The Stovebolt Site Forums The Shop Area Engine Shop I have a serious pilot bushing problem...

To all,

Put in a new clutch behind my 58 model 235, and while I was at it, removed the pilot bushing to put in a new one. First one was a standard brass oilite bearing, which when in place would not let the transmission mainshaft spin freely although the pilot tool fit fine.

Disassembled it all. Tried to put in another brass one, stuck it in the freezer prior to driving it in. Could not even get it to start. Checked crankshaft, no burrs or other obstructions.

Gave up trying to get this one to go, as it was getting very marked up. Got a very expensive Kevlar/Nylon composite one from Summit Racing, and just finished putting it in. It started off with the standard .593" inner diameter and fit nicely over the mainshaft prior to installation. Once installed, its inner diameter has also compressed to the point where the pilot tool won't even fit into it.

Removed it, have obtained 3 additional brass bearings. Have miked all,and all have the same internal/external dimensions, as also did the expensive composite.

Is there some secret to this?? I am being very careful to line the bearing up properly, and am at a loss to understand what is going on. Have tried grease, no grease, freezing, room temperature, nothing seems to work.

Will now pull out the expensive composite bushing and go back to a brass replacement, and it seems that pilot bushing removal is the only thing I am getting real good at.

I really want to get my truck back on the road. Anybody out there have any tips? Thanks for any and all assistance, I am at wit's end.

... not being there and not having the problem before I really can't say....but you should not have to drive any pilot shaft bushing up into the crankshaft.
That said can you get a pair of dial calipers up in there to check the crankshaft hole? It sounds as though there ia a "taper" in the crankshaft or it just plain compresses when you "drive" it in.
I'd take a look at the OLD one vs the new ones....nothing says you can't use your old one unless its messed up. Take your old one with you to the parts store.
Hmmm, I'm interested in what others say and what you find out in the end. Let us know.

there are 2 different ones with one being about .030" larger od which would be the one that would have gone into a p/glide crank. if you really have to beat the crap out of it to get it in there you have the one for the p/glide crank. if I an remember the part# off the top of my head they are like 56 and 56b. the proper one should go in fairly east
i would also mile the end of the input shafts to chk and see if the real one is not larger than the line up one
ron

Just curious how far the original bushing was in the crankshaft. Wondering if it was not in all the way and created a lip inside. When the new bushing goes in and hits that ridge maybe that is whats making it get tight? Just an idea??? Don

Richard - I had the same problem. The brass bushing is soft. If you beat on it very hard, it warps and won't fit the transmission shaft. I had to cut my first one out and install a new one. The second time around, I put a light coating of grease on the interior of the crank shaft, and the exterior of the bushing, and I put the bushing in my freezer for several hours. After the bushing was good and cold, I lined it up with the crank and drove it in. I placed the ball end of a ball and peen hammer on the end of the bushing, and then hit the other end of the hammer with a 2-pound sledge. This gave me uniform pressure on the bushing. The bushing was still very difficult to insert, but the second time it fit my transmission shaft just fine.

it is wise to have a proper driver to put it with. I am fortunate in that I do have equipment that I can make a lot of things with. even one turned on a wood lathe out of a good hardwood is fine
ron

Thanks to all.

I cannot find a reference to two different external diameters for this engine/transmission combo. At least according to the parts manual and manufacturer manuals that I have been able to examine.

The replacement bushings have been driven in to the same depth as the original; they are flush with the end of the crank so that none of the bushing is unsupported. I have examined the interior of the crank and can find no ridges or other obstructions that would hinder insertion of the bushing.

Norcal, if you weren't so far away in California, I would invite you over. I did try freezing the last one, but no luck. It could be that that bearing (which I did not have the opportunity to measure) may have been a few thousands over. I will try that on the next bearing to go in, which will be brass. I also bought a ball peen hammer today to try.

Two things left. I have made an insertion tool which may help, and an old line mechanic suggested a light sanding with 220 grit or better on the outside of the bearing to shave a few thousands off. Not real sure about that technique, as I know this bushing has to be tight to prevent turning.

Thanks to all of you for your input. Before I crawl under that truck again, anybody else have any other ideas?

the 235 and 283 take the same pilot bushing. the bushing that is .030" larger would fit the same years that had come with a power glide tran. if you were to put a std behind them you would have to insert the larger bushing. a p/glide crank does not come equipped with a pilot bushing as it is not required for that application. the only thing that differentiates for the partsman or woman is the suffix b after the part nbr.
I have experienced this. sometimes one has to be experienced to read a parts book and i did work at that back in the 60s anfd early 70'3
ron

Rock auto shows two different ones for your application. www.rockauto.com
#14650 = 1.093" od
#pb656hd = 1.096" od
Maybe this will help you.

