I'm getting mixed facts about my Jakes

[DrivingMissLazy]

Would it help to tye the selonoid into the buffer switch?

This way it would release when the jakes do.

??
Nick-

Sure sounds like a smart idea to me. That way there is no way to forget it.
Richard

[luvrbus]

Nick,you can get the bang as you called it out of the 740 with new trimmer springs take it to someone that knows Allisions ,not a dealer because they will install factory springs.i have a 740 in my Eagle and you can not feel any shift points it took me awhile but it shifts smooth now

[niles500]

Common sense will tell you no matter what other variables there are in play - the Jakes will cease to function when the tranny goes out of 'lock up' whether that is at 500 rpm, 1200 rpm, or any other rpm (as DML has stated) - if you have a AT that locks in 2nd, chances are it down shifts at 1100 to 1400 rpm (2 stroke and 4 stoke are different) - so you should never see 600 to 800 rpm on an Allison in 2nd or above (unless you have a tranny that lets you select lock in 1st,2nd as some have shown) - the manual tranny guys have other options - FWIW

[TomC]

On my V730, the shift from first to second is always smooth, no matter the pedal position.  What does cause a definite bump, is on easy acceleration, it shifts from 1st to 2nd then when it goes to 2nd lockup, can be a much stronger bump or lurch.  Very hard to adjust on a mechanical transmission.  Good Luck, TomC

[Nusa]

Seems like there should be an way to rig up an indicator light to indicate whether one is in lockup or not.

[Nick Badame Refrig/ACC]

Hi Nusa,

Now, that is a brilliant idea....

Any clues as to how??

Thanks
Nick-

[DrivingMissLazy]

While discussing Jakes, there is one more item that should be discussed, and that is exhaust valve clearance adjustment.

The Jake manual indicates either .059 or .063 inches (if my memory serves me correctly) clearance, depending on the style of engine.

When I had mine adjusted properly at .059 inches I found that I had good Jakes when the engine was still cold but the braking action diminished as the engine warmed up.

I then changed my valve clearance to .055 inches and it was almost unbelievable the improvement in braking action with this change.

I do not recall if this adjustment was with the engine hot or cold, but it would have been the condition of the engine when adjusting to .059 as directed by the Jake manual.
Richard

[JackConrad]

Seems like there should be an way to rig up an indicator light to indicate whether one is in lockup or not.

    A while back, I looked this up in my Allison manual.  There is a lock-up test port on the transmission. You could install a pressure switch in this port and connect it to a light in the dash. This is one one the ports that is used if you install a solenoid to keep the transmission in lock-up mode.  If I rememer correctly, lock-up pressure is within 15 PSI of main pressure.  Main pressure at full rpm is 175-200 PSI. 
    When I started running the wire on our bus for the Jakes, we added an indicator light on the dash that is connected to the input to the Jake solenoids. This light only lights when the jakes are activated.  Jack