Black Magic of the Clutch Release System

Black Magic of the clutch release system.

Why so many problems with the clutch release system on the Toyota 6 Speed Truck Transmission????

Simple, we believe it to be an overall design flaw. We have carefully watched the different approaches the OEM has taken with the different TSBs and so on and nothing done by the OEM has had any real effect on the issue. One try was to put a spring in the slave cylinder to keep the bearing in contact with the release fingers. That did not work because the OEM bearing is not designed to spin all the time and will wear out quickly.

The basic design seems to have worked well on the trucks of the past with the smaller engines and smaller clutch assemblies. The clutch on the 6 Speeds is stout and seems to overwhelm the old design.

Most people complain about this squeak noise when sitting at idle with the transmission in neutral. It is annoying and everyone hates it. Most think it is a bad throw-out Bearing and it is not. In most cases the bearing is perfectly fine. So, what is going on?

Here it all is in a very simple explanation. The squeak is caused by intermittent contact between the bearing face and the release fingers of the pressure plate. For whatever reason, the OEM has their release system designed so that the bearing is pulled completely off the pressure plate release fingers when the pedal is all the way up. There is a small air gap between the bearing face and the release fingers of the pressure plate. When the bearing does not touch the release fingers there is no noise or squeak.

Where the problem comes in is that the release system tends to side load the bearing into the quill causing uneven wear in the quill. The quill is part of the bell housing and it extends over the input shaft and it is the sleeve that the release bearing rides back and forth on. Now when this quill gets worn unevenly, the bearing tends to want to flop around a bit when there is no pressure on it and can sit crooked and one edge can stick out more than the other and use up this air gap and make intermittent contact with the release fingers of the pressure plate. When this happens, it presents as the dreaded squeak everyone complains about. In most cases the bearing is fine. It is not a bearing problem. If it was a bad release or throw-out bearing when you pushed the pedal down to release the clutch it would start to roar like a jet engine and there is no mistaking that. If it gets quiet when you push the pedal down it is not a bad bearing it is just this crooked bearing problem.

OK, so what to do about it. Easiest and cheapest is to just ignore it and let your high-quality truck you paid extra for sound like a worn-out POS. You can put all new OEM parts in there and still have the issue.

URD has what we call the bearing/sleeve repair kit. I will tell you right up front IT IS NOT A PERFECT FIX. Somehow people have gotten the impression we claim it to be and URD has NEVER MADE SUCH A CLAIM. We feel it is about 85% effective in resolving the squeaky bearing complaints.

What the kit has is a new machined sleeve made from 303 stainless steel and it slips over the stock quill and is anchored with some set screws. Then we supply a new OEM bearing from the dealership that is modified to fit over the new sleeve. There are also grease holding grooves cut inside the of the bearing to retain the grease so things stay nice and slick. The tolerances are also kept much tighter than the OEM combination. Now you have a nice smooth sleeve for the bearing to ride back and forth on. It is kept much straighter than a brand-new truck and it stays nice and straight when you release the pedal. This repairs the worn-out quill and provides a much smoother operating release system. Because the bearing is always nice and straight the intermittent contact is greatly reduced.



Now you are wondering why it is not a 100% fix. Again, we are dealing with what we feel is an overall design flaw. Over time as the clutch disc wears and get thinner and thinner. When this happens is the pressure plate moves more toward the engine and this causes the release fingers to move more toward the transmission. Over time as the clutch goes threw it normal wear cycle that air gap between the bearing face and release fingers can get used up and the fingers can start making intermittent contact again with the bearing and can start that squeak again. Again, there is NOTHING WRONG with the bearing it is the overall design of the system.

In the past URD did have a problem with the bearings we used in the kits. We started using bearings that you find in most all the aftermarket clutch kits and they are made off shore. That proved a very bad move for us. Long story short, those bearings were just junk and do not hold up. We ended up putting a very large amount of these release bearings in the trash and refuse to use them in our clutch or bearing/sleeve kits. We learned our very expensive lesson and now only use the much more expensive OEM bearings from the dealership that are then modified for our needs. Yes, some of those crap bearings made it into customer’s trucks and we did our best to warranty them out.

Another problem that we have seen time and time again is the stock quill snapping off the base of the bell housing. In the past to fix this it required that a new bell housing be installed at great expense. URD went to work to solve this problem and developed the FIX-U Hydro-Bearing Conversion kit. We make a T-56 transmission swap kit and in those kits, we use a GM style hydraulic release bearing where the slave cylinder and release bearing are all one part. It also has a very strong spring that keeps the bearing pressed into the pressure plate all the time and both spin together as one unit. This kit has saved many customers so far from a much more expensive repair. This FIX-U kit also works for trucks that have not snapped off the stock quill. It seems to also resolve the squeaky bearing complaints for good. So now there is another option for addressing the problem.



Currently URD offers three different options for release bearings:

1. OEM Toyota Release Bearing

2. The Bearing/Sleeve Repair Kit using an OEM Toyota bearing

3. The URD FIX-U Hydro Bearing Conversion Kit.

We offer our clutch kits with the above three options or the 4th options which is not to include a release bearing.

 

Gadget, thank you for this write-up in describing the problem. It sounds like unless we're willing to permanently modify the transmission quill, we'll either have to try the bandaid solutions or suck it up and deal with the noise. Appreciate your help in detailing the problem.

 

many thanks Gadget!, and very timely for me!

