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Discussion Starter #1
Finally, I get to put 68 KAT back on the road!

I have an X code 390 and my C6 transmission needs to be rebuilt or I need to replace it with an 4R70W.

I have read the topics regarding the 4R70W swap and believe that is the direction for me to go. I have a 2.75 rear end. Will the overdrive work with that low gearing? What about the bellhousing bolt pattern?

Another idea I had was to go with a wide ratio C6 from Broader Performance.

Advice?
 

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C6
1st - 2.46 2nd - 1.46 3rd - 1.00

C6 Wide
1st - 2.72 2nd - 1.54 3rd - 1.00

4R70W
1st - 2.84 2nd - 1.55 3rd - 1.00 4th - .70


With a 27.5" diameter tire both C6's will be at 2000 RPM at 60mph. The 4R70W at 2000 rpm would be running around 85mph (or 1400 rpm at 60). This was if you don't change your rear gears.




In 1st, this is how the 2 wide ratio's would feel (with your stock 2.75's):

C6 Wide Ratio:
1st - 3.04 (little more than 3.00 gears) 2nd - 2.90 (little less than 3.00 gears)

4R70W:
1st - 3.17 (or close to 3.23's) 2nd - Pretty much the same as the C6 Wide Ratio in 2nd. (2.92)


3rd gear is the same, and based off the numbers I just provided you I would go with something a bit higher, like 3.23's or 3.55's. 3.23's would put you at 70mph doing 1900 rpm. That is very good and the rear gears would feel like they were 3.73's in first with the 4R70W compared to the normal C6.



Therefore, if it were me, I would find out the cost of the C6 wide ratio, subtract that from $1400, and ask yourself if that number is worth your car being a good cruiser or not. Chances are it is going to be like a ~$5-800 difference. Ask anyone if they would like thier car to run 3.73's and 2k rpm at 70 on the highway for $1400 and many would jump, but for $5-800, most would.
 

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Discussion Starter #3
I can pick up a 4R70W from the local salvage yard for $185 out of a 2001 Crown Vic (61k mi). From what I have read, I would need a controller (Baumann?), crossmember, adapter, flywheel, throttle position sensor and driveshaft change. The Wide ratio C6 is an easier swap but (probably) would cost a bit more.
 

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I was saying $1400 because it seems with all the "needed" stuff the 4R70W swap runs about $1200-1400. Wasn't sure on how much a C6 wide ratio ran, but I was assuming it was going to be 2-300 for the rebuild plus a couple hundred more for the gears and work. Looks like the 4R70W is the way to go as long as you are willing to put in the work. There is a good swap writup done by Joe Gallagher on here that will show you everything.
 

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Discussion Starter #5
Yes, I saw Joe's post and know that it can be done. I think that covered everything except for the 390-4R70W adapter. I just hope I am up to the challenges...
 

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Discussion Starter #6
$850 just for the adapter to mate the 4R70W to the FE. I think I am going to go with a wide ratio C-6 from Broader Performance after all.
 

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There are 3 options from what I found for you. The first two you can disregard unless you like sharing your money with other's. Those two are (for information purposes):

Lentech's is 7976-AOD-BFFE @ $745.00 http://www.lentechautomatics.com/aodpricing.html
These guys have one http://www.transmissionadapters.com/ford_fe.htm @ "Call for Price" - More info: http://www.transmissionadapters.com/Ford_FE_to_AOD_install.htm

The last one is Performance Automatic
PA26390 is the Ford FE to C4 pattern (same as AOD/4R70W) one for $546
http://www.performanceautomatic.com/products/parts-and-accessories/bellhousings-and-rings/pro-fit-bellhousings.html


Not sure if $300 less makes it doable for you, but thought I would post it here for others that are contemplating it.
 

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So you are looking at $1400 for their 500hp Wide Ratio C6 shipped.


This is what a 4R70W would cost you:
Bellhousing - $574 Shipped
Transmission - $185
Driveshaft - $150 approx.
Flexplate - $50 (from 4.9 Ford)
Baumann - $610 (with wiring)
TPS - $110 (Holley 534-202)
Crossmember - $160 (w/ shifter linkage)
Total: $1319

So really, since the prices are about the same, it comes down to if having overdrive and a fully adjustable shift point transmission is worth the work.

Added: To be fair, there would be benefits to either:

C6 Wide Ratio:
New
Warranty
Easier to install and straighforward

4R70W
Overdrive
Adjustable shift points and firmness
Easier/cheaper to replace/repair once installed
Little higher gearing
 
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