What is my max towing weight and gvwr?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

88GMCtruck

I'm all 8-Luggy!
Joined
Apr 14, 2010
Messages
4,804
Reaction score
1,322
Location
Auburn, Wa: From Covington, Wa: Albion, Wa: Pullma
Am I not closer to a 4.10 then 3.73 ?
You are somewhat in a middle ground, being a K2500 your truck likely came with 245/75R16 from the factory - It could have been optioned with 265/75R16. In either case, your current tire size and gear ratio puts you between 3.73s and 4.10s with a 245/75R16 tires size, the same as 4.10s with 265/75R16 or lower than 3.73s with 265/75R16.

In any case, if you use the 350/4.10 gear chart instead, you'll be able to haul a 7,500 LB trailer and it'll put you at 13,500 LBS But keep in mind that your truck is heavier than a stock truck and is going to eat into that quite a bit, from a technical standpoint.

I towed a 19' Nomad with my 88 GMC. It was a regular cab stepside with 315/75R16 tires, a 14SF with 4.56 gears, 350 powered and a NV4500. It wasn't bad with a NV4500, the 700R4 has almost identical gear ratios sans the low first gear. Honestly the 350 moved it OK but wasn't great - keep in mind your truck is heavier than mine. At that time I had an actual GCW of around 10k, the trailer itself was something like 4,000 LBS or so.

What type/size trailer are you looking at?
 

Jacob

Newbie
Joined
Jan 9, 2016
Messages
42
Reaction score
7
Location
Ottumwa Iowa
Probably because your truck was made in 1990 before the internet was really a thing. I'm reading through the GM documentation from 1990 for the C/K truck and the information above was all it showed. Keep in mind that your K2500 is the 6-lug 14SF version, which in later years the 6-lug trucks with the 14SF were labeled as a 1500 and only rated to 6,800 LBS while the 8-lug 14SF trucks were labeled 2500 and were rated to 7,200 LBS just as yours is. 14FF trucks were rated at 8,600 LBS in 2500 form.

Here are the pages from 1990:
You must be registered for see images attach

You must be registered for see images attach


Your truck is 7,200 GVWR (Gross Vehicle Weight Rating). GVWR is the weight of the vehicle and everything on it. So the truck, you, fuel, gear in the bed, anything you've added (lift) and the tongue weight of the trailer you tow. The actual weight of the trailer is limited by your hitch, ball mount and the trucks actual GCWR (Gross Combined Weight Rating), which is not listed in 1990. GCWR is the actual weight of your truck, plus the trailer.

If we look at the 1998 trailering chart for a K2500 with 7,200 GVWR. You have 4.56 gears, with 35" tires, compared to a stock truck you are closest to a 3.73 gear ratio. A 350 powered K2500 4L60E auto truck with 3.73s can tow 6,000 LBS, and 750 LBS tongue weight.

Your GCWR is more of a function of the engine and gear ratio, since it's pulled weight. In your case, a 350 with 3.73 gears and an automatic can handle a GCWR of 12,000 LBS. Basically what this means, is your truck can be 7,200 LBS total, trailer can be 6,000 LBS total, but the combination cannot exceed 12,000 LBS. So if your truck was 6,000 LBS loaded and so was the trailer, you are golden.

Here is the page for trailering from 1998. This should be almost identical to a 1990, these trucks stayed largely the same.
You must be registered for see images attach

You must be registered for see images attach

They did use the 14sf 350 combo on 8600 gvwr vehicles. That is what my suburban is.
 

lucky67bsa

Newbie
Joined
May 13, 2015
Messages
15
Reaction score
3
So I've read through this and I'm still not sure what to do. I have a 3/4 ton 8600gvw. It has a 350tbi and a nv4500 5 speed. It has 3.42 gears now but I found 4.10 diffs. People keep telling me know to change them but when I pull my friends gooseneck I feel like I need the lower gear. I'm planing to buy my own 16 ft gn dump trailer and get a bobcat to start doing dirt work. Any suggestions. Sorry to intrude on the thread
 

lucky67bsa

Newbie
Joined
May 13, 2015
Messages
15
Reaction score
3
I forgot to mention my truck is stock height and 265/75/16 tires. People have told me it's not worth changing them
 

Supercharged111

Truly Awesome
Joined
Aug 20, 2015
Messages
12,616
Reaction score
15,243
TBI runs out of breath quick. You might try it both ways and see what you like best. I had 3.73 in my 88 C1500 with 235/75/15 and I felt like the stock 3.42 would have made it happier. Wasn't enough gear to pull what U pulled in OD and my current truck would do it with ease.
 
Top