Pilot Shaft to Bronze Pilot Bushing Clearance - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 20 (permalink) Old Dec 14th, 10, 11:46 AM Thread Starter
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Joe
 
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Pilot Shaft to Bronze Pilot Bushing Clearance

Pilot shaft is slightly worn, and it cleaned up and polished to .587". Dorman pilot bushing measures .593, for total clearance of .006"
Runout in pilot bushing measures less than .001".
Bellhousing runout measures less than .003" in both directions. (ie, north-south and east-west).
Will the somewhat sloppy pilot shaft give me problems?

Thanks in advance,
Joe
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post #2 of 20 (permalink) Old Dec 15th, 10, 3:35 PM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

It won't make life any easier for your input shaft bearing. however there has to be some clearance. .003" on a side isn't all that much.
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post #3 of 20 (permalink) Old Dec 17th, 10, 12:02 PM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

Quote:
Originally Posted by 1965tripleblack View Post
Pilot shaft is slightly worn, and it cleaned up and polished to .587". Dorman pilot bushing measures .593, for total clearance of .006"
Runout in pilot bushing measures less than .001".
Bellhousing runout measures less than .003" in both directions. (ie, north-south and east-west).
Will the somewhat sloppy pilot shaft give me problems?

Thanks in advance,
Joe
If you're using a Saginaw, Muncie or BW T10 and a bronze oilite bushing you will be fine. These transmissions have a ball bearing front bearing and will easily tolerate a little slack. Like charbilly said, .003" isn't that much.
Jim
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post #4 of 20 (permalink) Old Dec 18th, 10, 12:15 AM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

Also,in many cases " post install " the ID of the stock type pilot bushings is reduced significantly/enough (due to a very tight interfearance fit) to cause issues with even worn input shafts not being able to fully seat/enter the pilot busing not allowing trans to properly/fully seat against bell hosuing.

I have run into this 1st hand on the last 4 of 4 motor installs on man trans chevelles i have done in past few yrs.

I had to use a dremel tool with fine grinder to carefully/as evenly as possible remove just enough material to allow the input shaft to enter the bushing.

No issues post doing that on those cars 1 of which was my car that has gone over 7kmiles since doing that .

BYW,i have been at this stuff for over 40yr now and havent had any issues with input shafts not going into pilot bushngs post install untill the last 4-5 yrs when the mfg of some pilot buyshings went off shore.

And that includes my cars motor that i have owned for over 33yrs where motor and trans were out a few times over the 33 +yrs with same crank in motor the motor so no change there at all and no damage to crank where pilot bushing seats either.

The mfg tollerance & or metarial the pilot bushing are made of must have changed a bit over the yrs which why we are now having this issue that i see other fellow t/cr's had issues with over past few yrs too.

So do yourself a favor and install the pilot bushing in the crank with motor on hoist/cherry picker
& then prior to installing flywheel,clutch bellhousing have a buddy help you try test fitting input shaft of trans into pilot bushing to see if it still fite post insl;aloing bushing in crank.

I learned this the hard way the 1st time this happened to me a few yrs back.

If it fit's great, but if not it takes litterally 4-5 mins or less to carefully remove enough meterial from the ID of bushing to allow input shaft to properly seat,snug but not too tight all done prior to istalling the flywheel/clutch/bellhousing/and motor in car to find it's an issue.

If you dont test fit you run the risk of getting the motor in car and trans not going in all the way due to thisd issdue having to remove trans/bellhosuing/clutch/flywheel just to take 5 mins to remove enough metrial from bushing to asllow trans to fully/proerly seat.

BTW,i used stock pilot bushings from Doorman/Lakewood/Hayes/Carquest/etc,who knows if they all came from the same mfg or not.

They all looked a little different in color-texture from eachother but all had same non fitment issue post install in every casse weather it be sbc or bbc with muncie trans.

Let us know how it goes.

