48re problems

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burnin_murnin

New member
Hey guys
Lookin for any advice regarding my 48re shifting issues. Bought this 2005 Cummins originally showing a p0720 code for the output sensor. No big deal. Truck was holding onto 1st gear high rpms and shifting hard into I believe 3rd gear around 30-35mph. After replacing the output sensor the light stayed on and shifting did not improve. I scanned and cleared the DTC and engine light did not go away. I then checked wiring harness and it looked all good- no cuts... cleaned, dielectric greased and tightened all the underhood and frame grounds I could find and still not luck. Tightened forward band and flushed tranny fluid and it shifted better but not much... I’m leaning towards a possible governor pressure solenoid, transducer or wiring harness issue within the pan to fix the shifting issues but stumped on the p0720 code not going away... any help greatly appreciated, just kinda lost at this point.
 
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Does this truck have any aftermarket tuners, or trans pressure enhancers? What did the fluid look like when you changed it? What happens if you manually shift it on the column? What happens after you get into 3rd? Is the TTVA actually working? Check the harness at the adapter plate they love to rub right there it’s a PItA to get to it but a lot of chaffing happens there.
 
When my gov pressure solenoid went out, my truck shifted 1st to 3rd like described for whatever that's worth

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Justappumped24v said:
Does this truck have any aftermarket tuners, or trans pressure enhancers? What did the fluid look like when you changed it? What happens if you manually shift it on the column? What happens after you get into 3rd? Is the TTVA actually working? Check the harness at the adapter plate they love to rub right there it’s a PItA to get to it but a lot of chaffing happens there.
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It has a edge cts2 on economy tow, fluid was fried and low but no metal shavings in pan or on output sensor magnet tip, 1st and 2nd gear on the column both work why I initially tightened the forward band thinking it was still in tact. When the truck starts off and holds high rpms then shifts into 3rd it goes into 4th overdrive no problem.

Is the TTVA the black plug on top of the tranny pan on the driver side? That sensor is buzzing and I can feel it vibrate when key is on but ignition off..... I crawled up to check the wiring harness going up by the adapter plate and fiewwall and can’t see much up there but the ground strap going to the floor board I saw had a nice chunk rubbed out in it right about as far up I could see....

If I need a new harness, anyone have a link? Having a hard time finding one
 
Justappumped24v said:
Does this truck have any aftermarket tuners, or trans pressure enhancers? What did the fluid look like when you changed it? What happens if you manually shift it on the column? What happens after you get into 3rd? Is the TTVA actually working? Check the harness at the adapter plate they love to rub right there it’s a PItA to get to it but a lot of chaffing happens there.
Click to expand...

It’s got an aftermarket TQ so someone’s been in the trans but extent of it I’m unsure of.
 
burnin_murnin said:
It has a edge cts2 on economy tow, fluid was fried and low but no metal shavings in pan or on output sensor magnet tip, 1st and 2nd gear on the column both work why I initially tightened the forward band thinking it was still in tact. When the truck starts off and holds high rpms then shifts into 3rd it goes into 4th overdrive no problem.

Is the TTVA the black plug on top of the tranny pan on the driver side? That sensor is buzzing and I can feel it vibrate when key is on but ignition off..... I crawled up to check the wiring harness going up by the adapter plate and fiewwall and can’t see much up there but the ground strap going to the floor board I saw had a nice chunk rubbed out in it right about as far up I could see....

If I need a new harness, anyone have a link? Having a hard time finding one
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I still think you may have a solenoid issue, but when that harness runs through I usually cut it 6” from both plugs are re do it using solder and shrink tube with new audio quality wires for low resistance. Then reloom it. That noise sounds like the TTVA is working. The fact that the manual shift works means it’s definitely a electrical issue. If it were Me, repair the harness, then replace the solenoid. A sketchy harness can cause serious damage later
 
