys at JPC racing, Aaron and Dylan and the tech support at Quicktime (Holley) Ethan, super helpful.​
 
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