Keeping Allison in Lockup

[Lin]

Since we are planning a trip up and down the eastern Sierras on Hwy 395, I thought it would be nice to be able to have the Jakes work in 1st and 2nd gear.  As you know, the Jakes only work when the transmission is in lockup mode.  I have been told that there is a relatively easy fix that will keep the transmission in lockup, even in the low gears, when the Jake switch is on.  Does anyone know the parts and procedure to get this done?  Also, is any downside to the alteration?  Thanks,

[luvrbus]

Fire truck setup Lin 2 hoses a electric solenoid tying the test ports together I would not go that route that setup was design to be used when park pumping water locking the converter up but some people do it and get away with it not for me I have seen it tear up the flex plate your jakes work on rpm and oil pressure also got to the engine rpm's up.
Don't have any idea where Don has yours set but they should disengage at 900 rpm I still think it is a waste of wire for the 2 speed lol

[Lin]

Thanks Clifford,

I had not known about the flexplate risk.  I will watch to see at what rpm's the Jakes quit.  900 sounds about right though.  So, if I understand correctly, if I downshift and keep the rpm's high, the Jakes will stay engaged? 

I must say, I still like the two stage Jakes.  In any case, if that strand of wire was the biggest waste with this white elephant I would consider myself very lucky.

[lostagain]

I don't know what you have for an engine/trans, but as an example with my 6V92/HT740, I have to turn the Jakes off with the switch for the 3rd to 2nd down shift because it is too rough. Generally the Jakes are too powerfull in 2nd gear, let alone 1st. You'd have to be going down a cliff to be using the Jakes in 2nd gear. I come down 8% grades in 3rd with Jakes on, without touching the foot brakes much at all. I only have a 1 speed Jakes. 2 speed might be nicer.

On the 102D/7speed manual I used to drive for the hockey team, it had low/high Jakes. I hardly ever used low. I found it easier to manage the Jakes with the manual trans, because they turn off when you depress the clutch pedal.

Just my experience,

JC

[lostagain]

Lin, we typed at almost the same time. I think my set up is the same as yours, Jakes disengage at 900 rpm more or less.

It is not an issue because you should try to be in a gear that revs the engine fast, like above the shift point of around 1200 to 1500 (I forget now, I'm not in the driver's seat, LOL).

JC

[norules]

I have this in my Tranny notes --->  (1st gear lockup procedure)   will this help ?

"On the V730 (at least mine with an air controlled throttle modulator since I have an air throttle), when the bus is slowing down on the grade, you first will down shift from 3rd lockup to 2nd lockup. The next what feels like a down shift is the transmission going from lockup to converter mode in 2nd. When this happens, then pull the shifter (I have a 3-2-1-N-R shifter on the floor) down into 1st and the transmission will shift to 1st converter spinning the engine alot faster. Then pull up your foot about an inch off the floor and you should feel the transmission bump back into lockup mode. You can go up a hill with minimal heating on the transmission as long as it is in lockup mode. Suggestion- the gap between 1st and 2nd is pretty big, so when you get up to the top of the mountain and want to shift up, first floor the gas pedal again (remember you had the gas pedal up about an inch for lockup), and that will put the transmission back into converter mode, then manually shift it into 2nd converter for a much smoother shift then when the converter is locked up. Sounds confusing-but once this technique is perfected, climbing even a long grade in 100 degree weather should not be a problem-course you'll be going only about 32 mph! Good Luck, TomC"

[kwidd]

Allison has a service information letter from jan 95 on this subject.It is 1-TR-95  I got a copy of it from an Allison dealer. It's for the mt 600 series transmissions. It says it's for exhaust brakes. I would get a copy of it if I were you. thanks Kent

[luvrbus]

Kent, that bulletin is for a retarder at least mine is and besides a 8v71 doesn't use a exhaust brake  

good luck