Scott

SCOTT
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Last edited by SWHEATON; Dec 18th, 10 at 12:36 AM.
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post #5 of 20 (permalink) Old Dec 20th, 10, 3:25 PM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

A piece of emory cloth slipped in a slot hacksawed in end of a short piece of 1/4" dowel rod in a drill will help keep the ID round. Check fit often,a little loose is better than a little tight.Its going to swell with the heat. I have seen the bushing stick to the trans input stub and turn in the crank....makes a rriiiiip noise just as you let out on the clutch,same noise if its way oversize too.

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post #6 of 20 (permalink) Old Dec 20th, 10, 5:33 PM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

Quote:
Originally Posted by driveshaft-texas View Post
A piece of emory cloth slipped in a slot hacksawed in end of a short piece of 1/4" dowel rod in a drill will help keep the ID round. Check fit often,a little loose is better than a little tight.Its going to swell with the heat. I have seen the bushing stick to the trans input stub and turn in the crank....makes a rriiiiip noise just as you let out on the clutch,same noise if its way oversize too.
Speak for yourself, man.

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post #7 of 20 (permalink) Old Dec 20th, 10, 7:38 PM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

Now what are we talking about ......??
you just couldn't let it go,huh ?

New paint but still far from complete
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post #8 of 20 (permalink) Old Dec 21st, 10, 6:00 AM Thread Starter
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

Some bushings are slightly magnetic and others are not. Mine is. I have heard that most older ones have less iron content and more bronze. In any case, I put my old worn-out bushing (also a Dorman, magnetic piece) on the stove, and voila! It "sweats" oil which seeps out when it's heated!

I installed the bushing into the crank (the engine is installed in the car) by starting it with a lead hammer. I drove it into place with a cut-off piece of wooden broom handle and a 2 pound ball peen hammer. It took about 20 good whacks to drive it flush with the crank flange, which is where I want it. This position allows full engagement, with about 1/16" clearance between the step in the input shaft and the bushing when the trans is mounted on the bellhousing.

I took your advice and checked the fit of the pilot shaft AFTER the bushing is installed in the crank. I put EXACTLY ONE non-overlapping layer of electrical tape over the pilot end of the plastic alignment tool, miked it and it measures EXACTLY same as my trans pilot shaft. The "test" pilot shaft now barely fits into the new bushing which is now installed into the crank. WOW............that means that after installation, that bushing's ID decreased by .004-.005, because I figure I've now got (about) .001 clearance between the shaft and the bushing. You recall that it was .006" before I installed it on the crank. I verified with an extra Dorman bushing I have, and sure enough, it's sloppy at .006" clearance.

Question: Is there any way that a new bushing can be slightly cocked on installation? Since the bushing is 3/4" deep, you would think that it would straighten itself out if it is "started" slightly cocked, but by the time it is driven in to its full depth that it would end up straight. Thoughts? If this is possible, then would it be necessary to use a press to install the bushing on a uninstalled crank in order to ensure the pilot is installed dead straight? Could the bushing have deformed given the way I installed it?

Joe

Last edited by 1965tripleblack; Dec 21st, 10 at 6:18 AM.
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post #9 of 20 (permalink) Old Dec 21st, 10, 9:41 AM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

Quote:
Is there any way that a new bushing can be slightly cocked on installation?
Joe
I thought I was a worry wart! Put the transmission in and get some sleep. It will be fine.
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post #10 of 20 (permalink) Old Dec 21st, 10, 9:55 AM Thread Starter
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

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Originally Posted by GMJim View Post
Joe
I thought I was a worry wart! Put the transmission in and get some sleep. It will be fine.
Wellllllllllll .....................OK I can see why you would say that.

I didn't mention that this is the THIRD fookin' bronze bushing that has gotten boogered (hole expanded about 1/8" bigger than the pilot shaft), over the course of the last few years..............less than 7000 miles.

Trans is a PITA to R&R...............I'm gettin' too old for this crap.

