I am tryin to take the gear shift knob off of my 1990 Saab 900S. It does not screw off like most knobs do

Find a local auto electrician. A professional grade scan tool computer can check for trouble codes and also check transmission solenoid operation.

https://www.google.com/search?q=auto+electrician+near+me

https://www.google.com/search?q=92+Saab+900s+automatic+transmission+will+not+shift+into+gear

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Re-attaching the knob to the gearshift is the key...Look for a hole on the lower section of the knob...if you cannot see it...remove the bottom chrome piece from the knob, (pry apart carefully not to scratch the chrome housing...you should see the small hole normally includes a small allen insert screw or Phillips screw...must be screwed in to the gear shift shaft to hold in place...if you cannot compare...visit a local salvage yard to experiment..."Pic A Part" is a national self help salvage yard. Hope this helps. If the button does not stay in the gear shift knob...you can replace the knob (with button) only...remove the knob as described above. Hope this helps.

http://www.lelong.com.my/proton-iswara-genuine-parts-gear-lever-knob-bestauto-I1272714-2007-01-Sale-I.htm

Most gear shift knobs are just screwed on. Try turning it anti clockwise if yu can not see any screw holding it

My 95 XJ6 does not have the allen screw, all you need to do is get a good grip and turn it loose.

DOWN THE BOTTOM OF THE GEAR KNOB THERE MIGHT BE A SMALL HOLE WHICH WILL BE A GRUB SCREW IF SO PLACE THE ALAN KEY INTO SMALL HOLE AND UNDO DO NOT REMOVE AS IT IS VERY HARD TO PUT BACK THEN THE GEAR KNOB SHOULD BE TURNED ANTICLOCKWISE AS IT IS ON A THREAD AND SIMPLY KEEP TURNING UNTILL IT COME OFF

I own a 2006 9-3 Aero convertible and decided to replace the automatic shifter trim/boot. It's the part that shows the gear selections (P, R, N, D, & M). It required that I remove the shifter knob. First, slightly twist/turn and pull (perhaps wiggle is more accurate) down the shifter collar just below the knob. One to 1.5 inches should work. The ring inside the collar is what secures/tightens the clips of the shift knob against the shifter mechanism. Pull straight up on the knob. Done!

The shift pattern is standard 5 speed H: 1st is all the way up to the left, 2nd straight back and down from that, 3rd is up and slightly to the right of 1st, 4th is straight back and down from 3rd, 5th is up and all the way over to the right. Reverse has a reverse lock out collar under the shift knob that you grip with one finger on either side of the bottom of the knob and pull up while pulling back and all the way to the right.

There are two types of shift knobs. One that unscrews and one that the lower trim of the shift knob separates from the knob using a trim stick. After separating the lower trim from the knob pull upward to release the knob from the shift lever. If a new shifter assembly is being installed, unscrew the original shift knob or separate the lower trim from the knob and pull up to remove the knob from the shift lever. Screw the knob onto the new shifter assembly's lever no more than 14 turns or install the lower trim onto the shift lever then push the knob onto the shift lever and install the lower trim piece onto the shift knob.