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Discussion Starter · #1 · (Edited)
I am about to replace another transfer case switch. I have replaced both switches (the MT6 has 2) at least three times since I purchased the vehicle new. I don't lock the transfer case very often therefoe these switches don't see very many cycles. I can't imagine that it's wear. It's my understanding that it's the seal that starts leaking oil into the switch that makes it go bad due to internal contamination. A sealed on/off switch is just not that complicated. One would think that Toyota could make one that has an acteptable life span. However, this has got to be one of the most consistently defective parts I have ever encountered.
 

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This is a very popular site for FJC, and it is true that problems with those switches do on occasion pop up. It does not happen or reported a lot. There are more complaints about AT than those switches. I don’t think Toyota has a problem or those switches in general or can be classified as failures in themselves. I will agree that 3 switch failures for you personally is a lot. Hard to fathom that you were lucky enough to draw three bad switches out of the parts bin. It is also hard not to think that there may be another issue more likely than the likelihood of drawing three bad switches. Possibly the connector has a bad connection and when you change the switch you reseat it in a position that completes contact for a while. When you put a meter on the replaced switches are they indeed bad or are they labeled bad because the new ones ended the problem at the time?
 

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Discussion Starter · #3 ·
This is a very popular site for FJC, and it is true that problems with those switches do on occasion pop up. It does not happen or reported a lot. There are more complaints about AT than those switches. I don’t think Toyota has a problem or those switches in general or can be classified as failures in themselves. I will agree that 3 switch failures for you personally is a lot. Hard to fathom that you were lucky enough to draw three bad switches out of the parts bin. It is also hard not to think that there may be another issue more likely than the likelihood of drawing three bad switches. Possibly the connector has a bad connection and when you change the switch you reseat it in a position that completes contact for a while. When you put a meter on the replaced switches are they indeed bad or are they labeled bad because the new ones ended the problem at the time?
It's not just 3 swithches, It's more like 6 (3 ea of the 2 different switches on the 6MT transfer case) that I've had go bad. All from different sources. I have tested the bad swithches, while they were installed and also after removal. After failure they all test bad. Before they go completely bad they will work intermittently. Sometimes you can work the shift lever back and forth to scrub the contacts enough to make a connection. However, they will totally fail eventually. It is not the connectors, they're all good. If you search on the forum, and the Internet in general and you will see that this not an uncommon issue at all. That's one of the reasons a lot of FJ owners perform the "Transfer Case Switch Hack" to bypass the OEM switches completely.
 

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I am about to replace another transfer case switch. I have replaced both switches (the MT6 has 2) at least three times since I purchased the vehicle new. I don't lock the transfer case very often therefoe these switches don't see very many cycles. I can't imagine that it's wear. It's my understanding that it's the seal that starts leaking oil into the switch that makes it go bad due to internal contamination. A sealed on/off switch is just not that complicated. One would think that Toyota could make one that has an acteptable life span. However, this has got to be one of the most consistently defective parts I have ever encountered.
A failure analysis was done and reported on this forum about this problem. It is possible that the transmission/transfer-case breather is stuck. If that happens when the engine is running the heat will cause pressure to build up in both and this can potentially force gear oil past the switch seals resulting in failure of the switch. I have an 07 MT-6 and went through several switches in the the early years. Seeing that report on the breathers getting stuck prompted me to do the Scuba mod on all my breathers and change them all to filters higher in the engine bay (for front) and jack compartment (for rear). Over 100,000 miles and several years later no further switch failures.
 

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Discussion Starter · #5 ·
A failure analysis was done and reported on this forum about this problem. It is possible that the transmission/transfer-case breather is stuck. If that happens when the engine is running the heat will cause pressure to build up in both and this can potentially force gear oil past the switch seals resulting in failure of the switch. I have an 07 MT-6 and went through several switches in the the early years. Seeing that report on the breathers getting stuck prompted me to do the Scuba mod on all my breathers and change them all to filters higher in the engine bay (for front) and jack compartment (for rear). Over 100,000 miles and several years later no further switch failures.
I had read the failure analysis you refer to. However, I did not catch the part about the case breather. I will check that out.
Thanks for the info.
Dan
 

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I performed the failure analysis mentioned here, and have performed the same analysis on three different switches sent to me by forum members over the years. Internally, all the switches are identical, and the three I examined all failed in the same manner, with transmission oil getting past a rubber diaphragm seal and contaminating the internal electrical contacts. These switches control the rear diff lock, the front differential actuator motor, and the transfer case neutral light, but are all of identical design and construction.

