My friend who is putting a TKO in this 455 Buick is now going through the pilot bearing fiasco. He picked up a pilot bearing from a local parts store and its too big. The opening in the crank measures 1.060. The roller bearing was 1.100, not even close. He also had problems with bushings not fitting. I did give him a bronze bushing years ago that worked good, but I can't remember where I got it from.

Anybody have a measurement for the GM pilot bearing?

VINCE,I bought the std bronze bushing from 3-4 diff mfg's (who knws they may all get them from same source) and they were al extreemly hard to get into my crank and then the inne hole closed up a smidge uppon install and the input shaft would no longer go in even though the bushing fit fine oner shaft prior to installing bushing.

This is a common issues these days ,i ended up using a dremmell tool to as evenly as possible open up the inner hole in the bushing just a smidge untill the spare m20 input shaft i had lying around would fit.

Get a new bushing and leave it the freezer right untill ready for install and you could also use a hand help tourch to heat local area of crank flane just prior to bushing install too.

Chilling the bushing will get it to contract a little and heating the local area of crank where bushing seats with a hand held burnzomatic tourch will possibly get that to expand a smidge easing bushing install when it comming freshly frozen from the freezer.

But i had the same motor out a couple times in the mid 70's replacing the pilot bushing mult times and it was a heck of a lot easier to do back then and there were no issues with input shaft going into bushing either after it was installed either like these days.

I would not be surprised if over the past 30+ yrs the tollerance has slipped in the records from mfg to mfg to build/machine the bushings and thats why we are having the issues your talking about with todays pilot bushings.

I got the bushings that didnt fit correctly from DOORMAN,HAYS,ZOOM,GM,LUKE clutches and none of them fit right. They were all way too tight installing very hard and the inner dia closed up uppon install on all of them too so the input shaft would not fit anymore. Not all the bushings looked the same as far as material & color went so i dont think they were all obtained from the same mfg but who knows.

Sorry i dont have the gm spec for pilot bushing hole in the crank that your asking for but its likely just poor tollerance on the bushing thats the issues,not the crank which my motor was a good test for as i stated above.

I would have your local machinest turn a new bushing down a .001-.002 on outter dia only and i bet it will installe easier and the input will fit correctly after bushing is installed too.

Hope this helps shed some light on this issue.

Scott

Scott I went through some posts and saw your experiences. Its total BS. My friend todat just bough a GM roller bearing and it measured 1.095, still to big to get into his 1.060-1.070 crank. He took it to the machinist who will tun it down to ~1.72. Hope that works.

Anybody know how much (in terms of .000's) of an interference fit is req'd?

Scott I went through some posts and saw your experiences. Its total BS. My friend todat just bough a GM roller bearing and it measured 1.095, still to big to get into his 1.060-1.070 crank. He took it to the machinist who will tun it down to ~1.72. Hope that works.

Anybody know how much (in terms of .000's) of an interference fit is req'd?

I can give you the exact amount when I get back to school this weekend. I have a book that goes into the calculations for different types of fits. I think it will be about 4 thous though. :confused: Someone will probably have an answer for you though before then.

My TKO 600 'ate' two bushings. First was a roller bearing that came with it. There were no rollers left when I checked it while doing a clutch swap. Then I tried the bronze type. After I BEAT it in, it was so tight that lubricant was oozing from the bronze pores. I know its supposed to , but I am being a little dramatic. Then I ended up pulling the tranny again and reinstalling the clutch. I went back to a new roller bearing. I could not get it to fit. The original that I beat into the crank was distorted when I pulled it out which lead to the failure.
Out comes the dremel. One of the better tools invented. Material comes off of the crank. I leave .002 clearance and pop the new bushing in. Its a perfect fit.

