Tow Capacity 98 Gmc Suburban

wmwtn · August 16, 2011

Apologies in advance for asking another tow capacity question, but I know some of you guys are on top of this and I'm not.

I'm thinking my '98 GMC 5.7L 4wd 1500 Suburban is rated somewhere around 5,000 lbs towing but I'm not positive. Here is what it is:

1998 GMC Suburban 1500 SLT, 4x4 (push button transfer case), 5.7L, automatic, 3.42 gears, with factory tow pkg and factory trans cooler. Looking under the truck the rear springs look like what we (I'm old) used to call a "heavy half" set of springs, slightly smaller than a standard 3/4 ton but considerably bigger than a standard half ton. The vehicle does have a trailer brake controller (not from the factory but added later).

I've been pulling lighter loads for several years but now I'm wondering if I should risk hauling my Massey 231S tractor (4,200 lbs) + bush hog (640 lbs). When I add the weight of the 16 ft trailer, I'm guessing I'm probably right around 5,300'ish pounds. I'm in Middle Tennessee so the rig will need to go up and down several big hills. It will get to come down the other side of each hill but it will need to make it up the up side. It will need to be towed an hour or so for each trip if I decide to try it.

I don't want to blow up the old Suburban (about 140k miles on original transmission), so I thought I'd ask the experts. What do you think ? Haul it or pay a hauler ?

Thanks

wavery · August 16, 2011

If the vehicle is well maintained and the trans fluid changed at regular intervals, you should be OK. I would recommend changing over to synthetic ATF. It cools better and it doesn't burn like petrol ATF. Be sure to get the fluid out of the converter.

Your biggest concern might be tongue weight. I'm thinkin' you'll probably be closer to 6K# + whatever you haul in the Burb.

You'll want to keep the tongue weight 600#+ (to avoid sway). You need to find out what the max tongue weight is for that vehicle. I hope the trailer has brakes.

wmwtn · August 17, 2011

I think the tongue weight will be ok. The trailer is a tandem axle with brakes on one axle. The tractor balances on it pretty well and has been hauled on this trailer some years ago when I had an older truck with manual 4 speed. I sure do miss that old truck but my wife couldn't drive the manual.

I'm more concerned with the auto transmission in the Burb. I used to watch that old truck heat up going up the hills and then cool right down again on the way down the hills. But that was just the engine. Just not so sure if the auto tranny would just heat up and cool down again or if it or the converter might go boom...

wavery · August 17, 2011

The transmission temp will pretty well mimic the engine temp. Your best defense is a BIG trans cooler with a pusher fan and run synthetic ATF. 140K is pretty border-line for towing unless the trans has been exceptionally well cared for. If the trans fluid has ever been over-heated (Smelled burnt), I would pick a different vehicle.

Can you post a pic of your trans cooler?

I think the tongue weight will be ok. The trailer is a tandem axle with brakes on one axle. The tractor balances on it pretty well and has been hauled on this trailer some years ago when I had an older truck with manual 4 speed. I sure do miss that old truck but my wife couldn't drive the manual.

I'm more concerned with the auto transmission in the Burb. I used to watch that old truck heat up going up the hills and then cool right down again on the way down the hills. But that was just the engine. Just not so sure if the auto tranny would just heat up and cool down again or if it or the converter might go boom...

wmwtn · August 17, 2011

The trans fluid is standard, not synthetic. I don't think the trans has ever been overheated. No signs of burnt fluid and we've changed the fluid and filter since we've had it. We got it used with about 85k on it, and one thing that impressed me about the vehicle for my infrequent towing needs was that even though it had the factory heavy duty tow pkg, it had never been used for towing when we got it. The factory 7-wire harness was still laying right where the factory put it. It had never been hooked up. So all the miles are non-towing miles except for the few light loads I've used it with.

I'll measure the trans cooler. It is the factory cooler.

wavery · August 18, 2011

A pusher fan on the trans cooler helps a lot. It'll even help lower your engine temp:

The trans fluid is standard, not synthetic. I don't think the trans has ever been overheated. No signs of burnt fluid and we've changed the fluid and filter since we've had it. We got it used with about 85k on it, and one thing that impressed me about the vehicle for my infrequent towing needs was that even though it had the factory heavy duty tow pkg, it had never been used for towing when we got it. The factory 7-wire harness was still laying right where the factory put it. It had never been hooked up. So all the miles are non-towing miles except for the few light loads I've used it with.

I'll measure the trans cooler. It is the factory cooler.