Spigot / Pilot Bearing

[Banjo]

I'm not a professional mechanic, but have played with various engines & drive trains over the years, (mainly Toyota), but recently came across something, that has me scratching my head ?

I'm very familiar with the spigot or pilot bearing, that supports the front spigot of the gearbox input shaft, which is notoriously hard to remove sometimes, but can be accomplished with the grease/wet paper/white bread/compression technique. 

https://www.youtube.com/watch?v=Wvg5YtB4CQ0

I've always replaced the spigot/pilot bearing, anytime I've had the gearbox or clutch out, as it is not the place you get to often, & can become annoying if it wears out, or goes dry & squeals.

I am well aware of the need for the spigot bearing or bush, to keep the input shaft of the gearbox completely aligned, so that there is no shudder in the engagement of the clutch plate, which is directly "tied" to the gearbox input shaft via 19 or 21 splines, in our K series combinations.

KE Series Gearbox Input Shaft

This is borne out, by the fact that I have a 4 & a 5 speed K series gearboxes on my garage floor atm, & if I move the spigot point on the gearbox input shaft with my finger, there is some slop in it up & down, (couple of mm) which is "unwanted", in operation. There is movement, because there is a "single" front gearbox bearing, at the other end of the shaft, behind the front gearbox oil seal.  As this front bearing wears a little, any movement in the shaft is "amplified" because the spigot point is so far removed from the bearing mounting point.

So I bought my kids a 2004 Toyota Echo Hatchback, a couple of years back,  which is a great little roundabout, with extremely good economy. (700+klms to a 38 litre refill)

The clutch had a very slight shudder in it, when I bought it, so got a couple of hundred bucks off the price, when I purchased it.

I ordered an Exedy Clutch replacement kit, with everything included, like throw out bearing etc.

I've actually never taken a gearbox out of an east/west engined car previously, without removing the whole engine & gearbox, as a complete unit.  I also unfortunately don't have a hoist.

However, there is always a way, & to cut a long story short, the gearbox came out OK, along with the clutch & pressure plate.

What I then saw both surprised me, & concerned me. The Echo engine had no spigot/pilot bearing at the back of the crankshaft/flywheel.  The input shaft for the gearbox, had no spigot turned down point on the tip of it, which is usually how they look.

I had never come across this before, but with researched since, have discovered that there are other more recent Toyota engines, that also have no spigot bearing or bush.

So I put the new clutch in it, & put it all back together, & everything went well. So my son has been driving it around Canberra for a year or so now, & I recently traveled down there, from Brissy, & took a Yaris to him, & drove the Echo back again, to be used by my daughter.

I have noticed again that there is the slightest shudder, when taking off from a standing start in 1st gear. 

As the clutch is fairly new, & the flywheel face was very clean, when I put it back together, I can only assume that with 180K klms on the car, the front gearbox bearing, has a little wear & movement in it, which is allowing the other end of the shaft to move a bit, under take up.

I have no idea at all why the spigot/pilot bearing was "abandoned" in the design of the Echo 2NZ-FE engine & others ?  

Has anyone else on here come across this before, & experienced similar movement shudders ?  The only way I could see the designers removing the need for a spigot bearing, was if there were two front bearings in the gearbox, spaced slightly, or maybe one very wide bearing.

As I said, "Got me scratching my head ?"

Your thoughts or theories ?

Cheers Banjo    

 

     

Edited April 28, 2020 by Banjo

[altezzaclub]

The whole car is designed to last as long as one spigot bearing would... 

The shudder is more likely to do with the mounts in an East-West motor, they'd be a lot more sensitive to that than a F/R drive.

Maybe not having a spigot bearing at all doesn't lead to a shudder, or the shafts are shorter in new g'boxes, or a design change internally keeps the input stable. Pull the box apart and have a look!

It saved Toyota about $2 by not having one in there!

[Banjo]

Hi Keith,

               Since posting that yesterday, I've done a little more research, & found numerous references to clutch shudder on Yaris websites & forums. (Yaris use the same engine family as the Echo)   There are informed comments on there, that the shudder incidence is wide spread, & can often be solved by completely changing the brake fluid, & bleeding both clutch & brakes.

These model Toyota share a common reserve fluid tank, which is very hard to access, so doesn't get done often, or gets put into the "too hard" basket.

I'm not discounting it, as "stranger things have happened", but I feel absolutely no "sponginess", in the clutch pedal.  So what's to lose; so I'll try bleeding at the weekend, & see what transpires. 

P.S.  I take your point . . . . . "or the shafts are shorter in new g'boxes, or a design change internally keeps the input stable."   The shaft is certainly a bit shorter.

Cheers  Banjo

[ke70dave]

Interesting conundrum. I've never ever put a clutch in a fwd (thank goodness). so I've never come across it. 

I wonder if the input shaft is a lot shorter on a fwd so it doesn't need to be supported at the flywheel end? looks pretty short. 

[coln72]

From what Ive seen, FWD engines/gearboxes seem really well supported - 4 odd mounts (front, rear, left & right) over a short distance.  A lot better than our old K engines with 3 over a third of the length of the car.  Guess there is a lot less chance for bending/misalignment

[Banjo]

Hi Colin,

               Despite our old Corollas, only having three (3) engine mounts, two (2) off them counteract, the thrust motion of the engine trying  to "roll", or twist.

From my observation, the engine mount on the inlet & exhaust manifolds, takes the most thrust load, "in extension" (tries to tear it apart).  This particular engine mount, suffers more than most, because the rubber in the mount, is so close to the exhaust system, & the heat generated from there.  That's why Toyota, included a little heat deflector plate in the engine mount.  Unfortunately, it was attached with pop rivets, & often after years of use, becomes loose, & fall off, or rattle.

If any one of the three (3) engine mounts fail, it is usually the rear gearbox one. This one usually suffers from oil leaks, at the back of the gearbox, & separates from one on the mounted metal pieces, that make up the mount.   However, even a failed one, does not effect the roll or thrust movement of the engine, to any great extent. 

The Echo 2NZ-FE engine only has 3 off engine mounts.   The two (2) at the ends of the engine, (East / West), which don't resist the rotation thrust of the engine, very much, when releasing power.

This thrust movement, is taken up, by just one mount, at the rear of engine, in a "compression" mode.  There is no engine mount on the front of the engine, behind the radiator, in most East/West engine configurations. However, the third engine mount that does most of the work, to counter engine thrust rotation, is well spaced away from the engine, so has a large effect, as a result of mechanical advantage.   However, in most East/East engine arrangements, like the Echo, this engine mount is very close to the exhaust system, & the heat shields in this area are usually, pretty extensive. I had two (2) off the three (3) engine mounts out, whilst I changed the clutch, & both were in excellent condition, so I don't think, that the slight shudder I've experienced, is the result of engine mount deterioration. 

I'll let you know, if bleeding the clutch, has the desired effect.

Cheers Banjo

Edited May 6, 2020 by Banjo