My TKO 600 'ate' two bushings. First was a roller bearing that came with it. There were no rollers left when I checked it while doing a clutch swap. Then I tried the bronze type. After I BEAT it in, it was so tight that lubricant was oozing from the bronze pores. I know its supposed to , but I am being a little dramatic. Then I ended up pulling the tranny again and reinstalling the clutch. I went back to a new roller bearing. I could not get it to fit. The original that I beat into the crank was distorted when I pulled it out which lead to the failure.
Out comes the dremel. One of the better tools invented. Material comes off of the crank. I leave .002 clearance and pop the new bushing in. Its a perfect fit.

Strange, I have had no problems. Did you "force" the trans in by tightening the bolts? If so this is a no-no. Is your bell housing dialed in less than 5 thous concentric alignment? :confused:

I still have an original GM one that is for sure 35 years old. It is solid steel not bronze.

I have been carrying it around with me for this long thinking that one day I am going to use it. Probably after I finish playing with automatics in the Beaumont this is where the iron case Super T10 will go.

Well I put the digital caliper on it and it measures 1.095 outside and 0.590 inside.

I tested the fit on my Super T10 pilot shaft and it fits I would say just a bit loose, but then the tranny shaft has seen a few miles.

But it shows at least that even many years ago that 1.095 was the correct size of the bushings manufactured then.

Sandy, It is hard to believe that a bushing would be just plain steel - not that i doubt you, it is just that I'd think the heat would cause it seize on there eventually. I personally would not use it, but if you do, I'd get some hi temp grease or anti-seize on it.

Good luck.

I am not certain what the stock specs are, but a light press fit is usually about .0007" max interference and a med press fit is .0011 max interference. I personally think any more than that and getting the thing apart may be difficult.

THe clearance on teh shaft to the bushing ID, there should be min of a thou, likley a max of about 2 thou.

This is JMO in looking at that interference fit and medium running fit charts in my engineering text book. Hopefully someone else will add to this....

Ron,

I just put a magnet on it and it is for sure steel.

It is 0.75 inches long.

The last time I worked on a four speed car was back in 1971 on a car that raced in 1972. I had purchased a few from GM, one went into a 283 with a muncie and the other was a 427 with a muncie and ended up with just the one spare.

I sure would not try to press it into a 1.060 hole!

Well, I learned something new in GM using solid steel bushings; neat.

And I agree you won't press that into a 1.06 hole - that's an interference fit in a big way :D

I was taught .001" per inch of diameter for a press fit in iron or steel. Don't know if bronze is different.

I have a bronze pilot bushing I bought from OPG, about $6, I'm planning on installing some time this month.. Have to say I'm worried about it, with ALL the complaints I have heard on installations.. I can just see me finally getting the bushing in and than the trans won't go in that last 1/2 inch.
I will be using above mentioned measurements to check my bushing and hope for the best.

It doesn't surprise me that the sizes are all over the place. There is a complete lack of quality control in this country anymore.

Manufacturers have and actual interference dimension for pressed in bearings. The Oilite bronze bearings are pretty soft. You can't pound them in and expect them to keep their shape, especially when there is already too much interference. Any competent machine shop should be able to turn up an oilite bearing with the proper dimensions so that it will fit when installed. This same problem was posted here a year or so ago. Some things never change. When someone gets the dimensions right, they should start making the bushings and sell them. There is a good market for something that works.

Ill look in my engineering book this weekend and give you guys the exact dimension/tolerance for a interference fit.

The problem with your friends 455 crank is that it is either an auto crank or a '73-up crank. The factory didn't final machine the later auto crank's pilot hole. The crank pilot hole should measure about 1.092" with the proper depth. I would say to either remove the crank and have it machined or get one of the dick miller roller bearings that fit in to the convertor hub opening.

I would think the dremel method would introduce too much off-centeredness in something that needs to be very concentric to prevent vibration.

Ron,

I just put a magnet on it and it is for sure steel.

It is 0.75 inches long.

The last time I worked on a four speed car was back in 1971 on a car that raced in 1972. I had purchased a few from GM, one went into a 283 with a muncie and the other was a 427 with a muncie and ended up with just the one spare.

I sure would not try to press it into a 1.060 hole!

