MT654 to HT740 swap in 1984 MCI 9

Gthor · September 30, 2017, 01:14:14 PM

My gear is toast and I have determined that the MT654 is perhaps not enough transmission to handle the horsepower and torque of the 6v92. So, rather than throw more money away by buying a rebuild I am looking at upgrading to a HT740. Any advice, information or tips on making this swap would be greatly appreciated. The Morse shifter and modulator valve I have seem compatable but the bell housing and length of the transmission/drive shaft seem to be areas critical detail that need to be addressed. Bus is located in Eugene OR

eagle19952 · September 30, 2017, 02:27:46 PM

In what coach ?

chessie4905 · September 30, 2017, 02:58:56 PM

H :)eading to his post says 1984 MC-9. I would check if you can find MC-9 doner with transmission/ engine combo you have and buy trans, shifter, drive shaft and every other associated items you need to switch over. Maybe Luke or company near Danville Pa.on I80 or Easter in Basset, Va. or other place parting out busses near you. Much cheaper in long run instead of chasing parts. What state?

And welcome to the board!

Here's some more info on an old Post
http://busnut.com/forum/index.php?topic=1638.0

Gthor · September 30, 2017, 03:54:50 PM

Yes thanks, I had found that thread and it is a good one. After reading that and studying some specs online I decided that it would be good to upgrade to the HT740. My bus was a Yosemite bus with low mileage, 128,000, that was traveling up and down the mountains at slower speeds so I'm guessing that had something to do with the gear's early death.

Mileage might be another consideration. I have heard stories from the tour bus guys in Nashville of Eagles with a two speed gear boxes that got 14 plus miles per gallon - not sure which gear that would be but the 700 series Allison seems like a good choice.

chessie4905 · September 30, 2017, 05:19:14 PM

14 miles to the gallon is a pipe dream. 6to 9 is more realistic in a bus conversion.

TomC · September 30, 2017, 07:39:23 PM

Yes the HT740 is just about indestructable. But you can run the MT behind the 6V-92TA by using no larger than 80 injectors (300hp and 900lb/ft torque).

Gthor · September 30, 2017, 10:24:41 PM

Thanks for your input, not really trying to start an argument here. The specs I read give 780 max foot pounds of torque for the MT654 and I have a burnt gear box in my bus that has me convinced that's an accurate number. The horse power rating for my 6v92 was something like 330 so that also carries some weight in my decision to ditch the MT654 and go to a 700 series Allison. I found specs that give a length of 36.2 inches on the MT and 37.4 on the HT740 so my drive shaft length should be pretty close.

As per the mileage thing, I was the relief driver for a bus company which operated out of Nashville many decades ago. The owner swore his Eagles with 6v71s and 2 speed gear boxes got 14 plus mpg, not sure what transmission they had, two speed autos of ? type. I thought that was mighty impressive but not being the guy who fueled them I have no proof so.....Please don't shoot the messenger. Just looking for some input and advice from someone with more knowledge than I. Thanks very much for yours.

luvrbus · October 01, 2017, 05:49:23 AM

I doubt you will need to change the bell housing MCI stuck with the SAE 1 bell housing and used a drop ring to go from SAE 1 to the SAE 2 for the 600 series.
You will need a different flex plate I have one I will trade you for the one from the 600 series if you are interested and if you need the SAE 1 bell housing for a MCI I have a couple of those also.
You will like the 740 it locks ups in 2nd gear it's just a better transmission all the way around

chessie4905 · October 01, 2017, 06:42:53 AM

If the current driveshaft doesn't have enough movement at slip joint to accommodate longer transmission, there are many shops that can shorten and rebalance your existing shaft, and can change end if u-joint requirement is different.

Gthor · October 01, 2017, 09:29:44 AM

Aha! Great news!! Thank you!! I would be happy to trade the MT flex plate for a correct HT740 flex plate. I am not sure what a drop ring is but I'm guessing it might add length to the bell housing?

My drive line is splined and I'll have to take some measurements to determine how much play it has. I can be reached at 541-294-9530 to make arrangements for shipping on that flex plate. Many thanks for the assistance.

Now if someone has a solid HT740 out there?...😀

eagle19952 · October 01, 2017, 03:12:56 PM

Quote from: Gthor on October 01, 2017, 09:29:44 AM
Aha! Great news!! Thank you!! I would be happy to trade the MT flex plate for a correct HT740 flex plate. I am not sure what a drop ring is but I'm guessing it might add length to the bell housing?

My drive line is splined and I'll have to take some measurements to determine how much play it has. I can be reached at 541-294-9530 to make arrangements for shipping on that flex plate. Many thanks for the assistance.

Now if someone has a solid HT740 out there?...😀

I am not sure what a drop ring is but I'm guessing it might add length to the bell housing?..............
not much. it is an adapter/reducer/enlarger depending on what swop u are making.