question Jacks for 353's (and similar)

[JonP]

Hi guys,

 

Out of interest, for general workshop maintenance and repair what sort of jack would you recommend for use with a CCKW sized vehicle? There are bottle jacks capable of lifting up to 7 tonnes and I've also noticed there are trolley jacks capable of lifting similar weights (but more expensive).

 

Is one any better than the other? I get the impression the bottle jacks have a longer reach than the trolley jacks (so ideal for a tall clearance vehicle) as on my jeep I find my trolley jack doesn't reach every high point (chassis for example).

 

What about stability? I don't know how things are now but in the 70's it seemed for lifting trucks you'd use a bottle jack.

 

Obviously the vehicle would be lifted and then put onto suitable axle stands.

 

Any other advice on maintaining one of these beasts and the tools required would be very welcome as I'm thinking of getting another vehicle and the GMC is one of those under consideration.. I'm just a tad nervous about the weight of the thing (compared to a jeep)

 

Thanks

 

Jon

[Tony B]

You can good bottle jacks of around twelve tons for about £30/35 . Always better to be overjacked than under. Bottles do have a high lift, but quite a narrow top. I get round it by countersinking a piece of wood then sticking the top of the jack in that. I would never rely on a jack of any type alone. Been there lucky to get away with it. I'd rather invest in a set of good very heavy axle stands.

[ford 369]

as Tony says never rely on a jack alone (unless of course it is mr Beckett) a local gunsmith to me tried fixing the exhaust on his car a few years ago with only a jack for support,the neighbours found him squashed under the car 2 days later

[deadline]

The largest issue with jacking a cckw is that nothing is very close to the ground. Even the axles can be above the extended reach of most jacks.

 

You didn't mention what you wanted the jack for.. changing tires or swapping axles?

 

I have a Sears Craftsman 10 ton bottle jack that I sit on a 4"x4"x6" wood blocks that I stack as I lift the frame. You also need much larger jack stands (height wise).

[Stormin]

You can good bottle jacks of around twelve tons for about £30/35 . Always better to be overjacked than under. Bottles do have a high lift, but quite a narrow top. I get round it by countersinking a piece of wood then sticking the top of the jack in that. I would never rely on a jack of any type alone. Been there lucky to get away with it. I'd rather invest in a set of good very heavy axle stands.

 

Placing a piece of wood on top of the jack sounds quite dangerous. It's highly likely to split under the point load on the end of a bottle jack. Far safer if you need to pack up to place wooden blocks under the blunt end (bottom) of the jack, were the load is distributed over a much larger area. Problem with bottle jacks is they are still rather narrow on the base and prone to tilting so always chock wheels securely.

 

I have a 20 ton bottle jack and i've never actually used it in anger. I've done nearly all the jacking on my Ward La France using a Halfords 3 tonnes trolley jack. It lifts plenty high enough to change wheels with 11.00 x 20 tyres and has rapid lift until it gets to a real load.

[Tony B]

Yes Norman, should have said 'Pick wood carfully'. A god wodden base helps, especially on soft ground. The addition of a bit of beading round the jack base helps keep it in place.I

[deadline]

"10 ton bottle jack that I sit on a 4"x4"x6" wood blocks"

 

The wood is UNDER the jack. The jack SITS ON the 4"x4"x6" wooden blocks. Wood is quite strong in compression and I have a TM that shows several field expedient methods of jacking a CCKW with a single wood A frame. Its quite interesting and if you have a winch version it shows you have to lift the entire truck with A frames on both ends.

 

With a steel plate (say 1/4 or so inch think) you can put the jack under the wood (with the steel really only there to keep the head of the jack from crushing into the wood). I've helped a fellow lift a HOUSE with nothing more than a bottle jack and some 4x4s.

[Tony B]

One classic a lot of years back now. Outside Wotton Basset. A truck with a puncture on a bridge. The mechanic managed to jack the bottle jack through the bridge.:-D

[deadline]

Drive it flat... won't hurt it for a short distance.

[R Cubed]

Be very wary where you put the jack if you need to jack a certain wheel put the jack under the axle tubes on the axle ( do not jack on the centre diff casing, especially a split axle design they are not very strong ) just below the leaf spring position it has always worked for me. Also don't forget the hand brake on a GMC works on a band brake on the output of the transfer box which is connected to the rear prop shafts, so if you have one wheel on each rear axle off the ground and the truck is situated on a bit of a slope it will move off down the hill, only jack on the flat if at all possible, oh and bear in mind axle wind up as the rear two axles on the GMC are locked together both diffs have to go round together, so you can get wind up where the axles are fighting each other, when you come to jack any of the rear wheels as it comes clear of the ground it can spin a bit, probably only a couple of inches but under quite a lot of force, if you are not expecting it, it can be quite a surprise.