[quote=Richard G.]Thanks to all.

I cannot find a reference to two different external diameters for this engine/transmission combo. At least according to the parts manual and manufacturer manuals that I have been able to examine.

[/quote

the reason that you cannot find the larger bushing is or was not an application as such so if you are checking online parts books you look for a 235 with clutch and it lists a pilot bushing that goes with that application. if you look up for a pilot bushing for a crank that has a powerglide behind it there is no application. computor cannot think about that as it didn't have any data to back that up
the optioal bushing for the p/glide crank must be listed as an aftermarket item because the manuf never made it for that application as it never existed in their world. it was only manuf by demand aftermarket of people wanting to change over to a std trans from an automatic
I cannot tell you why the p/glide crank took a larger opening there. it is in the range of .025-.030", can't remember which so used .030 as a figure that was close.
this is why you need that old partsman sometimes other than the kid behind the counter can only sell you what he finds on his or hers computor
ron

I have experienced the same problem, two different bushing OD's, and the same solution- - - -a parts man who knows what he's doing! Measure everything before you try to assemble it- - -don't ASSume it's right because some parts store computer said so! The press fit on a pilot bushing should be no more than 2 or 3 thousandths, or it will be very hard to install and the ID will start to shrink. The other option would be to ream the bushing out to the correct diameter after it's installed.
Jerry

The latest in the pilot bearing saga...

Got the proper diameter part (finally)and put it in the freezer. Climbed under the truck to remove the very expensive Kevlar/Nylon bearing with a tap (what I have used previously) and the blasted thing shredded. Now off to buy/rent a regular puller but will not be able to get back to this until next weekend now.

The worst part is that I was trying to finish it up as it was supposed to be in a parade next Saturday.

Thanks to all of you for your help. I cannot believe how frustrating this has been. Will keep you all posted.

you should be able to take it out with a hammer and chisel, just be carefull of putting a nick in the bore. but if you do it would be easy to fix and wn't bother anything
ron

To remove the bushing and take wet toilet paper & stuff it into the hole of the bearing. Fill it up and use a wooden dowel pin or any thing else that fits the hole snugly and tap the pin in pushing the TP inward. Pull the pin out & put more wet TP & repeat tapping the dowel in & then pushing more PT in the bushing hole. Continue repeating untill the bushing is pushed out. As funny as this sounds I have used it several times to remove brass pilot bushing w/o problems...Joe

I use a method like Joe's, however with grease.

I've done it w/grease also, BUT w/TP it is less messy....Joe

these methods all work fine, I was addressing an o/size bushing that had been forocd in
ron

So were we, he has to get whats left of the pilot bushing that was forced in out and thats what we were telling him to do w/out using a chisel & having the chance of boogering up the end of the crank.

everyone to their own. I guess that depends upon their skills
ron

Since he's dinged up the inside of the bushing with a tap, it's going to require an expanding-type puller with a slide hammer attached to remove it. The various methods using wet paper towels or grease need a smooth inner surface on the bushing to work properly. I'd suggest using a die grinder and a carbide rotary file to hog it out to a thin shell, and a cape chisel to split the remaining material and allow it to shrink away from the crankshaft bore.
Jerry

or a 3/4 drill bit if it will centre and thank you for the name for that chisel,
ron

Reviving this thread, as I had the same problem- Pilot bushing would not come out and new one didn’t want to go into my 261. Slide hammer would not budge the old bearing. Solution:

Insert a pipe thread tap that you can get started in there and thread until you reach the tapered portion of the tap- then stop. Insert 5/8” course thread bolt and chew through the threads that you made. The bolt will reach the back of the crank and it will push the pilot bearing out. It was unbelievably easy, and no pounding was required.

I mic’d two new pilot bearings and they had two different O.D.’s: 1.0935 and 1.0960. Otherwise they were identical.