I was given a heads up from Auto Gear when putting in my new M22w and that was to put a magnet to the bushing and if it was steel was to pitch it and get a actual bronze one. I ended up going to the local tranny/rear end rebuilder and his were bronze.

My friend went and got a new pilot bearing from GM and it measured about 1.095. The other aftermarket one he had was bigger, so that one went back. His crank measures somewhere around 1.083, but it hard to get a good measurement b/c the motor is on a stand right now, and there's alot of bronze debris left in the hole from the prior bushing. So the crank may indeed be OK in terms of sizing. Not sure what year the crank is, it was from Advance Auto.

Think you are right on about the cranks not being finish drilled for standard transmissions in later model year cars.

It is not very hard to take a bit off the pilot bushing with emery cloth that comes in long strips.

For the rear spindles on Corvettes, the bearing is a press fit and so setup is very tedious unless you modifiy the spindle so the bearing will slip on. Modifying the spindle is easy, put it in a vise and carefully go around the area where the bearing sits with emery paper till you get enough material off so the bearing can be pushed on by hand. This makes setup of the assembly very easy. The bearing is held in place and tight by a big nut with a cotter pin. The pre-load is set with shims.

So it is worth doing a bit of measuring before you take the press or hammer to it.

Especially harmonic balancers as we have read about in other posts.

Ill look in my engineering book this weekend and give you guys the exact dimension/tolerance for a interference fit.

That is what I did. I presumed it would be Running and Sliding Fit class RC5 or RC6. Not 100% on that, but those seemed to makes sense based on the description. I am interested to hear your findings Brett...

Think you are right on about the cranks not being finish drilled for standard transmissions in later model year cars.

I've seen some that were not big enough in diameter and/or not deep enough.

It's a lot nicer to have all that squared away long before the trans is crushing your chest while you're laying on the garage floor.

That is what I did. I presumed it would be Running and Sliding Fit class RC5 or RC6. Not 100% on that, but those seemed to makes sense based on the description. I am interested to hear your findings Brett...

I think a running and sliding fit would mean it can still move and turn freely, which a pilot bushing can not, otherwise we would not need to hammer them in. Below I chose an interference fit, however, it may fall in the transitional type of fit. I photocopied the page for types of fits and I guess I will let you guys choose if I chose correctly or not. :confused:

Sorry it took so long to get back to you guys. So looking at my book, I would say you would want it in the category of:

"
"interference medium drive fit" H7/s6
For ordinary steel parts or shrink fits on light sections, the tightest fit usable with cast iron.
"

NOTE: This is assuming the crank/pilot bearing diameter to be an ideal dimension of 1.06". If this is incorrect, continue calculations as I did but replacing the 1.06" number with the correct number. Regardless, the tolerances for this size range will be the same.

For the Crank tolerances:

Using the International Tolerance Grades level IT7 for a size range of .96-1.20", DeltaD should be .0008".

Dmax= 1.06"+.0008"= 1.0608"
Dmin= 1.06"

For the Pilot Bearing Tolerances:

Using the International Tolerance Grades level IT6 for a size range of .72-1.20", DeltaD should be .0008".

From the Fundamental Deviations for Shafts table, using the s deviation, (deltaF) is .0014".

dmin=1.06"+.0014"= 1.0614"
dmax=1.06"+.0014"+.0008"= 1.0622"


Answer!:
So reviewing, this means you would want an interference fit of .0006"-.0022".


Here is the table for what kind of fits. Think it should be Transitional or Interference?

http://i52.photobucket.com/albums/g34/Brettd85/fits.jpg


But it shows at least that even many years ago that 1.095 was the correct size of the bushings manufactured then.

If the correct size was really 1.096" for a 1.06" crank, I would say that is an extreme/impossible press fit, thats .036" of interference! :eek: :confused:

The problem with your friends 455 crank is that it is either an auto crank or a '73-up crank. The factory didn't final machine the later auto crank's pilot hole. The crank pilot hole should measure about 1.092" with the proper depth.

