Manual transmission Fan Club and BS thread (All Generations Welcome)

There really isn't a way to generate lots of heat in a manual transmission. Low or no transmission oil can cause unnecessary friction thus heat, but that's about it.
If the load is too heavy the clutch will be the sacrificial component with a manual. Similar to the torque converter in an auto.

 

Mostly right. A clutch and associated parts are not meant to "slip" under load. A progressive load, such as towing up a hill will kill the engine before the clutch slips (if everything is in good working order). The likely sacrificial parts will be of the overdrive, 5th and 6th in a 6 speed or 5th in a 5 speed. Overdrive is not meant for towing, it is meant for fuel economy.

 

I've actually asked before if 5th gear was safe for towing in the 6MT. It is implied that 5th is safe for towing in the manual as it states 5th may be used for engine braking and for vehicle charging.

 

I've heard that you should mostly stay in 4th when towing and could maybe go into 5th if you are on a truly straight and level part of the freeway. Then you can cruise in it. But really should go back to 4th if there's any grade.

 

I've never really treated overdrive gears special, if the engine and truck aren't struggling then I'll use 5th (and now 6th). I keep the RPMs up if the truck is working but otherwise I figure if the grade is flat then there's nothing wrong with letting the RPMs come down and save some gas. If there's no torque being developed, e.g. very little throttle, then everything's just spinning. It's when the engine is being given a lot of fuel so a lot of energy is being converted into torque that you create the damage to the transmission.

My feeling is you don't have to treat it any different just because you're towing, it's really that you don't want to abuse your transmission under any conditions. For example, maybe you don't have a trailer but are heavily loaded for camping or there's a crazy headwind then you should be careful about not using high gears, low RPM then either. The same issues arise with people who put big tires on their trucks without re-gearing to match. They tend to wear out OD gears and sometimes other gears. For example my old truck had a W56 5-speed and 3rd and 5th would both wear out from damage like this. I'm not a mechanical expert but I understand it's got to do with the countershaft bearings and the constant run gears.

How I determine this is more a feeling from experience, but if I can't accelerate in the selected gear or find myself getting beyond 75% throttle a lot then I'll downshift. IOW, my top gear and cruising speed is conditional with the situation. On flat Interstate with very little wind I might be fine with 6th gear (assuming it's safe to travel that fast with your load, which is a different question), but with a headwind the truck has to work too hard to hold 6th so I travel in 5th at a speed appropriate for the RPMs. But climbing a pass at altitude I might not be able to use gears above 4th or even 3rd sometimes. There's been times when even WOT in 4th isn't doing it, so I'll sit in 3rd gear at 40 MPH for 15 minutes until I get to the top.

 

The clutch being the designed point of slipping would be where any heat (if any) will be generated. I guess I over generalized my reply.

Yeah, if the driver doesn't work the clutch before stalling, the engine will chug to a halt. If he allows the clutch to slip due to excessive weight on a steep hill, he could expect some extra wear on the clutch (and heat at the clutch) for sure.

 

I'd doubt Toyota would intentionally design a clutch to slip. Perhaps, but seems like you'd want the transmission to tolerate more than the engine can develop and the clutch to be higher than at least the engine and probably the transmission's limit as well. The clutch is the thing in the system that you can count on to wear so that it's holding threshold will come down over time.

 

Swapped my tranny fluid yesterday with Redline MT90. Old fluid came out Caramel color. Replacement oil was a light transparent fluid with a orange/pink hue to it. If my 6MT was shifting smooth before, it is shifting much better now. No more occasional notchyness on some gears.
reverse goes in with little effort now
1st gear feels easier to shift into
2nd gear engages much quicker and smoother now
3rd gear no more occasional notchyness, 5th gear feels butter smooth and gets sucked into gear quickly

 

I can't Drive something with that Darn Automatic thing in it the Last time I did I tried to Down Shift for a stop sign....... I stopped alright about 45 foot from the sign with everyone yelling at me because I tried to push the Brake pedal to the floor in order to down shift. Both My Tacoma's have Manual Transmission and everything I have had except a Tundra has been Manual.

 

These transmissions are tuned for so much fuel economy they program it to downshift as little a possible I imagine. Better fuel economy at the cost of more wear on your brakes and rotors. The only automatics that I've driven that downshift more frequently amd intelligently are in commercial trucks with Allison series and Aisin.

 

Exactly. The clutch is the designed point of "give" in the system (slip). This does not mean it is designed to slip on it's own without user input (unless worn, or pressure plate is worn). It is just the item in the system that is predetermined to transfer power from the motor to the transmission with slip in mind to get things going.
Yes, we all slip the clutch slightly when we get moving. The amount of slip is completely up to each user.

 

I imagine clutch torque and horsepower rating are lower than the transmission it self.

 

Absolutely.
I would venture to guess that this manual transmission could easily handle 400 to 500hp, but highly doubt the clutch could handle it for very long, or at least the pressure plate wouldn't have the spring rate to hang on very long. Toyota manuals transmissions and rear axles have always been farely stout.

 

This is only time there should be any wear on the clutch, when you engage and disengage it. Otherwise it should last indefinitely.

 

Exactly.

I've got 220k miles on my factory gen 1 Taco clutch and it's got lots and lots of life left in it.

 

Did the same thing except I was driving my wife’s Aunt’s automatic Honda Accord with both of them in it. (I owned a manual transmission Accord at the time.) So I saw our freeway exit and casually “floored” the clutch to downshift. Yeah, her Aunt was not impressed.

 

The Aisin AY-6/Toyota RA60 is rated for 345 ft-lb and the 1GR-FE in my truck is rated to develop 266 ft-lb peak. The 3rd gen is going to be similar, but I don't know the values immediately.

What I don't know off the top of my head is the clutch. I think the clutch disk is 10" OD and the friction surface is about 3" that gives an friction area of 40 sq-in. I think the stock pressure plate has a normal force of about 900 lbf. Assuming a coefficient of friction of 0.4 I think the stock clutch is probably capable of about 325 ft-lb. This is a SWAG, a really, really wild one with lots of assumptions...

 

I have to get after my clutch in my 2008 at ~85k but it's only because the throw out is chirping. It doesn't slip or anything. My 1991 only got one clutch in 287k and that was only because I had it apart at ~200k to put in the Marlin so I figured there was no reason to put the old one back in at that point.

 

My throw out was chirping, and squealing for quite some time around 130k, then quit making noise. Still works at 220k. Around 150k, the dang pedal sounded like I was stepping on a dying duck. That too went away on it's own. Go figure?

Now it's my son's problem when shit finally fails on that truck, as I have the '17 to play with.

 

Not sure if it's going to be a problem with the RC62 in the 3rd gen, but the RA60 doesn't have a pilot bearing and there's no support from the flywheel. The shaft where throw out rides is only supported by the extension from the transmission and the input shaft only by the input bearing. What happens is the throw out wobbles and begins to chirp when the friction disk wears down, when this happens it begins to gnaw into the transmission extension, which is aluminum and not a bolted-on piece like in previous Toyota/Aisin designs. Point is chirping with the newer 6 speeds is something you need to be aware of because it indicates the start of a real problem (there was a TSB early on in 2nd gens for this) and not just a worn bearing. My intention is to pull it apart to put in URD's steel speedi-sleeve, which gives the T.O. bearing something more substantial to slide on without ruining the transmission housing.