Towing capability
 

Hey everyone, been on here for a while but this is my first post. We are buying a toyhauler and my question is has anyone towed a 14,000 lb trailer with a stock 305. I have a 65 1500. I've had this truck since I was senior in high school when my wife and I started dating. We are not buying another truck truck to pull this camper. Are there any mods that you would suggest to make it easier. Your comments are very welcome and appreciated

Re: Towing capability
 

The usual mods many of us do is upgrade to the 4412 Holley 500cfm carburetor, dual exhaust and Electronic ignition. My preference is the GM HEI, a few have even done a 4bbl conversion. :upyes:

Re: Towing capability
 

Thanks bigblockv6 but that really doesn't answer my question. I need to know if this truck with its current configuration is able to safely tow a 14,000 lb trailer. I know about those mods and have done the carb and dual exhaust. Those are nice upgrades but that's not going to make it pull the load I'm asking about if it can't already do it

Re: Towing capability
 

I think you'll have no problem getting it moving, but my concern would be getting it to stop. 14,000 lbs is a lot of pounds to brake down from 60-0 or heck even 40-0. Maybe upgrading the brakes would be a good idea. Cecilia has a hard enough time stopping with an empty trailer on her butt.

Re: Towing capability
 

Thanks a lot. Been toying with the idea of 4 wheel disc. Also was thinking of making it a dually. Will be putting airbags on it this weekend. My biggest concern is will it be able to pull it. I can fix the suspension and brakes. Don't want to put a lot of money into it and then have to a motor swap. I've had 3 of these and this is my baby. I want to keep it as close to original as possible

Re: Towing capability
 

While I'm sure your truck with the 305 would tow a 14,000 pound trailer, I wouldn't recommend it. If you could always stay on flat ground (hard to do in Colorado!) you could probably get away with it most of the time. Personally, I wouldn't even think of towing a trailer that heavy in the mountains without at least upgrading to disc brakes in the front, a power booster, and dual brake circuits. Just be prepared to go REALLY slow up the hills!

Re: Towing capability
 

Gimmie1965, my suggestion for a serious power increase and keeping the V6 is to upgrade to a 401M V6 then you'll have plenty of power to pull 14,000 trailer. The 401M V6would be basically a straight drop in as long as it has the 6 bolt flange on the crankshaft for the flywheel.

Re: Towing capability
 

I've have thought about that also. Not quite that big. There's a junkyard in pueblo thats about 45 min south of me that hat 3 351m at one time. Was thinking about going down to see if he still had them

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With "1500" that means you have a C10 that is a 1/2 ton pickup truck? It won't handle 14k. I have a 1972 C20 (3/4 ton) that I converted to a C30 (1 ton) with a 4:10 dually rear end, big brakes off a 1989 1 ton truck (front disks, rear drums), vacuum booster, 5k rear air bags, trailer brakes, LS1 engine, 5 spd NV4500, digital dash, ETC (make that a LONG ETC!), lol. I have pulled 14-15k with the truck and I've had 8k on the steel flat bed and I would not recommend anyone doing that with similar setup as mine, much less on a 305 1/2 ton truck. Even with my big brakes, brakes are still the weak point.

Re: Towing capability
 

I thought the GMC 1500 series was 3/4 ton. But even if it is, pulling 14,000 lbs uphill with a 305 would be a very slow process. My 1500, that I am sure is rated at 3/4 ton, needs downshifting to get up some California hills without a load, and spends most of the time in third (counting the granny as 1) when going uphill with any sort of load. If your toy hauler is a trailer (not 5th wheel, which I have not seen behind these old trucks) there is another potential problem. Where the bumper with its hitch plate is welded to the frame might not be heavy enough metal to pull such a big a load. At least that is what the welding shop told me when I put a 2" receiver on the old truck to pull a horse trailer - this is not a problem with the bumper, but how it is attached to the frame.