Justappumped24v said:
I still think you may have a solenoid issue, but when that harness runs through I usually cut it 6” from both plugs are re do it using solder and shrink tube with new audio quality wires for low resistance. Then reloom it. That noise sounds like the TTVA is working. The fact that the manual shift works means it’s definitely a electrical issue. If it were Me, repair the harness, then replace the solenoid. A sketchy harness can cause serious damage later
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I seriously appreciate you’re input man. Thank you.
Noticed a buzzing sound today underhood coming from that adapter area of the harness I can’t see.... can I unplug both plugs and pull the harness out to inspect it fairly easily? Any issues with unplugging it? I’m not home at the moment to look myself
Thanks tho!
 
burnin_murnin said:
I seriously appreciate you’re input man. Thank you.
Noticed a buzzing sound today underhood coming from that adapter area of the harness I can’t see.... can I unplug both plugs and pull the harness out to inspect it fairly easily? Any issues with unplugging it? I’m not home at the moment to look myself
Thanks tho!
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It’s been some time since I’ve done one I’ll check tonight at the very least you can disconnect it from the transmission and pull it back into the engine bay.
 
Justappumped24v said:
It’s been some time since I’ve done one I’ll check tonight at the very least you can disconnect it from the transmission and pull it back into the engine bay.
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Disconnect at the TTVA your saying correct? Or does the harness plug in elsewhere? Like I said I’m not home now just trying to visualize it
 
burnin_murnin said:
Disconnect at the TTVA your saying correct? Or does the harness plug in elsewhere? Like I said I’m not home now just trying to visualize it
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Unplug the entire harness, neutral safety switch, 8 pin connector, TTVA plug and output. If it’s 4x4 unplug that too, and then pull it out through the engine bay see if there is any damaged wires
 
Justappumped24v said:
Unplug the entire harness, neutral safety switch, 8 pin connector, TTVA plug and output. If it’s 4x4 unplug that too, and then pull it out through the engine bay see if there is any damaged wires
Click to expand...

Unplugged and inspected the wiring harness last night a the plug in the drivers side of tranny up forward near the tranny cooler and adapter plate and found a wire broke in half. Repaired and reconnected the harness and tranny is shifting great! Slight slip if I get on it but then again I don’t know when it was last rebuilt. Only issue now is the engine light is still on for the P0720 output sensor code!!!! What the heck...
 
burnin_murnin said:
Unplugged and inspected the wiring harness last night a the plug in the drivers side of tranny up forward near the tranny cooler and adapter plate and found a wire broke in half. Repaired and reconnected the harness and tranny is shifting great! Slight slip if I get on it but then again I don’t know when it was last rebuilt. Only issue now is the engine light is still on for the P0720 output sensor code!!!! What the heck...
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So everything is functioning correctly, Speedo is working? What brand of sensor did you install? I’ve seen issues with the connection on either side of the plug and also seen bad sensors out of the box
 
Justappumped24v said:
So everything is functioning correctly, Speedo is working? What brand of sensor did you install? I’ve seen issues with the connection on either side of the plug and also seen bad sensors out of the box
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Just whatever they had at the local oreily... master brand? Maybe? That kinda sounds right....
I think at $20 I’ll go buy another buy I did notice output sensor plugs for sale also... to check the plug just use a volt meter?
 
Justappumped24v said:
So everything is functioning correctly, Speedo is working? What brand of sensor did you install? I’ve seen issues with the connection on either side of the plug and also seen bad sensors out of the box
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Yes everything is working on the dash including Speedo, Cruise, tach, etc nothing weird
Abs/brake light on but scanners reading no abs sensor front left
 
burnin_murnin said:
Yes everything is working on the dash including Speedo, Cruise, tach, etc nothing weird
Abs/brake light on but scanners reading no abs sensor front left
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Usually the pins will push out of the connector or be bent or broken, yes you can ohm them out though. You can also test that sensor with it plugged into the truck with the key on, by back probing
 
Justappumped24v said:
Usually the pins will push out of the connector or be bent or broken, yes you can ohm them out though. You can also test that sensor with it plugged into the truck with the key on, by back probing
Click to expand...

I’ll dounle check but nothing looked goofy when I was inspecting it before but I’ll let you know! Thank you!
 
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