I have a 29' travel trailer and have towed it once were I parked it on the property I own. It is much heavier to tow than my Kubota 2500 4x4 tractor with backhoe. Trailer spec's: hitch weight 660lbs, trailer GVW 7660lbs, single axle electric brakes. I plan on taking the family on trips and need to make our truck tow ready. I have a 5.7L '99 GMC Suburban 1500 4x4. I would have gotten a turbo diesel if I know what I know now.... (long time DTR reader) Anyway don't know what the differential ratio is. Is there a way I can find out from the service parts identification sticker inside of the glove box? The owner manual says I have 3.42 or 3.73's.
I have a load leveler hitch, the kind with the tension bars to prevent the rear end from sagging low. I don’t think the stock rear sway bar is strong enough for the weight I will be towing. Anyone have suggestions for a heavy-duty sway bar?
The tires I have are Firestone Wilderness LE 265 70/R16, 2 steel sidewall 2 ply polyester, what ever that means. Are these tires good enough for heavy loads?
I was thinking about getting an oil cooler and a transmission cooler. Any suggestions here?

Thanks for the input..
Tom

 

Just to clarify, your trailer with the Kubota weighs 7,660 pounds?? And the TT is heavier than that?? I assume that means you don't know the weight of the TT??

The first thing I would do before anything else is check the GCWR for your Suburban and then weigh the whole rig when fully loaded with fuel and all of your gear. I could be wrong, but I think fully loaded and hooked up you'll be way over the GCWR. If that's the case, I'd come up with a Plan B.

I can't help you with the gearing in the rear, but in due time someone will come along that knows more about it than me. I hope it's the 3.73's and not the 3.42's though....

I wouldn't feel comfortable towing any kind of weight with Firestone Wilderness tires...especially when they're only 4 ply tires. In my opinion you need to upgrade to at least an 8 ply tire (D or better).

Assuming it's an auto an oil and transmission cooler would be a VERY good idea.

Hope that helps....and I'm sure someone will correct me if I'm wrong about something.

 

As far as the rear-end ratio, either the sticker in the glove box of one on the radiator cover under the hood should have it on there. If not, crawl under the vehicle and look on the rear diff, and somewhere on it it should have a number that your dealer can tell you what the ratio is.

As for tires, with the loads you're talking about, at LEAST load range D (the tire will say on the side what the load range is), and preferably E would be recommended. Usually, the ply rating will give you load range: 4-ply is load range B, 6 ply is C, 8 ply id D, etc.

As for pulling that load with that vehicle, do like Hoss says, wiegh everything on a local truck scale, and you will probably find yourself a good bit over your GCWR, as well as you rear axle being over its GAWR. Hope this helps.

 

In responce to Hoss the Kubota tractor and trailer weighs about 5000lbs together and the TT GVW is 7660lbs. Yes the truck has an auto transmission.

I figured I was going to need better tires. Thanks for comfirming this guys.. I guess I should be getting the coolers too. I will be looking under the hood and if I don't find it there I will have to look for the numbers on the differential. Thanks GrampasRam

I need some clarification on 2 items. I know what GVW means, Gross Vehicle Weight. But what does GCWR and GAWR mean?
Tom

 

In responce to Hoss the Kubota tractor and trailer weighs about 5000lbs together and the TT GVW is 7660lbs. Yes the truck has an auto transmission.

I figured I was going to need better tires. Thanks for comfirming this guys.. I guess I should be getting the coolers too. I will be looking under the hood and if I don't find it there I will have to look for the numbers on the differential. Thanks GrampasRam

I need some clarification on 2 items. I know what GVW means, Gross Vehicle Weight. But what does GCWR and GAWR mean?
Tom

 

GCWR- gross combined weight rating...truck and trailer
GAWR-gross axle weight rating

hth

 

You can also jack up the rearend, turn a tire exactly once around, and count how many times the driveshaft goes around. It might be kinda hard to tell since the two possible ratios are pretty close together. I will either go around 3 3/4 times for the 3.73, and a little less than 3.5 times for the 3.42

 

In the glove box there should be a RPO code sticker... Here are the two axle codes to look for...

3.42 - 10,000 GCWR RPO code "GU6" 1500 series only

3.73 - 11,000 GCWR RPO code "GT4" 15 and 25 series

Speaking from experience towing with my '96 Z71, here are my suggestions...

-Add a tranny temp gauge and another tranny cooler. Biggest cooler you can find. The 4L60E is going to be the glass jaw in this setup. A mild shift kit would be ideal.

-ALWAYS leave the tranny in drive or drop to a gear that suites the condition. Your motor can live with a few hundred more RPM and you can live with a few less MPH and MPG. Your tranny will thank you for it.

-The 10 bolt is going to be working, so synthetic is a must. An extra capacity or aluminum cover can help keep things cool too.

All of that being said... I've gone past 140k in that truck and wouldn't hesitate to hop in it and drive across the country and back... I regularly towed my rock crawler or 23 foot boat, both usually loaded with gas and gear. Original motor that doesn't burn a single drop, original tranny which has nice red fluid & still shifts firmly, and a rear end with a beautiful contact pattern... Good trucks, you just have take care of them and drive sensibly.

 

[quote author=erics76 link=board=11;threadid=17720;start=0#msg165904 date=1059590903]
You can also jack up the rearend, turn a tire exactly once around, and count how many times the driveshaft goes around. It might be kinda hard to tell since the two possible ratios are pretty close together. I will either go around 3 3/4 times for the 3.73, and a little less than 3.5 times for the 3.42
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The way you stated it will work if it is limited slip rear axle, if not then you have to turn one wheel a complete turn and then the other wheel a complete turn to get the count.