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Old 10-20-2013, 08:50 AM   #1
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Throttle Position Sensor MD3060

We've had some curious shifting patterns from our RV since we bought it... Hard downshifts from 5th to 4th, and sometimes it seems to hang on to the gears a little too long when upshifting, causing some seriously radical forward momentum when it does finally shift. The 5th to 4th downshift is the most annoying... the upshifts seem to get better as the tranny gets warm. Both of these issues seem to be intermittent, meaning once in a while the shifts seem perfect.

There are no codes.

I originally thought this behavior to be how an older transmission might operate, but after test driving another old RV with the exact same motor and tranny as ours for a friend the other day, I am starting to think there might be something wrong with ours. The one we test drove was just as smooth as silk upshifting and downshifting.

I have recently changed the tranny fluid to transynd and replaced the filters. The original fluid still looked good - nice and red, and no burnt smell. I've also taken apart every connector attached to the tranny and the computer for cleaning and reaseating. All of them looked good as well. None of this has had any effect on the shifting.

I am starting to wonder if there's something wrong with the throttle position sensor. The cables are all intact, but there could be something wrong with it electronically... Does anyone know what the resistance should measure across the TPS from idle to full throttle? I can't seem to find this information anywhere.

If anyone has any additional information, i would appreciate it. It seems others have had this problem too, but I never seem to find any followups that offer a resolution to the issue.

-cheers
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Old 10-20-2013, 03:39 PM   #2
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This may help.

I also have the entire Allison MD3060 troubleshooting manual, if you send me a PM with your email I'll send it to you. It's over 5 mb and too big to attached here. When my TPS went bad I could not get the tranny to shift into gear. It was sending a WOT signal and inhibiting shifting into drive. When I finally got it to go into gear it shifted erratically. Kind of sounds like what yours is doing. I had codes though.
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File Type: pdf Allison MD-3060 TPS adjustment.pdf (143.4 KB, 127 views)
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Old 10-20-2013, 07:03 PM   #3
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Thanks for offering the file!

I did a little work this afternoon on the Allison, and got some strange results. I removed the TPS and bench tested it with a multi-meter. Resistance looked to run smoothly between 2000ohms and 15,000 ohms. I'm not sure if those are the right specs or not, but I figured if it was working smoothly without any "dead spots" that it's probably ok. I went ahead and put the TPS back in.

Then, I read somewhere that someone had some issues with their allison because of grounding so I proceeded to check the chassis grounds. I removed the big braided cable and scraped the surface of the frame to remove the paint (kind of can't believe they didn't remove the paint under the bolt for the ground) and then reattached with a little dielectric grease. I also found two more grounding bolts a little further up the frame and I simply twisted them back and forth and then retightened them.

I then went for a test drive. Holy cow was this thing acting different. The upshifts seemed just right... but all the downshifts were about 600 or 700 rpm higher than they used to be. I actually kind of liked it for getting slowed down, but it wasn't exactly smooth. I drove it for a little bit, and before long it stopped downshifting so aggressively and the pendulum swung the other way, and it would hardly downshift at all. At one point, I was coasting at 30mph and the tranny was still in 6th gear. It eventually downshifted and then upshifted normally upon acceleration.

So then, I get home... pull into the garage, and let the engine idle to cool the turbo down. While I'm sitting there I figure what the heck lets check for a code, and low and behold i get a D1-2112, which is a throttle position sensor failed low code. I don't know what that means, but there's definitely something up. Looking for input here before I call the allison guys.

Thanks in advance...

