Toyota 4 Runner Auto changing out of overdrive.

Submitted: Monday, May 05, 2008 at 16:52

ThreadID: 57299 Views:3889 Replies:5 FollowUps:10

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Member - Terry E (NSW)

Could anyone tell me what would cause my 4runner (1992 always serviced, 180,000km) would be operating quite normal and suddenly the speedo stops working and then on its own changes back to 3 speed and then just as suddenly changes to first gear. When it first happened I stopped and when starting again it went normal for some time but now it is getting worse. Regards from Terry.

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Reply By: baldman - Monday, May 05, 2008 at 16:59

Monday, May 05, 2008 at 16:59

Terry,

is it doing it when it is cold, mine has also just started doing it but only when it seems the engine is cold. Once it is warmed up it seems to be ok.

AnswerID: 302152

Follow Up By: Member - Terry E (NSW) - Monday, May 05, 2008 at 18:10

Monday, May 05, 2008 at 18:10

No it runs OK when cold for a certain distance and when it warms up it does it. Thanks for your reply. Terry

FollowupID: 568212

Follow Up By: baldman - Tuesday, May 06, 2008 at 19:07

Tuesday, May 06, 2008 at 19:07

Terry,

try putting a post on this website

http://www.toyotasurf.asn.au

they also have a section for 4 runners so someone there might have experienced the same problem

FollowupID: 568420

Follow Up By: Member - Terry E (NSW) - Wednesday, May 07, 2008 at 09:16

Wednesday, May 07, 2008 at 09:16

From one bald man to another, thanks for your input,but I think I may be getting somewhere. I took my car to a Toyota dealer and I thought for a while that they weren`t to sure about it the way they were talking to me but they have had the car for a couple of days now and seem to have the problem in hand. (I hope) They had to first farm out to an Auto Electrician to rectify the speedo and then nailed the other problem down to a speed sensor. (At least thats what I think they said) I might add that I forwarded them an e-mail with a copy of all the replies I received from the `Explore Oz` forum so maybe all you people out there helped them nail it down. I`m not real computer literate so not sure what you mean by puting a post on that website, if you could give me a clue maybe it might help someone in the future if I did this. I hope to get the car back to-day. For anyone interested the sensor was quoted at $350. Regards from Terry and thanks again.

FollowupID: 568491

Follow Up By: baldman - Wednesday, May 07, 2008 at 17:38

Wednesday, May 07, 2008 at 17:38

Terry

the post should have read forum, the website address I gave you is a forum for all surf and 4 runner owners.

I have been able to source solutions to problems and advice on problems with my runner.

FollowupID: 568592

Reply By: Peter 2 - Monday, May 05, 2008 at 18:36

Monday, May 05, 2008 at 18:36

Check the connections to the speed sensor(s) in the trans especially the output one, which will probably be in the transfer case tail.
If the connections are tight and clean then check all connections back to the puter box that controls it.
If all appears to be ok with the wiring and connections then you can remove(unscrew) the sensor and make sure the end inside is clean and free of sludge/minute particles.
the speed sensors are actually a magnet which a stepper ring rotates past so will attract particles from gears and the trans as it wears. They run only a few thou away from the stepper ring so it doesn't take much to affect the magnetic field.
Best to get a workshop manual as I'm not familiar with your particular transmission /transfer setup.

AnswerID: 302169

Follow Up By: Peter 2 - Monday, May 05, 2008 at 18:39

Monday, May 05, 2008 at 18:39

I forgot to add that the transmission dropping back to a low gear etc is a symptom of an electrically controlled transmission going into limp home mode.
also check eath/ground straps between the transmission/transfer/engine and chassis/body for good clean and tight connections.
Battery voltage is ok?

FollowupID: 568218

Follow Up By: Member - Terry E (NSW) - Monday, May 05, 2008 at 19:20

Monday, May 05, 2008 at 19:20

Thanks Peter, atleast your the only one who seems to know what they are talking about,I have spoken to the NRMA technical Dept and they couldn`t help much. Many thanks from Terry.

FollowupID: 568233

Follow Up By: Peter 2 - Monday, May 05, 2008 at 19:55

Monday, May 05, 2008 at 19:55

Might be worth making some inquiries re the trans so you know how it all works.
On the H1 Hummer there is an input speed sensor (gives engine RPM's to CPU), transmission output speed sensor (which tells the CPU what revs the output of the trans is doing and hence what gear it is in) and a speed sensor on the output of the transfer case (which is fed to a splitter box and one feed goes to the speedo to provide ground speed and one to the CPU to give it final drive revs).
If the reading on one fails (it is usually the transfer case which doesn't have an internal filter like the auto to remove small metal particles in the oil due to wear which in turn build up on the magnetic sensor stopping it working.
I gather you have changed the ATF and had the filter cleaned regularly ;-)) dirty ATF will also muck things up.