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Old 03-12-2017, 07:43 PM   #1
87Skier
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Any 6L80/6L90 experts out there?

I have a chance to get a low mile ls 4.8 engine with 6L90E. I would like to put this in my 72 Jimmy and use the NP205 behind it.

The issue is that the 6L90E is a 2wd transmission, and for the price I can get this 2wd transmission for I can't find a 4wd unit. It's basically half of what I can find elsewhere.

So, this leaves me with the issue of getting the 2wd transmission to work with my 205. I plan on using an Advance Adapters kit: http://www.advanceadapters.com/produ...ransfer-cases/ but this is only for 6L80 and 4wd 6L90.

I think this transmission will have the 36 spline output shaft. Can anyone confirm this? It's in a 2013 Chevy Express 2500. I have vin if needed.

If it is the 36 spline shaft, can I buy the 6L90 4wd shaft (29 spline) and tear the transmission apart to replace this? Could I run a 6L80 shaft instead?

Could I purchase or have machined a 36 spline input for a np205?

Thanks!
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Old 03-12-2017, 08:46 PM   #2
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Re: Any 6L80/6L90 experts out there?

Yes, 2wd 6L90E's have a 36 spline output, Swapping to a 29 spline 4wd output would be your only option.

6L80E Output Shafts do not fit 6L90E's because a Ring Gear is part of the output, The ring gear on a 6L90E is about a 1/2" taller to match the taller pinions on the carrier.

Machining a 205 input to 36 spline would probably reduce the wall thickness to much, Not sure though. And would have to find someone who would bore, spline, & heat treat a one off part.
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Old 03-12-2017, 10:06 PM   #3
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Re: Any 6L80/6L90 experts out there?

I thought that was case! Any reason someone who hasn't been in one of these before shouldn't disassemble, replace the shaft and reassemble the transmission? It has 50,000 miles on it and seems a little premature for a rebuild.
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Old 03-12-2017, 11:07 PM   #4
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Re: Any 6L80/6L90 experts out there?

Quote:
Originally Posted by 87Skier View Post
I thought that was case! Any reason someone who hasn't been in one of these before shouldn't disassemble, replace the shaft and reassemble the transmission? It has 50,000 miles on it and seems a little premature for a rebuild.
They're pretty easy to tear down, The HUGE center support snap ring is the biggest hurdle, You "can" walk it out with a screwdriver but it's risky for the case being so thin in places, I recommend using the correct pliers!

There was a change in the Outputs between 2010 & 2014, Early ones have a stamped shell that is friction welded to output shaft with a snap ring holding in the Ring Gears. Has holes cut in the shell for VSS pick-up
The later one has integral Ring Gears, Has protruding bosses for the VSS pick-up.

Pull the pan & check which Output you have! The later 4wd part was on national back-order from GM the last time I checked & no dismantlers had one either. This is a 2014 6L90E that has the raised bosses for VSS pick-up (red arrow).

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Last edited by clinebarger; 03-12-2017 at 11:17 PM.
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Old 03-13-2017, 04:47 AM   #5
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Re: Any 6L80/6L90 experts out there?

When I get it I will pull the pan and check it out. If I recall correctly, the van manufacture date was 10/2012, so this could be either output shaft style. The pictures I've seen online of the part look identical. Are these the correct part numbers:


early 6L90E 4wd shaft: ACDELCO 19260888
(in stock at amazon/summit and everywhere else)

later 6L90E 4wd shaft: ACDELCO 24264191
(Amazon est ship date 1-4 weeks, Summit 3/28/2017)

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Old 03-13-2017, 08:13 PM   #6
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Re: Any 6L80/6L90 experts out there?

Quote:
Originally Posted by 87Skier View Post
When I get it I will pull the pan and check it out. If I recall correctly, the van manufacture date was 10/2012, so this could be either output shaft style. The pictures I've seen online of the part look identical. Are these the correct part numbers:


early 6L90E 4wd shaft: ACDELCO 19260888
(in stock at amazon/summit and everywhere else)

later 6L90E 4wd shaft: ACDELCO 24264191
(Amazon est ship date 1-4 weeks, Summit 3/28/2017)


OK, I got it figured out......

The change started in March 2012....But WAS NOT fully changed over 'til the beginning of the 2013 production year (9/12), So yours should be equipped with the late style output. (I would still check)

Delco 19260888 is to retrofit earlier units, Come with the ouput & VSS sensors, If you have the early stamped drum.....You will need this one.

Delco 24264191 is the replacement part for units already equipped with the late output & VSS sensors.
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Old 03-14-2017, 04:06 PM   #7
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Re: Any 6L80/6L90 experts out there?

Thanks for clearing that up.

