Seneca RPM question

[Life on the Verge]

We just purchased a 2015 Jayco Seneca 37FS with the Cummins/Allison. We tow a 4500lb toad. On flat grade rpms are above 2500 and it won’t accelerate above 63-64 mph. It’ll maintain that speed climbing hills without a problem. With overdrive engaged it drops to 1600 rpms or so with plenty more power to accelerate. Does this sound like normal engine/transmission behavior?

[Robbbyr]

Originally Posted by Life on the Verge

We just purchased a 2015 Jayco Seneca 37FS with the Cummins/Allison. We tow a 4500lb toad. On flat grade rpms are above 2500 and it won’t accelerate above 63-64 mph. It’ll maintain that speed climbing hills without a problem. With overdrive engaged it drops to 1600 rpms or so with plenty more power to accelerate. Does this sound like normal engine/transmission behavior?

If you have the overdrive locked out you only have gears 1 - 4 and that is the max speed you will get with the engine at or near its rev limiter. I have done 80 mph at times with mine with the overdrive enabled so I have use of all 6 gears. On the highway I run with the overdrive enabled most of the time unless it is shifting in and out excessively.

If you are asking if you should keep the overdrive enabled at highway speeds I say "yes" in most circumstances.

[Life on the Verge]

Thanks Robbbyr. That’s what I’ve been doing. I can feel the extra gears kick in & see the rpms drop when I switch on the OD. Seemed right to me. I just needed make sure I wasn’t the only one using OD like that.

[Robbbyr]

Originally Posted by Life on the Verge

Thanks Robbbyr. That’s what I’ve been doing. I can feel the extra gears kick in & see the rpms drop when I switch on the OD. Seemed right to me. I just needed make sure I wasn’t the only one using OD like that.

As I indicated, most of the time my overdrive is enabled. Only when I feel it is advantageous to drop it out of overdrive do I use my switch.

At some point (2017?) Jayco/Freightliner did away with the overdrive cancel switch. Some owners of those newer units have indicated they wish theirs still had one; I like having the ability to control overdrive lockout when I feel it can help performance.

[Les7h]

The only time that I disable overdrive is if I want to limit my downhill decent ( if I’m at a slow enough speed ) but most of the time the exhaust brake is sufficient Les

[Dananu]

Originally Posted by Robbbyr

If you have the overdrive locked out you only have gears 1 - 4 and that is the max speed you will get with the engine at or near its rev limiter. I have done 80 mph at times with mine with the overdrive enabled so I have use of all 6 gears. On the highway I run with the overdrive enabled most of the time unless it is shifting in and out excessively.

If you are asking if you should keep the overdrive enabled at highway speeds I say "yes" in most circumstances.

I also seldom turn off overdrive. I recently programed my scan gauge to show what gear trans is actually in. I discovered that with cruise control at 62 mph trans never shifted to 6th. By slightly accelerating trans would shift to 6th and then hold 6th at 60-62 with cruise.