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Best way to swap my 3.55s out for 3.15s

Furious18

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I have a 18 a10 pp1 car and need to swap the 3.55s out now that I’m boosted. What’s the most cost effective way? Does anyone know if I can swap just a pumpkin or need the whole carrier?

thanks in advance!
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kent0464

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I have a 18 a10 pp1 car and need to swap the 3.55s out now that I’m boosted. What’s the most cost effective way? Does anyone know if I can swap just a pumpkin or need the whole carrier?

thanks in advance!
If you’re mechanically inclined, the cheapest way is simply swapping out the ring and pinion.
If you’re paying to have it done, it may be cheaper to source a whole pumpkin and have it bolted in.
 

Mikepol2

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I think the 3.15's use a different pumpkin than 3.55 and higher. Also not sure if you can change the ring and pinion without removing the pumpkin from the car. If both of those are true then there's no decision to be made - just swap pumpkins. It's really hard to find a good gear guy, and the pumpkin swap isn't that hard. Not easy but doable in your garage with jackstands.
 

80FoxCoupe

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I think the 3.15's use a different pumpkin than 3.55 and higher. Also not sure if you can change the ring and pinion without removing the pumpkin from the car. If both of those are true then there's no decision to be made - just swap pumpkins. It's really hard to find a good gear guy, and the pumpkin swap isn't that hard. Not easy but doable in your garage with jackstands.
Housing is the same. 355 and 315 use different differentials.
 
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Furious18

Furious18

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I don’t think you can put a 3.15 ring and pinion in a 3.55 torsen. Atleast that’s my understandBig.

does anyone know what year auto 3.15 pumpkins will fit?
 

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80FoxCoupe

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I don’t think you can put a 3.15 ring and pinion in a 3.55 torsen. Atleast that’s my understandBig.

does anyone know what year auto 3.15 pumpkins will fit?
Again, all the housings are the same. The 315 will need a different differential than the 355.
 

1MEAN18

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You need to find someone with a 3.15 that wants to swap entire diff for a 3.55, they are different housings.
 

CraigJ

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Currently swapping the diff on my 16 GT manual from 3.55 to 3.15

3.15 complete pumpkins are pretty cheap. $200 upwards as every one tends to want 3.55/3.73's etc.

Cast (rusty pumpkin) are from manual cars and all aluminium pumpkins are from autos. The flange is different between the two.
I don't know if the flange is the same between 15-17 and 18+ autos though.

Not a bad job to swap. You can get away with just removing 1 half shaft (and hub) then as you drop the diff out just feed the other shaft through. Saves having to strip the hubs of both sides.
Found this out as the RH half shaft didn't want to come out of the diff so dropped it still attached.
5961AC7F-8DC7-4652-BC49-9AA570D199A2.jpeg
 
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Furious18

Furious18

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Thanks everyone! Is there a general consensus as to how much power the factory diff will hold?
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