I was ordering parts for my engine swap today and this came to mind. If this has been covered here in the past, forgive me. I thought this is important enough to put it out there for anyone converting to a manual trans from an automatic (possibly only Powerglides, not TH350 or TH400) on a Chevy engine in the 60's and likely other decades as well.
There are two different dimensions (O.D.) of pilot bushings to go in the back of the crankshaft. I don't know all the exact years, or engines so you will need to do some measuring if you do this. The pilot bushing that was in an original manual trans engines has an O.D. of 1.093". The bushing you may need to install into the back of the crank if the car was originally an automatic with the smaller hole in the crank is 1.060". Dorman lists the bushing for conversions (the smaller OD, 1.060" bushing) as being a # 690-034.1 The original manual trans bushing (1.093") is a Dorman 14650, or GM 3752487. ***Note, the Dorman 14650 is listed as powdered metal. I hesitate to recommend a metal bushing. They don't appear to last like a bronze bushing does.
If anyone has knowledge of specific years these special bushings are needed for a conversion, please add to this thread.
I believe at some point all cranks came with the same bore and eliminated this problem but I'm not certain. Dorman says after 1967 there is no need for the special bushing but I'm not convinced that's accurate. ***Update 1-16-19*** I ordered and received Pioneer pilot bushing PB-656-HD off ebay and it's the right one for my crankshaft which is from a 1968 model 427. It's the right size and there's not a hint of the magnet grabbing it.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
Interesting, I didnt know that the hole in the cranks were a different size. Back in the day I used to grind the outside of the bushing down a bit so it would fit. Never had a problem, I just thought that it was crappy aftermarket parts.
perhaps you could machine a small size crank hole bigger?
-- Edited by SGS Welding on Friday 23rd of November 2018 09:59:28 PM
-- Edited by SGS Welding on Friday 23rd of November 2018 11:00:55 PM
There are two very strong opinions, two different camps on this pilot bearing vs. pilot bushing discussion. You can take my input for what it's worth but I will never use a bearing. I've seen a few times where the bearing has failed and it absolutely shreds the input shaft on the transmission.
I have seen a pilot bushing wear out the odd time but with no other damage, just replace the bushing and proceed. Because it's way softer than the input shaft, no damage is done when it fails. To me, it's a no brainer. However, some guys say you are living in the dinosaur age if you use a bushing. I'm fine with being a dinosaur if it saves me time, money and effort repairing damaged transmissions!
And with that said, I'm sure someone here will say "never again will I use a bushing"!
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
I agree with Carl. I have seen a lot of input shafts worn out due to that bearing. Soak the bushing in oil overnight before install and it will outlast that bearing.
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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).
The roller bearings do cause grief and I have had many here myself with the snub of the input shaft worn out. I have also replaced many of the bearing type with the bushing type because of this and when the customer did not want the shaft fixed/replaced and all times it was 100%. In looking at this, anyone that knows how to drive a manual transmission will realize to take their foot off the clutch went at a stoplight or when they are stopped talking to someone. This is when the damage occurs because the bearings fail. Also the race of the bearings are manufactured of a harder material than the input shaft. The shaft is soft in comparison.
I have had to teach many people this over the years to remove their foot of the clutch pedal when stopped as they don't realize the damage it causes or may cause. I don't believe the bearings are bad to use but I do appreciate the bushing more because it is more forgiving.
I have never heard of anyone soaking the bushing because they are always oil impregnated right from new. Not sure how the brass would absorb more lube..
This 5-speed transmission is out of a 1998 1/2 ton Chevy with a 4.3 L engine.
-- Edited by 67Poncho on Monday 26th of November 2018 11:48:39 AM
I have never heard of anyone soaking the bushing because they are always oil impregnated right from new. Not sure how the brass would absorb more lube..
Thanks for the very interesting information regarding the bearings......I'll definitely stay away from those.
Regarding the the oil impregnated brass bushings......I didn't know that was something they did to brass bushings.
I know when we needed bushings requiring oil for certain machining operations we would use Oilite Bronze bushings.....
I wondered if Oilite Bronze could be another option?
Maybe best to stick with the tried and true working method and buy the right pilot bushing for the job and leave it at that.
-- Edited by Greaser on Monday 26th of November 2018 01:00:49 PM
I have never heard of anyone soaking the bushing because they are always oil impregnated right from new. Not sure how the brass would absorb more lube..
I wondered if Oilite Bronze could be another option?
-- Edited by Greaser on Monday 26th of November 2018 01:00:49 PM
Sintered oilite-type bushing. GM p/n 3752487 or Doorman p/n 690-014 are similar to this
"Good" pilot bushings that GM and the good NAPA bushing is an oilite made of sintered bronze. If a magnet is attracted to it, this indicated an iron content- which isn't recommended in many cases.
