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georog2 · 10-11-2015, 07:03 AM

I have a 2004 Southwind 37C, Workhorse W22 with Allison Transmission. Has run flawlessly for 30k miles. Started new trip and after about 70 miles at 60 MPH will not automatically downshift on grades. Stays at about 2200 RPM until I manually downshift. Check engine light came on.

Arch Hoagland · 10-11-2015, 11:41 AM

When was the last time you changed the transmission fluid and filter? My 2004 did NOT come with Transynd and needed to be changed frequently.

Do you know what the check engine light code was?

georog2 · 10-11-2015, 12:56 PM

Thanks, Mr. Hoagland. First it wasn't the check engine light but the "Service Engine Warning Light". My bad. Second it may, as you suggest, be the transmission fluid and filter. It was changed 23,000 miles ago but it's been about five years.

dieselclacker · 10-11-2015, 07:07 PM

Quote:

Originally Posted by georog2

I have a 2004 Southwind 37C, Workhorse W22 with Allison Transmission. Has run flawlessly for 30k miles. Started new trip and after about 70 miles at 60 MPH will not automatically downshift on grades. Stays at about 2200 RPM until I manually downshift. Check engine light came on.

What RPM do you normally run in fifth gear while traveling. I usually travel at around 2000/2100 RPM in my Workhorse in fifth gear. Why would you want to manually down shift if it is holding 2200 RPM?

TimLoon · 10-12-2015, 06:15 PM

On the side of the Allison 1000, there is an electrical switch that your gear selector is hooked to. (Just can't think of the name of it, neutral safety?). These are known to go bad and when they do, they make your tranny do crazy things. With mine, it would make my tranny get stuck in a gear. No down shift or up shift. Not an expensive part if you buy direct at Allison and was easy to change. Mine was just picky about the adjustment.
I am sure someone here has the name of the part. NTSB?

georog2 · 10-20-2015, 09:50 AM

I want to close out this thread as have been in a campground since the original post and was not able to test solution. I changed the ATF and filter. The "Service Engine Warning Light" went out and it downshifts fine now. In cruise control, downshifts when about 2 mph speed lost (and subsequent RPMs, dieselclacker). It may have been a little low on fluid as well. It took a little over 10 quarts to refill and I only took 9 quarts out. Thank you Mr. Hoagland.