THank you for using just answer.
If this noise is only present when the transmission is in 4th gear then yes this noise will be isolated to the internal gearing in the transmission unit.
I can fully understand that it is hard to invest $3,600 in a vehicle that is 8 years old, however there are alternate options here.
What the dealer is quoting you here is a genuine toyota remanufactured transmission, what I would consider here if I was you is to install a used transmission. Usually you can get a used transmission from a salvage yard for around $1,500 and they offer a minimum of a 90 day warranty on the unit, most good salvage yards offer extended coverage on replacement engines and transmissions that extend up to 2 years time for a small additional charge. The labor time for replacing a transmission is about 5 hours on this truck so if you were to install a used transmission you could basically cut this repair bill in half here.
Thanks for your answer Peter.
I finally found several mentionings of the same problem on forums - with no better answer then you gave me. Actually quite a few of them. Different mileage - same issue. Which tells me there is no guarantee that the "new" used transmission wouldn't fail at any time, which could be in 2 years and 1 month. Then I have to spend $2K again.
To help prevent that from happening can you please answer few other questions below. If you could answer #2 in detail I would be happy to accept your original answer as well.
1) What would be your guess of the root cause of that issue? (Please exclude the lack of transmission fluid or having old fluid). Is that 4Runner design flaw where transmission becomes a "weak link" to transfer engine's power to the rest of the power train and wears out prematurely? Is that other parts on a way from tranny to wheels that are typically overlooked, not greased on time and put extra load on transmission (and engine) making it to fail over time? I still don't get why 4th gear is failing and not the others.
2) What are the most important moving parts between transmission and wheels that transfer power and require periodic greasing on 4Runner from your experience? I don't mean those parts that have fluid in them and are part of scheduled maintenaces. Many people are experiencing different tranny problems on older 4Runners and I would like to take preventive measures as much as I can in order to avoid such issues in future. For instance one problem was remedied by greasing a slip-yoke - what are other parts like that?
Thanks a lot for your help.
To answer your questions here:
1- Keep in mind that this is a very large production vehicle, you may find 100 blogs online complaining about the same problem but when we produce tens of thousands of these a year this is not a "common" or "widespread" issue. While yes I have replaced several of these transmissions I have plenty of high mileage 4 runners that come through all of my dealers shops and never have an issue. Typically if you do heavy off roading with this vehicle or of you tow with it on a regular basis then yes it will cause more wear and tear on the unit. I do ocasionally see where the main planetary gears on this particular transmission will make a sound similar to a shot gun as they seperate and then it will completely destroy the unit and render the vehicle completely unmovable. You would have to see the inner workings of this transmission and see how 4th gear is setup to really understand how it works, the vehicle rides a majority of it's mileage in 4th gear and gear lash on a worn transmission can cause more noise in this gear then in others as it increases.
2- These items will not cause your transmission to fail. If you do not properly maintain the driveshaft or the rear differential then you can experience premature wear and failure on these items howeve these items will NOT cause the transmission to fail. If you do not properly grease the universal joints on the driveshaft then the u-joints can wear out and develop freeplay. Same with the rear differential, if the fluid is not maintained and or the level falls low it can destroy the ring and pinion in the rear differential. The 2 most imporant things to prolong transmission life here is to keep the fluid clean and cool. If you install oversize wheels, do off roading, do towing or commonly accelerate hard then yes the transmission will take more abuse. My best friend purchased a 2001 4 runner brand new and now has over 300,000 miles on it and has never replaced an engine or a transmission. Just a point here that this is not a issue with all units.
I bought this vehicle 3 moths ago with "no problems" - that's what that same dealership told me after they inspected vehicle. After I put 500 miles on it before that sound appeared. I am sure previous owner (he was 2nd owner who had vehicle for about 7000 miles) was aware of the problem and figured out a way to hide the sound to get rid of the vehicle. Now I just wonder what he may have done to have sound disappeared. He was nervous when they were inspecting but clearly they did not identify the issue.
And last thing - you may have already said that but I would ask to be sure... I literally don't have money to fix transmission immediately. I drove another 500 miles after that sound appeared - for how long it would live before it collapses? I don't have another vehicle and need to earn money to fix that one. I don't do any heavy driving now, simply drive in town from home to work. Is it relatively safe to use it for another 200, 500 or 1000 miles?
If he knew of the noise it was probably very faint or only present only after driving for a long period of time, there is no way to "hide" a noise from a transmission.
If this noise ONLY happens in 4th gear then I recommend you keep the overdrive off for now to lock out overdrive. If this noise is the gears collapsing it sould literally go at any time.