A "good" pilot bushing is an oilite. Oil is put into the sintered bronze material under a vacuum- an impossibility w/non sintered material- being as how a solid bronze part has no real porosity of any kind.
An oilite bushing contains all the oil that the material can "soak up" already. The amount of pressure that's used when it is sintered will determine how much porosity- and how much oil it can absorb. Different applications will have different properties.
Adding additional lube other than a slight amount as an installation aid isn't recommended and will serve only to attract/collect debris coming from the clutch and clutch plate, dirt, etc. An oil-bearing material like oilite has all the lube it needs already incorporated into the material itself, anything additional is not needed.
-- Edited by 67Poncho on Monday 26th of November 2018 01:15:58 PM
Agreed George, the old standard pilot bushing is just fine. It was rare back in the day to see it needing replaced more often than when a clutch replacement happened, and of course when the clutch is out already it's a simple task to pop a new bushing in.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
I have never heard of anyone soaking the bushing because they are always oil impregnated right from new. Not sure how the brass would absorb more lube..
I wondered if Oilite Bronze could be another option?
-- Edited by Greaser on Monday 26th of November 2018 01:00:49 PM
Sintered oilite-type bushing. GM p/n 3752487 or Doorman p/n 690-014 are similar to this
"Good" pilot bushings that GM and the good NAPA bushing is an oilite made of sintered bronze. If a magnet is attracted to it, this indicated an iron content- which isn't recommended in many cases.
A "good" pilot bushing is an oilite. Oil is put into the sintered bronze material under a vacuum- an impossibility w/non sintered material- being as how a solid bronze part has no real porosity of any kind.
An oilite bushing contains all the oil that the material can "soak up" already. The amount of pressure that's used when it is sintered will determine how much porosity- and how much oil it can absorb. Different applications will have different properties.
Adding additional lube other than a slight amount as an installation aid isn't recommended and will serve only to attract/collect debris coming from the clutch and clutch plate, dirt, etc. An oil-bearing material like oilite has all the lube it needs already incorporated into the material itself, anything additional is not needed.
-- Edited by 67Poncho on Monday 26th of November 2018 01:15:58 PM
I was very happy to find that NAPA had the bronze bushings. I ordered 2 of them. Picked them up today at NAPA and I only had to take one look at it to know it wasn't good.... I brought it home and it failed the magnet test miserably, so back to the drawing board. I must be able to find a bronze one somewhere but so far it's eluded me.
And I don't want to put this bushing in. I tested the really shot bushing I pulled out and sure enough, it's full of metal too. I wish I could find an old GM bushing. Might have to suck it up and pay ebay prices to get one...
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
I just spent about an hour online and I did manage to find one seller who specifically states "Heavy Duty Clutch Pilot Bushings Are Manufactured Of 100% Bronze" but I either have to run to the US or pay a crazy shipping amount to get it here. Regardless, whoever has one and however I get it, I'm going to pay what it takes. I am NOT putting in a magnetic bushing. Seeing the one I pulled out of this crank convinces me that it's bronze or nothing.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
I just spent about an hour online and I did manage to find one seller who specifically states "Heavy Duty Clutch Pilot Bushings Are Manufactured Of 100% Bronze"
I am not sure why they call the bronze bushing the heavy duty one. I do know that using any other than a bronze one is looking for trouble. The correct bushing measures about .593" ID. The one I removed from my crankshaft was .798" ID, give or take. I say give or take because it's so hammered out it's not perfectly round but it's way over what it should be.
I admit to not knowing until recently that the bushings seemed to have slowly gone away from bronze to steel/bronze blend. I assumed that any pilot bushings with the bronze appearance were good, but that is certainly not true. The 2 I picked up at NAPA look to be bronze but the magnet grabs them real hard.
I see no reason why you can't get a shop to make you a bushing assuming you have the correct material to start with.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
I see no reason why you can't get a shop to make you a bushing assuming you have the correct material to start with.
That's what I was thinking.
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Prince Edward Island
'64 Parisienne CS "barn find" - last on the road in '86 ... Owner Protection Plan booklet, original paint, original near-mint aqua interior, original aqua GM floor mats, original 283, factory posi, and original rust.
I had mentioned before about soaking the bushing in oil overnight. Well what I used to do and I think works better is: squish the bushing hard with your finger and thumb with oil in it. You will see the bushing sweat oil through the outside. Now install it. Im not sure if these were iron mixed bushings or not. Just did it and no comebacks. In the picture Im using a bearing style just as a mock up as I dont have a bushing one.
