Hi Everyone, I have a 1989 Ford F150, regular cab, short box, 302 V8, 5speed ZF-S5-420 manual swap, 4x4 with 33x12.5 inch tires and a 3.55 rear end. I have also installed a high capacity all aluminum 3inch radiator and Super Springs on the rear leaf springs. I have a bumper hitch but not sure what class it is. I just bought some land on a ridge in the mountains of East Tennessee and I need to buy a braked trailer to haul cut trees, building materials and construction/land clearing equipment. My question is how much can my truck tow? My truck is so old and it is hard to find anything online. I was thinking about getting an 18 foot braked flatbed trailer but I would like to know how much weight I can tow with a braked trailer up and down the mountains of East Tennessee.

Lastly to increase towing capacity what can I do short of buying a bigger truck to upgrade my own truck? Do I need to try and increase the horsepower and torque of my engine or upgrade suspension, axles, rear end, hitch or brakes?

Cheers,
Alex

 

Nothing you do will change the GVWR sticker that the truck came with. That's just a fact of life. Sure, you can change components to make yourself feel better about what the truck can handle, but it doesn't change the sticker. On the very off chance that you get stopped, the officer would likely look at your axle ratings and your tire ratings. If you're over either of those then you're over and a ticket may be issued. The GVWR and the payload capacity are made up of a number of components: tires, wheels, leaf springs, leaf spring brackets, brakes and frame.

I couldn't find a towing guide that goes back as far a your model year, but check out the ratings way down the page of the link below:

https://letstowthat.com/ford-f-150-towing-capacities/

 

Hi Jim, thanks for the reply. My GVWR sticker on the door says 6100lbs so does that mean, I can tow a 6100lbs braked trailer with my truck? I don't know what my payload capacity is but I have put a little over 3,000lbs in the bed before no problem but it would be nice to know what my truck is rated for.

Also I checked the link you posted for a 1996 truck and the manual trucks have a tow rating that's almost half of an automatic. Why is that? In 1996 were the manual transmissions really weak? I put a heavy duty ZF S5-42 in mine from an F250 so the transmission shouldn't limit what I can tow.

Cheers,
Alex

 

GVWR is the most that the truck should weigh, including any payload. If you loaded up a pallet of concrete in the bed, the total weight on both axles should not exceed the GVWR.

I doubt that your payload is much more than 1500 lbs. The half ton trucks of that era didn't have much payload. My '07 Nissan Titan was around 1400 lbs, if that.

I don't know why the manual transmissions are rated so much lower than the automatics. I do know that the automatics are very efficient compared to those produced decades ago.

 

Take a read through this

https://www.qtacfire.com/blog/vehicl...t-do-they-mean

For trailer towing, for the truck you are mostly concerned about the gcwr and then the gawr for the rear of the pickup.

I will take a look and see if I can find some charts for you.

1980s pickup trucks are not at all like new pickup trucks for towing.

There was drastic improvement between 1995 amd 2005 and even more improvement since then.

I regularly run 40,000 pound gross weight on F550s now, that was unheard of even 10 years ago.

 

That is supposedly from a 1988 ford, best I could find on the internet (gcwr should be listed in your manual if you got one - I figured mine out on a 1985 by calling a dealership with the vin).

 

So for 7800 gcwr, you probably have a 5000 pound pickup you'd be good for a 2800 pound trailer.

You can weigh your truck to get a better curb weight (go to a cat scale) and find a better gcwr (call a dealership with a nice parts man that might have the manual, I had a buddy that used to work at a Ford dealer that found mine for me on a truck I used to have)

Good luck

 

Oh, hitches go by class. Need to check that too.

Look up the class of the hitch (your rear bumper) and then see how much that class can tow.

Also have to have the right ball.

But it all starts with the gcwr, then go from there.

 

I can confirm the above, for this vintage F150 the tow ratings were found in the owners manual and the cargo capacity is calculated by subtracing the current curb weight from the GVWR found on the drivers door pillar. I have a '90 manual that states that the max trailer weight for this truck was about 3k, but to add insult to injury you have effectively derated you truck even further with those oversize tures. The autos were rated for about double that but in reality that much weight is well beyond what these old things should tow, the brakes are too small, frame is too weak, the motor is WAY underpowered, and the transmissions were fragile. For what you are doing and where you are doing it you should have a 1-ton diesel, you may not understand why now but the first time you blow out your brakes coming down a hill towing a load or struggle to climb hills in anything but 2nd gear you will start to understand.

 

I tend to agree with everything above. The biggest issue I see here is the oversize tires combined with the 3.55:1 rear end. Everything between the transmission and the rims will be stressed climbing up and down hills with a trailer, let alone with trees on the trailer. 4x4 low range will make it easier on the clutch and engine, but those are the two parts of this platform that I'm least worried about.

 

I am confused, my truck's door tag states I have a GVWR of 6100lbs, given that my truck is approximately 4,000lbs so my truck is supposed to be able to carry 2,100lbs in the bed with nothing but the brakes on the truck. I find it hard to believe that my truck can only tow 3,000lbs with a braked trailer, the trailer has its own brakes. I was thinking my truck should be able to tow approximately 5,000-7,000lbs, is this totally unreasonable?

 

4,000 lbs curb weight seems a little light to me. If you run it across a scale, you'll know for sure what it is. Even a scale at a rock/landscape yard is close enough.

 

Your truck weighs between 4500lbs and 5000lbs.. a trip to the scales will give you a more accurate number.

What it's rated to tow and what it can tow at the limits of failure are two different things. The factory rating takes into account all the physical components and factors in what can be accomplished without shortening the life of any one of them. The 1/2 ton manual transmissions were not considered to be very robust so trucks with them were derated compared to the auto equipped trucks, you addressed that weakness with the ZF swap so it can be argued that the truck should now be rated for 6k towing like the autos. I have towed that kind of weight with my '90 1/2 ton and it wasn't confidence inspiring but yes it can get the job done.

 

Most states say trailers of 2500 lb must have brakes and the others at 3000 lb so the brake side should be good.
Now you will not be driving like the truck is unloaded and be storming up to stop lights & signs.

If they run 250's with 300 six's and tow more weight than your truck your 302 should be ok.
Like the 300 six it will be slow but will get the job done.

Them large tires should be changed out for the stock size or a gear change from 3.55 to say 3.70 or a little lower to 4.10 being you have a ZF with over drive.
The smaller tires and lower gear will make it easier on the clutch when taking off from a stop, less slipping.

You swapped out the rear springs but you may still need to use a weight disturbing (WD) hitch to level out the truck & trailer if the nose weight is too high.
This will put the weight back on the front steer and level out the truck & trailer.
It can also help on controlling sway as will the trucks tires filled to max PSI.

On the hitch I would not use that bumper ball but a frame mounted hitch that is made for a WD hitch set up.
If the above is all in place I would pull a trailer of say 5000 lb but 7000 lb might be pushing it.

BTW I have set up my 81 F100 flare side with a 300 six / NP435 with AA over drive (split gears) / 2.75 rear gear to pull my 20 ft open deck car trailer, with brakes, that I figure is 5000 lb with a car on it. It will be slow but I am sure it will get the job done!
I have also towed with many different cars & trucks and trailers so I know what my limits are.
Dave ----

 

First, I tend to agree with everything above.

Keep in mind that you haven't improved the transfer case, axles, the rest of the driveline, and brakes while you have made it harder on all of those by moving to larger tires. Will it do it? Probably. Will you hate it. Maybe. Will it do it many many times for the jobs you describe? Maybe, but the stress will add up eventually. I can't tell from here if that will be the first trip up/down or the tenth or the fiftieth.