Rear Diff Swap (Torsen)

[MrMike]

I've read a pile of threads about this. It seems like this is either plug and play for people or a total nightmare.

Obviously, I do not want it to be a total nightmare. I want to swap the diff out to a Torsen, change the rear ratio in Forscan (if necessary) and be done. I understand that if I get a newer than 2017 rear diff I will need a driveshaft or new pinion. I've already decided I'd swap the driveshaft in that scenario.

I'm a ways out from actually executing on this, but my next set of mods will involve dropping the rear sub-frame again. As I suffer from a case of Slippery Slope Syndrome ™ , I'm going to replace other stuff back there while I'm at it. The #1 priority is a new Torsen diff and a cooler like @GTP's.

I don't need the Mustang to get from A to B, but I also do not want to spend the rest of my life troubleshooting a rear diff.

What is the least risky way to go about getting a Torsen diff I can be 100% certain will not be a piece of crap?

1. Buy the newest and lowest mileage rear diff I can find, likely from Midway Mustang
2. Buy a full rear sub-frame with the lowest mileage I can find
3. Pay an experienced shop to build a rear diff for me
4. Drive 8 hours to @shogun32 's garage

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[Oakley]

pumpkin + driveshaft for that pumpkin year and model would probably make it plug and play.

the torsen is worth it. its flawless in its operation.

 

[GTP]

I considered changing 3.15 to 3.55 on my previous car. Learned that the flange is different between auto and manual. And that the pinion torque is 300#!

I gave up on the idea and eventually replaced the whole car.

I agree with previous post that plug and play is matching things for the simplest conversion.

 

[MrMike]

pumpkin + driveshaft for that pumpkin year and model would probably make it plug and play.

the torsen is worth it. its flawless in its operation.

That's the leading option currently. I can buy a new driveshaft and pick it up at the dealer, or go with an aluminum or CF aftermarket if I want to risk NVH.

I guess I'll keep a watch at Midway Mustang for the newest one I can get. I don't care whether it's 3.55 or 3.73.

I considered changing 3.15 to 3.55 on my previous car. Learned that the flange is different between auto and manual. And that the pinion torque is 300#!

I gave up on the idea and eventually replaced the whole car.

I agree with previous post that plug and play is matching things for the simplest conversion.

That is exactly why I would replace the driveshaft in that situation instead of changing the pinion. Everything I've read indicates it is a huge pain and if you mess it up it can damage the diff.

I know to some it's silly, but this is my forever car for a list of personal reasons. Before doing a single mod I did the trade in for a Mach 1 or pre-order a DH debate.

I'm just concerned because to me the diff is like a black box. I have friends who can help me, but none have experience w/diffs aside from remove and replace. I guess that's the good news, I'm comfortable swapping the diff and driveshaft.

 

[bankyf]

I considered changing 3.15 to 3.55 on my previous car. Learned that the flange is different between auto and manual. And that the pinion torque is 300#!

I gave up on the idea and eventually replaced the whole car.

I agree with previous post that plug and play is matching things for the simplest conversion.

While 300ft/lbs is probably close, there is not a torque spec for the pinion. I honestly would guess it's higher. We definitely had a near death experience torqueing mine, which is complicated by the fact that you can't do it mounted to the car.

 

[MrMike]

While 300ft/lbs is probably close, there is not a torque spec for the pinion. I honestly would guess it's higher. We definitely had a near death experience torqueing mine, which is complicated by the fact that you can't do it mounted to the car.

Ford Performance has a guide for replacing the pinion flange that mentions measuring the torque of the current installation.

https://performanceparts.ford.com/download/instructionsheets/FORDINSTSHTM-4851-M8A.PDF

This thread was enough to make me think I would be in over my head building a differential.

A hydraulic press or large vice to hold the differential seems to be required.

 

[bankyf]

Ford Performance has a guide for replacing the pinion flange that mentions measuring the torque of the current installation.

https://performanceparts.ford.com/download/instructionsheets/FORDINSTSHTM-4851-M8A.PDF

This thread was enough to make me think I would be in over my head building a differential.

A hydraulic press or large vice to hold the differential seems to be required.

That's rotational torque, which is the proper method. That number is typically in the range of 20-30 in/lbs

 

[MrMike]

That's rotational torque, which is the proper method. That number is typically in the range of 20-30 in/lbs

Gotcha, thanks.

 

[GTP]

While 300ft/lbs is probably close, there is not a torque spec for the pinion. I honestly would guess it's higher. We definitely had a near death experience torqueing mine, which is complicated by the fact that you can't do it mounted to the car.

Yeah it's a situation of researching for a qualified dealer trans tech and pay them to do it.

 

[bankyf]

Gotcha, thanks.

Replacing the flange really isn't that bad. You could probably do it in the car and it won't take that much torque. The only special tool you will need is an in/lb torque wrench. The massive amount of torque is only required to cruch the crush sleeve when doing a new pinion.

 

[MrMike]

Replacing the flange really isn't that bad. You could probably do it in the car and it won't take that much torque. The only special tool you will need is an in/lb torque wrench. The massive amount of torque is only required to cruch the crush sleeve when doing a new pinion.

Which is what would be required if I was building a diff (e.g. swapping from Traclok to Torsen) right?

 

[bankyf]

Which is what would be required if I was building a diff (e.g. swapping from Traclok to Torsen) right?

You will need several other tools, including a dial indicator to build it. Just swapping to a torsen with the same ring and pinion isn't a horrible job. Replacing the pinion is where it gets significantly more difficult.

 

[MrMike]

You will need several other tools, including a dial indicator to build it. Just swapping to a torsen with the same ring and pinion isn't a horrible job. Replacing the pinion is where it gets significantly more difficult.

That kinda makes me wonder if I've misunderstood the effort required, but I'm assuming it's still easier to swap the whole pumpkin.

I thought swapping from Traclok to Torsen in an existing diff required full disassembly. Doesn't it all have to come apart because the gears sit on the traclok?

 

[Oakley]

You will need several other tools, including a dial indicator to build it. Just swapping to a torsen with the same ring and pinion isn't a horrible job. Replacing the pinion is where it gets significantly more difficult.

messing with a pinion flange also has to do with the crush washer to unless you have torque specs for just the flange without the crush washer installation for the pinion gear you're rolling the dice on a critical component. i wouldn't. whole pumpkin is the way to go imo.

 

[bankyf]

That kinda makes me wonder if I've misunderstood the effort required, but I'm assuming it's still easier to swap the whole pumpkin.

I thought swapping from Traclok to Torsen in an existing diff required full disassembly. Doesn't it all have to come apart because the gears sit on the traclok?

Definitely still easier to swap the assembly. You have to remove and replace the assembly either way. The pinion does not have to come out if only replacing the carrier(tracklok or torsen).

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