3.55 gear install and SPEEDO CALIBRATION?

[monte87]

Hi guys,

I am going to have a shop install a set of 3.55s gears on Saturday, replacing these stock 3.15s, should def be a diff for sure.
Question-> How do these S550 cars get there speedo calibrated? Back in my time via foxbodies it was a simple 15 dollar speedo gear and your done..
Thanks Anthony

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[Superspirit]

It's done by changing a code in the as built data with forscan. The last I heard forscan won't recognize a 21my. I would check the forscan thread for updates.

 

[monte87]

It's done by changing a code in the as built data with forscan. The last I heard forscan won't recognize a 21my. I would check the forscan thread for updates.
[/QUOTE
Thanks for reply.. oh ok, cool deal thanks. Can the shop use a tuner to do this?
Thanks Anthony

 

[Lbj]

Are you changing the complete Differential because 355 gear will not fit in a 315 housing

 

[monte87]

No, changing ring and pinion gear only. Why cant the ring and gear be swapped out??

Are you changing the complete Differential because 355 gear will not fit in a 315 housing

 

[br_an]

I've been looking at doing this too. The 3.15 is a tad underwhelming on my base GT

 

[br_an]

No, changing ring and pinion gear only. Why cant the ring and gear be swapped out??

I don't think you can do that

 

[Lbj]

Just letting you know that I was told that the 355 will not work if you put in a 315 housing so double check just to be safe

 

[monte87]

I don't think you can do that

If it has an IRS rear end I'm more than sure it can be swapped out. They sell kits for it on American muscle. Unless I'm missing something here.

 

[monte87]

Just letting you know that I was told that the 355 will not work if you put in a 315 housing so double check just to be safe

Ok, thanks for reply. I will def, thanks for heads up. Appreciate it

 

[Lbj]

Any time please keep us informed

 

[Superspirit]

It's not the housing, is the carrier that the ring gear bolts to. Not sure of the breaking point. I think it's 3.55 up and 3.31 down. But am not positive where the split is.

 

[br_an]

If it has an IRS rear end I'm more than sure it can be swapped out. They sell kits for it on American muscle. Unless I'm missing something here.

I've been looking into doing this too, and I forget the exact reason, but I believe the differential housing is different for the 3.15 (aluminum) vs the 3.31 on up (iron), and it might be size thing too. I'm sure the helpful fellas on this sub that know why will weigh in.

this thread might have some helpful info
https://www.mustang6g.com/forums/threads/switching-from-3-15-to-3-55-gears.96697/

 

[WildHorse]

If it has an IRS rear end I'm more than sure it can be swapped out.

Nope. Unless Yukon or somebody sells a totally different tooth count ring/pinion than Ford does for the 3.15 specific carrier. If that's the case, it'll be noisy AF fuck. Hard pass.

 

[monte87]

Nope. Unless Yukon or somebody sells a totally different tooth count ring/pinion than Ford does for the 3.15 specific carrier. If that's the case, it'll be noisy AF fuck. Hard pass.

So then what needs to be changed inside the pumpkin? The carrier to mate to gear set?? I'm confused

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