643 allison trans

[keith]

iam looking for a 643 allison to mate up to my 5.9 cumm i have a good 545 3 speed but i want 643 4 speed with overdrive....

keith

[bus-bro]

The mt643 and at545 mate to different bell housings (SAE #2 for 643), so you'd need to find that to. at545 is 4 speed, so is mt643 (that's what the "4" stands for.) mt643 does not have overdrive.

[keith]

How can i make it an overdrive or can i just put a lockup converter ????

[opus]

643 has a lockup. No overdrive.

[keith]

so,you say put a lockup converter in the 545 and it would make it like a 643 ?????

[bus-bro]

If that's possible a lot of people would want to know how to do it. Not that I know, but I don't think it's possible. The 643 would still be a beefier transmission.

[keith]

i have a buudy who owns a converter shop and ill see if he can make mine a lockup converter and the cost $,,,also anybody got a 643 for sale ????

[bluebird90]

Just some info...The at545 IS a 4 speed.
545and 643 are 2 differant animals.
the 545 uses a #3 flywheel housing, the 643 uses a #2, If you have an adapter ring between the flywheel housing and trans you already have a #2.
Depending on how big your bus is the 545 will do you just fine.
I have a MT643 that came from behind a cat 3208 that I,m selling. if interested , email me direct...epp@wavecable.com.
I,m in Port Angeles , wa

[bluebird90]

Forgot to mention...the 643 is NOT an overdrive transmission. It,s direct in 4th gear