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Discussion Starter · #1 ·
i have a 1971 Torino with a 429 cj, C6 tranny, with 9" rear end with 3.50 gear with 26" tires.
I push almost 3,000 rpms at 60 mph, and would like to reduce that by swapping out the tranny for an overdrive trans, since all i do is mainly cruise anyway and would like to travel on the interstate from time to time.

I have been informed by a local engine/trans rebuild shop that an AOD will not fit to a BB only to SB engines, and that i should look at getting an E40D instead to handle the power of the 429. This shop has a E40D for $1,050 tested and dyno'd and delivered, but you need a stand alone computer to tell it when to shift which from what i can find can cost at least $500.00.

So my question is: is their a cheaper alternative to the E40D option?

Any advice on Swapping out my C6 would be greatly appreciated...
 

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Since you are just cruising and going on the interstate how about going to another rear end gear.

2000RPM AT 60MPH with 26" tire you should use a 2.58 gear.

here is a calculator:

http://www.summitracing.com/expertadvice/storydetail/calcsandtools/Gear-Ratio-Calculator/


Also with the information you gave would tell me you are running a 3.87 gear or your speedo is not accurate to the tire size you are running.

But then again I could be all wet!
 

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Discussion Starter · #3 ·
Thanks for the response.

Yea the tag on the rear end says 3.50 but that could be wrong, and my speedo is off by 10 mph according to the gps app on my phone.

I have been toying with the idea of changing the rear end gear. I have a buddy with an open 3.00 9" i am thinking of getting and just swaping it out. My rear end has a detroit locker in it according to the guy i bought it from, but it is locked at all times and has horrible turn radius.
 

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There not cheap but a great switch to keep those rear gears & get your cruise speed at 60mph down to about 1900-2100rpm is stick a Gear Vendor under/overdrive on the back of that C-6.
Its a fairly straight forward swap, no tunnel mods & with the "over" gears you have 6 forward speeds in manual mode, or switch to Auto mode & it shifts 1,2,3 into OD for you
Final drive with your C-6 & a Gear Vendor unit is .68 stock.
A simple switch,either on the floor or on the shifter controls the GV unit.
The unit "splits" each gear, so the drop between gears is only 300-400rpm, keeping your motor in its sweet spot at the flip of a switch.
Gear Vendors have a pretty good site if you want to learn more, or drop me a pm & i'll share my limited expierence !
 

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lentech makes an adapter to hookup an AOD behind a FE, so they may make one for the 429. I think out the door with tranny and adapter is 3200.00 but I won't swear to it. At least then you won't have a computer checkout thier website lentechautomatics
 

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Dunno if you really want to go with a E4OD. I have no experience with them myself but ..... there's a fella with a '67 Fairlane that has attended the last couple of West Coast Fairlane Mini Meets with one. He has it behind a stroked 527.

In speaking with him - he said that he would never use one again, as the they are complicated to set up (and as you mention, need a computer to run) AND they are huge, so you will probably have to slice the trans tunnel to get it to fit.

First thing, as other have pointed out here, figure out what rear end you really have. Don't take someone else's word for it. Simplest, cheapest thing is to swap out the pumpkin for easier cruising.
 
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