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Matt, Engineer
Category: Transmissions
Satisfied Customers: 21973
Experience:  Mechanical Engineer BEng Hons22 years experience in car engine industry, 10 years in formula 1
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I have a 95 Saab 900 se. It's an automatic. I was driving it

Customer Question

I have a 95 Saab 900 se. It's an automatic. I was driving it and it started acting like it had a flat tire. It shook bad. Got out and no flat. Drove again then started doing the same thing shook bad I stopped at light and started to go but car wouldn't go in drive so I shifted to 3 and was able to drive 1/2 mile shook bad when braking again and had to shift to 2nd and got another 1/2 mile to my moms and I parked in reverse and was fine when idling and started fine. Reverse was good. Came back to park it in driveway about 4 hours later and I started it and reversed worked and I put in drive and it was fine but started doing same thing again. What could it be. Could it be a sensor or and axle.?
Submitted: 1 year ago.
Category: Transmissions
Expert:  Matt replied 1 year ago.


I'm assuming that there's no check engine or other fault lights on so this could be a suspension issue

- jack the car up so the wheel is off the ground (you’ll need to do this for all 4 corners) and shake the tyre from top to bottom and from side to side (with someone holding the steering wheel on the front) there should be no play in either direction. Any play in 1 direction will usually require a joint to be replaced, if there’s play in both directions then the wheel bearing may be at fault. If theres play only up and down its the strut top mount - to find this one you have to shake the suspension strut it self up and down with the wheel off the ground - so you may need to remove the wheel to check this one.

Now with the car jacked up on that side with the wheel about 2 inches off the ground use a steel bar under the wheel and lever the wheel up and down slightly, you should be able to look at the end of the axle and see if the suspension arm is moving up and down separately to the axle.If so replace the bush

To feel if there's a worn strut top bearing then lightly hold the spring by hand and have your assistant move the steering from left to right with the wheel on the ground - a worn bearing will feel 'notchy' through the spring. The wheel needs to be on the ground for the test to load up the bearing

Customer: replied 1 year ago.
Front struts and assembly are brand new that's why I asked if it could be an axle. because if it sits and it will move again but start up a little down the road when driving? no check engine light my triangle light is on due to my srs light and abs light sensor need to be replaced but no engine light...
Customer: replied 1 year ago.
Just to clearify the car shifts to drive but wouldn't drive when in drive after I stopped at light. so that is why I shifted to 3rd and then to 2nd. Then when letting it sit I could drive it in drive.
Expert:  Matt replied 1 year ago.


I've known an ABS fault to sometimes give issues like this

so I'd suggest to check the wheel speed sensors and I'd first check the connections at all four corners first for any signs of corrosion or chafed wiring.

The sensor is located in the wheel hub so you'll have to remove each wheel in turn to inspect them all.

Also check that the toothed wheel that the sensor points to is clean and free of any debris.

you can check each sensor's function by plugging the two output wires into an AC voltmeter and spinning the wheel quite quickly, you should get a voltage signal that increases with rev's.

Its possible that the fault is only a bad connection to one of the wheel sensors.

This may be remedied by removing each wheel in turn and unplugging each sensor and cleaning the contacts with a squirt of electrical contact cleaner. Then refitting.

Customer: replied 1 year ago.
is it possible to use a check engine tester to tell me what abs cable is bad again? But like I stated I don't think that is problem since it has been on for the last 3 years.
Expert:  Matt replied 1 year ago.


OK thanks for that reminder

yes a reasonable diagnostic device should be able to tell you what corner sensor is at fault

but to get back to your issue

if the suspension is OK and you doubt its the ABS then lets try looking at the automatic transmmisson

I'd take a look at the colour of the transmission oil it should be a dark red colour if its black then its needs changing together with its oil filter. Also check its level with the gearbox warm and just after you've moved the selector through all the positions leaving it for a few seconds in each one and then back to park.

You can top up the box through the dipstick tube if required and make sure you use the correct oil for your car as the fluids are not all the same. Some manufacturers recommended a change of the type of fluid - Speak to the local dealer and parts dept - they will advise you on the updated fluid to use..

If that’s all OK then check all the electrical connections of the gearbox, remove each connector in turn and spray with contact cleaner. Check that the wiring to the gearbox is in good condition with no chafing or frayed wire

If this is OK then check the selector lever linkage / cable under the car for any broken parts and or missing bolts as if this is coming adrift then it can rub on the car body or just bind up

Then - you should top up if low and re try it - or, if its level is ok - and condition is ok - then the next step is to drain it off - open it up and clean the filters inside -- refill and retry it..

Customer: replied 1 year ago.
Drove it again to move and it seemed like brakes were grabbing on one side. Not sure if that was because of abs or not? only does it when braking.
Expert:  Matt replied 1 year ago.


sounds like it would be worth checking over the brakes

I'd strip the calipers down and check that the pads are in square and true with no debris in the mounting slots, also inspect the caliper mounting faces for any dents, burrs, or debris which would cause them to be bolted up out of true, also remove the disc and do the same for its mounting face on the upright and inside the disc.

If you still have an issue then it could be a flexible brake line has partially collapsed and is producing a one way valve, this can't always be seen from the outside but you can test to see if there's any residual pressure in that caliper by cracking off the bleed nipple after stamping on the brake a few times

Another possibliity is that one caliper is sticking slightly so the piston isn't retracting on its seals

in which case that caliper will need rebuilding with new seals or replacing

Expert:  Matt replied 1 year ago.


do you still need help?

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