Inside the "Super 8.8" Rear End

[WD Pro]

Hi @JohnVallo great information. You sound like you know a lot about diffs. I wondering if there is something wrong with my rear differential. We have performance pack cars in Australia. Early this year I had diff problems which the dealership said was LHR diff bearing. The replaced it but I have felt the back end was never quite the same. It seems to lose traction a lot and feels like its the LHR. It's just not as stable. Anyway last week a strange thing happened going out the driveway. The RH rear tyre was on uneven ground, and slightly in the air. When I accelerated the wheel just spun and the LH rear didn't get any traction, the car did not move. I thought this was strange and reversed a bit to even the car up then drove off. Should this happenas I thought as a LSD it should have engaged the other wheel and made traction......is my diff rooted. As I said I've never been 100% confident all was righ since the fix. Any ideas

A Torsen rear-end will respond this way.
To get traction when one wheel spins, just pull emergency brake a little to put resistance on rear wheels and then both rear wheels should get traction.

John may not know (or I may be wrong) that your Aus PP spec car, like our euros and UK’s gets the trac loc and not the Torsen diff - that may result in a different response

@JohnVallo - I know that TBR can be altered by elements of the design and components, but are you aware of any TBR differences between the models across the mustang range i.e. does a 350r or a 500 CFTP have a different TBR when compared to say a PP1 ?

I ask because I picked up a rumour (can’t remember where from …) that the aftermarket Ford Performance Torsen may be different than the factory Torsen.

Following on from that, I understand that TBR after manufacture can be altered a little by oil weight and slippiness i.e. a thicker oil will give a lower TBR when compared to a thin oil with a load of friction modifier. Do you have any experience with this ?

Finally, are the standard Ford drain and fill plugs magnetic ?

Sorry for all the questions, but you seem to be the best guy go ask … !

Cheers,

WD

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[JohnVallo]

are you aware of any TBR differences between the models across the mustang range i.e. does a 350r or a 500 CFTP have a different TBR when compared to say a PP1 ?
Not aware of any differences in the Torque Bias's
I have heard rumors of differences, but not verified.
I have not had any experience experimenting with TBR's
For an exact answer You might reach out to JTEKT.

Torsen - Wikipedia


Finally, are the standard Ford drain and fill plugs magnetic ?
Yes, All the Mustang S550 rears I have taken apart have this fill-Drain plug:

 

[WD Pro]

are you aware of any TBR differences between the models across the mustang range i.e. does a 350r or a 500 CFTP have a different TBR when compared to say a PP1 ?
Not aware of any differences in the Torque Bias's
I have heard rumors of differences, but not verified.
I have not had any experience experimenting with TBR's
For an exact answer You might reach out to JTEKT.

Torsen - Wikipedia


Finally, are the standard Ford drain and fill plugs magnetic ?
Yes, All the Mustang S550 rears I have taken apart have this fill-Drain plug:

Thank you very much

WD

 

[TeeLew]

@JohnVallo

I can't remember how much we talked about this previously, but I thought you might find this interesting.

I have an EcoBoost which I am using to Auto-X. Because of the lower RPM nature of the Eco, most Auto-X courses end up between 2nd and 3rd gear. It's a very clumbsy gearing combination that makes several shifts a lap inevitable.

In an effort to be able to run almost any course by launching in first and then running the rest in second gear, I am installing a 3.15 rear end. The down side to the 3.15 is that none of the performance differentials are available. The Torsen and everything else is made for the 3.31 and numerically higher gears. The only LSD available for the 3.15 ring size is the Trac-Lok, which has relatively low locking capacity, next to no preload and only lasts a couple slip events before burning up the friction material. It's not a great combo. So, I've made my own differential plates (water jet cut) to help address these problems.

The stock plate thickness allows for 3 drive and 3 driven plates. I have made mine thinner, so I can get 4 of each on either side for more total lock. Further, I've made them from hardened 4142 tool steel, so wear shouldn't be much of an issue. I've found a preload block off of Alibaba for $15 that I think I can use for that function. In the end, I know that I'm probably giving some away to a Torsen or OS Giken, but I think I'll be a hell of a lot better than a stock Trac-Lok. At the very least, especially since I'm changing to an Al housing, I'll be a lot lighter.

