Transmission advice needed 8v71 - 4 speed manual '72 MCI 7

[dparker]

All,

I have a 72 MCI7 that I converted.  The bus has a 4 speed manual transmission.  While driving the bus the transmission became stuck in 2 gear, all the external linkages and shift levers on transmission indicate neutral and unit will not shift to any gear.  The reverse shift solenoid operates and the linkage into the transmission operates.  The bus will move and it will operate in second gear, even though it appears to be in neutral.

I intend to have my mechanic pull the top cover to check internal linkages, slides, forks etc.  I am looking for any advice anyone can provide as well. 

Also can anyone tell me if there is a direct bolt on Alison auto transmission for this engine and bus drivetrain, also if this is the case what is involved in controlling and installing the selector in the driver area.

thanks in advance

David

[buswarrior]

Allison HT740 is the transmission of choice.

In an MC7, you will have cooling issues, as your rads were not sized to accommodate the  heat of the auto tranny. The auto tranny needs a cooler, that is usually fed by the engine coolant. There are ways to work around this via adding heat exchangers.

If your 4 speed is toast, with a little patience, you should be able to get a straight replacement here or over at BNO (busnut.com) or a newer 5 speed manual that someone else is taking out in an auto tranny swap.

happy coaching!
buswarrior

[dparker]

Thanks for the post.

Will the HT740 just bolt in? 

As to the cooling, I installed a new 20KW generator, to make it operate quieter on the exterior of the coach, i was considering remoting the radiator for the genset, do you have any idea for of the cooling capacity that I would be needed for this tranny as possible i could oversize this radiator and use the transmission cooling loop that is included in some radiators a 24 volt fan and i could be ready to go ... your thoughts

[TomC]

On my 10kw Powertech, I remote mounted the radiator with a single inlet squirrel cage blower with a 1/2hp 2spd totally enclosed fan cooled ball bearing electric motor.  High spd going down the road and low spd for quiet night time use.  Works well.
The Allison HT740 is the bolt in choice.  The HT748 is the transit version with a hardened input shaft and crisper shifts.  You'll have to add either a oil to water cooler through your radiator, or add a oil to air cooler with electric fans-then no strain on the radiator.  The shifter can either be electric or cable-I have cable and it works just fine.  Good Luck, TomC

[Tom Y]

David, Have you looked at the other posts with tranny problems? There are several with stuck in gear problems that may help you.  Goodluck  Tom Y

[steve5B]

  Hello,

I had the same problem  a few years back, what happened to mine was the levers got stuck between gears. The guy that fixed mine went through the spare tire compartment  and removed the plate to the shifter and it was fixed in about 20 minutes.

Hope that this is the same thing.


Steve 5B............

[dparker]

Thanks for the input --

In the past I have attempted to search -- so far to no avail -- does someone have suggestions on what i would type in to search for stuck in gear tranny problems --

thanks