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4L70E Swap 6L90E

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Old 04-24-2008, 10:17 PM
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Default 4L70E Swap 6L90E

I've got a VMax ECSB and have the main parts

6L90E
New T Case to go with it.
Filler Tube and Indicator
Tranny Cooler P/N 08 Denali PU
Tranny Lines P/N 08 Denali PU
Adapter and Gasket T-Case to Tranny

What else do you think it would take to make it 100% factory functional

Wonder if I can install a 6 speed dash cluster and shifter. Or if the all the wiring in the dash is different. Wish I had access to a parts book so I could see how many parts are actually different between my 4sp truck and the 6sp trucks.

I'm not sure if I'm going to pull the trigger on the install yet though. And if anyone has a 6sp Core let me know, the core charge was a grand...

Last edited by MNC5; 04-24-2008 at 11:04 PM.
Old 04-24-2008, 10:55 PM
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Originally Posted by MNC5
I've got the main parts

What else do you think it would take to make it 100% factory functional

Wonder if I can install a 6 speed dash cluster and shifter. Or if the all the wiring in the dash is different. Wish I had access to a parts book so I could see how many parts are actually different between my 4sp truck and the 6sp trucks.

I'm not sure if I'm going to pull the trigger on the install yet though...
Answer me this. Do 08 trucks come factory w/ 4L70E? What config(Crew, or EC)?

I thought 70e was a TBSS tranny?

I always try to read conversion threads to see what others are attempting. I seen a few tranny conversion threads going. 6 spd, whether M6 or A6 seem to be a hot topic. I hope GM recognizes, & throws a bone to the A4-A6 swap crowd w/ a harness or further support, along w/ harness. Good Luck.

Do it. Get parts book for both. I've done a conversion. I was told get book for my truck & the swap motor/engine.

Last edited by fastnblu; 04-25-2008 at 01:48 PM.
Old 04-24-2008, 11:02 PM
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1,000.00 core charge? Damn
Old 04-25-2008, 08:30 AM
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I dont think it will work. There is something in the motor or a computer that makes the 6L90E work.

I wish some one could figure it out. Id love to do the swap behind my 8.1L suburban.

That new trans has a LOW first gear and high over driver. Moms denali with the 20" turns 1700 rpms at 80 mph. the suburban turn 2300 at 80 with 373's and then the turck turns 3000 at 80 with the 4:10's
Old 04-25-2008, 06:32 PM
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Did it come with a wiring harness? If not I assume you will need one to let it talk to the ECM.

I can take pics of my truck if you want Dennis. Just let me know what you'd like to see.
Old 04-25-2008, 06:39 PM
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Speartech does a lot of harness adapters
Old 04-25-2008, 08:40 PM
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Originally Posted by XLR8NSS
Did it come with a wiring harness? If not I assume you will need one to let it talk to the ECM.

I can take pics of my truck if you want Dennis. Just let me know what you'd like to see.
Thanks but I'd hate to make you crawl around under your truck...

I've got an adapter coming from SpearTech, he was hoping to ship it Monday. Wiring will be the trick... I wish I had access to the GM parts site. I'd like to know if the complete wiring harness is different for the 6 speed or just sections of it.

The driveshaft will need to be shortened by around 2 inches. And the yoke end is different too...Is the yoke end interchangeable at the U joint?
Old 04-26-2008, 08:23 PM
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Originally Posted by MNC5
I've got an adapter coming from SpearTech, he was hoping to ship it Monday. Wiring will be the trick... I wish I had access to the GM parts site. I'd like to know if the complete wiring harness is different for the 6 speed or just sections of it.
The only part of the wiring harness that I could tell was different was the transmission connector pigtail. The 6L80/90 harness also doesn't have the TCM connection up front at the core support by the ECM. All the pins at the electrical center connection are the same (save for the 4WD Low) switch. I have the schematics for the 4L65E trucks and the 6L80/90 trucks.
Old 04-26-2008, 08:28 PM
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You will also need a flash of the BCM for cruise functionality and such from what I have been able to determine.. Don't forget you need the 6L80/90 transmissions files for the ECU to talk to the TCU. Basically you have everything you need to do the swap. The transmission will function without the cluster and shifter changes but you wont have the ability to manually select gears. If you do the swap let us know if you have the manual controls just by swapping the shifter but not swapping the cluster.

Last edited by Wide Open; 04-28-2008 at 06:53 PM.
Old 04-27-2008, 11:05 AM
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Originally Posted by MNC5
I've got an adapter coming from SpearTech, he was hoping to ship it Monday. Wiring will be the trick... I wish I had access to the GM parts site. I'd like to know if the complete wiring harness is different for the 6 speed or just sections of it.

The driveshaft will need to be shortened by around 2 inches. And the yoke end is different too...Is the yoke end interchangeable at the U joint?
I'm interested on how this goes, especially the wiring. Post pics if u get the chance.

Originally Posted by Wide Open
The only part of the wiring harness that I could tell was different was the transmission connector pigtail. The 6L80/90 harness also doesn't have the TCM connection up front at the core support by the ECM. All the pins at the electrical center connection are the same (save for the 4WD Low) switch. I have the schematics for the 4L65E trucks and the 6L80/90 trucks.
Those schematics would def. be nice to have in this situation.


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