Stuck in 4th gear

Topic: Stuck in 4th gear (Read 3142 times) previous topic - next topic

Stuck in 4th gear

June 27, 2012, 12:35:31 am

So...I just attempted to leave for a trip, but I'm having problems with the transmission. After about 10 miles into the journey, the transmission started changing gears very erratically. These changes happend while I was on 35mph roads. Once I got the the freeway, the transmission would not shift to fifth or sixth gear. Then I noticed that my VmsPC showed the the gear selected was 6, but the current gear was 4. This was confirmed by the touch panel, which showed 4. I was not able to move the transmission to any gear. Fortunately I was able to limp home. Will probably have to unload the coach and pack the Suburban, as Jen has to be in OKC for a dog show Thursday morning. That is, unless I have some type of epiphany as to the reason my transmission is stuck in 4th gear. Grrrrrr

Re: Stuck in 4th gear

Reply #1 – June 27, 2012, 12:39:47 am

Sounds like a throttle or brake switch sensor combined with a retarder trying to force the tranny to think it was needed to decel to the preselect gear

Re: Stuck in 4th gear

Reply #2 – June 27, 2012, 12:40:08 am

Low hp from the motor?

Re: Stuck in 4th gear

Reply #3 – June 27, 2012, 12:44:04 am

Yes, low HP...pulling away from a stop in 4th was painfully slow. And yes, the retarder would intermittently work.

Re: Stuck in 4th gear

Reply #4 – June 27, 2012, 12:56:49 am

One other thing....the spedo was jumping all around, from 0mph to 70mph...while I was actually doing approximately 20mph. Going to let the engine cool over night, and then attack the problem first thing in the morning. As Jen doesn't show until early afternoon Thursday, I have a nice buffer to get this problem fixed.

Re: Stuck in 4th gear

Reply #5 – June 27, 2012, 01:03:57 am

Quote from: aspenpilot – June 27, 2012, 12:44:04 am

Yes, low HP...pulling away from a stop in 4th was painfully slow. And yes, the retarder would intermittently work.

Check fuel filters would be my first guess.

Bob

Re: Stuck in 4th gear

Reply #6 – June 27, 2012, 01:08:43 am

Hey Bob,

Both fuel filters were changed yesterday, as this was to be the first trip of the season.

Re: Stuck in 4th gear

Reply #7 – June 27, 2012, 01:15:47 am

Quote from: aspenpilot – June 27, 2012, 01:08:43 am

Hey Bob,

Both fuel filters were changed yesterday, as this was to be the first trip of the season.

Sounds like a vacuum leak.

Bob

Re: Stuck in 4th gear

Reply #8 – June 27, 2012, 01:28:42 am

I'll post my finding in the morning. Thanks to all.

Re: Stuck in 4th gear

Reply #9 – June 27, 2012, 06:30:59 am

How much fuel in the tank? How long has the coach been stored, at what temp? Could new filters be plugged?

Re: Stuck in 4th gear

Reply #10 – June 27, 2012, 07:48:04 am

You have the Allison electronic transmission. Not vacuum controlled.

Use the up and down arrows (at same time) with ignition on, engine off to check for diagnostic codes.

What d codes is it showing?

And also, check voltage. Since it is electronically controlled, low voltage to the two positive feeds to the Allison ECM will cause all kinds of strange issues.

http://www.allisontransmission.com/servlet/DownloadFile?Dir=publications/pubs&FileToGet=SA3360EN.pdf

Brett

Re: Stuck in 4th gear

Reply #11 – June 27, 2012, 08:08:41 am

Quote from: wolfe10 – June 27, 2012, 07:48:04 am

You have the Allison electronic transmission. Not vacuum controlled.

Use the up and down arrows (at same time) with ignition on, engine off to check for diagnostic codes.

What d codes is it showing?

