6L90 refresh/rebuild?
 

Installing a 6L90 soon. Trans has just over 50k on it and came out of a running ZL1 Camaro. Wish I could just run it as is but have to do a tear down to change the output shaft for the t-case adapter. So the question is if clutches etc look good should I leave it be. Considering a couple of "upgrades" such as a 4/5/6 boost valve and apply piston. Will be my first 6 speed tear down, have done a th350, 4L60e and a 4L80e. Can not be that different, right?

Re: 6L90 refresh/rebuild?
 

You have some really big snap ring pliers?

Re: 6L90 refresh/rebuild?
 

Suggest you do a lot of research on this one before you commit...

Below you will find the ratio differences between a 6L80 and 4L80

Along with some other thoughts....

6L80/90 boxes are a totally different animal build wise from a 4L80 style...

6L80/90

Note...Notice no 1:1 in this trans
4.03
2.36 -- 58.56% (high) RPM Retention 41.44% RPM DROP
1.53 -- 64.83% (high) RPM Retention 35.17% RPM DROP
1.15 -- 75.16% (high) RPM Retention 24.84% RPM DROP
0.852 -- 74.09% (high) RPM Retention 25.91% RPM DROP
0.67/.70

4l80/85
2.48
1.48 -- 59.68% (high) RPM Retention 40.32% RPM DROP
1.00 -- 67.57% (high) RPM Retention 32.43% RPM DROP
0.75

Hope that you know that 6L's will not work with LS1 based engine.

If your going to put LS2 in front of it check with Mast Motorsports or others and make sure their ECM will work with it.

Mast Motorsports are the only one I know of that claims to have LS 2 ECM that will work with it.

Only GM's LS3/7 or 9 ECM work with it.

:chevy::chevy::chevy:

Re: 6L90 refresh/rebuild?
 

These should work

Re: 6L90 refresh/rebuild?
 

Thanks for the suggestions, none of the things you mentioned should be a problem. Trans is being swapped with the LSA it was originally behind along with the ECM that was in the same car. TCM already matched to ECM should not have to reprogram anything. Just disable vats, focus on tune and shift points. Not sure why people bring up the no true 1:1. It does not really matter, 1:1 or 1:15 is just another gear as far as overdrive trans are concerned. Gear spacing is better with the 6L over 4L especially at the top end. The low 1st gear will be good to get my large tires moving. With the 5.38 gearing I will be running am going to have a final drive ratio a bit lower than the stock vehicle had. Right where I want it.
So..... I have heard these transmissions are pretty reliable. Do not really want to go full aftermarket on the innards. Should I do a full rebuild?

Re: 6L90 refresh/rebuild?
 

The huge center support snap ring is the biggest hurdle......Though the snap ring CAN be walked out & back in with a modified flat blade screwdriver, It's best to use the correct pliers.....Those will probably work.

Oversize Clutch Boost Valves require Tooling & a Fixture to install. I wouldn't be surprised if you found some distressed frictions & wouldn't be a bad idea to refresh the unit.

Re: 6L90 refresh/rebuild?
 

Thanks for the input. Not sure I want to spend the extra money on the fixture for the valve. Kind of wanted to avoid changing all the clutches as they seem to be more spendy for this trans as apposed to others. I know what the smart thing to do is though. Not sure about the Sonnax "zip kit" if it is something I should install.

Re: 6L90 refresh/rebuild?
 

Your exactly right, no 1:1 isn’t a big deal at all. I hate the 4l80E in my 1998 K2500. My last couple company trucks have all had 6L90’s and they are a far better tranny in my opinion. The huge spacing in between the gears in the 4l80 always has you with either too much gear or not enough, especially with bigger tires. The 6l90 always seems to be able to keep the the engine in the power band. I’d still be interested in those 6l90 Camaro parts when you get to that point Richard. I’ve put over 250,000 miles across 2 different 6l90’s and have never had so much as a weak shift. It’s a strong unit, and I believe you will like it a lot.

Re: 6L90 refresh/rebuild?
 

At that low mileage.....You won't need a Zip Kit. You can easily inspect the frictions when you tear it down for the output shaft change.

Re: 6L90 refresh/rebuild?
 

Have a 4L80e in my 2000 C2500 work truck (OBS) Not really happy with it. Always going in and out or overdrive. Shifting horribly now, actually stalling the engine in reverse. Purchased from from my old boss and have to do a tear down to correct the rebuild from a local transmission shop. Took a crap after only 6000 miles warranty was 5000. They will not warranty it.
I generally hang on to to everything I have until it is up and running. Have not forgotten about you.

Re: 6L90 refresh/rebuild?
 

Thanks for your recommendations!

Re: 6L90 refresh/rebuild?
 

I know what your mean, my K2500 is starting to stall in reverse too. It still shifts good. I guess I can’t complain too much as it has 200,000+ on it and I know for sure it’s the original transmisson. 100,000 of those have been pushing 35’s around with stock 3:73 gears. That said the 6l90 performance is superior in every way.