[jaseology]

So the automatic shifter assembly inside the car only engages Park and slides loosely/freely between all the other gears. When sliding freely between all the other gears the transmission appears to be in neutral because I can push the car in any gear (except Park, it engages in Park). What can be the issue? I checked underneath the car and the linkages are all intact and moving.


Any help is appreciated. Thank you.

 

[rbohm]

an automatic is not like a manual transmission. it uses clutches and bands under hydraulic pressure to engage the gears. so when there is no hydraulic pressure on the bands and clutches, there is no friction, thus nothing to hold the car in place.

when the trans is in park, the parking pawl locks the output shaft into place, which locks the driveline and prevents it from turning.

 

[jaseology]

an automatic is not like a manual transmission. it uses clutches and bands under hydraulic pressure to engage the gears. so when there is no hydraulic pressure on the bands and clutches, there is no friction, thus nothing to hold the car in place.

when the trans is in park, the parking pawl locks the output shaft into place, which locks the driveline and prevents it from turning.

I didn't know this. How do I troubleshoot this? Just fill with fluid (transmission is drain right now), warm up, and test? If so, how many quarts of fluid does it take?

 

[rbohm]

I didn't know this. How do I troubleshoot this? Just fill with fluid (transmission is drain right now), warm up, and test? If so, how many quarts of fluid does it take?

troubleshoot what? that with the engine off there is no pressure on the clutches?

 

[jaseology]

troubleshoot what? that with the engine off there is no pressure on the clutches?

The shifter slides loosely back and forth without actually engaging any of the gears and this is with the engine off with the transmission filled with fluid and with the engine on with the transmission filled with fluid. The valves should have pressure in both of these scenarios, thus gears engaging, correct?

 

[rbohm]

unless the engine is running, there is no pressure in the system, because the pump that provides the pressure is not running. so again what is it that you do not understand about this?

 

[jaseology]

unless the engine is running, there is no pressure in the system, because the pump that provides the pressure is not running. so again what is it that you do not understand about this?

Okay, I understand now.



I guess the transmission might be shot since even with the engine on the gears don't engage.

 

[rbohm]

now that might be a possibility, or the shift lever is not engaging the valve body. start by pulling the oil pan and check to make sure the shift lever is properly engaged or not.

its also possible to have a bad pump as well, so check the pressures with the engine running.

 

[289vert]

If you mean you can work the shifter back and forward without using the button, except in park, it's a shifter problem and not the box.
Edit: just saw that there was no movement with engine running... is there enough oil in it?

 

[Grimbrand]

Two things you definitely want to check before trying to drive around or adding more fluid. First, make sure the linkage is actually moving the shift lever on the transmission. With the button pushed in so the detents don't prevent you from moving the shifter, you should still feel 'bumps' as the shift lever inside the car moves the shift select lever on the transmission. If they're disconnected, you can move the lever inside the car all you want and the transmission won't notice.

Secondly, with the engine idling, check the dipstick on the transmission. It's on the passenger side of the car, up by the firewall. The dipstick should read between the clear and simple-to-see marks. If it's too full, your fluid will get foamy and cause trouble as it is aerated by all the moving parts. It will probably leak, and since foamy fluid compresses (unlike normal transmission fluid) your car will not shift properly. If it's too low, your car probably won't want to go into gear at all. If there's no fluid on the dipstick, add one quart at a time till you see it on the stick. Then add half a quart at a time till it reaches the proper marks. Your fluid should be bright sparkly red. If it's not transparent, has a rusty or brown color, and/or smells burnt, your transmission may need to be serviced. It certainly needs the fluid changed. It is possible, and even likely, that if it's malfunctioning and has nasty looking fluid, changing it will not help your transmission out. That's not the fault of the new fluid though, just an indicator that your friction materials need to be replaced, or that something's got a problem. It is a good idea to always use Type F fluid in C4 transmissions. Modern friction materials do not all require it, but it has some advantages over a lot of the new fluid types, like anti-foaming agents and a friction modifier that will help give your car strong, positive shifts. (GM guys have known for years that putting Type F in their TH350 and TH 400 transmissions is a bit like putting in a shift kit.)

If you have original friction materials, they require Type F, and using any other kind will probably make it slip until all the friction materials fail, even if you later add more Type F.



Hope this helps!