I'll pickup the transmission at the end of next week and probably won't have time to check which output shaft I need until the first week of April.

So far the parts list includes:
- Correct output shaft
- Large locking snap-ring pliers
- Torx plus sockets
- Bellhousing to case seal
- Output housing/transfer case seal
- Pan gasket
- Filter
- Dexron VI ~ 8 qts


Check these parts:
- Common checks for cracks/wear/damage
- Pistons to be sure they aren't cracked
- Blocked screens or issues at the valve body ports

I'll be using the ATSG 6L80 manual for the teardown and reassembly.

Is there anything else I should replace or do to the transmission while I have it apart?
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Old 03-14-2017, 07:55 PM   #8
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Re: Any 6L80/6L90 experts out there?

The pan gasket is reusable.

Drain the converter by placing a flexplate over a 5-gallon bucket, Place the converter over the bucket, Buy a case of Dex VI.

You need a rear case seal & 2 plugs for the back of the case (6L 4wd transmissions are dry between the adapter & T-case), Drive in the rear case seal in before stacking the unit.

Grease the output splines with wheel bearing grease before stabbing the T-case.

Replace all the Torlon check-balls in the Valve Body if the unit has more than 50K on it, I've seen them wear out in 100K.

It may be better to just buy a compete seal kit from a trans part supplier.....It will come with the screen plate, Check balls, Valve Body to case seals, Rear case seal & plugs, Pump to case seal etc etc.

Have the TCC PWM apply turned off in the Tune, This prevents converter clutch burn-up. Also the reason for draining the converter......PWM apply of TCC is HARD on the fluid (Shearing).

If ANY discoloring/bluing is found on the converter cover......REPLACE the converter.
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Old 03-14-2017, 08:56 PM   #9
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Re: Any 6L80/6L90 experts out there?

Transmission is around 50k, so I'll replace the check balls

Parts list:
- Correct output shaft
- Large locking snap-ring pliers
- Torx plus sockets
- Transmission seal kit (rear case seal, plugs, etc...)
- Filter
- Dexron VI ~ 12 qts


Check these parts:
- Common checks for cracks/wear/damage
- Pistons to be sure they aren't cracked
- Blocked screens or issues at the valve body ports
- Converter for issues

As far as a transmission seal kit, I'm not seeing a kit that covers what I need without including a bunch of extra stuff. I may end piecing it together, but it doesn't really matter.

Good note on the programming out tcc pwm apply.
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Old 03-15-2017, 09:12 PM   #10
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Re: Any 6L80/6L90 experts out there?

Sounds good man!
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Old 03-19-2017, 06:05 PM   #11
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Re: Any 6L80/6L90 experts out there?

Just wanted to clarify some information here:

The 4L60/80 uses an external ECM and TCM, so the transmission is told when to shift by applying signals to the solenoids from outside the transmission.

The 6L80/90 uses an internal TCM with an external ECM that communicate over a CAN bus. Correct me if I'm wrong on this, but the ECM sends some information to the TCM, but the TCM ultimately decides when to shift and how the shift is done.

So, when tuning out TCC PWM apply, is this done on the ECM side or the TCM side?
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Old 03-19-2017, 08:52 PM   #12
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Re: Any 6L80/6L90 experts out there?

Quote:
Originally Posted by 87Skier View Post
Just wanted to clarify some information here:

The 4L60/80 uses an external ECM and TCM, so the transmission is told when to shift by applying signals to the solenoids from outside the transmission.

The 6L80/90 uses an internal TCM with an external ECM that communicate over a CAN bus. Correct me if I'm wrong on this, but the ECM sends some information to the TCM, but the TCM ultimately decides when to shift and how the shift is done.

So, when tuning out TCC PWM apply, is this done on the ECM side or the TCM side?

You really need to talk to a tuner about this, If it was a 4L80E/4L60E I could tell you exactly how to do it, But to answer your question......Trans & engine functions are separated in the tuning software no matter whether your running a PCM, ECM/External TCM or a ECM/Internal TCM.

I circled the Engine & Trans shortcuts.......
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Old 03-20-2017, 02:26 PM   #13
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Re: Any 6L80/6L90 experts out there?

I have no plan on tuning myself. I'm going to send it to someone to do the tuning for me. I'm only asking since it sounds like a lot of tuners only deal with the engine tune, and not the transmission tune.

I want to be asking the right questions, and definitely don't want to seal everything up on the transmission if I need to send the TCM in as well. I'm thinking I will need to send the ECM and TCM in for tuning.
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Old 03-20-2017, 07:07 PM   #14
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Re: Any 6L80/6L90 experts out there?

OK, Then....Yes the TCM would need to be on hand for the tuning.
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