6L80 in 1998 Tahoe

[phlorentz]

Has anyone put a 6l80 transmission in an older Tahoe to get better fuel mileage?

 

[kbuskill]

You need to check the gear ratios of the 6 speed.. I don't think this will accomplish what you are wanting and certainly not in a cost effective manner... by the time the conversion is done you would wear the truck out before you saw any return on your investment due to fuel mileage gains.

If you are 2wd then a rear gear ratio swap would provide better fuel mileage gains for MUCH less money, where you intend to do most of your driving would determine whether you go with taller (numerically lower) or shorter (numerically higher) gears.

In all honesty though your right foot (read acceleration) plays the biggest role in fuel mileage followed by your need for speed (read higher speed, not acceleration) and several other factors like tire pressure and size, unsprung weight, vehicle maintenance like plugs and wires, air filter and oil changes and idle time and some might even argue octane rating.

Driving style is the biggest.

Perhaps check in with Black Bear Performance for a fuel mileage tune.

I know this probably wasn't the answer you were looking for BUT I hope it helps you to make an informed decision.

All of this is just my 2 cents and YMMV.. Pun intended... lol

 

[swathdiver]

Not sure. It has its own computer that cannot talk or interact with the models older than the Gen IV engine and GMT900s. Such would be an obstacle to getting it to work in one.

 

[swathdiver]

Right Ken, my wife drives my truck and I get it back empty and the avg down in the 8s! When I drive its at least 2 mpg higher! She says its too much fun not to get on it.

 

[kbuskill]

Not sure. It has its own computer that cannot talk or interact with the models older than the Gen IV engine and GMT900s. Such would be an obstacle to getting it to work in one.

This is obviously another obstacle but I assumed the OP may have done enough research to know this already.... there are stand alone computers available for these as it is becoming more of a popular swap in the hotrod scene with all the LS swaps.

The weak points of the 6l80, to my knowledge, are the torque converter and the TCM inside the trans.

 

[swathdiver]

What's wrong with the converter? I read that guys are putting in the ZL1/CTS-V converter in their trucks for more stall speed and same heavy construction compared with the aftermarket.

 

[kbuskill]

What's wrong with the converter? I read that guys are putting in the ZL1/CTS-V converter in their trucks for more stall speed and same heavy construction compared with the aftermarket.

Perhaps I misspoke... what I was meaning is... when my brothers 6l80 in his 2012 Silverado went south, my buddy at the transmission shop said the only thing they ever see wrong with these transmissions is either the converter or the TCM.... when they pulled my brothers and disassembled it they couldn't find anything internally.... clutches, steels, gears, hard parts etc... wrong with it.... my brother opted to go with a reman unit from LKQ anyway because the warranty was much better and nation wide and for the price it was a no brainer as my brother travels heavily for work.

Any way that is what I was implying... not that they have an issue per say but if there is an issue it is most likely one of those two.