[Kevin C]

So as I've mentioned, I'm picking up a T56 this weekend. Won't be installed for a few months, but I want to get a question answered. I searched a little, but almost everything just touches on the subject of calibrating for rear end gears.

TR3650 gear ratios with my 3.73 gears and 285/35/18 tires (Speed @ 6,000 RPM) calculated in:

1st: 3.380:1 = 36 MPH
2nd: 2.000:1 = 61 MPH
3rd: 1.320:1 = 93 MPH
4th: 1.000:1 = 123 MPH
5th: 0.670:1 = 184 MPH

RPM @ 60 MPH in 5th = 1,980 RPM

2003-2004 Cobra T56 gear ratios (Speed @ 6,000 RPM again):

1st: 2.66:1 = 46 MPH
2nd: 1.78:1 = 69 MPH
3rd: 1.30:1 = 95 MPH
4th: 1.00:1 = 123 MPH
5th: 0.79:1 = 156 MPH
6th: 0.63:1 = 196 MPH

RPM @ 60 MPH in 6th = 1,860 RPM

So, how would I go about calibrating for the actual transmission gears? I'm running 1,980 RPM @ 60 MPH right now, and with a T56 swapped in I'll be running 64 MPH @ that same 1,980 RPM, but it'll still read 60 MPH at that RPM, correct?

Heh, before I calibrated for the 3.73 rear end gears, I was running about 10 MPH over, now with a T56 I'll be running 4 MPH under. I'll be doing 64 when it reads 60.

I have an SCT LiveWire that I used to calibrate for the 3.73 gears, but it specifies that it cannot calibrate for individual transmission gears. I'm sort of lost right now on how I'd calibrate it. At least I've got a long time to figure this out.

[Jazzer The Cat]

I have done this swap and have TONS of info in my swap thread, but not much on specifics of RPM and actual speed.

The problem with your question is there are other factors in play here. The diameter of the tires for one and the rear gears for another (as mentioned). You will have to find a page with the math equasions and work them out to your options here.

Jazzer

[Kevin C]

Originally Posted by Jazzer The Cat The problem with your question is there are other factors in play here. The diameter of the tires for one and the rear gears for another (as mentioned). Jazzer

I mentioned everything.

Originally Posted by Kevin C TR3650 gear ratios with my 3.73 gears and 285/35/18 tires (Speed @ 6,000 RPM) calculated in: 1st: 3.380:1 = 36 MPH 2nd: 2.000:1 = 61 MPH 3rd: 1.320:1 = 93 MPH 4th: 1.000:1 = 123 MPH 5th: 0.670:1 = 184 MPH RPM @ 60 MPH in 5th = 1,980 RPM 2003-2004 Cobra T56 gear ratios (Speed @ 6,000 RPM again): 1st: 2.66:1 = 46 MPH 2nd: 1.78:1 = 69 MPH 3rd: 1.30:1 = 95 MPH 4th: 1.00:1 = 123 MPH 5th: 0.79:1 = 156 MPH 6th: 0.63:1 = 196 MPH RPM @ 60 MPH in 6th = 1,860 RPM

I mentioned my tire size, rear end gear ratios, supplied the gear ratios for both transmissions.

Tires - 285/35/18

Rear gears - 3.73

I'm looking for a method to calibrate it, I've already worked out all of the math. I figured that I do 60 MPH @ 1,980 RPM. With the T56 @ 1,980 RPM I'll be doing 64 MPH. So, my speedometer will be reading 4 MPH under from going from a .67 to a .63 overdrive gear.

I think I found one method, from browsing through your swap thread.

SPEED-CAL, 1999-2004 TREMEC CONVERSION KIT****::****Transmission Components****::****Drivetrain****::****Mustang Parts & Accessories Superstore - 1800Mustang

Jazzer, since I've been skimming through your swap thread, and know you've done it, did you calibrate your speedo? It's not a huge issue for me since it'll be running under, and not putting ghost miles on the car, such as what an uncalibrated 3.27 to 3.73 rear gear swap does. I just want to get it all taken care of at once.

[Kevin C]

Whoops, nevermind on that Speed Cal. I realized that 2003-2004 Cobra T56s aren't mechanical drive, and also go off of a vehicle speed sensor.

Maybe buying a VSS for an 03-04 Cobra would work, since I imagine it'd be programmed for their .63 overdrive.

