Allison 643 G vs 644 or 647

[bevans6]

does anyone know if these are equivalent transmissions or if there are mounting or other differences that would make an issue fitting to a 8V-71?

Brian

[kwidd]

They are all based on the same transmission. The 643 has the small converter and no adapters are available from allison. The other two have the big converter and adapters are available for them. If you are looking for a complete setup for a 644 I have one. Thanks Kent

[TomC]

Allison made dozens of builds within each model to accommodate different engines, mountings, PTO's, etc.  Without the transmission serial number, you can't know how it is set up. Good Luck, TomC

[Dreamscape]

What is the difference between these and the 740?

[TomC]

Jumping from the 600 series to 700 series is a totally different transmission.  The 600 is a medium sized transmission with capacity up to about 320hp and 900lb/ft torque.  The 700 series is a much larger transmission (largest made for on road vehicles) and rated to 445hp and 1550lb/ft torque.  I've seen the 700 series used in many high performance Diesel applications.  Like the Australian based Kenworth with a Detroit 16V-92TA with 4 turbos putting out close to 2000 horsepower.  Now that's a strong transmission.  Good Luck, TomC

[bevans6]

And it's enough bigger that it doesn't fit in my bus behind my engine...    

[luvrbus]

You have other options beside the 600 series the Z/F is shorter than a 740 and doesn't require all the drop down rings and spacers the 600 does it will bolt up to a sae1 bellhousing the drawback is the price of parts and finding them if ever it goes bad then you have the Voilt lt was used in the Houston Metro Eagles with a drop box



good luck

[TomC]

Personally-if I had a MC-5, I would without question switch to a 6V-92TA with the HT740.  You would have an easy 350hp with 1000lb/Ft torque.  Good Luck, TomC

[bevans6]

I hear you, money no object and someone else doing the work, no question I would have a 6V92 and 740 in a heartbeat.  But money's an object, and I have to do the work...   

I am exploring the options and  weighing the pro's and con's.  Carl up the street from me has a 5C with an 8V71T and a 640, and I am looking forward to seeing how it does, so far it is a sports car he says!  At the Palmetto Cove rally a lot of guys had Series 50's and thought that was the golden key, I measured and they seem to be dimensionally similar to an 8V71 so I would still have the same transmission restraints, plus I really suspect it would be a lot more expensive than a 6V92, but a modern-ish engine and different power delivery profile that would probably mean a diff change.

Who knows, but I do know this - I appreciate the advice and feedback every single time!

[luvrbus]

If you decide to go the 50 series route don't forget me I have 350hp 83,000 miles with a B400 that maybe for sale came from a Eagle the guy replaced it with a C-13 Cat and a B500 he was not happy with the series 50 in a 102 wide 40 footer bus but I bet it would send a 35 footer down the road



good luck

[bevans6]

Clifford, sent you a PM.

Brian

[robertglines1]

the 50series would be a hotrod in a bus in your weight class...the auto will spoil you... might get combo for not much more than the 600 series trans alone..would be a matched set...good luck   should gain fuel improvement in the 50% more range