[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?