[MoparPete]

Hello, Is it possible or can it be even done to remove a 727/904 and replace with a later model 4sp auto. trans. My gas mileage is the main concern, the GM boys can switch 200/350/400s over to 4L60E & 4L80E. Would I need a computer and harness or is their a converison kit/method already out on the market?
Thanks in advance for your Helpfull suggestions!
(early 70's Challenger, 360 w/727)

[squeek360]

you can put in a 4 speed auto ; however , you'll have to enlarge the rear portion of the trans tunnel to make room for the overdrive unit . aswell , you'll have to have a custom driveshaft made as the overdrive trans is longer. the newer 4 speed auto's are virtually identical to the 727/904 trans used in the challenger with the exception of the overdrive unit which is controlled electronically and the use of a lock up torque converter as opposed to the non lock up converters found in challengers. no controllers or computers are necessary for the conversion as the overdrive unit is merely engaged via a switch.
i would also suggest that if you do the conversion , only engage the overdrive when cruising , not when powerdriving. good luck , hope this helps :>)

[dave-r]

I am not sure but I think the transmission you are refering to is actually based on the A904 box. It is not an easy conversion.

[squeek360]

definitely not easy dave ; however , there are 2 different versions of the 4 speed auto used in newer trucks , one is based on the 904 and one on the 727. the technical chrysler designations are "A 500" for the 904 based trans and "A 518" for the 727 based trans. I should point out however that upon further research , I found out that the 518 has a non lockup converter ; where as , the 500 has a lockup converter. but as you stated , this is no simple task requiring major mod's (nothing I would consider doing espicially given the increasing rarity of the e body)anyway , I thought info on as even a modified challenger is a sweet machine. as well , both trans assemblies can be ordered directly from mopar performance part #'s P5249165 for the 500(904) , and P5249166 for the 518 (727))

[squeek360]

In above message , it should say "I thought I'd pass the info on as even" lol , and would also like to say that I love this website , thanks for putting it out in cyberspace :>) You definitely have one Canadian hooked :>)

[dave-r]

Probably easier to fit an aftermarket overdrive unit. There is a type that fixes onto the end of the trans I think.