The initial failure analysis is here:
Failure analysis: failed transfer case switch =...

First of all, I will say that it is EXTREMELY unlikely that your switch 'failures' are actually being caused by 'defective switches' --- there HAS to be some other factor involved that is either causing actual switch failures, or is giving the appearance of a switch failure when in fact it is something else.

On the 'defective' switches you replaced, did you absolutely confirm that the switches were defective by making internal resistance measurements using a quality digital multimeter?

The problem on all the switches I have seen is that in the 'closed' condition (mechanical plunger depressed), the resistance measured from several ohms to several thousand ohms. In the 'closed' condition, the resistance must be a tiny fraction of an ohm maximum, and to measure this low resistance accurately requires a quality multimeter like a Fluke, etc.

Switch internal resistance should be a tiny fraction of an ohm when closed (a few hundred milliohms max) and multi-megohms when open.

If your switches are actually failing the resistance test, the primary suspect would be a pinched breather line on the transfer case, which causes a buildup of internal pressure in the transfer case and forces oil past the rubber diaphragm seal inside the switches.

One other remotely possible cause is that at some point the transfer case was filled with an extremely low viscosity lubricant, flushed with a solvent, or is contaminated with something that softens the rubber seal inside the switch.

If the 'defective' switches pass the resistance test, then you have some other electrical system problem that is making you think you have a defective switch.

(If you still have any of the 'failed' switches, I'll be happy to perform the same type of failure analysis.)
 

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Discussion Starter · #7 ·
I performed the failure analysis mentioned here, and have performed the same analysis on three different switches sent to me by forum members over the years. Internally, all the switches are identical, and the three I examined all failed in the same manner, with transmission oil getting past a rubber diaphragm seal and contaminating the internal electrical contacts. These switches control the rear diff lock, the front differential actuator motor, and the transfer case neutral light, but are all of identical design and construction.

The initial failure analysis is here:
Failure analysis: failed transfer case switch =...

First of all, I will say that it is EXTREMELY unlikely that your switch 'failures' are actually being caused by 'defective switches' --- there HAS to be some other factor involved that is either causing actual switch failures, or is giving the appearance of a switch failure when in fact it is something else.

On the 'defective' switches you replaced, did you absolutely confirm that the switches were defective by making internal resistance measurements using a quality digital multimeter?

The problem on all the switches I have seen is that in the 'closed' condition (mechanical plunger depressed), the resistance measured from several ohms to several thousand ohms. In the 'closed' condition, the resistance must be a tiny fraction of an ohm maximum, and to measure this low resistance accurately requires a quality multimeter like a Fluke, etc.

Switch internal resistance should be a tiny fraction of an ohm when closed (a few hundred milliohms max) and multi-megohms when open.

If your switches are actually failing the resistance test, the primary suspect would be a pinched breather line on the transfer case, which causes a buildup of internal pressure in the transfer case and forces oil past the rubber diaphragm seal inside the switches.

One other remotely possible cause is that at some point the transfer case was filled with an extremely low viscosity lubricant, flushed with a solvent, or is contaminated with something that softens the rubber seal inside the switch.

If the 'defective' switches pass the resistance test, then you have some other electrical system problem that is making you think you have a defective switch.

