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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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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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Old 04-04-2017, 08:48 PM   #15
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Re: Any 6L80/6L90 experts out there?

I'm getting my parts list together here and missing a few items, specifically the rear case plugs and the valve body gasket/filter assembly.

Do you have a parts number for the valve body filter?

Are the rear case plugs a special item or are they the standard steel plugs similar to freeze plugs found in engine blocks? I was under the impression they would be a soft metal plug.

Thanks
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Old 04-05-2017, 08:08 PM   #16
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Re: Any 6L80/6L90 experts out there?

I do not have P/N's as all that stuff comes in a seal kit, The plugs are rubber clad.
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Old 04-06-2017, 03:57 AM   #17
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Re: Any 6L80/6L90 experts out there?

It appears that the AC Delco kit comes with the rear case plugs. I didn't realize they were rubber clad. Only see one seal kit that has the valve body screen.

Got around to checking out the transmission today. It has the newer style output shaft. I suspect it is still on back-order even though a few places still show it as being in stock. There seems to be a good amount of friction material in the pan. No dirt or metal in the fluid. Fluid was a bit dark, and was probably in need of changing. Not sure of the service interval on these transmissions/vehicles, but it may have never been serviced.

Everything look good to you?
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Old 04-06-2017, 03:21 PM   #18
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Re: Any 6L80/6L90 experts out there?

Here is the torque converter. Looks ok to me, don't see any signs of hot spots, except from the welds. See any reason to replace it?
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Old 04-06-2017, 08:03 PM   #19
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Re: Any 6L80/6L90 experts out there?

Take each clutch pack apart & check for distressed frictions, That is a lot of material in the pan for a low mileage 6Lx0E transmission.

The converter has not been overheated, Looks good, But if you can't find a distressed clutch pack/packs......That material is from the converter clutch.
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Old 04-06-2017, 09:14 PM   #20
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Re: Any 6L80/6L90 experts out there?

I ordered everything to change out the shaft today. RockAuto claims to have the output shaft in stock, but I'm skeptical they actually do. Once I have that I'll open the transmission.

If I do find bad clutches, should I rebuild the whole unit and replace the torque converter? If I don't find bad clutches, the torque converter needs to be replaced.


If the friction material is from the clutches, could this be due to low apply pressure from:
- leaky valve body space plate/checkballs
- a cracked piston
- leaking seals to apply parts
- a bad solenoid
- clogged filter screen


In case anyone is looking at this later and wondering about part numbers,
The part number for the solenoid screen assembly (red box in the picture) is:
ACDELCO 24236934
It includes checkballs and a few other seals.
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Old 04-08-2017, 09:12 PM   #21
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Re: Any 6L80/6L90 experts out there?

Quote:
Originally Posted by 87Skier View Post
I ordered everything to change out the shaft today. RockAuto claims to have the output shaft in stock, but I'm skeptical they actually do. Once I have that I'll open the transmission.

If I do find bad clutches, should I rebuild the whole unit and replace the torque converter? If I don't find bad clutches, the torque converter needs to be replaced.


If the friction material is from the clutches, could this be due to low apply pressure from:
- leaky valve body space plate/checkballs
- a cracked piston
- leaking seals to apply parts
- a bad solenoid
- clogged filter screen


In case anyone is looking at this later and wondering about part numbers,
The part number for the solenoid screen assembly (red box in the picture) is:
ACDELCO 24236934
It includes checkballs and a few other seals.
Just because it has distressed frictions doesn't necessarily mean something is wrong with the unit, In a heavy-low powered vehicle coupled with a exuberant driver......Damage can be done to the frictions.

A Clutch Pack can only handle so many apply-release cycles in a given time frame before the pack gets very hot & the ATF can no longer carry the heat away.

Here are some pictures of overheated frictions & steels from a 6L90E out of a Isuzu NPR-HD with only 25,xxx miles, Nothing was wrong with the unit hydraulically, electrically, or otherwise. 100% user error from repetitive downshifts & upshifts.





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Old 04-09-2017, 12:13 PM   #22
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Re: Any 6L80/6L90 experts out there?

I forgot about the ID10T error. Seems to be a common failure for just about every vehicle.

That really could be why the transmission has a lot of friction material in the pan. It was in a rental van with the 4.8L, which isn't super heavy or powerful, but we all know how a lot of people treat rental vehicles. Even if they weren't intentionally mistreating it, it could be like one of the several people I know who can't seem to figure out that you can use cruise control or just leave your foot in one spot and drive a consistent speed and don't have to bounce between 50 and 70 mph constantly.


Clearly I shouldn't reuse the distressed frictions (assuming there is only one set), but should I just replace that clutch pack?
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Old 04-09-2017, 07:43 PM   #23
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Re: Any 6L80/6L90 experts out there?

I would buy all new frictions & refresh the whole unit, I have had great luck with Raybestos friction modules on the 6 speeds.

http://www.ebay.com/itm/GM-6L90-Tran...-/222034303827

The steels as a whole set can get pricey, When you get it tore down....We will see what you need.
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Old 04-14-2017, 02:18 AM   #24
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Re: Any 6L80/6L90 experts out there?

Got the transmission apart, it looks decent on the inside. I uploaded pictures here and also linked to the full resolution versions. Should I just replace the torque converter?

https://1drv.ms/i/s!AqJisnJDkgyPiYk0JOlzx3HeHv5FlA
https://1drv.ms/i/s!AqJisnJDkgyPiYk1x_xN6RdlJvzf4A
https://1drv.ms/i/s!AqJisnJDkgyPiYk2WyHd8hg9hX-a4g

I had my brother take the pictures since my hands were covered in ATF, so they might be a little harder to see.
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Old 04-14-2017, 08:05 PM   #25
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Re: Any 6L80/6L90 experts out there?

I don't see anything wrong with the frictions, The material in the pan has to be from the converter clutch, I would either replace it or have it cut open & inspected.

Watch the snap rings that hold the backing plates in the drums, They have to be oriented correctly on some of the clutch packs.......
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