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Discussion Starter #1
I have been having troubles with shifting from P to R to D. There is sometimes a clunk heard in the rear end when I do so. The check engine light comes on intermittantly and I once I believe I was put in "Limp Mode". Also, the PRND123 sometimes is not lit up to tell me what gear I am in. These problem are intermittent though, and usually behaves normal.


Dealer says codes P0700 and P1093 appear, 0700 indicating a bad Transmission Control Module. Should I replace the TCM? What is the price of a TCM? Is there a better, higher performance version out there?


I bought my "02 truck used, with 54K miles.
 

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First, lets clarify the codes that have set. The P0700 is simply a code stored in the PCM letting you know that there are code(s) stored in the TCM. It is very unlikely you need a new TCM. The P1093 code is large fuel leak detected. This usually sets when the pump cannot build fuel pressure properly.


As far as the trans problem is concerned. I would start by checking your nsbu switch. It is mounted on the drivers side of the trans. The oem switch is black in color and is frankly not up to par with Allison standards. GM insisted on using there nsbu switch for reasons of cost saving. The oem Allison switch and the replacement switch from GM is tan in color. It is better sealed and comes with a shield. Once water intrudes the switch, it gets confused. That is where you problem is coming from. You can get a replacement switch from an Allison dealer or from my website.


The P1093 code is a covered item under your engine warr. I would have that further investigated as it may be a indication of trouble in the fuel system.


Eric


On edit: Here is a pic of the updated Nsbu


Edited by: dmaxalliTech
 

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Discussion Starter #3
Thank you for the quick responce.


I installed a new Nsbu (Allison version). Now there seems to be an alignment issue with the gear selector. I go from P to R ok. It feels like I have "two" nuetrals. The first N doesnt light up as N, but as a blinking R. As I drop the lever into D,3, and 2 it seems fine. It will not allow me to go into 1.


Thanks again for your help
 

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Discussion Starter #4
I am also running 285/75 BFG AT's as well, so I didnt know if the larger tire could cause issues with the Tranny
 

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Mike Bradford said:
Thank you for the quick responce.


I installed a new Nsbu (Allison version). Now there seems to be an alignment issue with the gear selector. I go from P to R ok. It feels like I have "two" nuetrals. The first N doesnt light up as N, but as a blinking R. As I drop the lever into D,3, and 2 it seems fine. It will not allow me to go into 1.


Thanks again for your help
Mike,

The swithch is adjustable.

If you look at the picture of the switch, there is that skinny metal "alignment" tab that should be in place when installing the switch. After installing the bolts, you remove it. The purpose of that tab is so you install the switch in the same orientation as the old one was installed.

If it was me, I would make sure it's removed (the tab) then loosen the mounting bolts of the switch and rotate it and retighten. Kind of hit and miss.Edited by: hoot
 

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It's easier to adjust with some help and safer .... But best done on a lift ....

Truck off ignition on run ...
What needs to be done is select 1ST gear and adjust NSBU till indicator is illuminated on steering column ... Snug and run thru the gears checking for accuracy, adjust accordingly ...

Caution don't get rolled over chock wheels take all percautions ...


Mac
 

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Discussion Starter #7
One of the bolts is covered by the electrical connections. I would need to remove these in order to loosen the bolt. I assume I would loose all feedback to PRND123 indicator in the process. So how would you know if the 1st is highlighted or not while you are adjusting if the connectors are unplugged?
 

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Leave the one under the plugs loose enough to adust. Once you find the right spot, tighten the front bolt, pull the plugs and tighten the back one.
 

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actually the adjustment should be done in Nuetral, The metal lock tab locks the switch into nuetral. With the tab gone and with out the tool that we use to adjust them, its gonna be trial and error
 

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Discussion Starter #10
Thanks guys, I got it. It wasnt fun, but your expertise made it alot easier.


Have a happy holdiay
 
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