Community Forums

buddybybee · 04-04-2013, 09:05 AM

I have a 1996 Holiday Rambler Navigator with an allison 3060. When I am under 62 mph and let off the throttle the trans starts downshifting and will shift through the gears to 1st and nearly stop the coach if you don't give it some throttle. Help anyone?

jlfbatonrg · 04-04-2013, 09:18 AM

Check to see if your Exhaust Brake is turned on. Sounds like that might be the problem.

Steve Ownby · 04-04-2013, 09:20 AM

Is this a new to you coach or are you a long time owner & this condition just started? It's sounds like the engine brake/ exhaust brake is activating. Does the transmission select a lower gear when you release the throttle? What happens above 62?

buddybybee · 04-04-2013, 09:27 AM

I am new to this coach, don't think jake was on, trans is selecting lower gear. Above 62 it didn't seem to do it.

Steve Ownby · 04-04-2013, 11:27 AM

Quote:

Originally Posted by buddybybee

I am new to this coach, don't think jake was on, trans is selecting lower gear. Above 62 it didn't seem to do it.

When I had a coach with the 3060 the shifter indicator had a display that indicated gear selected and gear attained in a side by side display. If your gear selected is lower than 6 then the Jake brake in on and is signaling the transmission to select a lower gear. It's usually 2nd or 3rd.

EngineerMike · 04-04-2013, 11:41 AM

If you have an ISC engine, you have an exhaust brake, basically a butterfly valve in the exhaust line that clamps shut to retard the engine. If you have an ISL, they usually have a Jake or engine brake which operates the valve train to do the same thing; some ISL's on cheaper rigs came w/exhaust brakes. There should be a switch to turn this on/off, and if its the ISL Jake it will have Hi/Off/Low.

When operating in decelerating mode, the retarder brakes act to use the engine as the retarder to accomplish deceleration w/out so much use of "service" brakes (foot pedal). The engine computer also notifies the Allison "we are in retarder mode" and the trans initiates what folks in the trade call "shift hunt." Allison is programmed for a lower gear to seek, sometimes 4th, sometimes 2nd, but it can be set for whatever gear you wish below 6th. As the rig decelerates the trans shifts down to keep rev's up which increases effectiveness of retarding (engine tries to push more air but is blocked from passing it).

If your coach does not have the side-by-side shift pad indicator showing gear-sought/gear-attained as Steve explained above, you will have to ascertain the programming thru observation or have the computer read (the setting is in "Parameters" in the trans ECM programming). Anyone w/Allison software, correct pigtail, & reprogramming privileges in their software load can do the reading & reprogramming.

Skip426 · 04-04-2013, 11:43 AM

X2, on exhaust/engine brake is turned on, or active when the switch is turned off.

Above 62 MPH , the trans would only go to 5th and be barely noticeable , unless you look at the tach, or the gear shift display. Below 62 trans would go to 4th , then drop a gear every time the RPM goes below 2000.
If your trans control is a single didgit display like mine , then the indicator should change from 6th to 2nd as soon a the throttle is released, indicating the exhaust brake program is active.
If your exhaust brake is active with the switch off, you have a switch or wiring problem.
Sorry , I see Mike and I are saying the same thing, he types faster.

buddybybee · 04-04-2013, 06:06 PM

I checked out the coach today. The jake brake is off. No codes in trans selector and the selector was set for 6th as the highest gear. Still downshifts when I lift off the throttle. Could it be a tps that is causing it?

Steve Ownby · 04-04-2013, 06:16 PM

Quote:

Originally Posted by buddybybee

I checked out the coach today. The jake brake is off. No codes in trans selector and the selector was set for 6th as the highest gear. Still downshifts when I lift off the throttle. Could it be a tps that is causing it?

When you lift off the throttle, does the gear selected remain 6 or does it select a lower gear? I understand the gear attained drops but does the selected gear in the display change?