1

I'm going to be doing a bit of heavy towing with my truck. Up to and sometimes over its rated weights (approx 7000lbs). What can I do to add the necessary power and transmission performance that I'm going to need?

closed as too broad by chilljeet, Rory Alsop, Nick C, DucatiKiller, Bob Cross May 15 '15 at 0:07

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • @RoryAlsop - 7000lbs is only 3.5tons. The Avalanche has a towing capacity of 7000lbs. The OP is suggesting going over that at some point, by some unknown amount. – Pᴀᴜʟsᴛᴇʀ2 May 13 '15 at 11:00
  • @RoryAlsop - The truck itself weighs right in that same arena. I'm looking up some other stuff which will definitely be an issue. – Pᴀᴜʟsᴛᴇʀ2 May 13 '15 at 11:07
  • @Paulster2 Gross or curb weight? My 2004 Suburban 1500 which is virtually the same vehicle has a curb weight of 5300 lb. I don't usually tow full up on passengers and cargo, so the latter is probably more accurate than the GVWR. – dodgethesteamroller May 18 '15 at 22:14
  • @dodgethesteamroller - According to Edmunds.com, the gross weight for a 2004 Suburban is 7000lbs. I used to own a 2004 'Burban Z71 myself. Great truck/ride. – Pᴀᴜʟsᴛᴇʀ2 May 18 '15 at 22:22
  • @Paulster2 I know what the gross weight of the truck is. But to figure out your "everyday" weight or what the truck will weigh as a tow vehicle, manufacturer-quoted curb weight is more relevant than the GVWR, unless you plan to drive around with four people and a bed full of cargo all day long. – dodgethesteamroller May 18 '15 at 22:47
2

tl dr - Upgrade to a 2500 or 2500HD pick-up.

There are several issues you'll notice when hauling at the maximum and over the maximum of the towing capacity of the Avalanche.

First off, the 2007 & 2008 MYs came with the 4L60e transmission. Why GM ever put these in a pickup truck is beside me. These were meant to go into passenger cars. While they are supposedly supposed to be able to handle 400 lb ft of torque, when you throw them with a huge load, they tend to fail rapidly. The only cure for this is to get a 3/4 ton pick-up with the 4L85e which can handle the heavy loads. This doesn't mean the 4L60e will expire on the first load, it just means it will fail a lot faster with consistent towing. Starting in 2009, the Avalanche came with the 6L80e, which could also handle the loads. The only alternative is to actually modify your truck with the a 4L85/90e or 6L80e transmission. GM finally decided the 4L60e wasn't going to cut it for their pick-ups (after a lot of customer complaints), so put the beefier transmissions in the rigs to support towing a lot better. Please note, if your Avalanche is a 4wd vehicle, this adds a whole other complexity to getting this done.

If the vehicle is going to be pulling any hills, the 5.3L engine will just not have enough torque. You will be lugging up the hills in 2nd gear driving at 35mph. This can be overcome by putting a larger engine (6.0L or newer 6.2L), which will have a better torque curve and plenty of power. There are also head/cam packages which could be added to your 5.3L, but it costs money either way. Another option is to put a supercharger on the stock 5.3L. As long as you don't go crazy, you can boost your engine without too much of an issue, but the life expectancy of the engine will go down, so be prepared. Don't forget you'll need to have the engine control module tuned for the specific setup as well.

You would also need to ensure the rear differential is at least a 4.11:1 ratio drive. If you have the 3.73:1 or (heaven forbid) 3.42:1 ratios, your in for some mighty arduous towing. Again, if this is a 4wd model, you'll have to do work on the front end as well as the back end for the gear change.

The last thing you need to worry about is to ensure you can actually stop the vehicle and the trailer. This is one of the areas most overlooked. One of the issues is, if what you're towing exceeds the weight of the vehicle towing it, stopping becomes an issue. You'd need to ensure there are excellent trailer brakes and a trailer brake controller installed in your vehicle. This will help control the vehicle and trailer, but depending on the load would still be worrisome.

All-in-all, this might seem doable. With all of the upgrades, you are still looking at dropping a ton of money into a vehicle when in reality you'd be better off just getting a more robust vehicle to do the job. The upgrades I've laid out here are not exhaustive, just what I've come up with off the top of my head. If you are not able to do the work yourself, it's going to cost some money to make it happen. IMHO, if you want to do this, you should trade your pick-up in on a 3/4 ton truck or maybe even a 1 ton. Your pocketbook will thank you with greater safety of yourself, your passengers, and cargo.

Not the answer you're looking for? Browse other questions tagged or ask your own question.