A friend's Toyota sienna just wont move on the highway, the suv was later towed to his mechanic workshop,they later told him the gear is bad.
my question now is how do you know that the gear is about to have a problem(my friend said the ATF was well gauge)what then could have gone wrong that the user need to put into consideration.

The question is what did he do before then.

Was any service performed?

kingboy:

A friend's Toyota sienna just wont move on the highway, the suv was later towed to his mechanic workshop,they later told him the gear is bad.
my question now is how do you know that the gear is about to have a problem(my friend said the ATF was well gauge)what then could have gone wrong that the user need to put into consideration.

infor missing

type of transmission, did it crank when trying to start, or it would start but wont engage in gear

fear not, i had numerous expirence on this ,if you don't mind let me come to run
my scanner on it. You tell the mechanic what to do ,or not him conderming your engine.

Scan your car:From 5k

https://www.nairaland.com/nigeria?topic=570969.msg7389414#msg7389414

Regards.
fear not

Every problem starts small. The problem is we sometimes do not notice the small signs when they show.

B4 d gear gets that bad, it must have shown signs like
a) slow response to firing i.e acceleration. This delayed response may be imperceptible to a passenger on the ride but the person who usually drives it will notice but will usually assume it is nothing.
b) When a gear is engaged from parking or neutral, the vehicle immediately experiences a certain ferk or force. If there is a delay slight but noticeable delay before this jerk, there might be an issue.

So what could be the cause or these dalays which signify the possibility of an automatic gear problem? Three things come to mind:

1) Like you already said, ATF gauge -If the oil in the gear pump is not enough
2) Loss of oil fidelity - Just like engine oil, all oils loose fidelity with use. It makes sense to drain oil after sometime and replace it with fresh new oil - just like engine oil.
3) Overworking the gear system: Even though auto gear changes by itself, it still follows the normal process of going from gear 1 to 2 to,  gear 5 or   6. Some people depress the accelerator with the intention of moving the car from gear 1 to 5 in once push-down. T oil pump in the gear is being overworked and with time will give way. The fibre wears and with time will wear out.

[size=16pt]Bottom Line is[/size]:

If the engine is working well but the gear won't engage, the oil pump in the gear has broken down as a result of the above possible reasons. Most times, if a good mechanic changes the pump or the fibre or the entire gear system, the cars comes back to normal. It requires some money and seasoned expertise.

@coollany
the mechanic changed the pump but later found out that the fibre and some metal stuff are broken and he advise a change(the said gear use the same type with Camry gear)

i notice that my rpm is below 1 and when my gear is changed from P to R you feel some kind of force like the engine is about to come down,i hope that this is not a sign and how often is it advise to change the ATF oil(most mechanic will tell you the oil that came with it is good)
also notice when i am reversing uphill i have to depress the pedal for it to climb.

i am asking all this just to be on the safer side,for i love my vehicle to be in good order.

''the mechanic changed the pump but later found out that the fibre and some metal stuff are broken and he advise a change'':
Just in line with what I have said.

''i notice that my rpm is below 1'':
If you mean when the car is steaming, that is warming up, it is normal. When a car is started in the morning, the rpm gets to 1 or more but will later drop to about 0.7. But it has nothing to do with the gear. I'd say yours is ok.

''when my gear is changed from P to R you feel some kind of force like the engine is about to come down'':
Since I cannot see the car, I cannot concretely say whether this is ok or not. But be rest assured that there is always a perceptible jerk. One feels this jerk more with older models of cars. With newer models, the jerk is not as much. So, yours may be normal. You can see a trusted mechanic if you are still uncertain. If you feels it more than you ought to compared to similar models of your car, then maybe one or more of your engine sitting - that thick rubber upon which a car engine in mounted - is bad (that's what i suspect in your case). Again, not a sign of gear problem.

''how often is it advise to change the ATF oil(most mechanic will tell you the oil that came with it is good)'':
If your Mechs say the quality of the oil that came with the car is better than what we have here, it goes without saying. But they certainly are not saying you should drive that one that came with it through out the life of the car.
Unfortunately, i don't think we have local methods of checking the efficacy of car oils - viscosity, purity et all. We tend to judge by sight, feel or measure by length  of usage. Anyhow, just ask a good mechanic. Depending on usage, i'd recommend change of gear oil once a year or once in two years.


Bottom line:
Since I am not with you to assess these, take what i say as a guide. You need a properly trained honest mechanic who can assess it better.

disregard typo errors.

@coollany bro yo blow my mind, i am an engineer (not a practicing at that), i know what keeps the engine running his proper maintenance and i totally agree with you.about the jerking i will change the engine sitting below the engine cos i have changed that on top.its nice talking with you will keep you posted on progress report.

just contributing my quota to making a brother happy.
glad 2 hv made any impact. thanks 4 d compliment.

@coollany an others
i suggest we talk more about maintenance tips,atleast this will wake up our sleeping mtce culture

Hello @coollany, u sound professional. Do u have a workshop or somethin like that? I need ur guide and professional advise? <chibenx@yahoo.com>

@walkabout :

Actually I am not.
Just that I have been driving cars with automatic gears over time.
I don't have a workshop either. Hope I didn't disappoint you.
Cheers.

@Kingboy:

Sounds good!

see what i mean the maintenance thing is a good idea and Nigerians are shy about it.
@coollany
i dont mind you given us tips like "do you know" i.e if you have things that you know we should digest when it has to do with mtce of cars

@ coollanny
the gear has been replaced and fixed after long driving because the guy said he was given one week's grace on the gear.
we noticed heavy jerk and the seems to be softer than expected also some changes was noticed which was during the Drive (a feel of jerk is noticed which is not like that b4.

hope this is ok or he needs to change it.

@kingboy:
the unfortunate thing here is that we cannot grade the magnitude of a jerk the way that of an earthquake can be graded. So when you say jerk, small jerk or big jerk, I cannot relate with the intensity of what you describe the way i would if i were there. But a rule of thumb in is : if it doesn't feel right, then it ain't right. If you hear unusual noises, experience rough movement or see car parts that are not sitting properly where they ought to, raise an alarm until things are meaningfully explained to you.

@COOLLANY
GREAT SAYING, I ADVISE HIM TO RETURN TO THE MECHANIC,FORTUNATELY HE AGREED TO TAKE IT TO LADIPO FOR FIN TUNING AND THAT THE ENGINE SITTING BELOW THE ENGINE COULD BE THE REASON FOR THIS JERKING.

IN ALL AREA I AM ENJOYING THIS AVAILING ME THE OPPORTUNITY TO CHECK MY SIENNA AND LISTEN TO THE STRANGEST OF NOISE ALSO I NOTICED THAT WHEN DRIVING WITH THE AC ON YOU RARELY HEAR ANYTHING GOING ON THE ROAD, I ADVISE THAT ONCE IN A WHILE(IT WONT KILL) WE SHOULD LOWER THE GLASSES FOR FRESH AIR AND TO LISTEN TO ANYTHING STRANGE ESPECIALLY ON A BUMPY ROAD.