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AKIQPilot · 01-22-2018, 09:42 AM

Hello all. This question is concerning a Workhorse Chassis 8.1 Chevy and Allison 6 speed combination. I read on another forum that the overdrive switch on the dash is actually a 3 position switch. The poster described that when the switch is in the "Off" or down position both overdrive gears were locked out and the transmission only used 1-4th gears. In the middle position the 1st overdrive was activated and 5th gear was available and when the rocker is switched to the "On" or up position the second overdrive, 6th gear, was available.

I have looked through my Workhorse and Allison operators manuals and I can't find any reference to this middle position on the rocker switch. I know that my 2006 Winne has the 6 speed MH2100 transmission and I know the overdrive switch on the dash is a 3 position switch. I have not owned the motorhome for a super long time and I typically just leave the overdrive switch in the "On" position. Typically if I switch the transmission out of overdrive I push the rocker all the way down to the "Off" position.

Can anyone shed some light on this. Does my overdrive switch on the dash control both 5th and 6th gears or does it just control the second overdrive.

I will be back to the coach in about 2 weeks so I will do some experimenting then but I thought I would ask the experts about this beforehand.

Thanks

Scarab0088 · 01-22-2018, 10:33 PM

Our RV has the Allison 6speed 2100 mated to the 8.1L.

The "Overdrive" switch on ours has 3 detents; On - second over drive off - both overdrive off.

I use the switch very often in the big hills and mountains of the west. Pulling the transmission out of OD when I want to keep the engine in the best power-band.

I also use the OD switch to use the engines' natural back pressure to gently brake the RV on hills.

Ours also has the "Grade Brake" (adjacent switch) that works very well when automatic hard braking and speed control is desired, but it will rev the engine over 4K RPM. Since I avoid running over 4K RPM, the Grade Brake gets less use than the OD off switch.

That's just we do.
Best luck

AKIQPilot · 01-23-2018, 10:00 AM

Quote:

Originally Posted by Scarab0088

Our RV has the Allison 6speed 2100 mated to the 8.1L.

The "Overdrive" switch on ours has 3 detents; On - second over drive off - both overdrive off.

I use the switch very often in the big hills and mountains of the west. Pulling the transmission out of OD when I want to keep the engine in the best power-band.

I also use the OD switch to use the engines' natural back pressure to gently brake the RV on hills.

Ours also has the "Grade Brake" (adjacent switch) that works very well when automatic hard braking and speed control is desired, but it will rev the engine over 4K RPM. Since I avoid running over 4K RPM, the Grade Brake gets less use than the OD off switch.

That's just we do.
Best luck

Thanks Steve that is just what I was looking for. I use the grade brake like you do, sparingly. I think it drops down a little prematurely and I don't like the high RPM's.

I will be back in the coach in about 4 days. I will be checking out the overdrive switch a little more closely.

AKIQPilot · 02-01-2018, 11:28 PM

Drove a few hundred miles today. My OD switch works just like it should. Off, 1st overdrive 5th gear and 2nd overdrive 6th gear. Its nice being to downshift to 5th on slight/moderate inclines and stuff.

Thanks for confirming the answer guys.

Scarab0088 · 02-01-2018, 11:29 PM

Thanks for the follow-up

tmw188 · 03-16-2018, 08:00 PM

Is the 2100 a 6 speed only if so is the 2000 the 5 speed model?

edgray · 03-17-2018, 08:10 PM

Quote:

Originally Posted by tmw188

Is the 2100 a 6 speed only if so is the 2000 the 5 speed model?

I’m not sure, but I’m thinking 2000 is the series number, and I believe the 2100 that WCC used in the early model years of the W-24 is the one that didn’t contain a PP and therefore those early W-24s got the J72 AAPB. Once Allison came out with the 2350 version, the AAPB was no longer needed. I’m sure that all the Allison Trannies used by WCC became six speeds in 2006, regardless of series.

edgray · 03-17-2018, 08:19 PM

Quote:

Originally Posted by AKIQPilot

Drove a few hundred miles today. My OD switch works just like it should. Off, 1st overdrive 5th gear and 2nd overdrive 6th gear. Its nice being to downshift to 5th on slight/moderate inclines and stuff.

Thanks for confirming the answer guys.

The switch is actually used to determine which gear selection is prevented. in other words, the middle position prevents the tranny from upshifting to 6th and the “ bottom “ position allows it to reach 6th gear. This assumes the coach builder mounted the switch correctly and used the top of the switch (when depressed) to prevent 5th AND 6th, aka no OD or OD off. Your dash display should show which gear you have achieved, and if it reaches 5th but not 6th then the switch should be in the “middle” position. Hope I’ve made this clear as mud. [emoji2]

tmw188 · 03-17-2018, 08:25 PM

Quote:

Originally Posted by edgray

I’m not sure, but I’m thinking 2000 is the series number, and I believe the 2100 that WCC used in the early model years of the W-24 is the one that didn’t contain a PP and therefore those early W-24s got the J72 AAPB. Once Allison came out with the 2350 version, the AAPB was no longer needed. I’m sure that all the Allison Trannies used by WCC became six speeds in 2006, regardless of series.

I think your right, I have the 2100MH 5 speed with the J72 AAPB with the Ahrens selector.

dbarton291 · 03-19-2018, 12:43 PM

Just some fun FYI: All the 1K/2k transmissions have all the hardware in them to be a six speed and have been from the beginning of production. What determines which ones are five or six speeds is the program in the TCM.
Same for the 3K/4K transmissions.
If you have a five speed, Allison won't approve a recal to a six speed unless they get a form signed by the vehicle OEM. One of the reasons is not all drivelines can handle the extra RPM generated by sixth gear. The results of a driveline that is spinning beyond its intended design intent is rather dramatic.
The overdrive switch is installed by the OEM and uses some programmable options in the TCM to perform the 6th gear off and 5th gear off functionality.
Kind of a neat option.