Hello & All Trac 4wd System question

Celicast185

New member
Hello to everyone! :)

This is Gerald from Peru, I'm the very proud owner of a 1992 ST185 Toyota Celica GtFour RC (one of only 3 originals here in my country), the car is like my son I love it so much and I want to keep it in my family for ever. For that reason, I was searching for some information about Toyota's All trac system, in order to understand it very well and avoid possible damages. There is not so much info on the web.

I know the system has 5 main components: Front, center and rear differentials, transmission and the transfer case, but the main thing I need to know is how much strength is this last piece? or which part suffers most by the misuse? I have to confessed that I have done two terrible things to my car: First, when I bought it 4 years ago, I took it to the mandatory vehicle inspection and I totally forgot that it had 4wd system! :bangshead: (it was my first time with this baby and also the Technicians were just as stupid as me because they didn't realize too :withstupid: ) and the car was tested in a 2wd common line to inspect the brakes (means that only 2 wheels of the same axle spin and the others 2 are stopped, first the front and then the rear wheels). I realize myself of that mistake the next day, but there was no sign of failure in the car, I reviewed system with a mechanic and it worked properly. This year I was on a circuit and I blocked the rear wheels to take a very tight corner :doh: (just one time because it was a very risky situation and I needed to avoid a crash). I was very afraid of the system has some damages, but the car still running pretty good, until today there is no noise of differentials, transmission, nothing strange, so that's the reason of my question, I always heard that this bad practices could kill the 4wd systems and I want to keep mine in perfect conditions. Do I need to check any special part of the system? maybe something internal? :shrug:

Thanks to all, any information would be very appreciated! :notworthy:

Gerald

P.D. I would like to post some pictures of my car, but I don't know how to post them here, maybe in another section...
 

underscore

Well-known member
If they were able to spin just the one end of the car without the other trying to move my guess would be the viscous coupler is fried, but I don't know offhand how to test them in the car. If you dig around in here you may be able to find a way to do it.
 

Celicast185

New member
underscore":luqlkvvd said:
If they were able to spin just the one end of the car without the other trying to move my guess would be the viscous coupler is fried, but I don't know offhand how to test them in the car. If you dig around in here you may be able to find a way to do it.

Thanks for the info, it's very interesting, I also thought that I would have a problem with the transfer case, but I found this info about typical symptoms of a coupling failure: "Most often, you will notice unusual noises at a specific speed or any time you shift gears, once the problem becomes more apparent, you may start to notice more than just unusual noises. It may actually become difficult to shift gears (impossible) and drive the vehicle..." This is not my case, my car still running very well and without any noises, I can shift gears smoothly (yet), but now I know what piece I need to review, just to confirm if everything its correct. Thanks buddy! :)
 
There is a lever on the transfer case that would disable the rear drive component - for very short periods of time. However, it would not be meant for the kind of testing you had done. If it was used, it would at least have reduced the issue.

I quite frankly agree - your viscous coupling is likely gone. If it happened just a short time ago, the debris from the clutches probably haven't worked their way through all the internals of the quadruple case to cause the symptoms that are typical - yet.

If I were you, I would pull the plug on the bottom of the quadruple case and check the oil condition. That is a very specific oil that is a combination of GL-5 gear oil for hypoid gears, but without the chemistry that causes extreme slipperiness (allowing the synchros to still work). So if you loose some oil doing this, make sure you have some of this kind of oil available to top off. If you notice something other than transparent oil coming out, that should tell you the viscous coupling or something else gave way quickly in the process you put it through.
 

underscore

Well-known member
93celicaconv":oi5yuxyd said:
There is a lever on the transfer case that would disable the rear drive component - for very short periods of time. However, it would not be meant for the kind of testing you had done. If it was used, it would at least have reduced the issue.

From my understanding it would be fine for the testing on the front end, but when spinning the rear end a different part would've broken (a metal sleeve thing by the VC but not the VC itself).
 
underscore":1wrwsn64 said:
93celicaconv":1wrwsn64 said:
There is a lever on the transfer case that would disable the rear drive component - for very short periods of time. However, it would not be meant for the kind of testing you had done. If it was used, it would at least have reduced the issue.

From my understanding it would be fine for the testing on the front end, but when spinning the rear end a different part would've broken (a metal sleeve thing by the VC but not the VC itself).
I am referring to the level as shown in the BGB, page 4 of the manual transmission section of the Service/Repair Manual:
 

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I don't see the thread you attached talking about this test feature. Either way, we are saying the same thing - use it at risk. If the OP of this thread had his running FWD turning only with the rear locked, and nothing appeared wrong, chances are the viscous clutch was already gone on it.
 

