6L90 refresh/rebuild?

[Richard]

Originally Posted by AussieinNC

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.

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?

[57taskforce]

Originally Posted by Richard

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?

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.

[Richard]

Originally Posted by 57taskforce

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.

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.

[57taskforce]

Originally Posted by Richard

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.

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.