Re: 727 to 518 swap...

["Jim Blair" <carnuck@xxxxxxxxxxx>]

A: Adding overdrive to the Jeep trans would have to be the same as the did 
with the 518. It's valve body controlled (shape is the same as a 727 with 
lockup almost) and the O/D planetary is in the tailstock. I came up with a 
simple design that would use a 727 4x4 output shaft and either have a 
slipyoke or flange to attach a Tcase to. There is NO 518 for the big block 
Mopar, so guess how many others (besides '80 up Jeepers and '72 up AMC 
drivers) would be interested? I built a version of this with crude parts 
about 15 years ago (couldn't swing the collateral for a loan to build them) 
on a 1 ton Dodge truck. I modified the "6" speed auto (out of a 5 ton) to 
work, then decided a better way was with real gears.


From: farna@xxxxxxx
Subject: Re: 727 to 518 swap...
To: mail@xxxxxxxxxxxx
Message-ID: <ADVANCES62xhiV6jwjr00004530@xxxxxxxxxxxxxxxxxxxxxxx>

On July 20, 2005 Jim B wrote:


Yeah, there is an adapter from Advance Adapters for a Chevy trans to AMC 
engine. I don't know how Lexus gets 5 or 6 speeds -- there has to be a 
different valve body and I would think gearing. The AW4 isn't a three speed 
with OD added to the back -- it's a four speed trans with fourth gear having 
a high ratio. At least it is shifted that way -- there is no way to "add" OD 
to a lower gear in the Jeep valve body. It may be constructed as a three 
speed with an additional planetary set for OD, I haven't looked that close 
at the specs. Or Lexus could use a looser torque converter and use lock-up 
as another "gear".

The trans controller is built into the engine computer on 96 and later 
models. Using a Toyota controller has other problems than just the 
likelyhood that they are built into the engine controller. The Supra version 
I looked at had an electronic gizmo (probably a stepper motor?) in place of 
the TV cable. Obviously it was computer controlled. The separate controller 
may be an 87-95 Jeep exclusive.

I like the tailstock adapter idea, but I'm willing to bet there is n demand 
since it would really only affect AMC people. Mopar guys can swap the 518 in 
directly, of course.