I don't have much time to play with it for the next couple weeks, but after that, I'm going to stick it in and see what we've got.

 

[boB]

@JohnVallo

I can't remember how much we talked about this previously, but I thought you might find this interesting.

I have an EcoBoost which I am using to Auto-X. Because of the lower RPM nature of the Eco, most Auto-X courses end up between 2nd and 3rd gear. It's a very clumbsy gearing combination that makes several shifts a lap inevitable.

In an effort to be able to run almost any course by launching in first and then running the rest in second gear, I am installing a 3.15 rear end. The down side to the 3.15 is that none of the performance differentials are available. The Torsen and everything else is made for the 3.31 and numerically higher gears. The only LSD available for the 3.15 ring size is the Trac-Lok, which has relatively low locking capacity, next to no preload and only lasts a couple slip events before burning up the friction material. It's not a great combo. So, I've made my own differential plates (water jet cut) to help address these problems.

The stock plate thickness allows for 3 drive and 3 driven plates. I have made mine thinner, so I can get 4 of each on either side for more total lock. Further, I've made them from hardened 4142 tool steel, so wear shouldn't be much of an issue. I've found a preload block off of Alibaba for $15 that I think I can use for that function. In the end, I know that I'm probably giving some away to a Torsen or OS Giken, but I think I'll be a hell of a lot better than a stock Trac-Lok. At the very least, especially since I'm changing to an Al housing, I'll be a lot lighter.

I don't have much time to play with it for the next couple weeks, but after that, I'm going to stick it in and see what we've got.

It's a lot more work and $$ but would the MT82-D4 with it's 2.10 2nd gear do what you want and still be compatible with a Torsen? Apart from that what you are doing is some real good engineering and fabrication! I autocrossed in the 80's and like you I went through a diff clutch pack in only a few events. :(

 

[TeeLew]

It's a lot more work and $$ but would the MT82-D4 with it's 2.10 2nd gear do what you want and still be compatible with a Torsen? Apart from that what you are doing is some real good engineering and fabrication! I autocrossed in the 80's and like you I went through a diff clutch pack in only a few events. :(

I have a 2020 with the taller gearing. I drive my car a ton on the freeway, so the 3.15 is no big deal to me in daily life. I couldn't give a shit about the stoplight grand-prix or drag racing. There's very little down side that I can see other than the diff.

 

[JohnVallo]

@JohnVallo

I can't remember how much we talked about this previously, but I thought you might find this interesting.

I have an EcoBoost which I am using to Auto-X. Because of the lower RPM nature of the Eco, most Auto-X courses end up between 2nd and 3rd gear. It's a very clumbsy gearing combination that makes several shifts a lap inevitable.

In an effort to be able to run almost any course by launching in first and then running the rest in second gear, I am installing a 3.15 rear end. The down side to the 3.15 is that none of the performance differentials are available. The Torsen and everything else is made for the 3.31 and numerically higher gears. The only LSD available for the 3.15 ring size is the Trac-Lok, which has relatively low locking capacity, next to no preload and only lasts a couple slip events before burning up the friction material. It's not a great combo. So, I've made my own differential plates (water jet cut) to help address these problems.

The stock plate thickness allows for 3 drive and 3 driven plates. I have made mine thinner, so I can get 4 of each on either side for more total lock. Further, I've made them from hardened 4142 tool steel, so wear shouldn't be much of an issue. I've found a preload block off of Alibaba for $15 that I think I can use for that function. In the end, I know that I'm probably giving some away to a Torsen or OS Giken, but I think I'll be a hell of a lot better than a stock Trac-Lok. At the very least, especially since I'm changing to an Al housing, I'll be a lot lighter.

I don't have much time to play with it for the next couple weeks, but after that, I'm going to stick it in and see what we've got.

This is very interesting, Applaud your creativity!
This is like the shit I used to do when I was racing...
I was reading several of your posts in the
SCCA CAM-C Thread

Seems like you are Firm on the 3.15
When they say there is no Torsen, for the 3.15 have you looked at this:
https://torsen.com/product/ford-super-8-8-3-151/

If it were me, and I had to use the 3.15 gear, I think there is a good possibility it could be accomplished using a standard "Super 8.8" Torsen T2 Differential. I may do a write-up of my idea/theory when I get some more time.