2003-2004 Ford Mustang Speed Sensor - Motorcraft - Rear, Driver Or Passenger Side

[Black Bullitt]

I don't see how the gear ratios of a transmission is going to throw off the speedo. The main thing on speedo calibration is the rear gear and the revolution counts of the rear wheels. Think about it this way. Rev the engine in neutral...it has nothing to do with the transmission, so RPMs aren't going to be off by swapping transmissions. Just calibrate your speedo with the correct rear gear and the correct tire revolutions.

[Kevin C]

Originally Posted by Black Bullitt I don't see how the gear ratios of a transmission is going to throw off the speedo. The main thing on speedo calibration is the rear gear and the revolution counts of the rear wheels. Think about it this way. Rev the engine in neutral...it has nothing to do with the transmission, so RPMs aren't going to be off by swapping transmissions. Just calibrate your speedo with the correct rear gear and the correct tire revolutions.

Do the math. If that's the case, you could have any gear ratios you want in the transmission, and you'd be able to do the same speed as any other vehicle on the road with the same tires and final drive ratio.

285/35/18 tires + 3.73 rear end gears + .67 overdrive gear @ 1,980 RPM = 60 MPH.

285/35/18 tires + 3.73 rear end gears + .80 overdrive gear @ that same 1,980 RPM = 51 MPH.

The VSS goes off of the output shaft of the transmission, transmission gear ratios affect that output shaft speed, therefore altering the VVS's readings, and essentially confusing the speedometer.

You can't have an overdrive gear of .67 that reads 60 MPH @ 1,980 RPM, and expect it so read that same 60 MPH @ 1,860 RPM, which is where my car would hit 60 with a .63 overdrive T56. It's just simple gear ratios. You need to calibrate for transmission gear ratios if you do a transmission swap.

I can see you didn't even bother to read my whole original post. I mentioned that my car is currently calibrated for 3.73 gears and 285/35/18 tires via SCT LiveWire. So, think about it this way, the vehicle speed sensor (VSS) reads the output shaft of the transmission. It doesn't go off of revolutions of the tires, it strictly reads the transmission output shaft speed.

With stock 3.27 gears, 285/35/18 tires, stock .67 overdrive TR3650, I'd be doing 60 MPH @ about 1,730 RPM. Now I'm doing 60 MPH at 1,980 RPM with the same tires, and 3.73 rear gears. The vehicle speed sensor was calibrated to think that 1,730 RPM = 60 MPH, which is why it was reading 10 MPH uncalibrated with 3.73s.

If you change any gear ratio in the drivetrain, whether it be rear end gears, transmission gears, or a tire diameter change, it will throw off the speedo.

[Black Bullitt]

First off I don't need you telling me to do the math and secondly I read your post, so you don't need to start acting pretentious. Keep your 3650...problem solved.

[Kevin C]

Originally Posted by Black Bullitt First off I don't need you telling me to do the math and secondly I read your post, so you don't need to start acting pretentious. Keep your 3650...problem solved.

Sorry, but I'm looking for people who have done the swap, and already have gearing basics down. To be honest, I went out of my way to save a little extra during 2010 to buy a 2001-2004 GT specifically for the stronger TR3650, but it's just not holding up. All I have performance wise are Bama custom tunes, a BBK CAI, Flowmaster catback, 3.73 gears, and it's not holding up. 2nd gear synchro is pretty much gone, that's the whole reason for the swap to a T56. I'm picking up the T56 this weekend, having a level three Viper rebuild done at Tick Performance in a few months, Spec stage 3 clutch, aluminum flywheel, etc. I'm doing it right the first time so that when I'm making some real power, there's no need for a redo.

Keeping the 3650 isn't an option. I eventually want to go for a single turbo setup. If it isn't holding up N/A with probably barely 240 RWHP, it won't hold up to 400+ RWHP from an On 3 Performance turbo kit running 10 PSI. Then again, the engine it's self won't handle too much more than that.

[Black Bullitt]

I've seen the 3650 hold up to a lot more than N/A builds. Unless someone beat the hell out of it, it shouldn't be going out, so easily. Give D&D Performance a call. They have actual swap kits, so they may have some insight on what to do.

I know this is for a fox body, but just read it.

http://www.stangnet.com/mustang-foru...ml#post7879794

[Kevin C]

I was checking out their site and blow by racing. BBR also sells D&D's swap kits. I asked the guy who I'm buying the T56 from what he did to calibrate his speedo since it's coming out of a salvaged GT that the T56 was swapped into in the first place, no answer yet.