-cheers
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Old 10-20-2013, 07:16 PM   #4
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I'll have to check into the TPS adjustment... when I was under there looking around I was wondering if perhaps that needed adjusted, but I don't think there is any adjustment on the cable itself... nor the mounting brackets it's hooked to. Hmmm,

-cheers
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Old 10-20-2013, 07:22 PM   #5
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A few weeks back I had an Allison tech look at mine cause it wouldn't shift into drive or reverse....turns out it was idling too fast...however, I also complained to him that it was shifting a little rough...so he hooked up his computer to the OBD and reprogrammed the shift pattern which has made quite a difference...both up and down, much smoother ...just my thoughts!!!!
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Old 10-21-2013, 04:45 AM   #6
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Originally Posted by Piker View Post
So then, I get home... pull into the garage, and let the engine idle to cool the turbo down. While I'm sitting there I figure what the heck lets check for a code, and low and behold i get a D1-2112, which is a throttle position sensor failed low code. I don't know what that means, but there's definitely something up. Looking for input here before I call the allison guys.
IIRC the D1-21-12 code is what I was getting when I had my problems. A new TPS solved the problems but I'm not sure it's a DIY fix because the Allison service center had to hook up their diagnostics computer to get the new one set right.
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Old 10-21-2013, 04:58 AM   #7
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Originally Posted by logansrun View Post
A few weeks back I had an Allison tech look at mine cause it wouldn't shift into drive or reverse....turns out it was idling too fast...however, I also complained to him that it was shifting a little rough...so he hooked up his computer to the OBD and reprogrammed the shift pattern which has made quite a difference...both up and down, much smoother ...just my thoughts!!!!

Yep.... 750 RPM is about the max I've found.
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Old 10-21-2013, 05:04 AM   #8
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I've been down the same road before :-)

Here you go.. the resistance values are on the 2nd page, bottom
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File Type: pdf TS2470EN WTEC II.pdf (52.3 KB, 106 views)
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Old 10-21-2013, 07:38 AM   #9
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Just got off the phone with the Allison tech... he told me two things...

1) After changing to the synthetic oil and replacing 18 year old filters I needed to have the adaptive shifts reset. He said that the computer makes such slight changes that even after 6000 miles it probably wouldn't be able to compensate for the difference in fluid flow.

2) It sounds like the TPS is probably ok, but the linkage is probably worn out of adjustment. He said that in order to set that properly, as was stated by someone else above, I will need to bring it in so they can hook it up to their diagnostics computer.

So I guess it's time to make an appointment with the Allison shop... $$

And to boot, while I was under there, I noticed I have an axle seal leaking oil all over my brake rotor and caliper. Nice. When it rains it pours. I just replaced those seals when I put new brakes on last summer... and it's one big job to pull that all apart. I guess I should feel blessed to have the tools and know-how to be able to do it myself. C'est la vie.

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Old 10-21-2013, 12:09 PM   #10
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after looking closely at the TPS adjustment sheet, I'm thinking that the tps linkage had the Closed throttle position outside of the 50-200 count area. I'm guessing the closed throttle position was closer to 20 based on all the more distance the cable had to be pulled out to hook it to the throttle lever assembly on the pump. I'll bet when I messed with it the other day, it actually dropped down into the "error zone" below 14 counts (or .100").

I think I understand this concept well enough to go ahead and adjust this myself. A pair of dial calipers should be all I need. I'm thinking to adjust the length, however, I'll have to drill a new hole for the linch pin that holds the end on the cable... by changing that, I can effectively shorten the cable up a bit and put the TPS into the sweet spot of 50 - 200 counts. or between .350" and 1.400" of it's stroke. Then when I take it to the Allison guys, hopefully all they have to do is hook it up to the diagnostics computer and reset the computer...

I just hope it drives ok on my way there after adjusting the sensor without resetting the computer. It's about 60 miles...

wish me luck

-cheers
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Old 10-21-2013, 05:16 PM   #11
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Update:

Ok, so tonight I get home from work and start measuring the TPS.

The first thing I measured was the overall stroke... it was .735" according to my caliper measurements. The trouble shooting manual says the stroke should be between 85 and 130 counts, each count being .007", so somewhere between .595" and .910". So it's pretty much right in the center. (.595+.910)/2=.752" .... Good deal.

Now that I know the overall stroke, I can figure the exact position where closed and wide open throttle positions should be according to the chart. The manual says the total stroke should lie between 50 and 200 counts... translate that to inches and you get between .350" and 1.400", the exact center of which is .875". If I want the stroke to run exactly in the center of 50 and 200 counts (.350-1.400), then my closed throttle position needs to be set at .875-(.735/2)=.508" OK, cool.

