Allison Shift Selector

[vigibill]

I have two questions about my 2005 Newmar Kountry Star 3910 DP with an Allison 3000MH transmission.

1. The shift selector indicates only the gear requested, not the gear engaged. I heard the newer selectors indicate both. Can my older selector be replaced with the newer model for a reasonable cost? Anyone done this?

2. When decelerating from highway speeds with the exhaust brake engaged (65 mph) the transmission downshifts OK until 3rd gear. At that point the RPMs hit max and the transmission suddenly upshifts back to 4th for a few seconds then downshifts back to 3rd. This may happen more than once until the rpms are in a safe range. To me this sounds like the shift point for 4th gear is set too high. Anyone else have this problem? Thoughts or advice?

Thanks,
Bill Vaglienti
2005 Newmar KSDP 3910

 

[dbarton291]

RE: Allison Shift Selector

vigibill - 4/18/2010 4:11 PM

I have two questions about my 2005 Newmar Kountry Star 3910 DP with an Allison 3000MH transmission.

1. The shift selector indicates only the gear requested, not the gear engaged. I heard the newer selectors indicate both. Can my older selector be replaced with the newer model for a reasonable cost? Anyone done this?

2. When decelerating from highway speeds with the exhaust brake engaged (65 mph) the transmission downshifts OK until 3rd gear. At that point the RPMs hit max and the transmission suddenly upshifts back to 4th for a few seconds then downshifts back to 3rd. This may happen more than once until the rpms are in a safe range. To me this sounds like the shift point for 4th gear is set too high. Anyone else have this problem? Thoughts or advice?

Thanks,
Bill Vaglienti
2005 Newmar KSDP 3910

The new selectors with two digits are used in fourth gen controls. You probably have WTEC III controls. The difference is the entire control system, not just the selector. Earlier controls had two digits, also. Customers feedback was that the two digits were preferred, so when fourth gen came out, they went back to the two digit display.

Sounds like your controller may be programmed to preselect D4 when the exhaust brake is engaged. I'd get to an Allison authorized outlet and check that out. They can be reprogrammed to preselect D2 and that may solve the situation you describe.

Hope this helps.

 

[vigibill]

RE: Allison Shift Selector

dbarton295,

Thanks for the prompt reply, looks like I may be stuck between generations of transmission builds.

When the exhaust brake engages it calls for second gear (as shown in the single digit indicator). I think the transmission is downshifing too soon to third gear (programmed shift point is too high), causing the engine to overrev and upshifting until as lower speed is achieved. I will be taking it in for service later this month and discuss it with the folks at Cummins.

Bill

 

[dbarton291]

RE: Allison Shift Selector

vigibill - 4/19/2010 12:58 PM

dbarton295,

Thanks for the prompt reply, looks like I may be stuck between generations of transmission builds.

When the exhaust brake engages it calls for second gear (as shown in the single digit indicator). I think the transmission is downshifing too soon to third gear (programmed shift point is too high), causing the engine to overrev and upshifting until as lower speed is achieved. I will be taking it in for service later this month and discuss it with the folks at Cummins.

Bill

Hmmm. I wonder if the transmission cal is the right one for the engine you have. You may have an RPM mismatch. This one is kind of a stumper as you describe it. Is this issue new, or has it always done this?

 

[vigibill]

Re: Allison Shift Selector

It has always done this. After thinking about it I think it does the same thing with the exhaust brake "off". I have never asked anyone to look at it as it does not seem to be causing a problem. I can prevent the "upshift" by applying the service brakes and dropping my speed about 5 mph just as it downshifts. I have put this on my list for the next time I have the coach serviced at a "Allison" qualified center (Cummins Southwest, Houston, TX).

Thanks,
Bill

 

[dbarton291]

Re: Allison Shift Selector

vigibill - 4/25/2010 11:28 AM

It has always done this. After thinking about it I think it does the same thing with the exhaust brake "off". I have never asked anyone to look at it as it does not seem to be causing a problem. I can prevent the "upshift" by applying the service brakes and dropping my speed about 5 mph just as it downshifts. I have put this on my list for the next time I have the coach serviced at a "Allison" qualified center (Cummins Southwest, Houston, TX).

Thanks,
Bill

I didn't see Cummins Southwest in Houston on the Allison service locator. (www.allisontransmission.com and select Service Locator) Do they have an Allison Transmission sign out front?

You might call Jason C. at Stewart & Stevenson's service department at their I-10 branch in Houston and ask him what he thinks about what you've got. They are the Allison distributor in that area.