Converting to Allison, what would be needed ?

[scanzel]

I have noticed that on the gov web sites the military is getting rid of many new Allison automatic transmissions. 654, 740, 754's etc. I have the 8V92 with a spicer in my Prevost what parts would be needed to convert over and which trans would be the best choice. www.govliquidation.com search Allison and many come up for bidding.

[Emcemv]

Steve, I can't help with the details but I'll tell you I could not imagine driving our bus with a standard transmission, you would love the automatic if you can do it!

Bruce

[luvrbus]

You really want a 754CR with a 1st gear start not 2nd gear start the 754's the military uses are DR deep ratio with a 2nd gear start the 740's are standard 740's with a low ratio converter that gives you a lower ratio in all 4 gears  

The 754CR is a nice transmission behind a 8v92 in a bus IMO the 654 would be useless behind the 8v92 and you would need a drop ring or change the bell housing to make it fit

[muldoonman]

You really want a 754CR with a 1st gear start not 2nd gear start the 754's the military uses are DR deep ratio with a 2nd gear start the 740's are standard 740's with a low ratio converter that gives you a lower ratio in all 4 gears  

The 754CR is a nice transmission behind a 8v92 in a bus IMO the 654 would be useless behind the 8v92 and you would need a drop ring or change the bell housing to make it fit

What's the difference between the 754CR and the 755Cr 5 speed that's in my bus?

[luvrbus]

The 755 is electronic controlled nice transmission isn't it   

[muldoonman]

Couldn't imagine shifting one of these buses. I can barley hit the button.

[sledhead]

after searching for mth's I never found the electronics to work with the ht 755 so gave up and my ht 740 is still working great .     
If you can find a ht 754 it would be a better choice

dave

[eagle19952]

Here's a good deal...and free.... ...
Hydraulic Control:
http://www.utxchange.com/pdfs/MechanicsTips/MT1366EN.pdf

Electronic Control:
http://www.utxchange.com/pdfs/MechanicsTips/MT1958EN.pdf

Operators Manual Allison-AT-MT-HT-Transmissions:
http://igor.chudov.com/manuals/M939-Series-Trucks/Allison-AT-MT-HT-Transmission.pdf

[TomC]

You can only run a HT700 series transmission with the 8V-92TA because of the torque. The HT740 is a 4 spd, the HT750DR is the same transmission with an extra deep 1st added (2nd through 5th are the same as 1-4 on the HT740). The HT754CR is a close ratio 5 spd. 1st, 2nd and direct 5th are the same gear ratios as the HT740. Instead of the big jump at 3rd, Allison installed two gears to better split the ratios for road speeds. The HT740 is the most rugged (it is the choice of Diesel hot rodders), with the HT754CR getting the best performance. Except for the DR, all have 3.692 1st gear and direct drive final gear (no overdrive). Dirt reliable, no electronics-except for the HT755CR & HT745. Good Luck, TomC

[luvrbus]

Allison's are fun to play with on my end they are intimidating to some because of their size but really a simple transmission in design one can change the ratios on all Allison's the 754CR has a low gear of 3.19:1 with 1st gear start not a 3.69:1 then the 741,745 and  the 755 can be changed back to the non electronic by changing the valve body tons of fun a lot you can do with a Allison besides just enjoying the driving pleasure
 

[TomC]

Gear ratios as published:
HT740- 3.69, 2.02, 1.38, 1.00
HT754CR- 3.69, 2.02, 1.58, 1.25, 1,00
HT750DR/HT755DR- 7.97, 3.19, 2.02, 1.38, 1.00

[luvrbus]

TomC the 754 had to be over the serial no 20084 before the 3.69 ratio was even offered the 3.69:1 ratio is for second gear start transmissions in the 754 line it is the same ratio the 750 DR uses for second gear fwiw the ratio for 1st gear starts for the 754CR

1st  3:19
2nd 1.89
3rd  1.55
4th  1.24
5th  1.00

8 torque converters available to change the ratios they change the ratio in every gear except 5th it stays 1.1:
look in the manual on 1-13

good luck

[TomC]

Can only go by what Allison is advertising on their brochures. I'm sure there are numerous gear sets available. The 4 spd transmission Allison makes for the M1A1 tank is based on the HT740. Good Luck, TomC