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2006 Volvo 780 surging while using Cruise Control


Parrformance
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I am suspecting a dirty/failing speed sensor cussing surging while using CC.

Perhaps someone else has experienced this and might have some tips?

In my mind I am thinking of checking and cleaning the sensors around the tail shaft of the Eaton ten speed with Autoshift.

Thank you,

Michael

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Which engine is in the truck?  Is around same time frame as my 05 with C15 in it.  Does the Volvo have a Warm Up fast idle off cruise as Cat did?  Easy way to check of speed or tach sensor as the Cat also has Two Engine Speed sensors, one for Dash Ga and Cruise the other for ECM if does have that warmup rpm adjust.  I replaced my Trans speed sensor where cruise is fully functional now.

Dave

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    We have. 2000 Volvo. The cruise worked but not on big hills. It would wait till it had to pull hard to stay in the speed.

 

   So I just used the pedal to help the cruise control until it was doing its thing.

 

    I try to stay ahead of replacing things before they really are needed. So I ordered a throttle position sensor. Installed it.

     So I took the truck for a drive. It fixed my cruise problem.   Just by chance I guess.

  

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Good tips, ddm502001: the truck has the Volvo 12.1, and does have the fast idle I can set with the stalk. I will fire it up this weekend and see if it will hold a fast idle in neutral. Great way to isolate the speed sensor from the ECM Crank speed sensor👍🏽

The truck CC has worked flawlessly since I bought it, this is a new issue.

I am suspecting a dirty or corroded speed sensor that is intermittently giving good signal then dropping out.

Feels as though the truck thinks it is going up hill then downhill in just a few seconds.

If you can stand it, it will actually maintain the relative set speed albeit surging up and down.

Truck runs fine and smooth with the foot throttle.

Wrknrvr, I do plan to swap the sensor with new (from the dealer if available)as soon as I isolate it👍🏽

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I have an additional symptom to narrow down the offending circuit.

While searching the World Interwide Webasphere for a moving picture pertaining to the Eaton Fuller 10 speed with Ultrashift II, my memory got jogged to a couple of instances of abnormal shifts.

While traveling home last trip, after exiting the Interstate system from a prolonged steady 65 mph travel, the transmission remained in a gear longer than usual.

This occurred on an up shift as well as a down shift.

The video was referring to a couple of sensors on top of the tranny, one ☝️ bout speed, front right side of the x y shifter, and I think one rear left of shifter assembly.

I will check and clean all these sensors as soon as I can, hopefully by Saturday, and report back.👍🏽

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2 hours ago, Parrformance said:

I have an additional symptom to narrow down the offending circuit.

While searching the World Interwide Webasphere for a moving picture pertaining to the Eaton Fuller 10 speed with Ultrashift II, my memory got jogged to a couple of instances of abnormal shifts.

While traveling home last trip, after exiting the Interstate system from a prolonged steady 65 mph travel, the transmission remained in a gear longer than usual.

This occurred on an up shift as well as a down shift.

The video was referring to a couple of sensors on top of the tranny, one ☝️ bout speed, front right side of the x y shifter, and I think one rear left of shifter assembly.

I will check and clean all these sensors as soon as I can, hopefully by Saturday, and report back.👍🏽

Par,

I assume you are referring to the input and output sensors on the transmission?  If so be very careful removing them (if you can). They are plastic and if original VERY brittle. Supposed to be a 15 minute job to change out but took GeorgiaHybrid and I 9 hours after the output sensor literally crumbled leaving pieces down in a hole. I do know the output sensor has several “holes” to mount the sensor and you may be better served just mounting a new one in another hole and just leaving the old as a plug. BTW my truck is also a D12 with 10 speed.  Also beneficial to coat with some antiseize for future. 

Edited by SuiteSuccess
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Just finished it up today👍🏽

I’ll preface it by saying I chose to clean and dialectic all the connections at the transmission. Once I pulled a couple of connectors apart only to find pristine contact points, I decided to pull the plug out of the top port of the tail shaft.

I noticed a LOT of powdered rust and debris came out with the plug.

This prompted me to pull the lower plug as well.  Rusty powder poured out like water, the tone ring inside however was shiny clean.

I was hopeful this was the cause of the surging, but I chose to reach out to Nextran the local Volvo dealer to see if they had a new sensor in stock.

Mike said we have 1, quoted $47 so I put everything back together enough to drive the truck over to get it.

The cruise was somewhat better on the way over but not perfect.

I took the tools I needed and had the port cleaned and prepared with anti-seize so I could slide under and install the new sensor as soon as I had it in hand.

The drive home was exceptionally pleasant, the sensor corrected the surging cruise control completely, and improved the shifting of the truck.

The shifts are smoother, and seem to be at the appropriate timing.

With your advice Suite, I am planning on leaving the old sensor as a plug, Thanks for the advice, this made the job quick and painless.

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25 minutes ago, GeorgiaHybrid said:

Nothing like laying on your back, pick in hand, flashlight in your mouth with a mirror held by someone else to see what you are doing while trying to fish out 100 feet of wire and bits of crumbled plastic out of a hole in the top of the transmission.

Fun times....

Hey David, let’s do it again.  This time I might even bring the beer since it may be a shade longer than 15 minutes!  😜

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It was most definitely meant as an appreciative compliment, I was thankful for the advice to leave the old sensor well enough alone.

I was more than happy to learn from your adventure. 
 

I am quite surprised how much smoother the shifts feel, it had always shifted firmly. Having never driven an HDT with an Ultrashift I assumed it was supposed to be like that.

Well maybe just a little salt🤣 just kidding my friend, Thanks for the tip👍🏽

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3 minutes ago, Parrformance said:

It was most definitely meant as an appreciative compliment, I was thankful for the advice to leave the old sensor well enough alone.

I was more than happy to learn from your adventure. 
 

I am quite surprised how much smoother the shifts feel, it had always shifted firmly. Having never driven an HDT with an Ultrashift I assumed it was supposed to be like that.

Well maybe just a little salt🤣 just kidding my friend, Thanks for the tip👍🏽

BTW did you change out input and output speed sensors or just one?

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