(If you still have any of the 'failed' switches, I'll be happy to perform the same type of failure analysis.)
Thanks for taking the time to forward a detailed reply, and thanks for performing the failure analysis you posted previously. I did perform a resistance test on the switches that went bad. I also initially did a "jumper" test on the vehicle side of the connector. When the contacts were jumpered (shorted) the dash lights iluminated as if the transfer case had been shifted into a High Locked or Low locked condition. It's been a while since the last one went bad, and if memory serves, I only checked to see, if when in the closed position, I was getting continuity or not from the switch. The switches were bad. After replacement all of the dash lights would illuminate properly depending on the position of the transfer case shift lever. Unless there is something weird going on electrically to ruin only the switches and nothing else (unlikely) then the only electrical problem is the switches themselves. The first switch I had replaced was done under warranty (less than 100,000 miles) by the dealership. The rest have been replaced by myself. I now have over 300,000 miles on the vehicle. I will do a more thorough resistance check on the switch I will be taking out shortly. I will also be checking the breather for a blockage (I am now suspicious of this). I have not cut any of the bad switches open, but given that they would fail "intermittently" before complete failure I strongly suspect it was due to oil infiltration slowly contaminating the contacts. I am the original owner and the transfer case has never had anything in it but gear oil of an appropriate viscosity (Mobil 1 and Valvoline synthetic 75w-90). It's never been flushed with anything. I will be more than happy to send you the "failed" switch after I pull it out. PM me with the address to send it to.
Thanks again
 

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Alpine_FJ -

What's really odd is that your failure rate appears to be 10X or 100X the 'typical' failure rate for these switches across the entire spectrum of manual and automatic transmission FJ Cruisers Tacomas and 4Runners.

As the original owner you know the service and usage history for the vehicle, and the use of M1 and Valvoline lubricants should not be a factor.

I'll send you a PM with my address, I'm in S. California and will gladly pay shipping in the interest of knowledge gained performing a failure analysis of another one of these switches.

(At 300K miles, you obviously have taken care of the beast. Not to hijack the thread, but I'd like to grill you on overall reliability:
Are you still on the original clutch?
Any issues with the clutch throw-out bearing?
Alternator replaced at what mileage?
Still on original starter?
Wheel bearings?
Water pump?
Any other notable issues?)
 

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Alpine_FJ -

Before you replace that switch, perform one quick test if you can.

With engine off, sharply cycle the transfer case lever in and out of H, HL and LL ranges 50 time or more, just to see if repeatedly actuating the switch will break through the tarnish or contamination that's likely present on the switch contacts and restores switch function.

I ran into this exact problem with my '00 4Runner about 10 years ago, and after about 40 actuation cycles the switch suddenly closed and has operated reliably ever since then. I now actuate the transfer case lever several times every month just to 'exercise' the switch.

The switch itself is a rare example of poor design by Toyota (or one of Toyota's vendors). All electrical switches, especially those that only switch low-voltage, low-current loads like signaling an ECM, should be designed with a 'wiping' action that generates a sliding interface between the contacts when the switch is actuated. This tends to 'scrub' off any tarnish or contamination on the contacts, and expose clean, bare contact surface for a very low electrical resistance when the switch finally closes. This is usually SOP in electrical switch design.

The Toyota TC switches do not provide any sliding contact at all - the moving contact plate has a straight-line movement as the switch plunger is actuated, and then gently presses against the fixed contacts in the molded plastic part of the switch. This type of switch is very vulnerable to contamination on either the fixed or moving contacts.
 

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Discussion Starter · #11 ·
Alpine_FJ -

Before you replace that switch, perform one quick test if you can.

With engine off, just sharply cycle the transfer case lever in and out of LOCKED mode 50 time or more, just to see if repeatedly actuating the switch will break through the tarnish or contamination that's likely present on the switch contacts and restores switch function.

I ran into this exact problem with my '00 4Runner about 10 years ago, and after about 40 actuation cycles the switch suddenly closed and has operated reliably ever since then. I now actuate the transfer case lever several times every month just to 'exercise' the switch.

The switch itself is a rare example of poor design by Toyota (or one of Toyota's vendors). All electrical switches, especially those that only switch low-voltage, low-current loads like signaling an ECM, should be designed with a 'wiping' action that generates a sliding interface between the contacts when the switch is actuated. This tends to 'scrub' off any tarnish or contamination on the contacts, and expose clean, bare contact surface for a very low electrical resistance when the switch finally closes. This is usually SOP in electrical switch design.