And also, check voltage. Since it is electronically controlled, low voltage to the two positive feeds to the Allison ECM will cause all kinds of strange issues.

http://www.allisontransmission.com/servlet/DownloadFile?Dir=publications/pubs&FileToGet=SA3360EN.pdf

Brett

I agree. With the erratic behavior you describe, it sure sounds like low voltage. Alternator? Batteries condition? How long did you store without exercising the coach?
Peter

Re: Stuck in 4th gear

Reply #12 – June 27, 2012, 08:14:21 am

Brian, Classic symptoms of low voltage. Clean all battery connections and verify battery voltage. Tranny is programmed to go into limp mode on low voltage. BTDTGTTS
Gary B

Re: Stuck in 4th gear

Reply #13 – June 27, 2012, 09:07:21 am

The speedo jumping around makes me wonder if perhaps your sensor is dirty/bad. Not sure where it is located on engine but the equivalent of a crankshaft position sensor. My pickup does this occasionally, I remove the sensor, clean it and it's good to go. Also, like others have said, low voltage makes for erratic problems. Fire your genset, flip the boost and see if that helps.

Chuck

Re: Stuck in 4th gear

Reply #14 – June 27, 2012, 09:25:34 am

Going out to work on the coach now. The coach sat for about four months with no use. When I brought the coach from storage to the house, everything worked fine (about 10 miles of highway use.) I will definitely check the batteries and alternator. Both the starting battery and alternator were replaced last year. I will also look for any connections that may be loose or dirty. Thanks for everyone's inputs.

Re: Stuck in 4th gear

Reply #15 – June 27, 2012, 09:49:15 am

Batteries check out good. The control panel on the transmission pad indicates: d 1 6 3 4 0

According to the Allison manual Brett linked to, this means: Service brake status input, failed on

Hopefully this means some type of connector is loose.

Re: Stuck in 4th gear

Reply #16 – June 27, 2012, 10:24:36 am

You might also check your brake lights. Perhaps a brake light switch is stuck on the "on" position.

Check connectors and ground connections. The 3060 transmission in our SOB went into a "limp" mode when a speed sensor connector was pulled out by an accumulation of ice on the wire. It would operate just fine is 1, 2, or reverse, but would shift no higher.

Re: Stuck in 4th gear

Reply #17 – June 27, 2012, 10:57:20 am

J.D.,

I think you may be on the right track. After some troubleshooting this morning, I took the coach for a test drive. After about six miles I had to stop a a stop sign. When accelerating away, the transmission would not shift any higher than 1st gear...and the spedo was completely dead. When I got home, the error code showed d 1 2 5 1 1 Speed output sensor. So...when the engine cools down a bit, It's back underneath to once again ensure all connections are clean and secure.

Re: Stuck in 4th gear

Reply #18 – June 27, 2012, 11:33:13 am

Quote from: Gary Bouland – June 27, 2012, 08:14:21 am

Brian, Classic symptoms of low voltage. Clean all battery connections and verify battery voltage. Tranny is programmed to go into limp mode on low voltage. BTDTGTTS
Gary B

===========================================================

Hey all.....

I need to know more about "limp mode"....

....eh??
99 U320 with 450 cummins and 4060 allison.....
Full? torque 0 to 1400 rpm.....engine hits a ceiling @ 1400, tranny holds 2nd??

Limped home last week.....22mph is great for viewing the landscape, but.....!!

......Ol'Ben

"God don't make no Junk!"
(bats tell me that mosquitos just barely pass muster tho)

Re: Stuck in 4th gear

Reply #19 – June 27, 2012, 03:53:04 pm

*** Problem Fixed ***

As it turns out, J.D. wins the prize. The problem was a bad Output Speed Sensor. Just to be on the safe side, I also replace the Input Speed Sensor. I was fortunate to have an Allison dealer within a 45 minutes drive from my home. The whole job was VERY easy...except for the cost of the sensors.

Speed Sensor (Output) p/n 29543434 $225.00
Speed Sensor (Input) p/n 29543432 $115.00

Labor: A little dirt and grime on my hands

Re: Stuck in 4th gear

Reply #20 – June 27, 2012, 05:30:21 pm

Excellent.

With the Allison 6 speed (either 3000 or 4000 series) ALWAYS start troubleshooting by using the shift pad to check for diagnostic codes!

That is a routine part of my mechanical inspections and only takes 30 seconds.

Brett

Re: Stuck in 4th gear

Reply #21 – June 27, 2012, 08:43:41 pm

Thank you to everybody that assisted with my problem. We've been on the road for about 230 miles now, and everything is going great. Again, thanks!

BenDare2...as Brett said, perform the troubleshooting procedure with your touchpad...it worked great for me.

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