JRMunn

Re: Towing capability
 

A few other thoughts. My 64 1500 was originally equipped for a camper. It came with oversized front drums and vacuum assist brakes. The vacuum assist was removed after taking the camper off because the drums locked up too easy with no load. But even when new, the need for brake assist was recognized. And, assuming you have a standard transmission, how good is the clutch. The truck plus 14,000 pounds is a lot to ask from the stock clutch. The stock SM 420 transmission with compound low is probably up to the job, and you might already have a heavy duty (8 lug) full floating rear axle plus 4.10 rear end in a 1500. Also to be considered when stopping are the trailer brakes. If they can't slow the trailer down, then you will have a potential jackknifing problem - especially if the road gets slick. And thinking of some of the grades in Colorado, you might even need a fire extinguisher for the brakes. Sorry, but there are good reasons that today's big trailers are usually pulled by more modern 3/4 and 1 ton pickups with large engines, exhaust braking, and big disc brakes. I know because I pull a mid-sized 5th wheel (at about 14,000 lbs) with a Dodge 2500 that has a 6.7 liter Cummins diesel engine. It would probably pull a house, but I still have to let traffic by on steep uphill grades. And despite 4-wheel disc brakes and good trailer brakes, I am grateful for the engine brake when going downhill. The old GMC is a family keepsake and, with the bed lower to the ground, is great for loading. But I would not pull a big load with it and, honestly, I would hate being behind you going uphill or having you coming downhill toward me while pulling such a heavy load.

JRMunn

Re: Towing capability
 

You're confusing '60 to '66 model numbers with '67 and later model numbers. A half ton GMC from '60 to '66 is a model 1000. A three quarter ton is a 1500. A one ton is a 2500. Starting in '67 a half ton GMC is a 1500, three quarter ton a 2500, etc. "C10" is strictly a Chevy model number.

Re: Towing capability
 

Arubariba, 1500 applies to 67 and up half ton trucks, prior to that 1960-66 3/4 ton GMC trucks were 1500 series, 1/2 tons were 1000 series and 1 tons were 2500 series:lolsmack2:

Re: Towing capability
 

Thanks JRMUNN,
yes it does have the 4:10 full floating axle. The clutch has been changed. In traffic I have to put it in nuetral or else my leg gets to shaking so bad that I'm not able to shift at all. I have 5000lb airbags that I'm installing this weekend along with a new floor for the bed. Planning to make it a dually with 4 wheel power disc. My main concern is if the 305 will be able to pull it. I'm not concerned about speed. Looking at doing the 351m head,intake,exhaust swap in hopes that will help with pulling. It will be a 5th wheel setup at least that's the plan. Found a 82 gmc standard cab dually with a 6.2 diesel. Was really excited about it but after long thought I decided against it on the fact that it wouldn't be same truck.

Re: Towing capability
 

LOL, Living and Learning,:rowdybeer::rowdybeer::rowdybeer::rowdybe er::rowdybeer:

Re: Towing capability
 

Other than the aluminum radiator, clutch fan, taller tires and single into dual Flowmaster 10, mine is original. I did replace my 4:56 with 4:10, so I could do 65 mph. I tow our 4K lb camper all the time in the flatlands and able to maintain 60-65 mph unless a long hill. The early GMC 1500 is a 3/4 ton and is rated for 5K lb tow capacity.

I have towed 7K lb several times in the flatlands and in the Ozarks. In the Ozarks it’s not pretty... I can get up to 55-60 mph without too much trouble when it’s flat, but end up down shifting several times before I hit the top of the hills, doing 10-25 mph in a 55 mph zone. Not fair for other drivers, but I only do it when I rent skid steers and haul gravel.

I’ve never had any trouble stopping, since I installed an electric brake controller and make sure the trailers I tow either have electric or hydraulic surge brakes.

I couldn’t imagine towing 14K lb out on the road with the way our trucks are set up. As others have mentioned, you need a larger motor with additional torque and horsepower. Plus, there’s not enough gears in our transmission. 3rd and 4th gears are worthless for towing heavy on grades. If you’re idleing around on the property or dirt roads, granny low has a lot of guts. But if you don’t have enough tongue weight, you’ll lose traction. I have a set of off-road chains to put on sometimes when towing heavy on grades and breaking traction.

