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Old 08-30-2010, 11:34 AM   #1
20mercury
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Location: Lafayette Louisiana
Default Installing a pilot bushing in a '76 4 speed

Ok, I have concluded after taking the 4sp transmission "out and in" twice and installing 2 different pilot bushings that this job is a real pain. (Although the second install on the 4 sp went a lot quicker, so we are learning something, maybe).

On the first 4sp install, I could not get the 4sp input shaft to go into the pilot bushing. So I pulled the 4sp back out and checked the pilot bushing which turned out to be squeezed in on the id so the input shaft would not fit anymore. Maybe a bad install on my part I figure.

So I pulled that bushing out and got a second one.

My new bushing(s) miked .593 on the id and 1.093 on the od. The old bushing I pulled out (twice including the original) miked 1.090 on the od. And the 4sp input shaft miked .588. I checked the fit of the new unistalled bushing(s) on the 4sp input shaft and alignment tool both times and it fit great.

On the second bushing install, I noticed that as I tapped the new bushing in (super careful to tap square, slow and measuring to ensure square alignment), the bushing was necking down where it entered the crankshaft. So much so that a metal dowel .590 would not go in the bushing id anymore. Duh, so maybe the metal has to go somewhere I figure. So, as I tapped more, I also tapped out the id to .590 with the metal dowel and left a 1/4inch of length exposed or out as the original installation before.

Finally got the 4sp to go in on the second try with a some taps from a rubber mallet.

Any advice, is the Autozone pilot bushing or aftermarket bushings bad??? (I also lighted sanded and cleaned the recess id in the end of the crank and both bushings, so no trash or burrs I think) Are the roller bushings better? I understand transmission mechanics do not like this job either. What gives??? Anything to make this job easier?

(oh thanks to the CF on the bushing removal tip using a 5/8"NC bolt which I put a slight taper on with a file, this works great!)

Last edited by 20mercury; 08-30-2010 at 11:37 AM.
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Old 08-30-2010, 12:16 PM   #2
73, Dark Blue 454
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I've had two pilot 'bearings' fail so I'm back to using the bushings. The bushing is a very tight fit as you've learned. But it's hard to imagine that the ID can be significantly reduced form it's being pressed into the crank. Is this a factory crank?

Are you using the alignment tool to line up the input shaft and clutch disk? Even it's use can still lead to some tranny install headaches. What I've done when the tranny won't slide in is install the the cluth linkage and have somebody press the the clutch pedal while I'm stabbing the tranny. She'll slide right in once the disk is relaxed.
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Old 08-30-2010, 12:23 PM   #3
TopGunn
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Not sure if there's an issue with Autozone stuff or not but I've had similar experiences with undersize ID's on pilot bushings. I know I got a good one at NAPA but cannot honestly say where I got the bad one. I have a roller bearing now but only because the Tremec transmission requires it to honor the warentee otherwise I wouldn't.

When I was a kid we used to use an old transmission input shaft to install the bushings and never remembered having any problems.
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Old 08-30-2010, 12:25 PM   #4
TopGunn
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Quote:
Originally Posted by 73, Dark Blue 454 View Post
I've had two pilot 'bearings' fail so I'm back to using the bushings.
Yikes!!! I don't like to hear that man!
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Old 08-30-2010, 11:32 PM   #5
20mercury
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Default Thanks for the feedback.

Yes, I got the alignment tool to slide in and out very easily.

And yes, I talked my better half into pushing in the clutch in case the disc was hanging the 4sp up somehow.

I was using 4 and then 2 (top only) alignment pins (1/2"NC 8" long bolts with the heads cut off) to line up the 4sp going in and keep the weight off the disc (which I understand is a no no). I thought this helped, maybe not.

Maybe my crank (factory as far as I can tell, original engine, heads ect all look intact and original) was on the low end of the allowable tolerance?

Good idea on using an old input shaft to install.

Thanks again for the feedback.

Last edited by 20mercury; 08-30-2010 at 11:37 PM.
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Old 08-31-2010, 05:35 AM   #6
Solid LT1
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There is a BIG PROBLEM! with Chinese sourced pilot bushings today. Autogear transmissions has had so much trouble they brought out their own line of real Oilite bronze bushings.

Here is a link: http://autogear.net/whatsnew.php
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Old 08-31-2010, 05:35 AM
 
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