Hot Rods Using a floor jack to lift a car placed under the 9" ( center Pumpkin

I agree in principle but the nature of building cars from wrecking yard parts or sourced from people that don't know the history of a part makes it a crapshoot.
I know when raising a car this way in the past it never entered my mind and I still plan on doing it but it sure makes you think more about it.

 

I had a late model Mustang a few years ago and found the advise not to raise it by the rear axle. I did and didn’t die from it. The mfg’s may build them weak enough but I haven’t bent one yet.

Don’t believe everything you read on yuppie forums.

 

I used to work in a very cramped repair shop. Standard procedure was to back a car straight in then put a floor jack under the punkin and drag the back of the car around with the jack to get it lined up with whatever empty space was available. Never had any come back with bent housings.

 

Unbelievable!

 

The very different loads were (accurately) addressed by Relic Stew above.

Here's a pic from his post that should clarify the difference. If not, scroll up and read it.





As to whether that centered load is enough to break a rearend is a materials issue.

 

A lot of stuff we did 50 years ago seems unbelievable by today's standards.

 

I bent a rear end 90 degrees once and she liked it.

 

Crazy Steve nails it in post #29.

I watched a 4 wheel alignment job on a LSR car with a 9" rear that had been 'yard sourced. RR was discovered to be tweaked slightly horizontally. Who knows how it got that way but the rear end, chassis, and front end couldn't all be brought into square with each other until it was tweaked back straight.

Ed

 

Anything will bend with enough force applied. I personally don't think lifting the light half of a 3500 pound car by a jack under the rear end is going to do it. People tend to find too many things to worry about these days.

 

Some people spend to much time learning from the experts on the web instead of doing.

I have jacked cars in the rear using the punkin and on the front using the axle. First car I remember jacking up was when I was probably about 5 or 6 which means I have been jacking cars with floor jacks for close to 60 years. I was told then that I needed to be careful to not drop the car on my head so we can add another 30 or 40 years experience to that. LOL

 

Talk about overthinking.

 

I agree

 

My housing is painted... I place a shop rag over the saddle to it won't get scratched up.

 

I just read this thread and my take away is it is 25 minutes I'll never get back. Yes I am a slow reader.

 

surprised no one has mentioned this I used to work in a welding shop that specialized in 4x4 off road accessories they have braces that are welded along the top and bottom of of the 9" axle tubes....why because they bend....however unless your car/truck is going to be doing jumps or putting the entire weight on one rear wheel or you have trunk filled with several meters of cement I wouldnt worry too much...mainly make sure the pad is centered on the housing and not partially on the carrier

 

Ah yep...lol

 

And another thread rides off into the sunset.............................

 

Old wash mitts work real well also.

 

Funny, I get the guys that don't want to lift it on the axle... or on the subframe, or anywhere else suitable for jacking. They'd rather roll the jack under and just start pumping. Two exhaust pipes and a fuel line later, I now watch those dumbasses like a hawk.

 

Takes a slap into the outside concret wall a Perris Speedway to maybe bend one of those....a jack in the center is the least of a problem..

 

Some of us have done extensive torture testing on our components, stock car racing is the best test method I know.

 

Over the years I've seen a few bent axles but they have all been bent down not up.

 

Fake news

 

XXL, I get the static load as indicated in the above sketch. My point is the extremely heavy gear box in the center between the supports resisting movement. It is forced up and down by the supports and an extremely rapid fashion. Due to inertia, the gear box wants to stay still. Was wondering how must force is applied dynamicly. Bones

 

I had a 66 Shelby with stripes that I rebuilt and the pumpkin is where I always jacked up the back. I could barely afford the car so I will admit that I did not have a matching jacket or hat. Don't judge all owners of cars with stripes, we are all not dicks.

 

Just wondering if anyone that modifies these housings uses a real press, with a tonnage gauge, to re-straighten them after and could tell us how much tonnage it takes to push one around?

Gary

 

Usually they 'straighten' them by cutting the bearing ends off then welding them back on while using a fixture. But I have seen a guy use a press when the misalignment was more than he liked, and he didn't have to apply all that much pressure.

 

Most 9" rears are just sheet metal some heavier metal than others. The late Lincoln rears are real thin on the axle tubes for instance. I wouldn't expect that it would take much of a press to reshape on. LOL

One thing that has always scared me about jacking under the punkin is stability. I have been known to use the punkin as a jacking point, but if I am going to do much more than change a tire I prop it up toward the ends of the axle.

 

I have straighten several bent axle tubes from circle track cars. Bent from crashes not loads I set the rear on wheels stationary on 2 wheels. I then place string from center of each wheel. I then rotate the housing and watch for slack or tightness of string. this will tell if you have a toe in or out problem. I then take out rose bud torch and heat housing. most of the time the stress will relive and go straight. some times if its bad you can see it. earlier today I looked at my stash about 30 9 inch and another 25 other brand and found one 9 inch truck unit that had been overloaded. The owner had welded stops on the frame of the truck to keep it from bottom out. The guy was a scrapper

 

I've had Mopars all my life, I'm not too worried about bending the housings on them.
Several years ago, my son's friend was dirt track racing. He was involved in a crash where a car was airborne and landed on the left rear bumper of his car. The 9" was visually bent up to the left of the center section. I told him I cold straighten it, but he wouldn't like how I was going to do it. He fretted all week as he looked for a different 9" he couldn't find. About Thursday evening, I asked him if he wanted me to " straighten" hie 9". He finally gave up but wanted to watch and help. We set the assembly on jack stands, and pulled the left axle out. I was surprised it wasn't bent. The left stand was set towards the center before the bend, I took the Sawzall and cut 1/2 way through the tube at the bend. I fired up the torch and applied slow heat to the bottom of the tube until the housing appeared straight. We test fit the axle into the housing. I think we took 2 or 3 heating cycles before the axle slid in by hand smoothly. When I was happy with the fit, we pulled the axle out of the tube, and welded the nearly 1/4" gap at the top of the tube closed. When the weld was complete and had cooled, the axle still slid nicely into the tube, and we reinstalled the axle assembly into the car. The assembly has been in several cars since then, and the rear of the car has always been lifted with a jack under the center.
If the housing bends from jacking the car up, it was time for a different housing anyway. Gene