Safe 8 3/4 axle lift

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Dana67Dart

Dana67Dart

The parts you don't add don't cause you no trouble
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The FSM says don't lift the rear of the car by the center of the 8 3/4 housing.

So I have been lifting one side, putting in a jack stand then the same for the other side.

I'm always nervous that the first side will slip when I'm lifting the other.

During my 8 3/4 swap, I actually had the rear end slip off of the jack, luckily I had the tires on and was able to turn the jack handle fast enough to drop the rear in a more controlled manner without impaling the gas tank or floor boards.

I started looking for a safe alternative.

I found the Harbor Freight cross beam adapter.

Screenshot_20230815-185513.png


ALMOST what I was looking for.
The flat pads don't offer and resistance to the axle tubes from sliding off except for the resistance of the rubber.
Plus in their highest position they are 1 1/2 too short. The top cross beam hits the bottom of the housing center. So I had to use 2 pieces of 2x4 to take up the space.
now there was zero resistance to the axle tubes from sliding off.
my solution.
hard rubber "V" block for a boat trailer.
Screenshot_20230815-190223.png

it fits perfectly on the pads, is super dense, can be attached to the cross beam, "V" shaped so the axle is cradled and can't slip, and the rubber will not mar the paint on the tube.
PXL_20230816_004522160.jpg



It's easily removed, or rotate to store.
PXL_20230816_004646360.jpg

it works like a charm!
 
Neat!

I’ve been using the pumpkin to lift cars for decades now, not just Mopars either. Doesn’t hurt the housing any. Probably not the safest option because of the contact patch with the jack, but a little common sense goes a long way.
 
Is there anything solid in that V-block? Or just rubber?
 
72bluNblu said:
Neat!

I’ve been using the pumpkin to lift cars for decades now, not just Mopars either. Doesn’t hurt the housing any. Probably not the safest option because of the contact patch with the jack, but a little common sense goes a long way.
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Indeed. Sometimes overthinking is rampant.
 
Dana67Dart said:
Not overthinking, I just understand that physics and PSI can bend things:rofl:
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Well I don't. I've been lifting everything from the lightest imports all the way to OTR trucks by the third member since I learned to use a jack and have never bent anything. Sometimes understanding is imagination.
 
Dana67Dart said:
Just solid rubber
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So, nothing to stop the rubber from flexing backward if there’s a weight shift, dumping the axle out of the V and off the jack.

That kind of rubber can also split or chunk out. It’s suitable if it’s backed up by something that can’t flex. Even on boat trailers it’s usually part of a larger metal V, and in that application it’s just a bumper and not supporting thousands of pounds once the boat is positioned on the trailer.

I like the idea, but the rubber needs to be backed up by something solid. It can be a bumper or a cushion, but shouldn’t be used as a support.
 
72bluNblu said:
So, nothing to stop the rubber from flexing backward if there’s a weight shift, dumping the axle out of the V and off the jack.

That kind of rubber can also split or chunk out. It’s suitable if it’s backed up by something that can’t flex. Even on boat trailers it’s usually part of a larger metal V, and in that application it’s just a bumper and not supporting thousands of pounds once the boat is positioned on the trailer.

I like the idea, but the rubber needs to be backed up by something solid. It can be a bumper or a cushion, but shouldn’t be used as a support.
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It reminds me of those solid rubber wheel chocks. Same kind of rubber, I bet. The difference is, the wheel chocks have the ground to back them up.
 
RustyRatRod said:
It reminds me of those solid rubber wheel chocks. Same kind of rubber, I bet. The difference is, the wheel chocks have the ground to back them up.
Click to expand...

Very similar kind of rubber I would imagine. And yeah, the chocks are limited/backed up by the surface they’re sitting on. And they’re not supporting the entire weight of the car, just whatever small component is coming from the angle of the ground or the car.
 
I will ad my 2 cents I've had 8.75 rears in 9000lb imperial built derby cars and still lift with center of diff and that's welded in solid with zero give. No.to mention the violent side impacts against concrete barriers from other well built cars and I've only ever bent one rear end and that was a 10bolt chevy rear. Aint no way you will ever even flex one in an A body. Just to give you piece of mind.
 
I wouldn’t personally lift a heavy vehicle from a stamped housing, but light cars/trucks no problem. Most heavy duty vehicles have a cast center section, no issues with using it as a jacking point. But an old ford 3/4 ton with a 9”? I’m jacking from the frame just to be safe.
 