My crank hole is smooth and looks just fine. I measured the OD of the bushing that removed, and I’m sure it has been squashed, but it was 1.0925. Pics: Pilot bushing removed with 5/8” bolt

I think it’s going to take more than a few taps to get the smallest Pilot bushing that I have back in…we’ll see. [Edit] smaller bushing went in, but required firm smacks from my brass mallet- I did not have to “beat” it in, but it required a little more effort than others have described here. Pics of two bushings- smaller on on the left. They are actually different on the crank side- the smaller bushing has a bit of a nose on it: Two sizes of Pilot bushing, smaller one on left, showing front and back

A lot of the above drama can be sidestepped by acquiring a carborundum button hone a few thousandths larger than the transmission input shaft snout, and using a variable speed drill motor to fit the bushing ID to the shaft. Since the only time there is relative motion between the bushing and the input shaft is during shifting, or maybe idling in gear with the clutch pedal depressed at a stoplight, the fit isn't terribly critical.
Jerry

Thanks Jerry!

Wow have done those pilot bushings every way mentioned...surely in 14 years he has it fixed by now ! Also doubt it is brass probably sintered iron (is magnetic). Long ago they made a brass one could hear it squall 3 blocks away. Not good to ream the bore,will wipe the lubricant pourous suface closed.

Norcal Dave Those are magnetic I think,doesn't matter made to work !!

Just in case someone reads the 2009 portion of this revived thread with interest, the question was a pilot bearing to fit a 235 using a factory equipped Powerglide transmission (which did not use a pilot bearing) for a manual tranny (which did.) GM did not list one.

GM drilled all their 235 crankshafts for a pilot bearing, but did not machine the rough hole for a pilot in the cranks they used for the Powerglide since it did not need one. (Saved a few bucks.) Therefore, they did not make a pilot bearing to retro the Powerglide crank to a manual tranny...

I used a 235 out of a 57 Nomad w/Powerglide for my 54 3100 w/3sp manual. The pilot that came with the clutch kit was .030 or so too large in diameter. Wahhh!!! (It fit the machined hole for a standard 3 sp manual crank.)

Dorman 690-034 was the closest I could find to fit this raw hole and make this conversion. It mikes 1.060 which is a tad loose. I dimpled it about 20 times around the outside with a center punch and drove it in using red Permatex. Perfect.

As a career machinist for 27 years, I question whether this would be the best practice. Raw cast bores in the crank prior to being machined, as you said are .030” too small, out of round and not concentric with the rest of the machined crank. Some may be closer than others, but some bores could be offset at the limits of what it would take to clean up the bore to fit a standard bushing. If it was offset .010” it would also move the input shaft of the tranny placing undue pressure on the bearing every time you pressed the clutch it. Not something I would want to take a chance with.

You may have gotten lucky to have gotten one that did work, but I have my doubts if others would be so lucky.

A dial test indicator would easily confirm concentricity and out of round before installing a bushing and if it's .030" undersize it was probably rough bored so I think we're jumping to conclusions here.

The most accurate solution would be to fabricate a stepped bushing that centers in the larger, accurately machined diameter and steps down to fit into the rough bored area without actually contacting the crankshaft. I doubt that anyone but a machinist would be willing to go to that amount of effort or expense.
Jerry

Just a guess here, but wouldn't the hole in the rear have been machined enough to create a place for a live center for machining the main journals?

I would at a minimum, I would do a runout of the bushing bore (or the bushing itself). That would confirm if it is usable as is. As per the “Chevrolet Truck Shop Manual” the pilot bearing runout should not exceed .008” TIR (Total Indicator Reading). That is quite a large tolerance so it may not be so critical.

Dorman states the 690 034 pilot is "only used for automatic transmission conversion to manual transmission. Powerglide to 3 speed manual 1.06 OD."
Using guide pins, the tranny slides in place with no effort.
Runs smooth.

The hole in my '53 235 "w/Powerglide" crankshaft accepted the Dorman 690 034 perfectly and ran true with a 3 speed and a T5 transmission. That hole looked to be machined to me.
Kevin brings up a good point about the need for a concentric hole for machining the journals.

A dial indicator is your friend- - - - -like the slogan Sun used to put on all their test equipment- - - -"We test, not guess!"
Jerry

If the Shop Manual is calling out a tolerance, it is something that should be checked. That bushing is tough to change after it all reassembled.

I wish I had seen this thread last Fall when I was dealing with a stubborn pilot bushing extraction and install. Seems like shoddy workmanship on GM's part.

Seems like pretty good production cost control- - - -not doing unnecessary machining on a crankshaft that was not expected to last beyond the warranty period, 60 years ago. Did the foundry and the engine factory really care that someone would be trying to fit a square peg into a round hole nearly a century after the engine was made?
Jerry