What do you think , running off the ground.

I could use some thoughts about running through the gears while the rear is up on jack stands, and off the ground. I am just about done with this project and would like to see if the trans actually turns the rear tires, and if the brakes stop them. I would also like to get fluids pumped through the system. Any thoughts, positive and negative, would help.
Bob

 

Just think about where the car will end up if it comes off the stands. Remember Murphy's Law. I always put some big *** wood blocks under a car in addition to stands. Otherwise there's nothing wrong with doing it and looking for vibration.

 

Dragsters do it all the time.

Just make sure it is stable, I give the car a hard wiggle to make sure nothing
will slip off the stands.

And double check you didn't leave that 9/16 socket on top of the tire.

 

Good input by the others,add to it that don't let rear dangle,droup,jack it by the axle housing so the drive shaft is at were it normely runs so u-joints are not in a bind.

 

Anything that's had major work done should be run & checked for leaks, rattles, etc. before hitting the road. As long as it's a hard, level surface, & wheels are balanced, you should be OK. Sometimes this is the only way you can find a rattle or vibration.

 

If its got a standard transmission, you will be okay. If its an automatic, I wouldn't. Automatics depend on hydraulic back pressure to shift the valve body for changing gears---with no frictional drag on the rear tires, their will be no backpressure created---the ****** won't shift properly (I think).

 

I do it with with my muncie. I don't get carried away but go thru the gears slow.

-CC-

 

It's ok to do, just a couple of things...

Don't just put a single jack under the center of the pumpkin, use two jackstands near the axle ends or the car could tip onto a spinning rear tire.

Please be sitting in the driver's seat when you do this, not standing outside the car.

After you take it through the gears, it is easy to forget to put the brakes on to stop the tires from spinning (because the car isn't moving) before you move the shifter to reverse or park. This will make a bad noise.

Be ready to hit the brakes at any time.

 

I do it on everything I build , automatic or standard transmission . I don't run it for hours or anything like that , but up to speed a few times and then back down to see if the trans. shifts ok and if the automatics downshift as they should as they , or when they are braked and go back to an idle . I haven't hurt anything to date --you can locate a lot of problems a lot easire and safer this way --IMO

 

I warm up my coupe at the strip all the time this way. It has a TH/350 and it shifts through all of the gears just fine when it's off the ground. I believe they also have test run stands for auto transmissions and they spin them to test the operation...with nothing hooked up to them. Most automatics are hydraullically operated and rely on pump pressure. The pump is spun by the motor through the flexplate and convertor, so the trans should be "indifferent" to what is or is not hooked up at the rear yoke.

-Scott

 

Might be a good idea to have someone outside the vehicle to insure that BOTH rear wheels are spinning.
If only one rotates the speed shown by the speedometer is half the actual rotating speed of the single wheel, due to the interaction of the differential gears.

I repaired the torn wheelwell of a 2 door 1975 Chevelle many years ago.
The owner had been stuck in snow and got pissed off, revved it too high and the tire exploded when the rotating speed became too high due to the other tire being stopped. A large chunk of the shredded tire p***ed thru the top of the wheelwell and became lodged into the rear roof pillar area of the car.
It was completely impossible to remove the impaled casing so we cut off the excess and sealed it in with some new metal to cover the gaping hole. Surprisingly, the outside of the quarterpanel was totally undamaged!!!
Just to finish the sad story, the owner (a road salesman for a drug company) fell asleep at the wheel a year or so later and was killed in that same car!
I really believe some cars are just unlucky...

Just make sure your safe OK!?!?