Weighs a smidge over 5k lbs, has a 9” rear and Dana 44 front. Owned for over a decade, lifted with a floor jack on the center sections many times. Jacking from the frame with a regular floor jack isn’t really an option unless you’re using super tall blocks simply because of that height of the frame. And of course, floor jacks + super tall blocks is also sketchy.
IMG_4671.jpeg
 
MidnightSwinger said:
I wouldn’t personally lift a heavy vehicle from a stamped housing, but light cars/trucks no problem. Most heavy duty vehicles have a cast center section, no issues with using it as a jacking point. But an old ford 3/4 ton with a 9”? I’m jacking from the frame just to be safe.
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My Ford has a Dana 60 so it gets jacked up in the center. lol
 
RustyRatRod said:
YOU own a bump side? Cool.
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Yessir. My old man had a ‘78 F150 I drove a decent amount growing up. My wife wanted this one and I’ve got a soft spot for the old Ford trucks so we bought it.

‘71 F100 with a rebuilt 390. Upgraded to the later NP435/NP205 out of a ‘77 after my wife tore the output shaft out of the old single speed Dana 20 transfer case doing burnouts with the 35’s. The compound low in the NP205 is a great upgrade.

Still use it a bunch, especially in the winter
IMG_4093.jpeg
 
72bluNblu said:
Yessir. My old man had a ‘78 F150 I drove a decent amount growing up. My wife wanted this one and I’ve got a soft spot for the old Ford trucks so we bought it.

‘71 F100 with a rebuilt 390. Upgraded to the later NP435/NP205 out of a ‘77 after my wife tore the output shaft out of the old single speed Dana 20 transfer case doing burnouts with the 35’s. The compound low in the NP205 is a great upgrade.

Still use it a bunch, especially in the winter
View attachment 1716128571
Click to expand...
If the wife likes it, she's a keeper! I've had mine a little over ten years now. 75 F250HD (F253 on the data tag) AND it also got the camper special package. Old Gladys is one heavy duty truck.
 
Darter6 said:
Who would have thunk I've been doing it wrong for over 50 years..
As usual Mopars are tougher than even what the factory thinks.
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I really don’t think the factory was concerned about the strength of the housing, more like the lawyers were concerned about the pumpkin sliding off the floor jack
 
I have 4 original A Body 8 3/4 housings.

All 4 needed straightening.

You can lift your car by the center and unless you have measured it before the first lift and now and the housing is still the same then you have no idea if you have bent anything.

This image illustrates things

Screenshot_20230816-161309.png


Not to mention how does a housing get straightened

You apply force in one direction and resist it in the other.

If it was a cast iron center, and heavy wall tubes I would lift from the center without reservation.

But a formed sheet metal housing does not have the same type of strength.
 
72bluNblu said:
...my wife tore the output shaft out of the old single speed Dana 20 transfer case doing burnouts...
Click to expand...
She's a keeper!
To think I passed on a 383 4-speed Barracuda because my wife wouldn't drive it. In 13 years, she's never driven the 340 automatic. After that time though, having entered the final third of my life, I'm kinda glad I got what I did.
 
Dana67Dart said:
I have 4 original A Body 8 3/4 housings.

All 4 needed straightening.

You can lift your car by the center and unless you have measured it before the first lift and now and the housing is still the same then you have no idea if you have bent anything.

This image illustrates things

View attachment 1716128641

Not to mention how does a housing get straightened

You apply force in one direction and resist it in the other.

If it was a cast iron center, and heavy wall tubes I would lift from the center without reservation.

But a formed sheet metal housing does not have the same type of strength.
Click to expand...

So how much deformation can you have before your axles don't align with the differential? How straight were those housings from the factory you think?

Formed sheet metal? Have you looked at how thick the 3" tubes and banjo are? Welded one up by any chance? I have. Maybe technically it's "sheet metal", but you can do a whole lot of ridiculous stuff to one of those housings before it bends much.

Also, that drawing only accounts for equal loading. As in, the load is applied at the wheels, and is completely absorbed by the spring a short distance away. Except that's not how it always works. Because if you load one side heavily, one spring moves while the other does not. Which means the entire housing is a lever, acting through the pumpkin. If you get equal loads on both sides, sure, most is applied to the closest spring. But that's a single loading example out of many. Lifting the vehicle from the center of the rear axle can only ever apply about half the weight of the vehicle, less if the front/rear weight bias isn't 50/50. So on that old Ford for example it's no where near half the weight of the truck to lift it that way.

You do you, but if you use that beam with rubber blocks and no solid support behind them you're asking for a whole world of trouble. Because those rubber V-blocks are not intended to support that kind of weight without a supporting structure to keep them from deforming.
 
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