[JonP]

Thanks guys,

 

I've got a CCKW 353 now (shop van) so am looking at jack and stand options.

 

There are some high reach Clarke stands at 6 ton per pair. Although a lot of literature says that because you're lifting a corner of the vehicle then this is okay (the truck weighs around 6 ton, so 3 ton per corner) but I can't help these are sufficient as the weight limit is on the spec. I'd prefer at least 6 ton per stand but don't seem to be able to find any.

 

As for jacks, 10 - 20 tonne bottle jack. Should be sufficient methinks.

 

Jon

[deadline]

20 ton jack for a CCKW? Maybe if you want all 4 corners off the ground at the same time using one jack.

 

I refer you to the TM9-801 (April, 44) (available for free download here: http://www.tm9-801.com/tm9-801/index.php

 

Or you can do an online search of it here:

http://www.tm9-801.com/searchTM9/searchfiles.php

 

Page 20, "On Vehicle Tools"

 

41-J-72 Jack, hydraulic, 3-ton, with handle .......... Tool compartment

 

Thats all you need to work on a tire or raise one end. You are never going to see 100% of the total weight on a jack because the front/rear axles act as a pivot point and create a Class II lever, which reduces the the amount of effort required becuase it has a larger advantage than the load itself.

 

In a pinch, a 22inch 4x4 under the axle will lift it. Its a field expedient repair.

[JonP]

Fair comment. Its not the inability of the jack to lift the truck, but halfway through lifting the jack gives out because its lifting above its weight limit that I was concerned about.

 

But I take the point about changing a wheel. Then you are only lifting one corner of the truck.

 

Thanks

 

Jon

[deadline]

Its more of a 'process' really. There is no single point on a CCKW to jack the entire vehicle. And putting a jack under the differential can damage a split axle (and is probably not a good idea for a banjo), so you HAVE to do under the spring seats. If you take a 12,000lb CCKW and divide by 4 corners, that leaves you with 3,000 lbs on each corner (approx) and using a 6,000lb jack give you at least a ton of extra capacity.

 

For the cost difference of a 6 and 9/10 ton jack you might feel better with the larger capacity, but it does not give you a 'safety margin'... any jack can fail at any load.

 

I found out that you really must use the spring seats as a lift point, most other lift points are way to high for a normal bottle jack to reach. You also need much larger (height and capacity) jack stands than used for cars.

[JonP]

Thanks for that ) So I guess it boils down to trolley vs bottle jacks.. bottle jacks are cheaper and in most cases, I'd only be lifting the truck enough to get the wheels off the ground (and an axle stand underneath)

 

Also I suppose a heavier lift jack in itself will be heavier.

 

In terms of axle stands, do you have any experience of the ratchet types?

 

Again, I guess 6 tonne per stand (12 tonne pairs) will be okay for a CCKW. Initially I was considering 12 tonne per stand but now this is probably overkill and unnecessary expense.

 

Cheers

 

Jon

[JOURNEYMAN]

Hi jon,

i use a clarke 12 ton bottle jack on my gmc 353 ( no winch ) with a solid block of wood underneath

it to spread the load. The block is approx 14 inches long , 10 inches wide and 4-5 inches thick.

I have had no problem at all with this set-up,i also used it on my previous reo which was a lot

heavier on the front end than the 353 is. The use of the extra height of the block also ensures

that the lifting height of the jack does not become excessive. The jack and the block also fit

nicely in the trough at the back of the cab, behind the driver/passenger.

The axle stands i use are all individually 6 ton rating, also made by clarke, and they cope easily.

Hope this helps,

steve.

[R Cubed]

As a rough guide the front of a CCKW is heavier when jacking one front wheel as you are acting directly on the weight on that side, but on the rear when you jack one rear wheel up you are jacking half the weight on that side because of the inverse leaf spring acting on both axles like a sea-saw. An important thing to remember is steel on steel will slip much easier than it will with a piece of timber between.Also if leaving on stands for some time make sure they are near to the spring seats.

