Duramax Diesels Forum Truck of the Week
  #1  
Old 08-22-2018, 12:50 AM
801duramaxxx 801duramaxxx is offline
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Default 2001 LB7 is my Trans toast?

Hi, I'm new to the forum Ive searched every forum that i can find on this issue and have tried all the tricks and recommendations. I've just recently bought a 2001 lb7 duramax with the 5 speed allison. I got the truck real cheap and had no idea if it even ran. (Repo truck) batteries were toast and i had 1 good one that fit so i put that in and got her to start. I tried to put the transmission in gear and reverse works as it should but there are no forward gears working. At this point I've went over the harness and all the wiring up to where it goes up into the engine bay and can't see any bad wires. The Transmission is not setting any codes, I've tried unplugging the NSBU switch and main transmission connector (try to force it into 3rd gear limp mode) and replaced the turbine speed sensor because it was not reading anything.

I have HP tuners and when i have the scanner running the computer can see what gear the selector is in (dashboard is blank and I'm assuming its the cluster) and also shows the gear the transmission is commanding and they all show correct. in all forward gears the transmission is commanding 1st gear for a couple seconds and then commands neutral.

Dropped the pan to take a look inside and the fluid didn't look to bad but there was some debree, pretty good metal shavings and a small amount of sludge on the magnet.

I jacked the truck up off the rear wheels and reverse was working fine and then suddenly stopped. put it in neutral and back to reverse and it was working again and didn't have an issue. (just idling) but when i put the truck into any of the forward gears the tires move forward maybe an inch very slowly and then stop moving. Im starting to think that this may be a mechanical issue inside the transmission. Maybe a stuck valve/Solenoid not operating properly? should i be looking into a rebuild for the trans?
I'm not really sure where to go from here anyones input on the situation is appreciated.
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1991 k1500 6" on 35's, lm7 swap, nv4500, cam, tune, Full boltons

2001 Duramax 2500hd, 6" on 35s, bolt ons, Intake, Exhaust, edge juice with attitude.

1994 dodge ram 2500, CTD, bone stock

1997 Toyota 4runner, work truck 3" on 33's

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  #2  
Old 08-22-2018, 04:30 AM
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Sounds like your C1 clutches are toast to me
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Old 08-22-2018, 09:47 AM
801duramaxxx 801duramaxxx is offline
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That’s what I was afraid of is the Allison a very complicated trans? I’m pretty mechanically inclined and not afraid to tear stuff apart on my own but I’ve never rebuild a transmission would it be a good idea to tear into it and see if I can replace the clutches myself?
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1991 k1500 6" on 35's, lm7 swap, nv4500, cam, tune, Full boltons

2001 Duramax 2500hd, 6" on 35s, bolt ons, Intake, Exhaust, edge juice with attitude.

1994 dodge ram 2500, CTD, bone stock

1997 Toyota 4runner, work truck 3" on 33's

2010 Silverado 1500, 7.5" 35's, bolt ons, tune, Girls DD
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Old 08-22-2018, 09:53 AM
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You'll need more than clutches.
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Old 08-22-2018, 10:14 AM
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Typically when you see a lot of metal shavings in the pan, and you have the symptoms you have, you can bet that the sump filter is pretty plugged, which starves the entire transmission of fluid quantity and pressure, which causes excessive heat throughout, and makes quick work of destroying the converter, and the majority of the clutch packs in the trans, and also the seals, bushings, and bearings. It requires an extensive, complete thorough cleaning and rebuild, and you're heat exchanger cores should be flushed out also.
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"Sore Subject" - Still don't have time for it.
I would never have learned what I have without George Alexander, Mike Lovrich, David Browning, Matt Handwork, Ben Tyler, Evan Drosehn and countless members of this forum and others.
Thank you.

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  #6  
Old 08-22-2018, 10:26 AM
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I would take it to someone that really knows them. I wouldn't dare tear into one. Also read up on the housing. If I remember right they cracked on the front bell on the 01s. Might want to upgrade it while your in there.
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Old 08-22-2018, 07:57 PM
801duramaxxx 801duramaxxx is offline
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Thanks guys for the replies. I'm just gonna get to pulling the trans and having it built by a reputable shop. or maybe even order a reman unit but i want something that will handle a decent amount of power like a 200hp tune nothing crazy. heaviest thing i own is a 10,000lb max gvwr toy hauler that ill tow around occasionally, right now i tow it with my LS 5.3 swapped k1500 with a few mods to beef up the drivetrain, brakes and suspension and it does alright but i only get about 6mpg with the trailer hooked up around 8000lbs Im in Salt Lake City does anyone have any recommendations on where to get a reman unit or what shops to check out around my area.
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1991 k1500 6" on 35's, lm7 swap, nv4500, cam, tune, Full boltons

2001 Duramax 2500hd, 6" on 35s, bolt ons, Intake, Exhaust, edge juice with attitude.

1994 dodge ram 2500, CTD, bone stock

1997 Toyota 4runner, work truck 3" on 33's

2010 Silverado 1500, 7.5" 35's, bolt ons, tune, Girls DD
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  #8  
Old 08-23-2018, 05:12 AM
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Contact Evan at limitless diesel.
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Old 09-05-2018, 11:12 AM
801duramaxxx 801duramaxxx is offline
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well heres an update. i tore the trans out figured shops charge to much so id save myself some cash and ended up building it myself (first time I've ever looked inside an automatic transmission) my buddy had a book for allisons and i added a transgo jr shift kit, alto red clutches, and billet TC. it drives awesome now and shifts through all the gears perfect. the 2-1 shift is a little harsh though. just got it all back together last night and I'm trying to figure out if i can reset the TAPS through my HP tuners vcm scanner.
what are the other options for reseting the trans and putting it into fast learn mode??
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1991 k1500 6" on 35's, lm7 swap, nv4500, cam, tune, Full boltons

2001 Duramax 2500hd, 6" on 35s, bolt ons, Intake, Exhaust, edge juice with attitude.

1994 dodge ram 2500, CTD, bone stock

1997 Toyota 4runner, work truck 3" on 33's

2010 Silverado 1500, 7.5" 35's, bolt ons, tune, Girls DD
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Old 09-05-2018, 11:31 AM
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That 2-1 could be harsh. The ‘01 os is prone to that. Especially if it’s cold.
You might need a tech-2 to reset the pressures.
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Old 09-05-2018, 11:43 AM
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The '01 OS can take its sweet time learning. It's the dumbest OS out there.
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Old 09-05-2018, 04:45 PM
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Yep...
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  #13  
Old 09-05-2018, 05:23 PM
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Does HP tuners support full flashing AL5?
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Old 09-05-2018, 06:03 PM
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Quote:
Originally Posted by PureHybrid View Post
Does HP tuners support full flashing AL5?
I do believe so yes. I can confirm when I get back to the shop. I have hpt on my computer

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Old 09-05-2018, 07:57 PM
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Quote:
Originally Posted by PureHybrid View Post
Does HP tuners support full flashing AL5?
Why would you full flash it? Doesn't affect the adapts.
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