Limp mode after new planetary gears

Aug 15, 2022
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My gmc Sierra 2500 is in limp mode after replacing planetary gears in Allison 1000. Primary code is tcm(mil request). There are about 20 secondary transmission codes. Double checked all wiring harnesses. Any ideas?
 
Aug 15, 2022
14
0
1
I signed up to this forum to try to get assistance from experts so I can fix my truck myself. If I had the money I would have taken it to a shop the first time. Not looking for advice on who should fix my truck. I will get it figured out elsewhere.
 

gmduramax

Shits broke
Jun 12, 2008
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I signed up to this forum to try to get assistance from experts so I can fix my truck myself. If I had the money I would have taken it to a shop the first time. Not looking for advice on who should fix my truck. I will get it figured out elsewhere.
Without specific instructions on what you did, we cannot help.
 
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Aug 15, 2022
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Took the the trans out of the truck (04 gmc sierra 2500hd 4x4 Duramax with 212k miles) because it was grinding in 1st gear and didn't have 6k to pay the experts. I replaced the whole planetary gear set because a thrust washer was destroyed and one of the planetary gears looked bad. (I think it was the p2 planetary gear which I heard is a common problem) I didn't do anything else because I found the problem and don't have any transmission experience. I didn't even open the front side of the transmission. I didn't do anything to the valve body. I never had any codes before I took it apart. Since there are 20 transmission codes now I would guess it would have to be wiring. The only wiring done was disconnect harnesses. I am confident I assembled everything properly. Any other info you need that would help me out? Thanks for your effort.
 
Aug 15, 2022
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I had auto zone do the scan because I don't own a scan tool. I can go back to auto zone or buy a scan tool. Will a cheap scan tool work for this?
 

Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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I signed up to this forum to try to get assistance from experts so I can fix my truck myself. If I had the money I would have taken it to a shop the first time. Not looking for advice on who should fix my truck. I will get it figured out elsewhere.

You came here asking about a planetary gear set but never once told us the whole story or what to do on a proper tear down or rebuild of your issue. You attempted this and fucked up. Shit happens but when you come here again saying you have 20 codes but don’t post any, don’t explain what you did exactly to the T, and then fire back at us because you think we magically should know how to fix your issue, you are gunna have a hell of a time getting free help.

At the end of the day, we ain’t miracle workers. You most likely put a Torrington bearing in wrong, messed up a clutch clearance, put the wrong part in or destroy something inside. Most of this we won’t be able to tell you. An expert needs to put his eyes on it

Good luck
 

Bdsankey

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Like said above, it is very likely not assembled correctly. When a bearing fails the trans MUST be tore 100% down and everything cleaned/inspected to ensure that debris didn't end up somewhere else.

Your post also contains just about zero information. It's like you're asking us to solve world hunger with a single saltine cracker................
 

Leadfoot

Needs Bigger Tires!
Dec 27, 2006
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www.matpa.org
My gmc Sierra 2500 is in limp mode after replacing planetary gears in Allison 1000. Primary code is tcm(mil request). There are about 20 secondary transmission codes. Double checked all wiring harnesses. Any ideas?

First off: WELCOME

This site is filled with some great information and experienced/skilled members. Sadly one of OG transmission guru's recently passed, but there are still many on here that can help just as much.

That said, they are NOT on here all the time (some visit occasionally when they get a chance). They also can only help if/when there is enough information provided to help. Even then there are some issues which can only be diagnosed hands on or with a complete teardown.

I am very capable mechanically, I have completely restored an 80's pickup, done my own ring and pinion setups, transfer case rebuilds, assisted in building engines and even assembled a Turbo Hydromatic 400 for truck pulling. I learned enough on this and other Duramax forums (Dieselplace was big back in the day) that the Allison transmission is a much different design than transmissions I was used to. I read story after story of guys trying to build there own Allisons whether it be to save $$ or because they were just used to doing all their own work (or both), but quickly learned one SMALL error in assembling the transmission could lead to a really BIG repair fill to fix correctly along with the $$ spent to build it on your own in the first place. A torrington bearing facing the wrong way (happens a LOT) can wipe out a transmission. There are parts in the transmission that can cost as much (or more) than a complete running TH400 with warranty... I decided to drive 13 hours to Michigan to have mine built initially, and it saved me $ in the long run. I figured if I did my own transmission and got lucky it would cost me $X, and if I messed up it could cost me $X plus the cost of a total rebuild with Converter/cooler flush to remove debris, and it wasn't worth the gamble. Some day I may try my own, but it will not be on a daily driver or vehicle I can't afford to have down for some time while trying to see what I messed up.

Just fluid alone (if contaminated during a botched build) can be expensive.