[deadline]

I don't have a strain gauge on my shop gantry crane, but I after moving around a complete rear bogey unit and an engine I think the bogey assembly is heavier (tires, bogey unit, torsion bars etc).

 

The TM9 shows only a 700lb increase for the winch models (wo/w = 10,350 w/w = 11,050). The rough math still puts you at under 3,000 lbs per corner.

 

I guess a trip to the local scales would confirm this, but my experience is that a 3-6 ton bottle jack is fine, unless you happen to need to raise a loaded truck.

 

I use 3 ton rated (each) jack stands:

 

http://www.harborfreight.com/3-ton-heavy-duty-jack-stands-38846.html

 

I also have a poured concrete foundation in my garage, but I have jacked up an tipper on dirt and a 2x8 under the jack was more than enough to stop the jack and stands from sinking into the dirt.

[David Robertson]

Hi Jon, this is what i use for wheel changing etc : 3 ton trolley jack, bottle jack, wheel brace, shock wrench, wheel chocks, 12 x 12 timber and assorted smaller blocks. All the smaller items are kept in the truck, the 12 x 12s and the trolley jack live at home. Hope this helps, enjoy your new truck, regards David.

[JonP]

Steve, Cubed, deadline, David, thanks all for your replies.

 

That is exactly what I wanted to know - it is helpful to understand what people are actually using.

 

David - those are some serious chocks! (understandably :wow:)

 

I will be taking a trip to the local weighbridge when the weather is a bit warmer, but in the meantime I think I have sufficient info now to make a decision on the jacks/stands I'll be getting.

 

Cheers

 

Jon

[R Cubed]

Just a daft thought don't forget the wheel nuts down the left side of the truck ( as you sit in it ) are LEFT HANDED undo clockwise :nut:

[R Cubed]

Hi Jon, this is what i use for wheel changing etc : 3 ton trolley jack, bottle jack, wheel brace, shock wrench, wheel chocks, 12 x 12 timber and assorted smaller blocks. All the smaller items are kept in the truck, the 12 x 12s and the trolley jack live at home. Hope this helps, enjoy your new truck, regards David.

 

Are a shock wrench..... mmmm very handy bit of kit I wont use anything else to do the wheel nuts up.

[Big ray]

Jacking a truck up is a risky job any time, its important that the correct procedure should be followed, never cut corners, and if you should be working alone, you need to be particularly careful. Particularly with a bottle jack you run the risk of the jack slipping, or falling over if the truck moves.... a distinct possibility with a transmission hand brake, essential that the wheels are chocked from both sides with suitable chocks and the vehicle is on flat / hard ground. Axle stands should be positioned from the side of the vehicle, not crawling underneath, all of this just sounds so obvious, but I have seen it done wrong on so many occasions. On the subject of safety, I am amazed at how many times I see drivers jump from their motors and leave the engine running on a bank / hill. Apart from the fact that its illegal to leave a motor running unattended, the handbrakes on these old vehicles tend to suffer from wear on the paul and ratchet mechanism, add to that layers of paint or oil ingress and its not surprising that the handbrake can jump off..... there is no such thing as an accident, its a euphemism for neglect.:kissoncheek:

[deadline]

If you can get a jack stand under the axle without getting underneath the vehicle then you are either a midget or have 6 foot long arms. Reaching between the bogies is a dumber idea than crawling the 5 feet under the rear end and placing a stand under the spring seat. Placing jack stands under the front is somewhat easier, but still done from in front of the vehicle.

 

You *NEVER* want to be around a tire or other 'pinch point'. Your 'from the side' statement puts you in way to much jeopardy of being hit by the frame, body part or wheel. Approaching directly in front/behind a high ground clearance vehicle like a CCKW is the safest way. Next time you get the chance.. crawl under your CCKW from the front or rear to the axle and see how much room you have. Then, try to reach that same position from the side. Note where you have to place your arms and how close your head is to nearby large metal objects.

 

Even if a CCKW falls off the jack, there is at least 20+ inches of frame clearance. As long as you are not laying directly underneath an axle or a tire you are safe from being hit.

 

For a jeep or modern passenger car you would be correct.. the ground clearance of my dodge is 7 inches... The sidewall of a CCKW tire it larger than that.

[bradcckw]

I used the 3 ton floor jack method and blocked my entire truck up for my brake restore.

seemed to be good I put 1 1/8" concrete form pannels under each block point and jacking surfaces though helped plenty!