[filli57]

So I know this is far fetched and prolly more complicated than it is worth. But I absolutely hate our 4l60 it's junk, truck falls on its face all the time. We'll luckily within the year I will finally be able to do whatever my $$$ allows (will have a new to me daily driver for commute). My truck will assume the duties of offroad/hunting truck (large heavy tires). So it had me thinking instead of a v8 swap why not just swap in the 6l90? It would give me a 4:1 first gear, should get the tires rolling better giving me better acceleration and combined with 4lo a realitively good crawl ratio.

The 4l60 ratios are:
1st-3.059
2nd-1.625
3rd-1
4th-.696

The 6l90 ratios are:
4.027
2.364
1.532
1.152
.852
.667

I think it would really help our motors out especially the guys with big tires.
But someone with more information on how these bolt up can you chime in and say yes or no on could we actually mate it to our engines and could we control the computer within the trans?

 

[limequat]

The stock P12 PCM will not be controlling this trans, end of story.

However, it may be feasible to flash the PCM to manual trans and then try to splice in WTF ever box controls the 6l90.

 

[Rick_crew]

Doesn't the 6L80 and 6L90 have an internal controller?

 

[Supermodulation]

On your older truck, prior to 2008. You would need to upgrade your P12 PCM to a E67 PCM and need a T42 TCM + Harness for the conversion.
2008 to 2012 truck would only need a harness upgrade and the PCM/TCM re-flashed.

 

[1BADI5]

James, total harness or splice in?

This is an interesting thought or swap

 

[Rick_crew]

I'm intrigued..

I can hardly understand though why GM chose to locate the computer inside the transmission case. If it turns out that the heat and vibration cause excessive failure, it's gonna be damned expensive for them and the owners.

I've posted it here before...

In the mid 90's I worked for a company in South Carolina that was spun off the old Union Carbide. They make capacitors.

Chrysler made an electronically-controlled front-wheel-drive transaxle for the old K models that mounted the computer inside the transaxle housing.
The company I was working for had a production upset that resulted in some below-spec capacitors being shipped. It was only for a single production shift, but quite a few thousands of those unreliable capacitors were shipped.

That Chrysler transaxle computer had 7 or 8 of these capacitors that cost about 45 cents each.

Those 45-cent capacitors caused many transaxles to fail under warranty.
Chrysler had to pull the transaxles and crack them open to swap-out those computers.
It was a debacle.


Sure, today the state of the art is far advanced, and I'm sure GM has tested hell out of those transmission controllers. Still..... Inside a auto transmission is not a friendly environment for electronics. Solenoids are one thing, microprocessors are a different thing altogether.

 

[Supermodulation]

James, total harness or splice in?

This is an interesting thought or swap

There's a Plug in harness and TCM upgrade for 2008 to 2012 trucks is about $600.00
Prior to 2008 you would need to splice in an additional harness for the E67 PCM swap.

 

[FrEaK_aCcIdEnT]

Forget the 6L90, I want the 8L90!!!

im guessing a slight tunnel mod is in order. Lol

 

[efi-diy]

For an earlier truck - you could use

http://www.355nation.net/forum/v8-engine-drivetrain/85857-coming-soon-6l90-interface-box.html

Also you would an adapter plate & t/c spacer - I have them available.

 

[cherokeecanyon]

thats like puttin c-4 in an ant hill, i like it!

 

[Trice]

4L60 4L70 to 6L80 6L90 EZ Plug Play Swap Conversion T42 T43 Interface Module | eBay

 

[filli57]

what would be the best way to deal with the shifter? go to floor shift?

 

[FixxxerKH202]

Not to burst your bubble but you may have some fitment issues and I'm not sure if the T-case will bolt up without an adapter. It will also be about 6" further back than with the 4L60E.

The 6L90's are pretty bulky compared to the 4 speeds. This is a 6L80 in the pictures from what I've read the 90 is a tad bit longer.

 

[filli57]

Not to burst your bubble but you may have some fitment issues and I'm not sure if the T-case will bolt up without an adapter. It will also be about 6" further back than with the 4L60E.

The 6L90's are pretty bulky compared to the 4 speeds. This is a 6L80 in the pictures from what I've read the 90 is a tad bit longer.

you are correct they are roughly 1.5" longer than the 6l80e
the 4l60 should be 23.5 where as the 6l90 should be 25" (bellhousing to output)
some good info here
6L80/90E Swap FAQS - TBSSOWNERS.com Forums - The #1 TrailblazerSS Dedicated Owners Forum

 

[efi-diy]

Here is a picture of the atlas to SBC/LS bell housing pattern block adapter plate and Torque converter spacer installed on the back of a 4200 atlas. The I4/5 t/c spacer are a bit different. http://www.vortec4200.com/forum1/download/file.php?id=243

This install is getting a TH400 bolted up.