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71tr
04-18-2007, 12:37 PM
Just installed a new aluminum flywheel and noticed that the new pilot bush is a tight fit. The old pilot was nicely polished after 30yrs and fit in place freely, while the new unit is a snug match. Any thoughts on this, or concerns. Does this bush rotate with the flywheel or will it eventually rotate freely on its own?

RonMacPherson
04-18-2007, 12:38 PM
They are designed so that the input shaft turns inside the bushing. The bushing usually intact with the flywheel. A lot of "bushings" have been replaced by needle or roller bearing cups. Technology marching on.

tomshobby
04-18-2007, 01:05 PM
If using a bushing it needs to be a press fit in the crank and the pilot shaft needs to spin freely.

If the pilot shaft is too tight it can make shifting into a gear from neutral difficult because the transmission pilot shaft will tend to spin with the crankshaft. Ask me how I know!

RobT
04-18-2007, 01:06 PM
Do I remember these should be soaked in oil overnight before installation? I guess the bush is somewhat porous and the oil keeps it lubricated.

Rob.

martx-5
04-18-2007, 01:20 PM
We just replaced the clutch in a club members TR250, and ran into the same thing. The old bushing just fell out, and the new one was an interference fit.

Wonder what makes them get loose?? /bcforum/images/%%GRAEMLIN_URL%%/confused.gif

Brosky
04-18-2007, 01:37 PM
Whenever that happens, you want to take a close look at the input shaft of the transmission. There is a good chance that the bearing became stuck to the bushing and it was actually turning in the flywheel.

The tell tale sign is a black or dark brown ring around the tip of the input shaft, where it fits into the pilot bearing. Eventually after all of the spinning, it works loose of both and may just fall out.

A major cause of TR6 and other cars "clutch squeal".

PeterK
04-18-2007, 02:19 PM
From what I found out when replacing the pilot in my 3A, the bushing is supposed to be able to spin inside the crank.

The bush is soft and will never abrade the crank if it spins and serves the purpose of keeping the input shaft aligned.

It should not be a press fit item although a new one might have some degree of interference fit. ISTR that the TR3-4A pilot is the full depth of the crank recess and the TR6 pilot is much shallower so a slight interference would keep it from pushing inside the crank recess when you install the gearbox.

To remove the old one, squirt some grease through the pilot into the hole in the crank recess. Then use a dowel that is the same size as the hole inthe pilot to hydraulically push the old bushing out (wear goggles). Insert the dowel and pop it, and the grease will push it out and cover your face with grease!

71tr
04-18-2007, 02:30 PM
Okay, good info I feel a bit more comfortable. I'll check the fit of the tranny input shaft with the new bush before installing. What are thoughts on lubricating the bush prior to install?

DrEntropy
04-18-2007, 02:41 PM
If it's bronze, an overnight soak in oil. Some small amount of grease on the input shaft "nose" initially on transmission install as well.

Brosky
04-18-2007, 02:51 PM
Where most of the installs go wrong or bad is when the installer doesn't use an alignment tool and has to keep trying to force the transmission into the bell housing and the bushing gets all beat up from the input shaft beating against it.

If you have the clutch disc and pressure plate aligned properly and add a small amount of grease to the slight bevel or radius leading into the pilot bearing and also on the inside of the bearing, you should be fine.

Just keep any grease away from the contact face of the flywheel and clutch and pressure plate faces as well.

YankeeTR
04-18-2007, 03:01 PM
From what I found out when replacing the pilot in my 3A, the bushing is supposed to be able to spin inside the crank.

The bush is soft and will never abrade the crank if it spins and serves the purpose of keeping the input shaft aligned.

It should not be a press fit item although a new one might have some degree of interference fit. ISTR that the TR3-4A pilot is the full depth of the crank recess and the TR6 pilot is much shallower so a slight interference would keep it from pushing inside the crank recess when you install the gearbox.

To remove the old one, squirt some grease through the pilot into the hole in the crank recess. Then use a dowel that is the same size as the hole inthe pilot to hydraulically push the old bushing out (wear goggles). Insert the dowel and pop it, and the grease will push it out and cover your face with grease!
Peter,

I have to disagree with you on this one. The pilot bushing is a press fit into the crankshaft. The input shaft should spin inside of the crank bushing. The standard bearings are also 'oil-impregnated' so no lubrication of any kind is needed.

An old bearing may get loose inside of the crankshaft due to wear from the input shaft wobbling in the pilot bore and just plain old age.

Years ago I spent some serious $$$ on a Snap-On pilot bushing driver set... I wouldn't have spent the money if I could just plop a bearing into the crank.

AweMan
04-18-2007, 05:05 PM
I agree with YankeeTR it should be a tight fit, it is NOT supposed to spin inside of the crank. It should rotate freely on the trans pilot shaft But not loose as to wobble. Lube it lightly with some lithium grease {not too much tho, you dont want grease to get on the clutch surface.}

Brosky has a very valid point:
you want to take a close look at the input shaft of the transmission. There is a good chance that the input shaft became stuck to the bushing and it was actually turning in the crankshaft.
When instaling your trans, an alignment tool is a MUST HAVE item. It prevents you from buggering up the pilot bushing thus making it too tight a fit on the trans input causing the bushing to spin inside of the crankshaft.
If it isnt a tight fit in the crankshaft then M.H.O. is it isnt the right bushing for your application.
Just my Pennys worth
Kerry

Brosky
04-18-2007, 05:14 PM
To the best of my knowledge, there is no pilot bearing designed to spin inside the flywheel. They are designed to be stationary and the pilot shaft turns in side the bearing.