Celicast185

New member
Thanks a lot 93celicaconv and Underscore, this thursday I'm going to take the car to the workshop and make a complete inspection of 4wd system and see the real condition. I'm preparing myself to see broken pieces and more, hope the damage wont be so hard... :cry: Also, if the viscous coupling is gone, how much its a good price of a new one? (or used in good conditions).

Maybe it's a good chance to replace oil there, can you recomend any specific brand and grade? which one works pretty good in your cars?

Thanks a lot buddys!
 
The viscous coupling assembly is Toyota part no. 41330-20010, which can be seen in the view below. I am pretty sure this part has been long discontinued by Toyota. When it was available, it likely cost about $1,500.00 USD. The transaxle needs to be removed and disassembled to repair. I don't think the transaxle can be removed from the vehicle without the engine also coming out. The oil I used on these unique transaxle combination units is Toyota Gear Oil Super, Toyota Part No. 08885-02106, which is a special oil used in combination hypoid and synchromesh transmission assemblies. It runs about $25.00 USD per liter. There is a Redline product that has very similar characteristics to this oil that I believe is lower cost and more readily available.
 

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underscore

Well-known member
From reading other threads it may be possible to remove the viscous coupler with everything else still in the car but I can't say for sure. If the car is otherwise working well I would hesitate to start pulling things apart. The BGB may have more info on testing the AWD system or you could always try the more basic method of bombing around on a loose surface. I know from experience that an RC with everything working well has no problem kicking the rear end out on snow and ice, even at speed as low as 20km/h.
 

Numbchux

New member
Very good information in this thread!


93celicaconv":18er3tcv said:
The viscous coupling assembly is Toyota part no. 41330-20010, which can be seen in the view below. I am pretty sure this part has been long discontinued by Toyota. When it was available, it likely cost about $1,500.00 USD.

I just popped in to say this is still an active part number, but MSRP is $2021.15
 

Celicast185

New member
Thanks to everyone! The information you left here is very very interesting!

I 've found this and I want to share with you:

"Toyota Full time 4wd viscous coupling is filled with silicone fluid and is not computer controlled. A series of plates with holes and slots turn in the silicone fluid. Some plates are attached to the front axle driveshaft and some are attached to the rear axle driveshaft. Normally the plates turn at the same rate without relative motion. The silicone fluid becomes very viscous due to it's viscoelasticity as soon as the plates rotate at differentiating speed. The silicone fluid resists the shear generated in it by the plates with differentiating speed, causing a torque transfer from the faster spinning axle to the slower spinning axle, but only for a short time. Therefore, slight speed difference is required for torque transfer..."

According to this information, it is possible to rotate one axle totally independent from the other, but only for a short time, for that reason it is very risky to tow a car with all trac system for several miles, due to overheating of coupling and the consecuent failure of internal components. Due to this, I have a little chance to have my drive train in good conditions because the brake test I stupidly done, was only for near 8 seconds for each axle

I have hope now, this thursday I'm going to take the car to the workshop and test 4wd system, Thanks to all again! :notworthy:
 
If only 8 seconds for each of 2 separate tests, you will likely be OK. Wonder how the test was performed with all 4 wheels having torque on them at the same time. I can't picture the test that was done.

At any rate, you can get a feel of condition by getting all 4 wheels of the ground at the same time, engine stopped, transmission in 1st gear, then someone holding one rear wheel still (to allow no rotation) while another tries rotating the other wheel. It should be possible to turn the one rear wheel in this case, but only very slowly and with significant resistance. If this is what you find with the test, chances are high you are OK. But if one rear wheel turns freely in this test, your viscous coupling is gone.
 

Celicast185

New member
93celicaconv":5be39vf8 said:
If only 8 seconds for each of 2 separate tests, you will likely be OK. Wonder how the test was performed with all 4 wheels having torque on them at the same time. I can't picture the test that was done.

At any rate, you can get a feel of condition by getting all 4 wheels of the ground at the same time, engine stopped, transmission in 1st gear, then someone holding one rear wheel still (to allow no rotation) while another tries rotating the other wheel. It should be possible to turn the one rear wheel in this case, but only very slowly and with significant resistance. If this is what you find with the test, chances are high you are OK. But if one rear wheel turns freely in this test, your viscous coupling is gone.


