6 speed shenanigans. RA60F swap to RC62F

Well. Is it installed yet? Hurry up.

 

Not just yet. Still waiting on Tilton for my hydro unit. That, and I’m waiting for a couple of pieces I need for my lathe so that I can machine the spacers for the throw out bearing.

 

One cool thing on this trans is the neutral position indicator switch on the shifter housing. The RA trans didn’t have that.
I could use that for an added level of safety for a remote start system.




Bell housing to engine bolt pattern confirmed. They’re the same. That was the first thing I checked.

I did not receive the mount. So, I’ve ordered one of those.

 

Splines jive with 2nd gen disk.

 

21 spline, 29.X mm in diameter. Begging for a pilot bearing!

 

Looks like it’d be pretty easy to do.

 

Thank you.

What’s the overall length of that RA trans?

Edit: I measured mine while I had daylight today. It’s 27” long.

 

I wonder if that switch is for reverse or neutral?

 

BU switch is on the other side. This one is definitely neutral position.

 

Thank you for the feedback.

 

Very easy, a piece of readily available 12mm 4140, just need to determine diameter for press fit, length and how deep to drill the input shaft. Obviously, needs to be a very accurate hole. I have a 3' 4140 bar, if you want a piece? Bearing is Toyota 90363-12002, which is a standard rs6201 bearing, the flywheel should be ready to accept the bearing, the unit on my truck is.

 

I’m looking at the bearing. Seems simple enough.

If we made some sort of drill guide that slips over the splines maybe? Otherwise, I wouldn’t try drilling that shaft unless it was out of the trans. It’s got to be tough material too. Gonna be fun to drill.

 

Well kids. I have run into a minor hiccup.

The new RC transmission is pretty much exactly 28" long. The outgoing RA trans is 27" long.

Not the end of the world. But, It does mean that I'll be doing drive shaft modifications. Will need to shorten the rear shaft by 1” as well as lengthen the front shaft by 1”. I’m considering just using a 1” spacer for the front shaft.

 

Can I ask a question regarding the pilot bearing, it's come up in this thread as well as @Jowett's thread as well, what problem are you trying to fix by adding a pilot bearing, and how will a pilot bearing fix said problem?

I mean, it can certainly be added without too much trouble, but to what end?

Jeff

 

Just hypotheses at this point... short answers.... first, we can improve shift quality and synchronizer wear due to less clutch drag. Second, we can increase the strength of the transmission and reduce wear on several other parts.

Please feel free to argue against any or all of this!.... We may experience some clutch drag during disengagement, not enough to cause grinding right away, but enough to place extra wear on those synchronizers. The bending moment created by the clutch disc on the input shaft has got to be impressive. On the Taco, the disc is 275mm/10.8" in diameter and weighs over 4lbs. With the clutch disengaged at 6k RPM, even momentarily during a shift, it's floating out there in single shear. Is it moving and creating extra drag? Being in single shear out there could even create a radial vibration. A pilot bearing should quell or eliminate the issue.

As many are aware, when under power, the input shaft/gears and counter shaft/gears are attempting to push apart. This causes the unique long input and counter shaft to bend in the middle. The input shaft bearing then becomes a fulcrum... the input shaft and clutch splines are then loaded and forced in the opposite direction of which the gears are being forced. The clutch disc may be captured and engaged, but the hub with all of the sprung parts is seeing loads in a direction for which it is not meant. A pilot bearing will add considerable support, help prevent bending, and reduce loads on bearings.

 

I had not considered the high RPM shifting vibes. I suppose if the disc was way out of balance, It'd help. I was always under the impression that the pilot helped to fight clutch chatter by keeping the disc from moving in any sort of orbital fashion.

Performed correctly, adding the bearing can only help things. If you have the means, by all means, add it. I've actually already designed the drill guide to do it in my head. Would be fairly simple utilizing the 90363-12002 bearings as the actual bit guides installed in a spline-centric tube/sleeve.

At this point. With my truck, I'm going to have to consider this modification on the next go-around. I need to get this thing back on the road. I've already got PLENTY on my plate getting this trans to work in my truck. The driveshaft thing is a bit of a bummer. But, such is the way of vehicle customizing. Yay.

 

Yes, that is some the movement/deflection that we should be concerned about. I see the potential for some real gains by adding the pilot bearing.

 

Following along, the primary inertial force-induced drag caused by the clutch disc spinning will exist with or without a pilot bearing, so any significant difference in drag would more or less require an imbalance, either from the clutch disc's balance or due to bending/displacement in the input shaft due to gravity and bearing play. The extra drag would be experienced due to the added load causing additional friction in the input shaft bearings.

So the question becomes, how much displacement does the input shaft spline see due to gravity causing bending and bearing displacement, and is there a concern related to the the frequency of the vibration caused by that bending, i.e. is it near resonance so as to increase or not, and is it being cancelled and/or damped in some way.

With a short enough input shaft, the displacement due to bending will be small, and so the amplitude of any induced vibration will also be small. With correct bearing support, likewise. This is why you will see pilot bearings added to long external input shafts, even if they are fully supported (like the Aisin transmission Porsche uses, which in addition to being long also has a small necked portion to clear the differential, increasing the effective length), and also why transmissions without fully supported input shafts have pilot bearings.

Will the spinning clutch disc increase drag on a cantilevered input shaft? Yes. Is it significant though?

I was curious how much extra bending the shaft would see, the clutch disc sits approximately 145 mm from the input shaft bearing in the RC62F. The clutch disc weighs about 1.8 kg, the input shaft is steel and approximately 28 mm in diameter. The force would cause a deflection of the input shaft of approximately 0.003 mm. It's going to introduce some radial dynamic imbalance, but I would question whether the deflection would be enough to have an appreciable increase in moment of inertia or cause any sort of noticeable decrease in synchro life.

Without knowing or estimating the pressure angle and other dimensions, it's safe to say these forces are probably much higher than that of the weight of the clutch disc, the question of front bearing misalignment support would then need to be asked.

Everything you said is true of course, and a pilot bearing would definitely increase support on the shaft, reducing bending, some vibration, and some radial loading on the clutch hub. My question would still be is any of that loading, bending, and vibration an issue? Hypothetically it could be, depending on magnitude, but enough that a pilot bearing would improve shift quality, increase strength and shift quality in a statistically significant way? I retain a health skepticism.

Pilot bearings on fully supported input shafts are uncommon enough that I would almost say they don't exist. It feels like a solution to a problem that doesn't exist.

All that said, it's certainly not going to hurt anything by adding one, though I suspect any improvement aside from vibration would be hard to quantify empirically.

Jeff

 

Lol, I knew you would supply an excellent argument! I'll research further, then try gather up some specs in an attempt to prove some benefits here. We can try to calculate, but testing holds the most value for me... if only there was an easy way to install a dial indicator on the tip of that input shaft as it's running down the street fully loaded.

Note that the Porsche unit has a 3rd bearing between the necked down section and pilot, for a total of four bearings supporting that shaft. When the Porsche trans goes past the torque limit, 4th gear on the main shaft pushes away from the counter/output and splits the case.