• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

flywheel pilot bush

Share this page

Ok, pass on a little schooling taught to me by Bill Hays, you may remember Hays Clutches. After he decided to unretire he started Centerforce clutches.


The prime function of the pilot bushing is a locator tool for the input shaft of the trans so as to help prevent clutch "chatter" on clutch release. Pilot bushing and springs on the clutch disc are designed to eliminate chatter. When I took my pieces into Bill, to see if he could upgrade(after a short lifespan with both Moss and TRF clutches) he gave me a tour of his shop/factory in Midway City. Found a clutch disc and pressure plate that I am still using to this day. Ford Probe probes my memories. He told me that the pilot bushing should be STATIONARY in the flywheel. That if needed to stake the flywheel to hold the pilot bushing in place.

So I have a tendency to give his knowledge and expertise credence.
 
I'd like to see someone swinging a transmission like a hammer, with enough force and speed to damage a pilot bearing with the tip of the input shaft.

'Tain't happening!

A clutch disc alignment tool is handy, but it's far from precise or essential.
 
I dont suppose anyone has seen the results of someone using the mounting bolts to "suck" a reluctant trans into place. {NOT a good thing to do!}
Helped a friend once that screamed uncle and called me to come over and see if I could remedy why his trans would NOT go home {slide in flush against the bellhousing}
I Removed the trans and YEP he had tried puling the trans up flush by tightening the mounting bolts. Buggered the pilot bushing up but good! {NO alignment tool either B.T.W.} After much searching for the proper alignment tool and a new Bushing
everything went according to plan. And YES I have aligned the clutch disk by eyeballing it before and it worked after much josteling and wiggeling. I myself PREFER to use an Alignment tool, it seems to make life sooooooooo much easier.
 
Thanks everyone for your responses, I'm satisfied with the fit of the new bush. Now to get the tranny mounted!
 
tomshobby said:
Alignment tool, I love these modern conveniences. We used to save pilot shafts from bad transmissions. You could tell how much transmission and clutch work a shop did by their collection of old pilot shafts.
Click to expand...

Tom's right...
 
And yes I AM old enough to remember when, if you didnt have an old pilot shaft laying around eyeballing was your only hope.
Buying an alignment tool wasnt an option.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] I'd like to see someone swinging a transmission like a hammer, with enough force and speed to damage a pilot bearing with the tip of the input shaft.[/QUOTE]

I wish I had pictures of some of the transmissions that I've seen removed after experienced mechanics damaged the pilot bearings on installation. It can, it does and it will if given enough force and at the correct angle of contact between the input shaft and the bushing.

Not a issue worth arguing about, but one that's easy enough to prevent, so why take the chance? Pulling these transmissions isn't like the old GM 4-speeds of the 60's. Out and back in again in an hour and a half.
 
Oh I've seen some cock-eyed messes myself. Even made a few over the years, especially when I was young. Broke a bell housing cranking down the bolts to drive the transmission in on my first car.

Alignment tools are nice, but not necessary, as I mentioned. A 3/8" extension and a bit of tape do an equally dandy job of getting the clutch disc roughly centered. And roughly centered is all any of the tools do.

Using the bell housing bolts to walk the transmission down is quite effective and a perfectly acceptable practice, as long as you understand what you're doing. Back and forth across the input shaft, wiggling the transmission. For truthfully, very rarely will you encounter a transmission that you can simply slide in without any force.
 
LastDeadLast said:
OK, I'm confused. I just looked up the install of the "spigot bush" in the Bentley. They don't mention pressing in the crank, in fact just the opposite:


Quote from the Bentley:
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Fit the spigot bush into the back of the flywheel ensuring that it is a loose fit
Click to expand...
[/QUOTE]

To further confuse, I inadvertently purchased 2 pilot bushings for my TR4A (actually a TR3 engine but that's another story) from 2 different sources. The bushing being replaced was visibly worn and slid out easily. One of the replacement units slid in easily but when I tried the alignment tool it would not slide in. Not even close. I then picked up the other replacement bush and the alignment tool slipped in easily. However, it would not slide into the crank without major force. My transmission is out being rebuilt so I've got a couple of weeks to figure out what my next step will be.
 
I would certainly offer the 'too tight' bush to the input shaft itself to see if it slips on or binds. Obviously you can't do that until you have access to the unit.

I have never used an alignment tool (I use a used input shaft instead) so I do not know how precisely those tools match the exact diameter of the tip of the input shaft.
 
On a TR2-4A, the bush should slide easily into the end of the crank (with the flywheel removed). Sounds like you may have gotten the wrong part(s). It seems to be distressingly common these days.

The alignment tool I got from Moss many years ago proved to be worse than useless. It's still laying in the tool chest somewhere, but I can do a better job with my finger! And as mentioned above, an old input shaft is the best possible tool for the job. My point being, don't assume the alignment tool is right until you can compare with the real thing.

Likely you know this, but JIC, the front cover on a TR3 gearbox has to be shortened by about 3/8" to work with the TR4A clutch. Otherwise, it will work when you put it together, but when you step on the clutch pedal, the fingers will try to grab the front cover. Oddly enough, they never changed the part number for the cover, but the later ones are shorter.
 
I am sure the bush in my TR3 was not turning inside the crank. It was so rusted in place that it had to be removed in sections with a chisel. I probably would have left it in there, but I converted to the HVDA and the hole size is different. (The removed bush is pictured on the left.)
 

Attachments

  • 29192.jpg
    29192.jpg
    98.5 KB · Views: 138
Broke a bell housing cranking down the bolts to drive the transmission in on my first car.

I thought I was the only one to do that.BTW, After I did that, I was advised to use a broomstick handle. It worked!

















i
 
It also helps to use two bolts with the heads cut off
to guide and support the trans in addition to the alignment tool or spare input shaft.
 
Sorry to hijack a dead thread but I need some help.
We Own a 1974 TR6, had it since 1975. I've done a few clutch jobs on it and I can't remember if I replaced the pilot bushing the last time. The car works great for the first half mile now but then you can't shift it after it heats up. It Won't go in gear at all except after turning the engine off.
Two things could be wrong,
a)I put one of those bogus ass throw out bearings in it the last overhaul (1998 ish)
or
b) the pilot bushing has gone haywire. Any suggestions?
 
It could also be the clutch hydraulics. Have you done the usual checks: Fluid level, system bled, and make sure you are getting full throw at the slave cylinder?
 
Yeah I know but I don't think we put 2,000 miles on it since. We just checked the tranny fluid an it was a bit low so maybe that was the problem.
Thanks for responding and I'll let you know if that was the fix.
 
Back
Top