Simple question before I have to post the more complicated ones. How do I lift the back of the car correctly in order to run the driveline? Is there a safe, or correct way to do this?
Thanks you
Thanks you
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Re: C-3 on stands ??
Brad-----
There are several ways to do this but, SAFETY is the most important criteria. Both methods that I will suggest involve first chocking both front wheels on both sides(front and rear). Next, the car can be raised using a floor jack positioned forward of the triangular frame reinforcements found just forward of the rear wheels. With the car sufficiently raised, place jackstands under the triangular area or just forward of them on the frame rails. Make sure that the jackstands are securely positioned and then lower the car carefully and SLOWLY onto the jackstands. Check to be sure that the jackstand is straight and secure before removing the jack. Do not lift the car to a height any more than necessary for the operations that you are going to perform. The higher the lift, the higher the overall center of gravity and the more unstable the car.
A second method that I, personally, prefer is to use concrete blocks instead of jackstands. I do as above, but place concrete blocks, WITH THE SQUARE HOLES VERTICAL, under the "triangular" reinforcements. Then, I place sturdy pieces of wood(I use 2"X 8" sections about 18" long)on top of the concrete blocks. You can adjust the height by adding or subtracting the wood sections. Still, I do not recommend raising the car any higher than necessary. The concrete blocks, oriented as I mentioned, have FAR MORE compressive strength than is necessary and, in my opinion, provide for a much more stable and "slip free" lift. I always worry about jackstands "slipping", particularly with the car running and vibrating, and with this set-up, that worry is eliminated.In Appreciation of John Hinckley -
Re: C-3 on stands ??
Brad,
Some people lift the rear of the car by putting the floor jack directly under the diff. housing, then putting axle stands under the frame just in front of the rear kick-up. I lift one side of the car at a time from the side by positioning my floor jack about one foot forward of the frame kick up and immediately put an axle stand at the corner. I use a block of wood on the nose of the jack to avoid marking the frame paint. The axle stands are direct metal-to metal, I would prefer a few scratches in the paint to the car slipping and falling off (or on me!).
In any case, running the drive train with the car on axle stands is a potentially risky and dangerous practice. Are you sure you NEED to do it?
Mike '73 coupeComment
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Re: C-3 on stands ??
Geezer here. I have never liked running the drivetrain with the half-shafts at the full angle of the u-joints. Therefore, I would add an extra pair of jack-stands under the shock mounting brackets -- just enough to support the wheels and trailing arms and not to take any real weight off the frame supports. JUst my personal preference.
Geezer's MusingsComment
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Re: C-3 on stands ??
Thank you Joe....but I'm trying to run the drive line, which I can't do with the rear suspension hanging. Ol Geezer made a comment to the same effect. With my back tires hanging the half shafts are binding to the point of not being able to turn the wheels at all. I need a way to safely lift the bac wheels. I was thinking of the shock mounts, but do not know if the are strong enough to support the weight.
ThanksComment
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Re: C-3 on stands ??
Brad-----
Using a jackstand under the shock mounts as Old Geezer suggests is not a bad idea, at all. In fact, I may adopt that, myself, from now on. However, I have run the driveline with the car supported as I previously described and didn't have any problems. As far as I know, the system is designed to operate properly even at full deflection. Now, of course, I've never operated it at sustained high speeds and/or for long periods like this, but, I don't understand why anyone would want to.In Appreciation of John HinckleyComment
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Re: C-3 on stands ??
Thank you again. I don't see how you can run them hanging. Mine would bind and probably tear themselves apart. In laymens terms,if I'm picturing this right, the U-joint will hit the part that bolts to the wheel. At least on mine it does. It takes all my might to spin a back wheel by hand at full deflection. To be exact, it will spin about 3/4...then bind. Is this normal?? May be part of the problem I'm looking for.Comment
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Re: C-3 on stands (U-joint binding)
Brad,
Mine binds like yours.
I'm not sure why you want to operate the driveline while the car is in the air, but all the talk about where to place jack stands & concrete blocks makes me nervous.
BE CAREFUL.
Terry
TerryComment
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Re: C-3 on stands (U-joint binding)
Terry -- I'd like to add my opinions to this thread: There are valid reasons to want to run the drivetrain while jacked up (preferably with the half shafts in the normal driving position by supporting at the shock mounts); to listen for bearing / prarking brake / U-joint / differential noises. But I agree it's a dangerous undertaking.
To add to Gene Manno's comments about Scott Sinclair's jacking seminar at Sun Valley, someone asked about concrete blocks, and Scott's advice was to NEVER use them. The problem is (unlike wood blocks or metal tripods) concrete fails INSTANTANEOUSLY, without warning (no creaks or groans). Joe's idea of using a piece of wood at the interface will help to distribute the forces, but the problem is that there are so many shape and strength variants of formed concrete blocks [structural, cosmetic (non-supporting), etc.] that you are playing roulette with them. Far better to use a good single block of wood of similar dimensions, with the compression load taken normal to the grain.
GM did not DESIGN the drivetrain to bind when hanging. Otherwise, this would occur each time you crested a hill at excess speed, just before becoming airborne. Customers would certainly not tolerate any noise coming from the rear under these conditions. Binding when the rear suspension is not loaded may also be coming from contact of the inside wheel rim(s) with the end(s) of the spring, but I don't believe that even this should occur with stock rims/rubber.Comment
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Re: C-3 on stands (U-joint binding)
Wayne,
The reasons you mention for wanting to run the Corvette in the air are valid, however that doesn't put the drive train under "normal" loads and some noises, vibrations, etc. might not appear until under way. Additionally, other abnormalities might appear due to unusual loading of components.
I did have occasion to find bad balance on propeller shaft with vehicle in the air - I had been "fighting" that vibration for much longer than I would like to admit before the "put it up and look" suggestion found the problem. I hasten to add this was NOT a Corvette, and I had it up on a twin post chassis hoist.
Anyway, I simply wanted to make two points, which I will reiterate: My 1970 Corvette with almost all the 30 year old parts on it binds just like mentioned. I agree I wouldn't expect that it was designed to do this, but I am not sure just how thorough the engineering of these kinds of details were 30 years ago. I have heard from others of similar binding of the u-joints. This is not an isolated occurrence.
Again: Any large mass in elevation posses a great deal of kinetic energy. More simply: a falling car is a dangerous thing. LET'S BE CAREFUL OUT THERE! I am just trying to share some hard learned experience. It is no fun being around a falling car. Been there - done that - and I don't want to do it again.
Terry
TerryComment
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Re: C-3 on stands (U-joint binding)
The Joints will bind if lifted this is perfectly normal. I run them all the time to check rotor runnout and other items in the shop. I do it on a lift but there is no reason it can't be done on the floor. Simply place stands under the shock mounts. Make sure that they do not contact the tires or rotors. Lower the car down onto the stands to place the suspension in the normal operating position. Chock the wheels if the front is not raised and use proper caution.Comment
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Re: C-3 on stands (U-joint binding)
Thanks for the advice. The reason I'm doing this is I've had a vibration I've been chasing for 2 years now. It is driving me insane and taking 125% of the enjoyment out of this car. I'm hoping that watching and loading the suspension somewhat I can see or hear something. I will be posting that problem when I have time to go into all the details on what it's doing and what I've done to remedy it. But after listening to all your advice I think I will take the car to a garage ( a friend manages one ) and have the car itself supported on a lift. Thaks again.Comment
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