m83

Hi guys,

I need to pull a 7400# RV cross country (1-time trip) with 2012 Suburban 1500 RWD, with 5.3L V8 and 6-speed transmission. I plan to install a transmission cooler (Hayden Automotive 679), but am wondering whether I also need to install the engine oil cooler and 3.42 differential gear that come standard on the HD version of this vehicle. (Other than these 3 items, I believe my suburban and the HD version that has 8100lb tow capacity are exactly the same).

I read through a lot of messages on this forum, but most people seem to be speaking from theoretical standpoint; did anyone actually try pulling over 5000# on a 3.08 Suburban?

Thank you!

falconbrother

I pull a travel trailer, 5800 dry, 6500-ish loaded. My burb is a 2000 model, new-ish 5.3, 4L60e transmission. I bought a transmission cooler but, I decided not to install it, yet. The factory tow package seems to do really well. I seriously doubt that you need an oil cooler. Make sure that your total weights are below your max. 7400 dry means 8000 or more loaded. I believe that your drive train can handle it. I would suggest that you consider some Sumo Supersprings to replace those rear bumpers over your rear axle. They really make a huge difference in my burb. You're looking at a maxed out receiver weight is my guess. On my transmission I have learned to take charge of what gear it's in when pulling inclines and hills. The LS engines don't mind RPMs and the 5.3 isn't a low end torque monster. It makes it's power in the mid and upper RPM ranges. On a steep climb I pull mine down into 2nd (4L60e) and let the RPMs hover around 3000-3500 (+ - 55 MPH). It will pull 6500 very easy in that range and doesn't get hot. What you don't want is lugging and to have the transmission hunting for gears. The hunting and converter slipping is what creates a lot of heat. Once torque converter lockup happens the transmission will stabilize in temps.

7400 dry does seem like a lot of trailer weight. And, if you're hauling people and luggage and such you may be over the weight limit of your burb.

intheburbs

If you look at the Trailer Life Towing Guide, according to the 2012 model year guide, the 3.08 puts you at a limit of 5,100 lbs. The 3.42 only gets you to 5600, but having the cooling package gets you to 8100.

Regearing and adding cooling is a lot of expense for a one-time trip.

How much time do you have to make the trip?

I towed a 7,000-lb trailer with my '01 half-ton Suburban all over the country, including the Rockies. If it was me, with a one-time deal, I'd do it with my truck as-is, and just take it slow. 55-60 MPH max, with frequent stops every few hours to let things cool down. I'd buy a digital infrared/laser thermometer for $20 and frequently pull over to check the temperature of my rear axle, which is the weakest link and most stressed-out component. Heat kills things - I'd do it when temperatures are low, and if I had to do it in the summer, I'd drive at night and sleep during the day.

I'd also stop at a CAT scales to check my weights, and I'd have no passengers or gear, either in the truck or in the trailer. Even then, you'll still be very close to your Rear Axle Weight Rating.

in2pro

I believe the IR gun is a great idea for any towing, I keep one in the truck to check the trailer hub temps.

m83

Thank you guys!

I already bought a transmission cooler, and will be installing it (guessing a 2 hour job). I also bought a 3.42 rear gear, but not sure if I will be installing it or returning it (would have to take to a shop for this one).

I will be towing during the winter (within next month), and plan to tow for 3 days, 10 hours a day.

Sounds like an engine oil cooler may not be worth it, right? From what I read, they can be a pain to install on these cars.

m83

Forgot to mention that both car and trailer will be empty (except for appliances in the RV). Only the driver in the Suburban.

intheburbs

One last thing - don't be afraid to let the engine rev. Tow in fourth if you have to. You don't want the transmission constantly hunting gears. And in that context, the transmission cooler will help, because the trans pump is connected to the input shaft, so it turns the same speed as the engine. Faster engine speed means more pump speed, and when climbing steep grades, more heat.

Here's the worst I did towing in the Rockies last summer:

m83

Thank you again. Sounds like it should be OK to leave the oil cooler out and only install transmission cooler.

What's the cheapest option to re-calibrate the speedometer after swapping the diff gear - if I decide to go that route?

m83

I talked to a mechanic who works with differentials, and he said it's not worth it to change the gearing. I will need to break-in the new gear for about 1000 miles before I can safely tow with it (which is not an option for me for logistical reasons), and the quality of the aftermarket gear is likely worse than the stock one that's currently on the truck. So for now the plan is to only install the transmission cooler.

intheburbs

A new rear diff cover with cooling fins would also be a good idea. Again, if it was me, I'd be a lot more worried about the rear axle than the transmission.

Something like THIS.