Sagorsch Report post Posted March 13, 2017 Greetings, I have a 2002 Winnebago Adventurer with a Chevy Workhorse Engine and Allison Transmission with just under 68,000 miles. I drive 55-62 MPH on the highway. I have discovered my rig runs on lower RPMs (1800-2000) when I drive with overdrive (OD) engaged on level roads and highways. When I dis-engage the OD on level roads/highways RPMs jump to 3000-4000, regardless of MPH speed. In addition, when OD is disengaged I get a tar/sewer smell. Further, on hills with OD engaged the RPMs jump to 4000-5000. I have had the rig regularly serviced and checked out and have been told all is functioning properly. I would like to be enlightened as to whether or not the RPMs and smell as described above is normal. If not, what can I do about it? Also, I would like to be advised as to whether or not driving with OD engaged all the time is good or bad for my engine and/or transmission. Truly perplexed, Sharon Gorsch, F464157 Share this post Link to post Share on other sites
kaypsmith Report post Posted March 13, 2017 All good questions, OD engaged on level or smooth roads or downhill, the rpm's should lower, as that is what OD is designed for, improving mpg. In this condition the motor should be running slower which will improve mpg plus extend engine life. While in OD if the transmission detects a harder pull than should be then it will shift out of OD to the drive setting without it showing on the shift indicator but you will see a sudden jump in rpm, this is to help maintain speed of your vehicle. My personal driving habits is to place in drive position in around town traffic and if I am encountering a very hilly condition. As to the tar/sewer smell, I don't have a clue as to what that may be, hopefully an expert in this field will chime in. By the way, Welcome to the forum. Share this post Link to post Share on other sites
ianbullock Report post Posted March 13, 2017 I have a similar chassis, Workhorse with a Allison Transmission although mine is a 2010 Suncruiser. In mine the Allison is a 6 speed transmission with a digital display on the dash that indicates what gear it is in. Mine also has a tootle switch that allow me to toggle down to a 5 speed and if desired to a 4 speed which in essence disengages the OD. On the freeway usually leave OD on and in 6th. On secondary Routes, speeds of 50-55 mph, usually leave OD on and in 5th. On very hilly terrain also usually OD on and in 5th. So yes, generally the OD is on. No issues so far, As far as the smells you are noticing, you may have a ceiling vent open that is near your black water roof vent that is the culprit. At hwy speeds the back pressure may be pulling it into the MH. This used to happen in our 2001 Suncruiser. Ian Share this post Link to post Share on other sites
Sagorsch Report post Posted March 24, 2017 Thank you so much! I feel a lot smarter Share this post Link to post Share on other sites
