3:31 to 3:55 swap

[Wera750]

I have a 3:55 on the way for my base ecoboost, so I've been reading up how to do the swap. I'm confused though because I've read that the BCM can't be flashed and I've read that some people have been able to have their BCM flashed. I've also read that the Cobb and X4 tuner (which I have) can change the gear ratio. Has anyone done this swap? If so, what did you do?

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[Bomicino]

I'm interested too. Supposedly FRPP will have a "solution" 4th quarter.

 

[gzstang]

That's an awful lot of work for very little change in gear. You won't gain much with such a small change in ratio.

 

[Wera750]

Update, my local dealer says they can flash the BCM to accommodate for the gear. Cj pony parts suggested I call some dealers as they have had customers have luck with some dealers.

 

[ronv95]

Have you drove a eco with 3.55? I'm just wondering why you would want to spend a chunk of change on such a small change in gear. Why not go to 3.73s? To each their own though.

 

[Reds197]

That's an awful lot of work for very little change in gear. You won't gain much with such a small change in ratio.

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[Wera750]

So ended up that I have a 3:15, brain fart on my part. A word to the wise though, you have to change the carrier to change the gear in these cars. They don't compensate for the reduction of size of the pinion gear with the ring gear like they used to. They compensate with the carrier. The 3:55 was so far off on lash I couldn't take a good measurement. I wish I would have taken pictures. Long story short, I still have a 3:15 and I wasted about $60.

 

[Bomicino]

I'm confused, carrier as in the entire center section? I thought there were on 2 kinds. One that is aluminum. I went to the dealer I bought my car from, and I asked the advisor for a quote on ring and pinion install if I brought the diff. To them, he said about $700!! Labor only! I want what he's on. I'd like to be sure the FRPP 3.73 and install kit are good to go in my diff. Could you further explain why it didn't work for you?

 

[Wera750]

I'm talking about the piece that the ring gear bolts to. It holds the clutch packs and spider gears.

 

[mbreinin]

I would go 3.73. I have 3.55s.

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