I have always used the floor jack under the differential to raise rear of the car up. Then the jack stands go under the axels and i have room to work. A buddy was over and said not to do that as it "messes up" the rear end. Anyone ever heard of problems doing it this way?
Jacking the rear up using the differential. Yes or no?
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SailPointSeven
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I have always used the floor jack under the differential to raise rear of the car up. Then the jack stands go under the axels and i have room to work. A buddy was over and said not to do that as it "messes up" the rear end. Anyone ever heard of problems doing it this way?
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I've done that up to this point on my car but after reading that it could dent the rear diff housing and interfere with the gears, I've stopped. It's sure convenient though so I'd like to hear from anybody who's actually seen a problem like this in the past as well. Maybe filling your trunk with bricks and jacking but those diff housings seem pretty robust.
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I've been lifting both of my 68s that way for 15 (fastback) to 30 (coupe) years and haven't seen any damage yet. Like I said, put some padding on the jack to help protect the differential. Even my mechanic lifted the fastback that way, but he didn't use a pad and that's why I'm currently repainting the rear end. Sigh...
I've been lifting my Shelby under the rear end for 40 plus years this way. No problem, If you don't have a pad on the jack, use a block of wood. I'd say don't use a bottle jack but a floor jack is OK.
The 67 GTA I'm about to resto has been lifted under the so-called factory jacking points, sure enough, I'll be cutting into the boxes above the points to bend the sheet metal back down.
The 67 GTA I'm about to resto has been lifted under the so-called factory jacking points, sure enough, I'll be cutting into the boxes above the points to bend the sheet metal back down.
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I've heard many takes on this issue. I've even heard that a rear diff has built-in camber and if you jack it up by the pumpkin, it can alter that camber. (??)
But I've never heard of anyone actually damaging a rear diff by jacking it at the pumpkin; as long as they used a pad.
Of course, if you're looking for justification for installing that floor lift in your shop, this can help.
But I've never heard of anyone actually damaging a rear diff by jacking it at the pumpkin; as long as they used a pad.
Of course, if you're looking for justification for installing that floor lift in your shop, this can help.
Supposedly, jacking the car by the differential can cause the axle housing to bend as you're lifting by the center and the weight of the car is on the outboard ends at the leaf springs. I believe the Ford shop manuals back in the day said not to lift the car like that. 8.8 rearends use a cast center section with steel axle tubes pressed in. I could see one of those possibly getting messed up if jacked by the center section. I've been jacking 8" and 9" rears by the center section for 30 years and never had an problems.
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7,462 Posts
+1 with Laurie. It's a cast part. If housing is strong enough to drag race and hold up, a jack doing a dead lift isn't gonna bend, change anything. My son jacks his F250 on housing just fine.
It's like people believing "going outside when it's cold out and not putting on a jacket or you'll catch cold" NOT TRUE!!!
With many older cars I'd be more concerned about bending up older floor pans or frame rails jacking on them first!
It's like people believing "going outside when it's cold out and not putting on a jacket or you'll catch cold" NOT TRUE!!!
With many older cars I'd be more concerned about bending up older floor pans or frame rails jacking on them first!
8" and 9" housings are stamped steel. The center sections are cast.
Gotta be a wives tale. Otherwise wouldn't it bend the other way just sitting (weight of car on outboard axle sections) no support in the middle. Even if it was true- I can replace the diff easier than I can repair/replace torque boxes/frame rails- and those WILL bend for sure if you are not careful jacking so.... None of my buddys (ford mechanics) have heard of this issue.
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1,800 Posts
There was a write up in one of the mustang mags a few years ago. I think it was an axle build done by Currie. They showed how 'out of true' a 9" housing was by putting a steel rod through the tubes. Lining it up with spacer slugs and measuring it agianst the center opening of the housing. Then they proceeded to bend it back straight using a press.
It was a while ago, but from memory, they sited jacking from the center a possible cause for this.