Dunno.......maybe this is normal. If so, then what's the point of the Goddam thing. I would think that normal wear would see MAYBE 1/32" expansion at every clutch change, which would be (about) every 40,000 miles. Or, if you're like me and drive the car like it's supposed to be driven (hard), then every 20,000 miles.

Last edited by 1965tripleblack; Dec 21st, 10 at 10:25 AM.
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post #11 of 20 (permalink) Old Dec 21st, 10, 10:18 AM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

Used a brand new Lakewood(?) bronze and pulled my trans at 40 miles for a repair. Like yours mine had some wear in it and a small lip part way in.
I left it alone and like you have a little slop in the input shaft, not too bad.
How bad could it be with those miles I thought so left it in.

Quote:
This post is a duplicate of a post that you have posted in the last five minutes.
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post #12 of 20 (permalink) Old Dec 21st, 10, 9:38 PM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

Quote:
Originally Posted by cuisinartvette View Post
Used a brand new Lakewood(?) bronze and pulled my trans at 40 miles for a repair. Like yours mine had some wear in it and a small lip part way in.
I left it alone and like you have a little slop in the input shaft, not too bad.
How bad could it be with those miles I thought so left it in.


Children, try these guys for the right pilot bushings

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post #13 of 20 (permalink) Old Dec 23rd, 10, 1:59 PM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

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Children, try these guys for the right pilot bushings
hahaha! You must be getting old too!
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post #14 of 20 (permalink) Old Dec 24th, 10, 8:46 AM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

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Originally Posted by charbilly2001 View Post
hahaha! You must be getting old too!
Two days older than dirt

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post #15 of 20 (permalink) Old Dec 24th, 10, 12:27 PM
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Re: Pilot Shaft to Bronze Pilot Bushing Clearance

Quote:
Originally Posted by 1965tripleblack View Post
Wellllllllllll .....................OK I can see why you would say that.

I didn't mention that this is the THIRD fookin' bronze bushing that has gotten boogered (hole expanded about 1/8" bigger than the pilot shaft), over the course of the last few years..............less than 7000 miles.

Trans is a PITA to R&R...............I'm gettin' too old for this crap.

Dunno.......maybe this is normal. If so, then what's the point of the Goddam thing. I would think that normal wear would see MAYBE 1/32" expansion at every clutch change, which would be (about) every 40,000 miles. Or, if you're like me and drive the car like it's supposed to be driven (hard), then every 20,000 miles.
You checked the concentric bellhousing alignment but, did you also do a parallel check? The bellhousing parallel alignment spec is +/- .001" or a TIR of .002". Believe it or not, the paint on the face of the bellhousing that mates to the engine block and the trans mating surface may cause the parallel alignment to be out of spec. A parallel alignment check must have all of your bolts installed and torqued for a proper check. Have you verified the concentric alignment is still at .003"? Was your .003" spec TIR or +/-?

Quote:
Originally Posted by cuisinartvette View Post
Used a brand new Lakewood(?) bronze and pulled my trans at 40 miles for a repair. Like yours mine had some wear in it and a small lip part way in.
I left it alone and like you have a little slop in the input shaft, not too bad.
How bad could it be with those miles I thought so left it in.
All blow-proof and original bellhousing's need a concentric AND parallel alignment check with a dial indicator. Anytime you see premature pilot bushing wear, something is out of alignment.

Also make sure the bellhousing transmission locating register hole is for a passenger car and not a truck transmission front bearing retainer. This mis-match happens more than you think.

Bottom line: Your concentric alignment must be +/-.005" or .010" TIR and the parallel alignment must be +/-.001" or .002" TIR. It does NOT matter if you are using a TKO, Saginaw, Muncie, ST10, T56, Jerico, or G-Force transmission. It also does not matter what front bearing (radial or cup & cone) is used in any type of transmission. The bellhousing alignment spec is the same for ANY transmission. If not, you will have accelerated pilot bushing wear.

Granted, radial front bearing transmissions are more forgiving with bellhousing alignment specs but, the pilot bushing is not. A pilot bushing does not know what transmission is being used behind it.

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