Another thing I learned is having the proper scan tool is almost more important than having the correct hand tools. I believe you said you had code read at an Autozone. Not knocking that (I've done the same when I'm on the road and have had an issue in my car), but it does show you do not have the tools for proper diagnosis.

I'm no expert but have paid attention to posts over the last 20 years and I can say with a large degree of confidence that your transmission needs to be torn down, cleaned (at MINIMUM), and affected parts replaced. Even if you luck out and replace what you messed up and get it functioning again (not likely), you will have other issues soon after. The valve body is NOT very forgiving to foreign matter.

There's been plenty of posts of guys saying they "fixed" their transmissions only to come back a few months later begging for help.

The folks on here are more than willing to help, but ONLY if there is enough information. They've learned guessing only causes more issues and it's not like diagnosing a shifting issue with an old 700r4, C6, or TF727 where there were a lot less solenoids, computer controls, and more forgiving clearances/tolerances.

All that said, I do hope you get it figured out.
 
Aug 15, 2022
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Thanks for responding. Sorry to hear about MikeL. I think he passed 1 or 2 days after I signed up hear.
I did get a cheap scanner ($100) , cleared the codes and got 2 codes now p0700 and p0872 (t fluid pressure sensor/switch c circuit low). Not sure why AutoZone scan had 20 (secondary codes). I did have fluid in the pass through connector. Dried it out with air and trying to find a new one. Not sure how much time and money the truck is worth with 212k miles, rust is taking over and fuel in the oil. At this point maybe I will get lucky and get the code fixed and the truck will last a year or 2 without removing the trans again.
 

Bdsankey

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Feb 1, 2018
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Thanks for responding. Sorry to hear about MikeL. I think he passed 1 or 2 days after I signed up hear.
I did get a cheap scanner ($100) , cleared the codes and got 2 codes now p0700 and p0872 (t fluid pressure sensor/switch c circuit low). Not sure why AutoZone scan had 20 (secondary codes). I did have fluid in the pass through connector. Dried it out with air and trying to find a new one. Not sure how much time and money the truck is worth with 212k miles, rust is taking over and fuel in the oil. At this point maybe I will get lucky and get the code fixed and the truck will last a year or 2 without removing the trans again.
Fuel in oil is definitely not a good sign.

With that said, changing the harness is not a ton of cash or a ton of time.
 

2004LB7

Well-known member
Dec 15, 2010
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Norcal
Thanks for responding. Sorry to hear about MikeL. I think he passed 1 or 2 days after I signed up hear.
I did get a cheap scanner ($100) , cleared the codes and got 2 codes now p0700 and p0872 (t fluid pressure sensor/switch c circuit low). Not sure why AutoZone scan had 20 (secondary codes). I did have fluid in the pass through connector. Dried it out with air and trying to find a new one. Not sure how much time and money the truck is worth with 212k miles, rust is taking over and fuel in the oil. At this point maybe I will get lucky and get the code fixed and the truck will last a year or 2 without removing the trans again.
it won't last that long if you don't fix the fuel in oil issue
 
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Leadfoot

Needs Bigger Tires!
Dec 27, 2006
873
24
18
46
Western MA
www.matpa.org
Thanks for responding. Sorry to hear about MikeL. I think he passed 1 or 2 days after I signed up hear.
I did get a cheap scanner ($100) , cleared the codes and got 2 codes now p0700 and p0872 (t fluid pressure sensor/switch c circuit low). Not sure why AutoZone scan had 20 (secondary codes). I did have fluid in the pass through connector. Dried it out with air and trying to find a new one. Not sure how much time and money the truck is worth with 212k miles, rust is taking over and fuel in the oil. At this point maybe I will get lucky and get the code fixed and the truck will last a year or 2 without removing the trans again
Both those codes are ECM codes (P0700 is a generic code given to the ECM stating an issue with the transmission).

Autozone MAY have gotten other codes if they actually scanned the TCM and would help diagnosis of the trans. Some cheap scanners only check the ECM, and some cheap scanners will do the TCM but you have to specify before checking.

What scanner are you using? We can tell you if that will work and if it does, how to set it up to do it. If it doesn't, we can tell you that too and you can look for another scanner.

Where are you located? City/State as there may be a member close by who can assist.
 

Leadfoot

Needs Bigger Tires!
Dec 27, 2006
873
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The scanner is Innova 3040rs. I am in the Cleveland Ohio area. Thanks!

I couldn't find anything definitive so I am going to assume it does not read the TCM.

This one specifically states it will read the TCM, but obviously it costs more:

I have visited Cleveland for work, but don't know members from that area. Hopefully one of them will see this and offer assistance.
 

JoshH

Daggum farm truck
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Feb 14, 2007
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P0872 is a transmission code, so the Innova scanner does read those. There's a good chance some debris got into the valve body when you had the trans apart and caused the E shift valve to stick.
 
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