Every pilot bearing that I have installed or seen being installed had a press fit that kept it in place. I would not suggest that you install a bushing or bearing that is loose inside the flywheel unless you enjoy removing and replacing transmissions.

Sorry that I missed this in the first go around.

PeterK
04-18-2007, 06:31 PM
On both of my TR 4-cylinder cranks, the pilot fit is precise but slips in with after soaking in oil for 24hrs.(actually I have to check my HVDA manual to see if I soaked it or not), no tapping. I thought it should be a tap in fit too so I used some loctite green made for holding bearing races and such.

I talked to everyone about mine slipping in when I changed it. All the auto guys said no press fit too. Then I called Herman VDA about it and he said, torch it out (needed heat to break the loctite green bond), the bearing should not be locked in. True at least on a TR3-4A where the bearing fit the crank recess fully pushed home.

So after removing the pilot, cleaning up, I inserted with a little lube as Herman instructed. A nice smooth precision fit that I could stick my little finger in and move out and in. The pilot is soft bronze so neither the crank nor input shaft get worn from the bushing spinning. When you think about it, it really makes no difference as long as the input shaft stays centered. Maybe it doesn't spin, maybe they both (pilot and input shaft) spin, maybe just the input shaft. Who knows - we can't see in there to tell?

I also have a TR6 bearing and that thing is only like 3/4" thick, the TR4 bearing is about 1-1/4" long, same diameter as the 6. I've never seen the back end of a TR6 crank so I don't know how deep the pilot hole is. So the 6 might need the interference to keep from falling in if it's as deep as a TR4.

edit
btw - it's working and I'm not taking it out unless I have to!

Geo Hahn
04-18-2007, 07:10 PM
On both of my TR 4-cylinder cranks, the pilot fit is precise but slips in with after soaking in oil for 24hrs...

Same thing on mine (precise but not interference), but again that's a 4-cyl TRactor.

TRTEL
04-18-2007, 07:26 PM
The original bushings were a porous ('oilite' or sintered- created from a powder) bronze. You can see the pores especially with magnification. A lot of later replacements were bronze but made from cast or extruded metal with no pores. So the soaking doesn't help. though it should still be oiled. I never was quite sure what to use and have tried some greases, but have no truly long term results to relate. You find it (porous bronze that is) also in the generator/ starter bushes. It is a push fit in the crank. As long as the old one is not rattling around I don't see a problem with reoiling and reusing it.
Tom Lains
TS8651 & 58107

LastDeadLast
04-18-2007, 07:55 PM
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[/QUOTE]

71tr
04-18-2007, 08:54 PM
My flywheel seems to confirm the Bentley quote above. The engine side of the flywheel has a nice recess that fits the bush perfectly. Not sure if the end of the crank has a similar recess or not, the engine is at the garage.

Brosky
04-18-2007, 09:11 PM
Not to confuse or belabor this question, but when I said remain stationary, I did not mean to infer that it was a press fit with a lot of pressure. Just a slight bump with a wooden handle of a hammer to secure it, has always been my rule of thumb with GM cars and my TR6.

But then again, I thought, maybe I'm wrong, so I looked it up and here it is. I stand corrected, for the TR6, at least.

Right out of the original TR6 manual:

PeterK
04-18-2007, 09:38 PM
Paul,

Just to make you feel better, I also saw a writeup on the 6 that said to knurl the ouside of the pilot so that it doesn't spin. So the judge will declare a mistrial on this one.

But like I said, as long as it keeps the input shaft of the gearbox centered (presumeably to keep the input shaft bearing intact), it really doesn't matter if it spins.


PK

Brosky
04-18-2007, 09:52 PM
Good one!! Thanks, Pete!

RonMacPherson
04-19-2007, 12:25 AM
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.

foxtrapper
04-19-2007, 05:34 AM
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.

AweMan
04-19-2007, 08:30 AM
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.

tomshobby
04-19-2007, 08:44 AM
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.

71tr
04-19-2007, 08:46 AM
Thanks everyone for your responses, I'm satisfied with the fit of the new bush. Now to get the tranny mounted!

YankeeTR
04-19-2007, 09:38 AM
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.

Tom's right...

AweMan
04-19-2007, 10:53 AM
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.

Brosky
04-19-2007, 07:37 PM
<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.

foxtrapper
04-19-2007, 08:00 PM
Oh I've seen some ****-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.

Donniefree
07-15-2012, 09:54 AM
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 [/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.

Geo Hahn
07-15-2012, 10:20 AM
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.

TR3driver
07-15-2012, 10:24 AM
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.

TexasKnucklehead
07-15-2012, 10:57 AM
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.)

bnw
07-15-2012, 04:39 PM
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

karls59tr
07-15-2012, 10:06 PM
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.

Speedballer
07-17-2017, 05:53 PM
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?

CJD
07-17-2017, 06:17 PM
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?

poolboy
07-17-2017, 08:46 PM
a)I put one of those bogus ass throw out bearings in it the last overhaul (1998 ish)
But that's nearly 20 years ago !

Speedballer
07-17-2017, 09:25 PM
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.