I think this must be right. The crank is supposed to be ~1.092", not 1.06". That would mean the interference fit would be .0004", which falls within the range for a proper press fit calculated above or slightly looser, which would still function fine.

__________________________________________________ _______________

So reviewing everything, I think the problem must just be your friends crank, not the pilot bearings produced today. Granted there may be a few lemons out there. Good luck! :thumbsup: :beers:

Brett,

The OD of the bushing must be interference fit, as you have figured. I suspect that .022" will be quite a lot for a tap fit, unless a bronze bushing is more complaint than I think. I think anything more than a light/medium press fit will be out of what would be considered "in car serviceable", but I am just guessing.

For the ID of the bushing, the shaft will need some clearance for assembly. Also speed and temperature changes need to be taken into account.

My text is older, perhaps out of date. I will look at this again tomorrow if I have time.

Brett,

The OD of the bushing must be interference fit, as you have figured. I suspect that .022" will be quite a lot for a tap fit, unless a bronze bushing is more complaint than I think. I think anything more than a light/medium press fit will be out of what would be considered "in car serviceable", but I am just guessing.

For the ID of the bushing, the shaft will need some clearance for assembly. Also speed and temperature changes need to be taken into account.

My text is older, perhaps out of date. I will look at this again tomorrow if I have time.

You may be right. This is why I am thinking it might be a locational interference fit. I did not do an analysis on the id of the pilot bearing. That would probably be a "clearance sliding fit".

.022" or .030" is too much for an interferance fit. You'll beat it all to hell trying to get it in. BTDT, got the t-shirt. The inner hole will also squeeze down by that amount. Then the shaft won't go in. I'm in that club too but only 'cuz I was helping a friend. I would wager a half-a-thou (or maybe slightly less?) would be fine...both expand as they heat up so the fit should stay tight.

.022" or .030" is too much for an interferance fit. You'll beat it all to hell trying to get it in. BTDT, got the t-shirt. The inner hole will also squeeze down by that amount. Then the shaft won't go in. I'm in that club too but only 'cuz I was helping a friend. I would wager a half-a-thou (or maybe slightly less?) would be fine...both expand as they heat up so the fit should stay tight.

Its .0022, not .022".

If I misread and posted .022, my apologies. I must looked at it and though 0.022 ny accident, sorry.

0.0022" sounds like it might work, but I would not go any larger. I would agree with Scott; I think .0005 to .001 would be enough most of the time.

Its .0022, not .022".

Ooops. I must be getting lysdexic.

I just checked mesurements on this Bushing I bought from OPG. outside 1.096 inside .590. Also the magnet grabs on to it like a dog in heat. Its from Ram cluches as the package says.
I don't know what kind of metal it is, because it just isn't heavy as a solid piece of steel would be. Looks like another type of metal mixed with it. May be a good piece to use but I'll have to go with a solid bronze one

I just checked mesurements on this Bushing I bought from OPG. outside 1.096 inside .590. Also the magnet grabs on to it like a dog in heat. Its from Ram cluches as the package says.
I don't know what kind of metal it is, because it just isn't heavy as a solid piece of steel would be. Looks like another type of metal mixed with it. May be a good piece to use but I'll have to go with a solid bronze one

They are produced using sintered metal which is just powdered metals heated together under pressure. They probably use steel or iron for wear resistance, bronze for lubrication. Because this process creates excellent dimensional accuracy, I would expect all parts produced to be nearly identical. :beers:

Picked up a solid bronze bushing today by Federal Mogul part # PB-656-HD (Made in the USA) it measures: 1.095 outside... .590 inside
This seems to be the one I need.

Brett,
Seems like the mixed metal one would wear better than the solid bronze, and treat the tranny shaft better than straight steel.????

I think it would be best to have the bushing wear, much easier to replace than the input on the trans. I'd use the brozne one unless this is a race oriented machine. just my 2 cents -Ron

I think it would be best to have the bushing wear, much easier to replace than the input on the trans. I'd use the brozne one unless this is a race oriented machine. just my 2 cents -Ron

I'll take you up on your 2 cents, the bronze it is.