• June 19, 2020 - We've been making good progress moving into the new forums. Still much to be done. Thank you for your patience and understanding through this process.

Highway tow rig setup

Sabertooth^2

New Member
Hey guys. I recently took ownership of my dad's 2005 Avalanche Z71. It's at 199,000km, and runs great, aside from being a pig on gas. I just had to change all the brakes on it, have to fix a transfer case leak and rear main seal leak, but then other than rust under the paint, it'll be in great shape.

I'm looking to use this as a tow rig for highway use, and don't have much a need for any offroad ability. It's going to be pulling my racecar around.

What gets me about the truck is both the fuel economy, and the suspension feeling. It's definitely not optimized for cruising down the highway at speed, and I'm sure a lower setup would help with that. But what is there on the market that will work to lower it, as well as still be good for towing?

Also, how are these with O2 spacers should I want to make some test pipes to see if the cats are what's causing it to run at 16.5L/100 highway cruise (was around 9 when new). I'd rather not live with a check engine light until it's reflashed out, which I'm not looking to do immediately
 

ygmn

Staff member
Administrator
Moderator
Charter Member
PM 2020
PM 2019
PM 2018
PM 2017
PM 2016
PM 2015
PM 2014
PM 2013
PM 2012
SM 2011
SM 2010
SM 2009
SM 2008
SM 2007
SM 2006
SM 2005
SM 2004
SM 2003
Full Member
Ahhhh these things ride great and if yours does not maybe you need some suspension work or someone change what was stock.
Suggest going to our PROBLEMS DRIVETRAIN section to start thread and get feedback from others


If you are not getting 18 or more MPG driving normal o highway then well you should start with tune up and ensure no Check engine light.
There are proper tests for cats going bad first off you would have check engine lights.
If you have check engine light then get codes read and go to our PROBLEMS ENGINE section for help resolving issues.
 

Sabertooth^2

New Member
It did 26mpg new, now it does 14mpg. It runs great, no CEL, but is a gas hog. That's why I was asking about O2 spacers with a decat

As for driving, I'm used to sports cars. Trucks aren't much my thing, the suspension geometry feels all wrong to me. The roll center is what gets me most, so that's why I figure lowering it would be a nice go for driving, similar to what Chevy did for the street package ones. However, I still need to retain the ability to tow 5000lbs comfortably
 

ygmn

Staff member
Administrator
Moderator
Charter Member
PM 2020
PM 2019
PM 2018
PM 2017
PM 2016
PM 2015
PM 2014
PM 2013
PM 2012
SM 2011
SM 2010
SM 2009
SM 2008
SM 2007
SM 2006
SM 2005
SM 2004
SM 2003
Full Member
26 new?

OMG
never heard of anyone getting that unless instant MPG reading coasting downhill.

Most 2005 got the 18-19 mpg overall.
Maybe peak at 20mpg on highway
11-12 city

You 14mpg could be right foot releate which is where these engines suck fuel.

Ah trucks are different then cars
have a real frame with huge HEAVY body bolted on top.
Torsion bars up front
5 link in rear is better then most..
It will never feel like a car and the CG is above most car roof lines so yeah might feel a bit top heavy...
nature of the beast.

but if you haul 5000# leave it alone is best advice.
 

EXT4ME

PM 2020
PM 2019
PM 2018
PM 2017
PM 2016
PM 2015
PM 2014
PM 2013
PM 2012
Full Member
These trucks have never been known for getting good gas mileage.

I'm thinking 26 MPG would be some kind of record.

The lifetime average MPG on both of my trucks is around 14.2.

The only way I could get close to 26 MPG on either of my trucks would be if that truck was being towed by the other.

And I can assure you the truck doing the towing would more than make up for that.
 

Sabertooth^2

New Member
These are average figures from highway driving I'm worried about most. I reset the reading when on the highway, and see what it is when leaving the highway. It's not right foot related, as I test it with cruise control on, on some really flat ground

The truck spent most of its life doing 1km trips cold, so I would have a very hard time believing that the cats aren't plugged. I'm generally quite good at this sort of thing, and at 80mph my daily (Audi TT) runs at 50mpg compared to the 28mpg it's rated for, and 26mpg it did when I got it. I'm just unfamiliar with the platform and was hoping someone here had some experience with raising fuel economy and handling, while still being able to tow. I get that these trucks aren't fast either, but suspect they shouldn't be as slow as mine is. 0-60 seems to be in the 8-9 second range at an estimate, so that adds on to the bad cat suspicion. Hell, if someone had the operating temperature these cats are supposed to run at even, I could check that.


So, does anyone know if these ECU respond well to O2 spacers? Open loop testing isn't really what I want to be comparing to when the test pipes go on. And does anyone know of any lower setup that is good for towing still?

It's starting to seem like decat, aftermarket trans cooler, and slap a medium turbo on it with 6psi is the way to go. But I'd rather not do a standalone, so it'll be down to how these ECU run. But I'll read into that elsewhere and see if I can figure it out
 

ygmn

Staff member
Administrator
Moderator
Charter Member
PM 2020
PM 2019
PM 2018
PM 2017
PM 2016
PM 2015
PM 2014
PM 2013
PM 2012
SM 2011
SM 2010
SM 2009
SM 2008
SM 2007
SM 2006
SM 2005
SM 2004
SM 2003
Full Member
Maybe you should go and explore our PERFORMANCE section....

there many have modded the engine for more power
In mods custom are threads where people have lowered the truck - most seem to do it for looks.

Way more info in those section on what you are looking for then in this towing one.
 
Top