Re: Towing capability
 

At this point, you are out of my league with improvements. But about your main question, my experience has been that the 305 is underpowered for even loads in the bed. In my case, top speed in third gear is about 35 mph, and second is about 20 mph. Clark is right about trailer brakes, gears, and a bigger motor. Having lost all hydraulic braking when a front hose broke, I would strongly recommend a dual master cylinder system (which I have now). And I put a Holley 4412 (?) carburetor on my 305. It helps, but not enough for your situation. I am also not sure you could use 351 heads on a 305, but others probably know for sure. If they fit, magnum heads plus intake and exhaust manifolds would also help. But then you might have trouble finding enough gas stations. On paved roads with a 5th wheel setup, you are probably okay with traction, but be aware that the stock rear end is single wheel drive (not positraction). I would also worry about tire and wheel capacity, where your idea about dual wheels would help a lot. Finally (for me) there is a question of what happens if a patrolman wants to see if your setup meets legal requirements. This is uncharted territory for me. Good luck with your decisions and travels.

JRMunn

Re: Towing capability
 

[QUOTE=Gimmie1965;69267]Thanks JRMUNN,
Planning to make it a dually with 4 wheel power disc. My main concern is if the 305 will be able to pull it. I'm not concerned about speed. Looking at doing the 351m head,intake,exhaust swap in hopes that will help with pulling.

The 351M head, intake, exhaust swap won't do quite well with the 305, JR Munn was quite correct with that statement. This type of conversion will actually lower the compression ratio on the 305. You will be much better off like I mentioned before with a larger displacement V6 and a 401M that you think is too big is actually optimum for the amount of weight you intend to pull. Even if you come across a 351M that will be a significant improvement over the 305. As far as a dually conversion the 305 can handle that, for a while back in the 60's my father actually ran dual rear wheels on his 62 1/2 half ton with the 305D V6 and 3.54 gear ratio. Myself I yanked out the 305E out of my 68 K2500 and replaced it with a 478M V6 there is no substitute for cubic inches. The bigger V6 will still for the most retain the appearance of your 305.:thumbsup:

Re: Towing capability
 

I'm buying a canner ham trailer with a weight of 2700lbs. I too was wondering if I needed to change my brakes up front?

Re: Towing capability
 

I've towed 3400 lbs with Cecilia with no problems other than allowing more room to stop of course, but not much more than I'd do with any other truck. I think you'll be fine there.

Re: Towing capability
 

A 351 would definitely be an improvement over your 305, but a 401 would be better yet. There's one available near Portland, Oregon. See
https://portland.craigslist.org/clc/pts/6587789490.html The owner has lots of other '60 to '66 parts available too.

Re: Towing capability
 

Bigblockv6 What truck would I be looking for that would have the 401m in it and what year range. You said as long as it had a 6 bolt flange on the crank it should drop right in. What would I be looking for. Anything external on block that would tell me that or would have to just pull the tranny and clutch to find out

Re: Towing capability
 

What you would be looking for is a 1966-72 7500-8500 series truck which would be in a conventional cab H or J series, Tilt Cabs L, T and W series. Non Magnum 401s from 1960-65 could be found in 6500 series Trucks such as the Conventional cabs, B series and Tilt L series, still a vast improvement over the 305 and you can always upgrade to the Magnum heads and manifolds. Looks like Ed gave you a lead on a 401, if it's within you're driving range it's worth looking into:ok:

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Thank you. I need to head down to pueblo again and look at those. I don't remember what all he had. I know at least 1 305 and 1 351 for sure. I think he had 4 in those ranges. The one in Oregon is a little far for me right now. If it was next year definitely. The whole reason for this is we are selling everything and this will be our home. My wife is a nurse and she is going to school to get her p.a. we really thought about Washington or Oregon area. I think we are going to south Dakota for now but we will get there in the near future

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Your story reminds me of my own. My wife and I were living in St. Louis when we got married, and both agreed we wanted to move to Washington or Oregon. The closest we could get at the time was Idaho. After 3 years there we tried again, and made it to Oregon. After travelling on vacations to 49 states, there's nowhere else I'd rather live than Oregon.

Re: Towing capability
 

After a lifetime driving trucks of ALL sizes, most terribly under-powered and some short on available speeds in the transmissions, towing a 14,000# trailer behind a 305 V-6 powered pickup in the hills and mountains out west would a very, VERY slow process. I think a medium duty truck would make more sense, bigger engine, bigger cooling system, bigger tires & BRAKES! You can't expect to increase hp in your current truck without increasing all the other systems that the truck has, like gas tank size, more HP takes more gas, I'd look for a diesel. Bigger radiator and cooling system, brakes, axles, transmissions.

