Shift to Overdrive

[smokey5209]

I have a 2003 Pace Arrow with the 8.1 Chevy, and Allison tranny.

When travelling down the road the tranny will not shift into overdrive until 60 MPH. I think that that is a little high as alot of our roads are 55 MPH and I don't have the benefit of Overdrive. Is this normal or do I have a problem?

Thank
Ed

[edgray]

Smokey: Yes, that is fairly "normal" for the 1000 series WCC used. You can have the TCM re-programmed by an Allison dealer to allow the upshift to OD at lower speeds, but the engine won't like it. IMO, it is "better" to simply go fast enough to cause the up shift, and then gradually slow down to the posted speed limit. Also, understand that the while the difference in RPMs between 4th and OD may look significant on the tach, it does not seem to make a hugh differece in MPG, so I don't worry too much about the cost. In mountainous conditions I've driven all day long with the OD switched off, and I found that the higher RPMs can sometimes prevent, or at least delay, the more drastic downshift to 3rd.

I also confess, I'm a bigger believer in "don't fix what ain't broken"
Ed

[smokey5209]

Ed

I appreciate the information and will do as you said drive her up to the shift and than backoff.

Thanks
Ed

[DAN L]

Quote:

Originally Posted by smokey5209 I have a 2003 Pace Arrow with the 8.1 Chevy, and Allison tranny. When travelling down the road the tranny will not shift into overdrive until 60 MPH. I think that that is a little high as alot of our roads are 55 MPH and I don't have the benefit of Overdrive. Is this normal or do I have a problem? Thank Ed

brazels in centralia wa did a mod on my 5 sp ally about a year ago. they programmed my ally to shift into od at 48 mph, about 1600 rpm under light throttle. this mod works well.
the ally grade brake mod for my moho includes the above mod but is much more expensive. i can work the lever just fine when i need to select a lower gear for engine breaking.
brazels is a sponsor of this forum. i recommend that you call them and ask where you can get this mod accomplished in your area.

[alvinc]

Quote:

Originally Posted by smokey5209 I have a 2003 Pace Arrow with the 8.1 Chevy, and Allison tranny. When travelling down the road the tranny will not shift into overdrive until 60 MPH. I think that that is a little high as alot of our roads are 55 MPH and I don't have the benefit of Overdrive. Is this normal or do I have a problem? Thank Ed

My question is: What were the RPM's when it finally decided to shift to overdrive?

The decision by the transmission to shift is based on load and engine RPM's. I know my 2002 shifts to overdrive much sooner than 60 MPH.

One thing that comes to mind is that your rear axle may have small gear ratio for a 37 ft RV. The WH chassis was available with several rear end ratios (4.88 to 5.86) and you may have one that is a lower numerical ratio that the rest of us. This would cause your transmission to wait longer to shift to higher gears.

Some factors that affect shift point:
1. At what RPM does the transmission shift to overdrive (5th gear) on level or downhill?
2. What rear axle do you have and specifically what gear ratio?
3. What size tire rims do you have (19.5 or 22.5)?