So I checked to see where the closed throttle position was set at... this was easy. Just disconnect the cable and use my trusty calipers to measure the distance between the outside of the pin on the engine fuel lever and the inside of the slot on the slip link at the end of the TPS sensor cable. Doing this, of course, while pulling the cable taunt but not actually sliding the sensor. It measured more than I thought it would after looking at it last night... .370". or roughly 53 counts.

Now, this is not in the 14 count "error zone" at the beginning of the stroke, but it's barely inside the 50 to 200 count range specified in the manual... so I decided to go ahead and adjust the linkage by .125" to get the stroke right in the center. I tried drilling the slip link, but it's hardened, and I didn't have any carbide drills... so I decided to get brutish and I just bent the little 90 cable holder that retains the end of the tps cable and voila... I've got a closed throttle position of .510" (73 counts) and a wide open throttle position of 1.245" (178 counts)... or pretty darn close to that anyways.

I then cleared the 2112 code by cycling the ignition 5 times... and then went for a test drive. The code reappeared, and it shifted like crap... I'm not sure if that's normal because there was no diagnostic tool to program those points into the computer... or if the TPS is shot. I'll find out wednesday morning when I go visit the Allison guys. At least I saved myself $100/hour of shop rate by adjusting the linkage myself... providing I did it right that is...

all for now.

-cheers
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Old 10-21-2013, 05:30 PM   #12
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Piker.. couple of things.. the 3060 transmission is always learning, what they call "adapting" to various shift points, tps positions, etc etc. There are certain codes when set will cause to not "adapt", the 2112 is not one of them. In default it will assume full throttle at the TPS and you continue on down the road, sloppily, but you continue. Using the troubleshooting manual I posted eariler, I would measure the voltages in the TPS harness first before changing parts. In my case, I had to entirely re-manufacture my entire wiring harness from the 3060 up to the control pad and ECM. All my sensors were fine but I had odd voltage readings at the TPS, odd resistance values on the 3 sensors, (Output, Turbine, RPM) and obviously a LOT of crosstalk amongst the sensors due to casings on the wires being rubbed apart after so many years in service. That being said it took almost 30 miles for mine to re-learn everything afterwards. Sloppy shifts, horribly hard downshifts, lifting(rpm rev) between gears - oh yea.. it was messy. After about 30 miles it's back to normal again.
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Old 10-21-2013, 06:05 PM   #13
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Originally Posted by 94-Newmar View Post
Piker.. couple of things.. the 3060 transmission is always learning, what they call "adapting" to various shift points, tps positions, etc etc. There are certain codes when set will cause to not "adapt", the 2112 is not one of them. In default it will assume full throttle at the TPS and you continue on down the road, sloppily, but you continue. Using the troubleshooting manual I posted eariler, I would measure the voltages in the TPS harness first before changing parts. In my case, I had to entirely re-manufacture my entire wiring harness from the 3060 up to the control pad and ECM. All my sensors were fine but I had odd voltage readings at the TPS, odd resistance values on the 3 sensors, (Output, Turbine, RPM) and obviously a LOT of crosstalk amongst the sensors due to casings on the wires being rubbed apart after so many years in service. That being said it took almost 30 miles for mine to re-learn everything afterwards. Sloppy shifts, horribly hard downshifts, lifting(rpm rev) between gears - oh yea.. it was messy. After about 30 miles it's back to normal again.
Thanks very much for the info Newmar... if I were to measure voltage, where exactly would I measure it at? I assume that the allison shop will have all the voltages right at their fingertips when they hook up to the diagnostics computer? Maybe easiest just to let them figure it out?

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Old 10-22-2013, 01:12 AM   #14
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Similar problems, we finally received a throttle position failed low code. Looked at linkage and it was very worn - the TPS was outside of its control band. Tightened up / cleaned up linkage components as much as possible and replaced TPS. It was now producing a non-linear response to a linear throttle input. This is fairly typical of 17 year old plus TPS per the local Allison shop. Waiting for parts to finish the as new throttle linkage rebuild.
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