 

I have been trying to solve this issue for years on my 07. I replaced the clutch two years ago and now the issue came back. I agree this is the problem with toyotas design. I am a mechanical engineer and hate this design they have. I am now installing a sleeve kit and all new URD heavy fly wheel stage two clutch kit this weekend and hope this solves it for a long time. If I have the problem again, I am going to the hydro clutch solution.
Thanks for the write up Gadget.

 

It's a nice long write up, but in the paragraph starting with "Here it all is in a very simple explanation." there is a fundamental error in how the Toyota clutch works. There is nothing that ever forces the TOB away from the clutch fingers, there is no gap and there's only BS. Without understanding what the problem is the rest of the write up is pretty useless. Remember these guys are trying to sell you new TOB's and lots of them.

 

How do you like the URD heavy Flywheel and stage two clutch kit with sleeve kit?

I am hearing the squeak and have been reading up on solutions to the underlying problem. Any information about how it has worked for you would be forthcoming!

 

I've been reading all kinds of threads on here for the past few days about this trying to figure out if the throw out bearing is supposed to spin or not.
At first I though it wasn't, as gearcruncher's post stated.
then later in the same post it seemed that it is.
Now, Gadget you seem to put this to bed for me here. So I gather, the TOB is Not supposed to spin all the time.

I just replaced my engine, bolted on an entire AMS clutch kit [AMS AUTOMOTIVEKIT1590] from Rock Auto including:

• new Flywheel,
• new clutch disc,
• pressure plate,
• Throw Out Bearing
• slave cylinder
• master cylinder

I replaced all the components with the exception of the master cylinder, which seems to be fine. Greased up the input shaft prior to putting the bearing on, and greased the inside of the pivot arm with off road grease. I did not adjust the clutch pedal or master at all after bolting the trans back in.
I also deleted the clutch accumulator and replaced it with a coupling.

I did notice once I got it bolted up that the throw out bearing was touching the pressure plate fingers. Decided to drive it around a bit and see how it works before messing with anything. It is only 5.5" off the floor, which is about an inch lower than it is supposed to be.

The truck drives great. Clutch is very responsive. I tried to raise the clutch pedal up, which is what the TSB for this fix says to do. but I couldn't get a wrench on the nut.

I can hear the TOB spinning against the pressure plate. Makes me a bit nervous but it's not squeaking, and after everything I just did to the truck, I'm not too worried about a bearing spinning.

I have an appt with the Dealer on Thursday to have them go through my truck and fix / fine tune things a bit further. Since I am a bit spooked by this whole thing, I will ask them to adjust the clutch and take a look at this. We'll see what they say.
Seems like adjusting the clutch master cylinder push rod and pedal height may do the trick.

I'll keep yall posted. Thanks

 

Yes, the myth of "the TOB doesn't spin" has to be fed once again!

P.S. Just to be clear, I've posted about this on other parts of these forums so I'll just summarise here to make myself clear. The TOB is meant to, and does, turn all the time but the preload spring in the slave cylinder doesn't load the bearing enough and that's why they wobble, squeal and fail. I fixed mine 6 years ago by changing the spring in the slave cylinder and it has worked fine since. People get confused with old clutch designs where slave cylinders had a return spring and you had to set the gap to prevent the old TOB's from turning all the time. Owners have wasted thousands trying to fix a problem that cost me about $10 to fix.

 

I have read and appreciate your posts where you have tried to advise folks not to throw thousands on replacing TOB's and clutch assemblies only to have the same problem come back and am wanting to to the SC rebuild myself and had a question for you please:

Couldn't i just adjust the clutch free play from inside the truck such that it always applies a small amount of force to engage the TOB since it is made to spin continuously? Does putting in a stronger spring (04313-34011) and longer push rod (31473-35060) in the SC do this differently than taking out the free play by adjusting the free play adjustment screw?

Thanks in advance.

 

Not clear what adjustment screw you're talking about. If you mean the one on the clutch pedal the the answer is no.

 

Ok i think i'll have to look more closely at how the slave cylinder works again, i'm not seeing how the stronger spring + longer push rod acts differently than just adjusting the free play such that there is no free play and the push rod is partially engaged when the clutch pedal is not pressed.

 

Update from my trip to the dealer- TOB was not pushing against the plate. Was about 1/8" of an inch off, just how it's supposed to be according to the dealer.

 

Sorry for the late reply....what spring did you use when you replaced the OEM?

 

So Toyota’s TSB for slave cylinder tb and pivot forks is a ploy to get people to to replace all these items to get more money and so buying the new slave cylinder is a waste also do you have details on this and what part # for spring to replace? Thanks Tony.

 

It depends, if your TOB and/or transmission spindle are destroyed then my fix can't help you. Also, over the years Toyota may have changed parts and fixed this; it's hard to imagine they're that dumb. There is no part # since I just played around with springs until I got one that exerted about 7 to 10 lbs on the TOB. The Ford part has eternally confused people because all I used was the collar that keeps the spring centred on the piston and prevents it from jamming. My Tacoma now has about 100k miles (I don't drive that much) and it's quieter than ever.

 

What’s the spindle on the transmission?

 

I think he's referring to the quill or snout.

 

Wait a minute, wait a minute. I know I'm late to the party here, but let me get this straight - this whole thing is caused by the damn spring in the slave cylinder? That's it?

 

Yup, and a huge body of ignorance about how a modern clutch works.

 

My 2013 was squealing last year, had the clutch replaced, and now it is squealing again. Where can I get a new spring for the slave cylinder and is it really that simple?