I just bought a used 1995 Nissan Quest GXE from a private party and upon getting on the fwy, the transmission started shifting back and forth and the rpm's were jumping from 2000 to 4000. It only happens while I am on the fwy. Does anyone know what could be causing this? I tried to get my money back and the owner just texted me and said "Its just an overdrive sensor, the transmission is fine!" and will not refund my money. HELP!
I am a single mother and fulltime student without the funds to buy another car or a new transmission

Ok first of all just keep calm, there is no reason to believe that the transmission is faulty and requires work. If it shifts nice around town, and on the freeway it shifts into overdrive nicely then your tranny is probably physically ok. It really could be a lot of things so it's pretty hard to help with specifics.

Here's my advice: call the guy back that you bought it from, and calmly say "ok, if it's just a sensor that needs to be replaced I'm ok with that, but if it is something far worse such as a bad tranny, computer etc. than you need to give me my money back, I'll pay a mechanic to diagnose the problem if you agree to these terms", and get it in writing, actually if the guy isn't willing to sign anything email or text messages are better than nothing, and better than verbal agreements without a witness. Other than that you'll have to take it to a shop that you trust and get the problem diagnosed so you know what you're dealing with. The rule ALWAYS applies; "buyer be ware" - never purchase a used vehicle without an inspection first. I know this doesn't help you but you need to know who's responsible for what in this situation, and the seller isn't responsible to give your money back, so if you call him back make sure you stay calm because you're really at his mercy if he wants to help you out or not, try to play on his morality and guilt him into helping you if it's a major repair.

Chances are it could be a minor repair so don't stress out until you know the details of the problem - good luck!!

Thank you, I'm trying not to stress out, and I learned a valuable lesson...and now I know why people will pay double at the dealership for used cars. The reason I am freaking out is because I answered an ad for a 98 Quest and I asked again once I was there, if it was a 98, and she said yes. I got it to the DMV and it was a 95. I realize that was my fault to but because she lied to me and won't return my calls I just feel like I got ripped off!
Thanks again for your advice :-)

That sucks, you've got my sympathy, even though you should've checked it out in detail on your own instead of taking her word for it, I really respect people like you who basically have faith in people and actually are willing to trust. Yes, you might get burned sometimes but I'm like you, I like the feeling of being a good person and giving those around you the benefit of the doubt that they are good too and will be honest and fair. By being a good person and trusting, it's like doing a good deed - if I were selling the car for example, it would make me feel good that you trusted me and didn't act like a jerk questioning my word and demanding documentation and proof of everything. That's called treating people with respect and the way we'd all like to be treated and I believe it has the "pay it forward" effect.

In contrast, you could be a suspicious untrusting person, and you'd probably get further ahead in life but life isn't about being selfish and just looking out for yourself. Once society degrades to the point where nobody trusts anybody, then humanity has taken a step backwards and we're all missing the point of life.

Sorry to ramble, but I thought maybe I'd point out some good in this - even though you ran into a bad person and she took advantage of you, that does't mean everybody is like that and that definately doesn't mean that you should be like that either. You sound like a good person who trusts, and that's a very good thing. Don't let the bad people get you down or change you, next time will be better!!! (and it can't hurt to do a little discreet background checking and still take a person's word as legitimate).

This isn't a fix but if your vehicle has the ability to turn the OD off (button on shifter anywhere?) you could do that until you get it resolved - just to avoid the back and forth shifting.
Most newer vehicles have this. If you're towing, for example, it's good to be able to just take OD out of the equation in some circumstances.
Good luck.

did you found out the problem?

it seems that your vehicle was in "limp mode"

my problem with the 2002 model was the vehicle speed sensor

if your van can't go past a certain speed on the highway, past 50mph, its in that mode

i d/l the service manual from this site and performed the on board diagnostics to confirm

crawled under and remove/replaced the sensor

and i can now go back on the highway without that weird shifting

I would have someone check out the temperature sensor, and also make sure the engine is warming up to normal operating temperatue. Most Nissans lock out the overdrive unless the transmission and engine are warmed up. I'm not sure if the Quest is Ford-based or Nissan-based in terms of it's control... the older Quest was a joint venture between Ford (Mercury Villager) and Nissan.

Heath

Hi i am the owner of a 98 Quest and had the same problem i had noticed some dead spots as i accel in neautral and suspected a bad TPS sensor i got a new TPS and replcd it and guess what finito no more loco shifts on hwy had me scared
too good luck the sensor is not that expensive about 35 us