Rears, gears, etc....

Mike

Original poster
Member
Apr 8, 2012
42
More questions for the pros.....

I have a 2011 Suburban LTZ 4WD. It has the 6 speed tranny with the 3.42 rear. I tow a 6,000lb camper. My 2007 Suburban LTZ 4WD did a MUCH better job towing. The 2007 had 3.73 rear and 4 speed tranny. (i think it was a 4 speed). My gas mileage in the 2011 is worse than the 2007. The 2011 has less than 15k miles, whereas the 2007 had almost 90k. I ditched the 2007 in hopes that the 2011 would be a better pull. So far I am VERY disappointed. I've tossed around the idea of swapping gears, re-tuning, or both.

I'm just looking for some honest opinions and any help I can get. I've tried reading up at other chevy forums but you get such a mixed bag of answers and opinions. You guys were always right when answering my trailblazer questions, so I figured I'd pass this along to you guys as well.

I hope everyone is doing well! Thanks in advance for any help you have to offer!
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
Gear swap won't be cheap. Both from n rear gears n setups then finding a programmer for the computer.
 

glfredrick

Member
Jan 14, 2014
172
Gearing is the obvious choice. Simply stated, you are lugging the engine by towing with a 3.42 gearset in Overdrive. That may work out for fuel economy running empty, but with weight and wind resistance out back, you need to be solidly into the powerband of the engine.

It will be costly, but not out of reach. A set of gears should run somewhere in the $300 range (with a kit), and it will double or so your cost for installation. An alternative is to source a complete axle housing with the gears of your choice from a late model salvage and simply swap the entire unit. Might be good to swap the entire PCM also, but that may require re-setting the VIN number in the computer, etc.

An alternative is to run shorter tires,which effectively re-gears without all the hassles of changing parts. It is theoretically possible to run one set of tires in low profile for towing then swap back for regular driving having the best of all worlds.

The chart below calculates RPM versus tire size and axle gearing with a .70 OD transmission (typical of the 4L80E). This will at least let you know where you need to be with tire size, gearing, and engine rpm.

4447d1264289351-gear-ratios-gear_ratios.jpg
 

Mike

Original poster
Member
Apr 8, 2012
42
I'm cool with doing the gears. I know I'll need to match the rear and front differentials. I also know that the PCM will need to be reprogrammed. I dont put a price tag on 'piece of mind', which is what I dont have when towing my camper and my family. I have a 4+ hour tow coming in July. It's a relatively flat ground but even on flat terrain, my Burb struggles. Thanks for the responses thus far. I'll move on to my next questions.....

Does anyone have, or know of, any videos showing the gears being replaced? What gear would you recommend for optimum towing and optimum gas mileage? I have the 6 speed tranny and typically use 'Tow Mode' while towing. I dont want to do all the work for minimal results. If I'm going to do this, I want to make the best of it.

Again, thanks in advance!
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
You could try searching on YouTube. I've seen people on there take a rear end apart or put it back together, some explain it pretty well. Idk if there will be one of someone working on a burb but most rear ends have about the same inner-workings so you might be able to get a good idea on how to do it. Good luck!
 

Sparky

Member
Dec 4, 2011
12,927
A tune could also help with reducing the torque management which may help with the grunt desired.
 

Pittdawg

Member
Dec 5, 2011
538
Sparky said:
A tune could also help with reducing the torque management which may help with the grunt desired.
The new 6l80/6l90 is supposed to have better low end to due to more torque multiplication in 1st and the 5.3 doesn't lack for low end either so I suspect the torque management is a contributing factor. Go ahead and install 4.10s and when reprogramming have at least a good portion of the torque management reduced. BTW, your overdrive is .66 not .70 as referenced in the chart above meaning you should still have a damn good cruising rpm on the freeway with 4.10s.
 

Mike

Original poster
Member
Apr 8, 2012
42
Thanks for the responses. To be very specific, initial starts from a stop in 1st gear on level ground up to a slight incline aren't bad. Steeper inclines are tougher, as to be expected. If I'm cruising at 65 and have to slow down to 30, then want to get back to 65, the motor spends the next few minutes SCREAMING. I'm in the 4k RPM range most of the time. And to be honest, even while NOT towing, the get-up-n-go, isn't that impressive. I was expecting MUCH better results with this truck.

As far as tuning, is this something the dealer would do, or will I need to find a performance shop to do it?
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
A lot of people use PCMofNC to tune their pcm's. they do some kind of loaner deal too where that they mail you a loaner pcm then you swap it with yours and mail yours back to them. This way if the car is your daily driver you can still use it for that purpose while it's getting tuned. You don't have to do it that way though if you can stand being out a vehicle until they get done.
 

glfredrick

Member
Jan 14, 2014
172
Here are a couple of helpful videos:

Summit Auto Parts -- How to select a proper gearset

http://www.youtube.com/watch?v=81H0BwLymSg

Chevy limited slip explained

http://www.youtube.com/watch?v=MCxqUJCZGNU


"At home" gear change (this is not a slick professional video, but it is an accurate view of how one would change gears at home!)

http://www.youtube.com/watch?v=jh25DUyCWY8

Changing Chevy rear gears (another "at home" sort of video)

http://www.youtube.com/watch?v=LObfebayp6Y

Professional explanation

http://www.youtube.com/watch?v=nVb5WRUfM7Y
http://www.youtube.com/watch?v=dAqAqODmcj4
http://www.youtube.com/watch?v=zV-1-cGhNnQ
 

Forum Statistics

Threads
23,273
Posts
637,499
Members
18,472
Latest member
MissCrutcher

Members Online