You may want to read my new post, 3.15 Gear Ratio -Why it is different
here: (1) 3.15 Gear Ratio -Why it is different- | 2015+ S550 Mustang Forum (GT, EcoBoost, GT350, GT500, Bullitt, Mach 1) - Mustang6G.com
It clears-up a lot of rumors and false info about why the 3.15 differential won't work with the other ratios.

 

[TeeLew]

I didn't realize that 3.15 Torsen existed. Maybe you mentioned it and I was hell-bent on this other approach? Anyway, this was quite a bit less expensive (about 1/2?) and I like to fiddle with things, as you might have guessed. If the Torsen I already own in the 3.55 pumpkin will work in the 3.15, then all the better. Now I can acutally do some real testing.

 

[HoosierDaddy]

are you aware of any TBR differences between the models across the mustang range i.e. does a 350r or a 500 CFTP have a different TBR when compared to say a PP1 ?
Not aware of any differences in the Torque Bias's
I have heard rumors of differences, but not verified.
I have not had any experience experimenting with TBR's
For an exact answer You might reach out to JTEKT.

Torsen - Wikipedia


Finally, are the standard Ford drain and fill plugs magnetic ?
Yes, All the Mustang S550 rears I have taken apart have this fill-Drain plug:

Thanks. Shop manual does not call for locktite and I was doubting a dealer who told me they didn't use locktite after later seeing the red on the threads

 

[PC_GUARD]

Thanks. Shop manual does not call for locktite and I was doubting a dealer who told me they didn't use locktite after later seeing the red on the threads

When I drained mine, I cleaned up the magnet real well, and wound it back in. No leaks, and Im 99% sure I didnt use anything

 

[DrZed]

Thanks. Shop manual does not call for locktite and I was doubting a dealer who told me they didn't use locktite after later seeing the red on the threads

Good question. Why locktite and not a teflon pipe sealant or tape?

 

[Rmac88]

I'm very lucky to have stumbled upon this thread. John, your attention to detail humbles me and your write ups are extremely professional. So it looks as if the torsen rear assemblies do have some differences from a standard SRA. However, as far as the rotating mass and the pinion gear, it looks to be about the same situation as any normal rear differential. As you know, I am currently building my 2017 gt350 N/A and trying to achieve a certain ET before making the plunge and boosting the car. With that being said, swapping the 3:73 gears with either the 4:11 or the 4:56 ring and pinion is a current MUST for me and I will be doing so very soon. I think after speaking with you, the 4:56 swap seems more like the option I am looking for so I may have to utilize this post for reference. Once again, very informative post and it is much appreciated for educational purposes. You might need to make a YouTube channel in the future. Lol.

 

[TeeLew]

Hey John,

How many different Traction-Lol S-springs are there? I'd like to find the stiffest available for the Super 8.8.

 

[JohnVallo]

Only (2) That I know of:
1. F3TZ-4214-A
2. JR3Z-4214-A

Both may have the same tension

 

[hot rod]

Hi John,
thank you for sharing your experience. I also read your other Gear/Diff threads.


Now I'm swapping the 3.55 to 3.73 Ford Performance gears.
It is my first time working with a differential. So far, everything went well.
I noticed on the Pinion there is a number written by hand right in the middle where the crush sleeve sits. In my case it says 06. Could it be a hint for the pinion depth? Maybe + or - 0.06?

The other thing is when i set the pinion preload i had a good amount of break away torque. It was very hard to turn by hand and it went above the scale of the beam style torque wrench. Once it was moving, i was about 25 lb-in. What i read, this should be okay with new bearings. Is it normal that the break away torque is so much higher than the rotational torque? Maybe i haven't oiled the sealing enough?

And the last question, what about the Diff bushing inserts? Do you put them back in?
I experienced the same 40-65 mph whine when taping the Gas to hold the speed.
It immediately disappears when stepping on the Gas or completely letting off the gas.
Is this because of the bushing inserts or is this a setup thing? Can you get rid of the whine and have them installed?

thank you
Alex

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