The bad brake test was very simple: The car was positioned with the front wheels in a motorized rollers, the other wheels were in ground, gearbox was in neutral and handbrake was on, then the rollers start to move at low speed for 5 to 8 seconds, then a technician said "step on the brakes" and the idlers stopped, then the test was repeated for the rear wheels, gearbox in neutral and handbrake released.

About the test you mention, it is the same way for the front wheels? When you say 4 wheels of the ground, that means with the car fully raised, right?

Thanks a lot! :)
 
The brake test, as you described it, when testing the front wheels, provided the speed of the front rollers drove the front wheels slowly (say 1-2 miles per hour) for 5-8 seconds should have been OK. The handbrake would have prevented movement of the rear wheels (provided the hand brake was functioning properly.

The brake test, as you described it, would not work for testing the rear wheels. The hand brake cannot be engaged (it would prevent the rear wheels from turning). If the hand brake was not used on the rear wheels, when the rollers turned, the front wheels would have turned with it, unless the car body was somehow restrained, or the roller speed turning the rear wheels was exceptionally slow (turning the rear wheels puts force to turn the front wheels in this situation).

The test I mentioned was to check the viscous coupling. The front wheels are locked (because with the engine off and the transmission in first gear, the front wheels cannot turn without the engine turning). You want the front wheels locked to see how easy it is to rotate the rear wheels. If one rear wheel was not restrained, that unrestrained rear wheel would turn easily in the opposite direction the wheel being turned by hand would turn.

You could do this test with only the rear wheels off the ground, as the front wheels on pavement would prevent them from turning. But still have the transmission in first gear - don't want the front wheels to move while the rear wheels are elevated above pavement.
 

ATSTodd

New member
My cousin took her all-trac to be emissions tested many years ago. The technicians failed to realize the car was all wheel drive and strapped the car to the emissions dyno. The rear tires were on the ground while the front tires were spinning. They stopped the test when burning transmission oil began to pour out of the car. I assume it was heated by the viscous coupling. That car was never checked out by anyone afterwards and drove for thousands of miles. I imagine the VC fluid is damaged but who knows? Just one anecdotal story to say the OP's VC is probably not worth worrying about.
 

Celicast185

New member
93celicaconv":22a5fq3o said:
The brake test, as you described it, when testing the front wheels, provided the speed of the front rollers drove the front wheels slowly (say 1-2 miles per hour) for 5-8 seconds should have been OK. The handbrake would have prevented movement of the rear wheels (provided the hand brake was functioning properly.

The brake test, as you described it, would not work for testing the rear wheels. The hand brake cannot be engaged (it would prevent the rear wheels from turning). If the hand brake was not used on the rear wheels, when the rollers turned, the front wheels would have turned with it, unless the car body was somehow restrained, or the roller speed turning the rear wheels was exceptionally slow (turning the rear wheels puts force to turn the front wheels in this situation).

The test I mentioned was to check the viscous coupling. The front wheels are locked (because with the engine off and the transmission in first gear, the front wheels cannot turn without the engine turning). You want the front wheels locked to see how easy it is to rotate the rear wheels. If one rear wheel was not restrained, that unrestrained rear wheel would turn easily in the opposite direction the wheel being turned by hand would turn.

You could do this test with only the rear wheels off the ground, as the front wheels on pavement would prevent them from turning. But still have the transmission in first gear - don't want the front wheels to move while the rear wheels are elevated above pavement.

I understand, I'm going to test the rear wheels as the way you described, thanks!

About the brake test for the rear wheels, your observation is very smart, I'm totally agree, but I think that this test could be done because rollers were located at not the same level of the ground, I mean, they are located in a type of "hole" and no in the normal horizontal of the road, its like you were driving and then you get stucked in a big depression, obviously not so big, but maybe enough to prevent the advance of the car.
 

Celicast185

New member
ATSTodd":86pe8q2v said:
My cousin took her all-trac to be emissions tested many years ago. The technicians failed to realize the car was all wheel drive and strapped the car to the emissions dyno. The rear tires were on the ground while the front tires were spinning. They stopped the test when burning transmission oil began to pour out of the car. I assume it was heated by the viscous coupling. That car was never checked out by anyone afterwards and drove for thousands of miles. I imagine the VC fluid is damaged but who knows? Just one anecdotal story to say the OP's VC is probably not worth worrying about.

:cry: What a terrible situation! but, how much speed did those cars killers put in the front axle of the car? That test sounds like the car was with the gearbox engaged in 1st or 2nd gear, accelerating and then the failures happened ...
 

ATSTodd

New member
If I remember correctly they would do a low speed test and a high speed test. I think the high speed test was only like 25mph. It was still plenty to heat things up!
 
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