For 20+ years, I still jack my '67 up from the center housing. I do not let it sit there any longer than needed. FWIW.
It was a while ago, but from memory, they sited jacking from the center a possible cause for this.
For 20+ years, I still jack my '67 up from the center housing. I do not let it sit there any longer than needed. FWIW.
Same here for the last 32 years I have been lifting my 8 and 9 inch rear mustangs with a shop towel folded on the jack to protect the paint. I don't know about an 8.8, but I won't ever run a rearend that does not have an interchangeable "pumpkin" for quick gear swaps anyway so no 8.8 for me!
I don't buy that. It was in a mag and I am sure they were leading up to how much better the new currie 9 plus housings they sell were than a stock housing LOL. I had complete currie 9+ rearend in my 65 fastback that I sold and it is a nice piece.... it should be for the price they charge!
If the housing was out of alignment I would think it probably came from a large truck or other heavy vehicle and may have been bottomed out on the center section during heavy hauling, offroading,etc.
If the housing was out of alignment I would think it probably came from a large truck or other heavy vehicle and may have been bottomed out on the center section during heavy hauling, offroading,etc.[/QUOTE]
Or playing "Dukes of Hazzard"! Lets hope that fate only applied to Dodge chargers.
Or playing "Dukes of Hazzard"! Lets hope that fate only applied to Dodge chargers.
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1,800 Posts
Yeah, I am not buying or selling on this one! Currie is deffinately proud of their stuff, and not shy about pricing.
I will say to never underestimate peoples ability to tear up their stuff. I purchased a deralict '02 saturn SL1 to fix up for my daughter a couple years ago. (thought it just needed a motor). The PO was a teenage girl that drove the snot out of this little car. It only had ~86k miles and the motor was blown. The entire front subframe was bent upward almost 4 inches. This is a light little car. Beleive it or not, the rest of the front end was pretty straight. She must have been doing some 'dukes of hazard' maneuvers to cause this much damage.
Anyway, I think jacking from the center housing is fine. I do think it is possible to bend it if you try hard enough!!
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777 Posts
For what it's worth, I recently addressed this issue on my Boss 302 rear axle housing by providing a dedicated jack point/oil drain bung. I realize this isn't "concours", but there is plenty of merit to the modification. Have a look here:
1970 Mustang Boss 302 Restoration: Axle Housing Updates
1970 Mustang Boss 302 Restoration: Axle Housing Updates
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2,965 Posts
OK ... Facts
99% have been doing this for decades. Rear axle problems on "non-performance" cars are almost non-existent.
BUTTT... When simple engineering principles are applied, there is a fair amount of deflection in the rear axle housing when you do this.
Givens :
Upward force at the jack point (A)....................................approx. 500#
Downward force at each of the spring attachments (B).........approx 250#
Distance between (A) & (B) .............................................approx 2 ft
My guess is if you placed a dial indicator at the center of the housing, set up so it reads deflection from a reference line that remains a constant distance from both spring attachments, the center of the housing on my 8" stock rear end would deflect 1/16" to 1/8"!
That's a lot but it obviously springs back when the car is on the wheels, and it never has caused a problem. The axles, where their splines engage the center chunk, can be moved up and down WAY more than that without binding.
99% have been doing this for decades. Rear axle problems on "non-performance" cars are almost non-existent.
BUTTT... When simple engineering principles are applied, there is a fair amount of deflection in the rear axle housing when you do this.
Givens :
Upward force at the jack point (A)....................................approx. 500#
Downward force at each of the spring attachments (B).........approx 250#
Distance between (A) & (B) .............................................approx 2 ft
My guess is if you placed a dial indicator at the center of the housing, set up so it reads deflection from a reference line that remains a constant distance from both spring attachments, the center of the housing on my 8" stock rear end would deflect 1/16" to 1/8"!
That's a lot but it obviously springs back when the car is on the wheels, and it never has caused a problem. The axles, where their splines engage the center chunk, can be moved up and down WAY more than that without binding.
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