Hello & All Trac 4wd System question

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Hello & All Trac 4wd System question

Postby Celicast185 » Thu Oct 03, 2019 7:45 pm

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...
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Re: Hello & All Trac 4wd System question

Postby underscore » Thu Oct 03, 2019 8:22 pm

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.
★ 1991 GTFour RC ~ "Rebel Scum" ★
It's for sale! http://www.alltrac.net/phpBB2/viewtopic.php?f=64&t=52181
Build thread http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=44216
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Re: Hello & All Trac 4wd System question

Postby Celicast185 » Thu Oct 03, 2019 9:52 pm

underscore wrote: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! :)
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Re: Hello & All Trac 4wd System question

Postby 93celicaconv » Thu Oct 03, 2019 11:22 pm

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.
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Re: Hello & All Trac 4wd System question

Postby underscore » Fri Oct 04, 2019 2:29 am

93celicaconv wrote: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).
★ 1991 GTFour RC ~ "Rebel Scum" ★
It's for sale! http://www.alltrac.net/phpBB2/viewtopic.php?f=64&t=52181
Build thread http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=44216
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Re: Hello & All Trac 4wd System question

Postby 93celicaconv » Fri Oct 04, 2019 10:51 am

underscore wrote:
93celicaconv wrote: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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All-Trac Select Lever.jpg
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Re: Hello & All Trac 4wd System question

Postby underscore » Fri Oct 04, 2019 3:22 pm

That's what I'm referring to as well. In FF mode if the rear wheels turn the VC won't be damaged but this metal collar piece will break viewtopic.php?f=43&t=43503&start=30
★ 1991 GTFour RC ~ "Rebel Scum" ★
It's for sale! http://www.alltrac.net/phpBB2/viewtopic.php?f=64&t=52181
Build thread http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=44216
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Re: Hello & All Trac 4wd System question

Postby 93celicaconv » Fri Oct 04, 2019 4:41 pm

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.
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Re: Hello & All Trac 4wd System question

Postby Celicast185 » Fri Oct 04, 2019 5:03 pm

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!
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Re: Hello & All Trac 4wd System question

Postby 93celicaconv » Fri Oct 04, 2019 5:34 pm

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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ST185 Visc Coupling Ass'y.jpg
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Re: Hello & All Trac 4wd System question

Postby underscore » Fri Oct 04, 2019 7:06 pm

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.
★ 1991 GTFour RC ~ "Rebel Scum" ★
It's for sale! http://www.alltrac.net/phpBB2/viewtopic.php?f=64&t=52181
Build thread http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=44216
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Re: Hello & All Trac 4wd System question

Postby Numbchux » Fri Oct 04, 2019 8:28 pm

Very good information in this thread!


93celicaconv wrote: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
-Chux
'91 Celica GT vert, poly bushings, rear discs, etc., Summer DD
'87 unTurbo 4Runner, 1UZ swap, 35s
Outbacks, XT6, SVXs, and a couple Ford vans.
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Re: Hello & All Trac 4wd System question

Postby Celicast185 » Mon Oct 07, 2019 9:47 am

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:
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Re: Hello & All Trac 4wd System question

Postby 93celicaconv » Mon Oct 07, 2019 10:03 am

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.
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Re: Hello & All Trac 4wd System question

Postby Celicast185 » Mon Oct 07, 2019 10:33 am

93celicaconv wrote: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! :)
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