I think between the dozens of knowledgeable people on here, the people at Tick Performance, the seller of the T56 I'm buying, and D&D & BBR as last resorts, I'll get something figured out. Heck, maybe I should just put the GT up for sale, and just buy myself a Termi Cobra. It'd be simpler.

I might have found something with buying a replacement VSS for an 03-04 Cobra. Maybe I'll just email SVT. LOL.

[slikirish]

Maybe I'm being really retarded here, but could a tune not fix the speedo just like it does with rear end gears?

[Kevin C]

It may be able to, but not a run of the mill handheld tuner, such as my SCT LiveWire. Regular handheld tuners are only capable of calibrating for tire sizes and rear end gears. Maybe an actual dyno tuner (since they also will calibrate for rear end gears and tire sizes if you don't have a handheld) could calibrate for transmission gears.

I don't know.

I'm curious as to what everyone else who's swapped in a T56 has done.

[Black Bullitt]

I'd also call Dallas Mustang. They make the calibration unit you posted earlier and may have some insight into it as well.

It seems like it would make since to have it changed in the tune, but I'm no tuner.

Triple post got ya.

Whatever you find out post it up.

[Kevin C]

I'm hoping Jazzer calibrated his speedo for the .63 overdrive gear, so he'd be able to tell me what to do. Well actually, not just 6th, every gear ratio on the T56 is different from the TR3650 except for the 1:1 4th.

Looks like I'm going to be calling a lot of people if I can't get this figured out. I'm confident in Tick Performance's abilities though. They pretty much live for the T56

[WickedSnake00]

I was going to say...I'm pretty sure the Mustang uses a VSS sensor on the output side of the transmission. Otherwise it would have to keep track of the current gear selection and clutch slippage and use that to calculate speed based on the engine speed. Plus if you pop the clutch and let it free wheel, the speedometer doesn't drop off, it's got to be on the trans output.

As far as doing the corrections a tune should be all you need to recalibrate it. You shouldn't even have to worry about the gear ratios, because the only ratio that will matter is your rear differential gears, and tire circumference.

[Jazzer The Cat]

I had my tuner calibrate the speedo based on the final drive ratio:

3:55's + rotation per mile of tires = accurate speed reading along with mileage on the ODO. I had/have no concern as to RPM's vs. each gear I happen to be in for a given time. My particular concern was to have a reasonable RPM of 2200 or so for cruising at 50 MPH. My T-56 put the 5th gear smack dab in the middle of my previous 4th and 5th gears.

Jazzer loves his T-56

[WickedSnake00]

+1 to Jazzer. Right on the money. I've had to do this stuff numerous times for design optimization at work. Can't wait to get my T-56 though.

[Kevin C]

This is interesting. I do 60 MPH @ 1,980 RPM now, the T56 will have me at 64 MPH at that same 1,980 RPM, and 60 @ 1,860. But, you guys are saying it'll be fine with a simple rear end/tire calibration, which I already have done for my 3.73s and 285/35/18s.

I emailed Tick Performance again, and they're going to elaborate on the TR3650-T56 swap for me a little more, and figure out if it'll be a plug and play setup as far as the VSS goes. I'm assuming it is.

This is breaking my heart just talking about it. I'll have the T56 sitting in my house, every question answered, but I'm waiting a few months to have it installed. I'm saving for a second daily driver, before I get into any serious mods with the Mustang.

I think I'll actually enjoy having a second daily driver, that actually gets over 25 MPG. Plus, a little black Jetta won't be too bad looking either. Still have the fun of a 5 speed, the cool factor of a diesel with the TDI Jetta, about 50 MPG, and I think you can pick up an early 2000's Jetta TDI in decent shape for 5K or less.

[ytngt]

Here is my experience. I had a 4r70w for years, finally got a t-56 mag. The VSS (vehicle speed sensor) senses trans output speed not input speed. So going 3650 to t-56 should not be an issue. In SCT PRP there is a variable "number of holes for OSS sensor", for a 4r70w it's 6, for manuals it's 12. Then there is a variable for rear end gear ratio. Once these are set you speedo will be good.

Edit: Thanks to Jazzer, I used your write up to install my t-56. I left my reverse lockout solenoid and wired it to a switch. Any way I appreciate the time you took documenting the process.

[WickedSnake00]

Yeah, all it should be is a simple recalibration of a magnetic pulse sensor. I'm sure you'll love the T-56

Psh a TDI diesel? There's only one acceptable diesel and thats a Ram with the Cummins ISB 6.7L. Of course I may be biased.