If you were pulling a 14,000# trailer around off road no problem, but trying to not be an impediment to other traffic around you would be almost impossible. I've pulled trailers with around 3000-4000# with a similarly sized and powered truck, F-150 300-6 and NP-435 4-speed, and got along fine for 5-6 miles of level road. But 14,000#in hills would have best been handled with my 320 hp Cummins powered White semi-tractor. I did pull a trailer around 12,000# 200 miles on day about 12 years ago with my '96 F-250 Powerstroke on fairly flat Interstates thru northern Illinois and southern Wisconsin. Once I got into 5th gear I never had to downshift on a hill. My 7.3 PSD was 210 hp, 425 #/ft torque. 3.55 gears.

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In the almost 50 years I've had my '60 1500, I have towed some equipment rentals, as well as hay and firewood trailers.
These were short haul trips and probably all under 8000 pounds.
They pretty much felt stressed in both power and braking and required constant attention.
I just would NOT recommend towing that weight with your wonderful, old truck.
New trucks are outrageously expensive, but there are several that could do that job with ease, comfort and safety.

Re: Towing capability
 

It'll tow it, won't do it fast but it will. Have towed 10k with my 64 3/4 ton and getting up to 55 was no problem. Took time but on level ground it did it. Pulling a hill downshifting to 3rd at full throttle is Not uncommon....but even on a 95 degree day the motor hardly warmed up. Stopping is the biggest concern.....even 10k coming to a stop takes effort and requires scheduling ahead of time.

Unfortunately alot of these bigger v6's are going for outrageous prices so I'd consider a gear splitter.....don't see those every day and road ranger makes one for the sm420's.

Most of the loads I hauled or more like this. She still does it with ease.

Re: Towing capability
 

After years of truck driving, and many years riding shotgun with Dad, there's NO substitute for displacement and horsepower.
Had a situation one afternoon hauling concrete, '66 White, 165 hp Cummins and Spicer 5+4 transmission, loaded with 7 cubic yards of concrete I grossed 52,000#. I followed an old lady out of town, she was driving 5 mph under the speed limit, passing her was not possible, fortunately she turned off the US route down a side road and then I had a chance to flat-foot it, but with the slight hills when I got to the big S-curves 7 miles out of town I was only going 35-40 mph, had dropped gears on uphill grades I never realized existed, normally I slowed from 55 mph to 50 for those S-curves.
That's all horsepower, or more correctly lack of hp and conservation of momentum. The newer trucks with 208 hp V-8 555 Cummins I had to slow down from about 63-64 mph to 55, even drop a gear in the Power-sapping Allison suto trans.
We had a guy on another forum that bought a million mile Volvo semi-tractor with a 450+ hp 60-series Detroit diesel, Super 10 Road-Ranger, needs a new clutch. He was determined to put a 6-71 Detroit in the truck to pull his 14,000# RV, Combined driving experience of those telling him to NOT do that was around 50-60 MILLION miles. The 6-71 was referred to as a 238, meaning 238 hp in it's most powerful tune. 305 V-6 is just over half that, with many fewer gears. Your gross weight will be just slightly less. Cruising speed much less.

Thing that impresses me the most is the fact todays's 500-600 hp trucks can run so fast and get such good mpg, 6-7 mpg is common. My old '79 White RoadBoss II with 320 hp 903 V-8 Cummins, 6-speed Spicer trans and 4.44 rear gears got about 4 to 4.25 mpg summer and 3 to 3.25 mpg winter on blended fuel. Grossed 70,000# most of the time, geared to run 67 mph at 2500 rpm, which was my usual cruising speed. I got a speeding ticket and slowed down to 62 mph and mpg really didn't improve. I forget the name of the regional carrier, but followed one of their trucks for a while on I-70 out west running 95 mph down a grade, 80 mph up the other side about 6 yrs ago. Made a quick trip to just outside Boston a week ago, most trucks running 65 mph. Funny story, took a detour from my normal route thru Chicago, jumped off onto the Skyway, My wife's first impression exactly the same as mine 35 years ago, " All that toll money to go over a Big Purple Bridge?" Ran I-94 right thru downtown, on July 4th morning, saved over an hour and almost half a tank of gas.