vms display shows 5 5 - Printable Version
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vms display shows 5 5 - [email protected] - 04-20-2025
While cruising at around 63 mph display shows 6 6 meaning in 6th gear. all of a sudden it downshifts and shows 5 5. can someone explain. after a minute or so goes back to 6 6.
in economy mode on cruise control. never touched the transmission console.
RE: vms display shows 5 5 - hypoxia - 04-20-2025
Allison 4000 Transmission? Here are some of the manuals. My first thought is checking to see which TCM you have, I included a photo of old & new. The old style with all of the "dots" is a common failure point. Allison Locator I would call a large shop that rebuilds Allison transmissions such as WW Williams or Stewart & Stevenson as they will have the most knowledgeable techs.
RE: vms display shows 5 5 - Richard - 04-20-2025
A quick sanity check to see if it is actually changing gears assuming speed doesn’t change is to see if the tach jumps with the indicator change, If it doesn’t then the shift is not real. If it does then the Allison is actually shifting.
Do you have the jakes on when this happens? If so, turn them off and see if the problem persists.
The throttle position sensor could be flaking out on you telling the ECM to activate the jakes and downshift to 5th gear.
RE: vms display shows 5 5 - RussWhite - 04-20-2025
Great advice! Wish I had thought of that!
RE: vms display shows 5 5 - [email protected] - 04-20-2025
Jakes were in on position. I had thought Jakes are supposed to be locked out in cruise, otherwise it would seem to be unstable, speed up slow down etc.
RE: vms display shows 5 5 - Richard - 04-20-2025
Oh no, my coach would have a fight with the jakes when in cruise.
Turn them off and see if it clears up.
If it does, do we have a treat for you. There is a simple and cost effective way to rewire the jake switch in conjunction with a relay to have jakes and cruise without the fight.
And another thing, 62 mph is just where my Ally would achieve 6th gear, cruising at 63 puts you right on the cusp of it downshifting on it's own. If it is not the jake cruise conflict, try cruising at 64 or 65 to see what happens.
RE: vms display shows 5 5 - [email protected] - 04-20-2025
I thought when it downshifts, it shows 6 5, not 5 5.
RE: vms display shows 5 5 - RussWhite - 04-20-2025
No - the two numbers represent commanded and actual. If all is well, the transmission will shift to the commanded gear. 5 5 4 4 6 6 etc.
RE: vms display shows 5 5 - johnkosir - 04-20-2025
On 712 when I put it in drive the VSPM read 6 and what ever gear I am in starts 61 and the 1 changes to 2,3,4,5,6 as it shifts through the gears if I turn the jake on and have my foot off the throttle the shift console reads 5 the transmission shifts to 5th, the VSPM reads 55 54 53 as the transmission down shifts to keep the RPM up when I turn the jake off the console goes to 6 the VSPM goes 6 and whatever gear the transmission is in. 712 shifts in to 6th at 61 mph at lite throttle applications, on level ground and lite throttle it can stay in 6th at 58 mph. I would check what Richard said.
RE: vms display shows 5 5 - CaptainGizmo - 04-20-2025
Russ nailed it.
The numbers are what is "Commanded" or called for, along with "Actual" or what gear its currently in.
These will change on their own, when in "D". And, IF you shift manually...say, for example downshift to 3 when you're running 65mph, what you will see is: 3 6 until the road speed will allow a downshift to 5, then 4, etc...until the "Commanded" gear of "3" is obtained...AND THEN IT WILL STAY LOCKED FOR FUTURE UPSHIFTS. It will STILL DOWNSHIFT, however, all the way down to 1. But, as you speed up, the trans will run through the gears UP TO THE COMMANDED GEAR once again and hold.
HTH