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Old 04-23-2015, 03:34 PM   #1
rrb
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Hard down shift & speedometer fluctuations

The first issue I noticed was while driving on the highway with cruise control on, the speedometer would jump up 10 to 15 miles on hour and then drop back down. Shortly after that, the transmission started shifting hard from 4-3 and shortly after that 2-1. It doesn't shift hard every time and I can't find any pattern.

I inherited the RV and I don't believe it has been serviced in a couple of years. I will definitely be taking it in for service, but I am handy and if there is anything I can do beforehand, all the better.

thanks,


1994 Winnebago Vectra 35rq
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Old 04-23-2015, 04:29 PM   #2
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Welcome to iRV2.

It is possible your trans controller is getting erratic signals from the speed sensors located on the transmission . Located on the drivers side on a diesel pusher, there is one on the bell housing , one on the tail shaft, and on some applications a third 1/2 way down the side. My 99 3060 , 6spd , has 2 but the wiring connector is there for a third.
I'd pick up some wiring connector spray cleaner, and clean the connectors and the sensor pins after checking for corrosion.
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Old 04-24-2015, 10:36 AM   #3
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Thanks for the suggestion. I will add it to my check list and post findings.
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Old 04-25-2015, 03:57 PM   #4
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I went down the storage yard and checked the trans fluid level. Looked good and fluid looked clean. I cleaned the contacts on speed sensors. They looked clean, but cleaned them anyway. Took the rig out for test drive and hard shifting continues.
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Old 04-27-2015, 11:42 AM   #5
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I have read about resetting transmission to fast learn mode. Is it possible this will help?
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Old 04-27-2015, 12:08 PM   #6
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I have , operators manuals that cover 3000 and 4000 series Allison 6spds.
With WETC III & WETC IV controls , that are too large to post in the forums.
Your coach may be a WETC II so they may not be of any use.
The manuals were free downloads from the Allison web site.

allisontransmisson.com

But if you've been driving the coach, for any length of time the re-learn should not be required unless the chassis battery is disconnected for a number of hours.
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Old 05-12-2015, 08:26 PM   #7
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My brother took it to Ammco and they said that the sensors were ok and that it will cost $1300 for them to remove the trans and then they can give us price to repair. The minimum price would be around $5000. Does this sound reasonable? We feel we should get a second opinion. Any advice would be greatly appreciated.

thanks
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Old 05-12-2015, 08:29 PM   #8
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I think before you pony them bucks up, go to a real Allison shop. But read the links you were provided first.
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Old 05-12-2015, 08:39 PM   #9
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I doubt that Ammco would be the spot to have an Allison checked out or overhauled. Have you tried a search for an authorized Allison service facility. I wouldn't trust any shop that can't even tell you what might be wrong to take a transmission apart, to look for something that could be wrong.
There is another post , where the member was having issues with a throttle position sensor, something like that would cause the harsh shift , but wouldn't explain the speedo fluctuation.

I'll track it down and post a link.


EDIT: Got back in time . There may be helpful info in some of the links in this post.


http://www.irv2.com/forums/f123/need...-a-241235.html


I will keep looking.
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Old 05-12-2015, 11:12 PM   #10
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Thanks for the advice and the link. There is a Allison shop pretty close, so I will take it there and get it checked. I don't know what I would do without the great support.
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Old 08-11-2015, 08:36 PM   #11
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Quote:
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Thanks for the advice and the link. There is a Allison shop pretty close, so I will take it there and get it checked. I don't know what I would do without the great support.
I have been a trans tech for 30 years and am ASE master certified,DONT GO TO AAMCO,that is how they get you,take it apart and now you will pay anything to get it back,thats how they roll.Any reputable trans shop would diagnose and estimate within 20%.Of course you cant see the hard parts inside to see if anything is broken.Please take it to allison
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Old 08-11-2015, 08:37 PM   #12
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Originally Posted by rrb View Post
The first issue I noticed was while driving on the highway with cruise control on, the speedometer would jump up 10 to 15 miles on hour and then drop back down. Shortly after that, the transmission started shifting hard from 4-3 and shortly after that 2-1. It doesn't shift hard every time and I can't find any pattern.

I inherited the RV and I don't believe it has been serviced in a couple of years. I will definitely be taking it in for service, but I am handy and if there is anything I can do beforehand, all the better.

thanks,


1994 Winnebago Vectra 35rq
230HP 5.9 CUMMINS ALLISON 6 SPEED
sounds like a speed sensor,when the ecu sees the fault it raises the line pressure to keep from burning up the transmission.If this the case when you cycle the key(shut it off and restart)the firm shift should go away until the speed sensor gives a bad reading then it will start to shift firm and so on.
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Old 08-13-2015, 12:36 AM   #13
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has this been sorted? I would say it may the output speed sensor pulse wheel. It is located on the output shaft and is what the speed sensor reads. I see you have a 1994 vehicle and I am assuming it is 3000 series transmission. Back in 1994 the only thing stopping the pulse wheel from spinning was a little roll pin. I have seen numerous ones of these roll pins break, and cause issues as you have described.

Easy check, remove the output speed sensor and stick a small screwdriver in the hole. see how much movement you have in the pulse wheel, it should be minimal maybe only 1 mm. if you can spin it more than that or even freely, that is your issue. That will be why your speed sensors probably test ok, you have harsh shift and your speedo jumps.

Allison has updated the pulse wheel and output shaft in the last couple of years and we don't see this issue on later vehicles.

Love to know if it is fixed and what was found.
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Old 08-13-2015, 01:01 AM   #14
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has this been sorted? I would say it may the output speed sensor pulse wheel. It is located on the output shaft and is what the speed sensor reads. I see you have a 1994 vehicle and I am assuming it is 3000 series transmission. Back in 1994 the only thing stopping the pulse wheel from spinning was a little roll pin. I have seen numerous ones of these roll pins break, and cause issues as you have described.

Easy check, remove the output speed sensor and stick a small screwdriver in the hole. see how much movement you have in the pulse wheel, it should be minimal maybe only 1 mm. if you can spin it more than that or even freely, that is your issue. That will be why your speed sensors probably test ok, you have harsh shift and your speedo jumps.

Allison has updated the pulse wheel and output shaft in the last couple of years and we don't see this issue on later vehicles.

Love to know if it is fixed and what was found.
Dont believe anything aamco tells you they will say anything to get your money,most of them dont even know how to work a DVOM.A friend of mine took a pickup to them with a bad trans and i have built them so i asked some very specific questions and then we said we were coming to pick it up and when we got there, their whole story changed and the charges for the diagnosis were all of a sudden waived even though they said they had hours of diagnosis and fluids/filters.They knew they were lieing.Sounds like the post before this should also be checked.This could also be a wiring problem.
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