The Toyota TC switches do not provide any sliding contact at all - the moving contact plate has a straight-line movement as the switch plunger is actuated, and then gently presses against the fixed contacts in the molded plastic part of the switch. This type of switch is very vulnerable to contamination on either the fixed or moving contacts.
I have already done the shift in and out repeatedly over and over with virtually all of the switches that went bad. When they first start to fail this method will many times get them to work. However, at some point they apparently get so bad that doing this will no longer yeild any positive results.

I am planing to check the breather line to make sure it is not blocked. I am very suspicious of this being the culprit. However, there is one thing that is interesting. at probably around 175,000-200,000 miles I had removed the transmission so that I could install an upgraded throw-out bearing and replaced the clutch. This of course meant that I disconnected the breather line then reconnected it. At the time I was not worried about the breather line having any issues so I didn't do any inspection of it. But, I was having the switches go bad both before and after this.
 

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Discussion Starter · #12 ·
I swapped out the Left Switch and every thing works fine now. That switch is bugger to get to. However, if you unbolt the transmision mount cross bar and drop the transmission and transfer case about an inch its a piece of cake.
 
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Discussion Starter · #13 ·
I pulled the breather line end filter and it was not clogged. I'm going to perform the scuba driver mod and see what happens.
 

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2008
Automatic

4hi light not working on dash when engaged (GREEN indication). I'm having a bit of trouble sorting through the old treads to help me find a solution. the fj does go into 4LO and the rear locker does engage. I've seen a few old treads talking about bypassing the transfer case switch.

1) what is the part number for that transfer case switch for 4HI?
2) Is it the #3 switch located on the passer side of the transfer case ?

Any help with this would be greatly appreciated .
 

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@WhiteFJ08 I just replaced my 4wd switch, the only one on passenger side - it’s part#84222-35110. Just to confirm, you get absolutely no lights on your dash when you pull the transfer case lever? I had the same, and with new switch works perfectly now.
Access to the switch is a pain and greatly helped with a simple homemade tool mentioned elsewhere on the Forum, a 27mm socket with slot cut for the switch wiring. What also helped us was a belt tightener attachment in the wrench. Pics below. GL
Wrench Hand tool Wood Tool Kitchen utensil

Household hardware Gas Nickel Auto part Kitchen utensil

Cylinder Gas Tin Metal Aluminium
 

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Correct. I only light I get is the rear locker (solid red) when I engage it while in 4 lo. I tried to do the bypass, but had no luck . 4 lo engages perfectly… I can tell because when I throw it into 4lo , you can feel the FJ “squat “ a lil bit and I tested it out on some hills .

Bypass:
-cut the pigtail close to the sensor. Use the pigtail
( that’s still connected to the harness) and wire it to a single pole switch . now after I done all that … still no luck.

please feel free to ask me any obvious questions about my situation, I’m far from a mechanic lol .
 

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Yours really does sound like a classic switch failure, and will be fixed with a new switch. I’ve had a bypass and ended up disconnecting it - mine functioned with an additional switch on the dash which was a hassle.
 

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2008
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4hi light not working on dash when engaged (GREEN indication). I'm having a bit of trouble sorting through the old treads to help me find a solution. the fj does go into 4LO and the rear locker does engage. I've seen a few old treads talking about bypassing the transfer case switch.

1) what is the part number for that transfer case switch for 4HI?
2) Is it the #3 switch located on the passer side of the transfer case ?

Any help with this would be greatly appreciated .
There could be several reasons the 4WD light is not turning on:
1. The 4WD position switch on the transfer case is not closing, and the ADD is not engaging, so the front diff never is in 4WD mode;
2. The position feedback switch on the front diff actuatoris not closing, so even if the front diff is actually in 4WD mode, it's not sending the signal that turns on the light.

Font Slope Parallel Auto part Rectangle
 

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ok Thanks @debFJVT! I've went through the dealership and ordered part#84222-35110.I ordered part#84222-35099 thinking that it was the correct one, so I guess I have an extra. Question, in a pinch (on the trail fix) could you us part#84222-35099 on the4HI side? I'm just wondering if the only difference is the length of the sensor pigtail.
 
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